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1

Theoretical Investigation of the Enzymatic Phosphoryl Transfer of ?-phosphoglucomutase: Revisiting Both Steps of the Catalytic Cycle  

SciTech Connect

Enzyme catalyzed phosphate transfer is a part of almost all metabolic processes. Such reactions are of central importance for the energy balance in all organisms and play important roles in cellular control at all levels. Mutases transfer a phosphoryl group while nucleases cleave the phosphodiester linkages between two nucleotides. The subject of our present study is the Lactococcus lactis ?-phosphoglucomutase (?-PGM), which effectively catalyzes the interconversion of ?-D-glucose-1-phosphate (?-G1P) to ?- D-glucose-6-phosphate (?-G6P) and vice versa via stabile intermediate ?-D-glucose-1,6-(bis)phosphate (?-G1,6diP) in the presence of Mg2+. In this paper we revisited the reaction mechanism of the phosphoryl transfer starting from the bisphosphate ?-G1,6diP in both directions (toward ?-G1P and ?-G6P) combining docking techniques and QM/MM theoretical method at the DFT/PBE0 level of theory. In addition we performed NEB (nudged elastic band) and free energy calculations to optimize the path and to identify the transition states and the energies involved in the catalytic cycle. Our calculations reveal that both steps proceed via dissociative pentacoordinated phosphorane, which is not a stabile intermediate but rather a transition state. In addition to the Mg2+ ion, Ser114 and Lys145 also play important roles in stabilizing the large negative charge on the phosphate through strong coordination with the phosphate oxygens and guiding the phosphate group throughout the catalytic process. The calculated energy barrier of the reaction for the ?-G1P to ?-G1,6diP step is only slightly higher than for the ?-G1,6diP to ?-G6P step (16.10 kcal mol-1 versus 15.10 kcal mol-1) and is in excellent agreement with experimental findings (14.65 kcal mol-1).

Elsasser, Brigitta M.; Dohmeier-Fischer, Silvia; Fels, Gregor

2012-07-12

2

Biochemical control of CARM1 enzymatic activity by phosphorylation.  

PubMed

Coactivator-associated arginine methyltransferase 1 (CARM1) is a dual functional coregulator that facilitates transcription initiation by methylation of Arg(17) and Arg(26) of histone H3 and also dictates the subsequent coactivator complex disassembly by methylation of the steroid receptor coactivator family coactivators and p300/cAMP-response element-binding protein-binding protein. However, the regulation of CARM1 enzymatic activity and substrate specificity remains largely unknown. In this study, we report that CARM1 function is regulated by phosphorylation at Ser(217), a residue completely conserved in the type I protein arginine methyltransferase (PRMT) family of enzymes. Comparative analysis of the published CARM1 crystal structures reveals that the hydroxyl group of Ser(217) forms a strong hydrogen bond with the carbonyl oxygen atom of Tyr(154) to lock the cofactor S-adenosylmethionine inside the binding cavity. Phosphorylation of Ser(217) disrupts this hydrogen bond and subsequently abolishes S-adenosylmethionine binding and its methyltransferase activity. Importantly, Tyr(154) is also conserved in the type I PRMT family of enzymes, suggesting a general role of this hydrogen bond in maintaining the holo structure of the type I PRMT catalytic domain. Moreover, we found that phosphorylation at Ser(217) also promoted CARM1 cytoplasmic localization and that this translocation occurred mainly during mitosis. We propose that phosphorylation at Ser(217) serves as a molecular switch for controlling CARM1 enzymatic activity during the cell cycle. PMID:19843527

Feng, Qin; He, Bin; Jung, Sung-Yun; Song, Yongcheng; Qin, Jun; Tsai, Sophia Y; Tsai, Ming-Jer; O'Malley, Bert W

2009-12-25

3

Common Hydrogen Bond Interactions in Diverse Phosphoryl Transfer Active Sites  

PubMed Central

Phosphoryl transfer reactions figure prominently in energy metabolism, signaling, transport and motility. Prior detailed studies of selected systems have highlighted mechanistic features that distinguish different phosphoryl transfer enzymes. Here, a top-down approach is developed for comparing statistically the active site configurations between populations of diverse structures in the Protein Data Bank, and it reveals patterns of hydrogen bonding that transcend enzyme families. Through analysis of large samples of structures, insights are drawn at a level of detail exceeding the experimental precision of an individual structure. In phosphagen kinases, for example, hydrogen bonds with the O3? of the nucleotide substrate are revealed as analogous to those in unrelated G proteins. In G proteins and other enzymes, interactions with O3? have been understood in terms of electrostatic favoring of the transition state. Ground state quantum mechanical calculations on model compounds show that the active site interactions highlighted in our database analysis can affect substrate phosphate charge and bond length, in ways that are consistent with prior experimental observations, by modulating hyperconjugative orbital interactions that weaken the scissile bond. Testing experimentally the inference about the importance of O3? interactions in phosphagen kinases, mutation of arginine kinase Arg280 decreases kcat, as predicted, with little impact upon KM. PMID:25238155

Summerton, Jean C.; Martin, Gregory M.; Evanseck, Jeffrey D.; Chapman, Michael S.

2014-01-01

4

Phosphoryl Transfer from ?-d-Glucose 1-Phosphate Catalyzed by Escherichia coli Sugar-Phosphate Phosphatases of Two Protein Superfamily Types.  

PubMed

The Cori ester ?-d-glucose 1-phosphate (?Glc 1-P) is a high-energy intermediate of cellular carbohydrate metabolism. Its glycosidic phosphomonoester moiety primes ?Glc 1-P for flexible exploitation in glucosyl and phosphoryl transfer reactions. Two structurally and mechanistically distinct sugar-phosphate phosphatases from Escherichia coli were characterized in this study for utilization of ?Glc 1-P as a phosphoryl donor substrate. The agp gene encodes a periplasmic ?Glc 1-P phosphatase (Agp) belonging to the histidine acid phosphatase family. Had13 is from the haloacid dehydrogenase-like phosphatase family. Cytoplasmic expression of Agp (in E. coli Origami B) gave a functional enzyme preparation (kcat for phosphoryl transfer from ?Glc 1-P to water, 40 s(-1)) that was shown by mass spectrometry to exhibit no free cysteines and the native intramolecular disulfide bond between Cys(189) and Cys(195). Enzymatic phosphoryl transfer from ?Glc 1-P to water in H2 (18)O solvent proceeded with complete (18)O label incorporation into the phosphate released, consistent with catalytic reaction through O-1-P, but not C-1-O, bond cleavage. Hydrolase activity of both enzymes was not restricted to a glycosidic phosphomonoester substrate, and d-glucose 6-phosphate was converted with a kcat similar to that of ?Glc 1-P. By examining phosphoryl transfer from ?Glc 1-P to an acceptor substrate other than water (d-fructose or d-glucose), we discovered that Agp exhibited pronounced synthetic activity, unlike Had13, which utilized ?Glc 1-P mainly for phosphoryl transfer to water. By applying d-fructose in 10-fold molar excess over ?Glc 1-P (20 mM), enzymatic conversion furnished d-fructose 1-phosphate as the main product in a 55% overall yield. Agp is a promising biocatalyst for use in transphosphorylation from ?Glc 1-P. PMID:25527541

Wildberger, Patricia; Pfeiffer, Martin; Brecker, Lothar; Rechberger, Gerald N; Birner-Gruenberger, Ruth; Nidetzky, Bernd

2015-03-01

5

Vibrationally enhanced tunneling as a mechanism for enzymatic hydrogen transfer.  

PubMed Central

We present a theory of enzymatic hydrogen transfer in which hydrogen tunneling is mediated by thermal fluctuations of the enzyme's active site. These fluctuations greatly increase the tunneling rate by shortening the distance the hydrogen must tunnel. The average tunneling distance is shown to decrease when heavier isotopes are substituted for the hydrogen or when the temperature is increased, leading to kinetic isotope effects (KIEs)--defined as the factor by which the reaction slows down when isotopically substituted substrates are used--that need be no larger than KIEs for nontunneling mechanisms. Within this theory we derive a simple KIE expression for vibrationally enhanced ground state tunneling that is able to fit the data for the bovine serum amine oxidase (BSAO) system, correctly predicting the large temperature dependence of the KIEs. Because the KIEs in this theory can resemble those for nontunneling dynamics, distinguishing the two possibilities requires careful measurements over a range of temperatures, as has been done for BSAO. PMID:1420907

Bruno, W J; Bialek, W

1992-01-01

6

PLD2 has both enzymatic and cell proliferation-inducing capabilities, that are differentially regulated by phosphorylation and dephosphorylation  

PubMed Central

Phospholipase D2 (PLD2) overexpression in mammalian cells results in cell transformation. We have hypothesized that this is due to an increase of de novo DNA synthesis. We show here that overexpression of PLD2-WT leads to an increased DNA synthesis, as measured by the expression levels of the proliferation markers PCNA, p27KIP1 and phospho-histone-3. The enhancing effect was even higher with phosphorylation-defficient PLD2-Y179F and PLD2-Y511F mutants. The mechanism for this did not involve the enzymatic activity of the lipase, but, rather, the presence of the protein tyrosine phosphatase CD45, as silencing with siRNA for CD45 abrogated the effect. The two Y?F mutants had in common a YxN consensus site that, in the phosphorylated counterparts, could be recognized by SH2-bearing proteins, such as Grb2. Even though Y179F and Y511F cannot bind Grb2, they could still find other protein partners, one of which, we have reasoned, could be CD45 itself. Affinity purified PLD2 is indeed activated by Grb2 and deactivated by CD45 in vitro. We concluded that phosphorylated PLD2, aided by Grb2, mediates lipase activity, whereas dephosphorylated PLD2 mediates an induction of cell proliferation, and the specific residues involved in this newly discovered regulation of PLD2 are Y179 and Y511. PMID:19715678

Henkels, Karen M.; Short, Stephen; Peng, Hong-Juan; Fulvio, Mauricio Di; Gomez-Cambronero, Julian

2009-01-01

7

Enzymic phosphoryl transfer to carbon and oxygen acceptors: An investigation of the biosynthesis of 2-aminoethylphosphonic acid in Tetrahymena pyriformis W. and the kinetic mechanism and cofactor controlled substrate specificity of yeast inorganic pyrophosphatase  

Microsoft Academic Search

This research is concerned with the study of two enzymatic systems which catalyze phosphoryl transfer reactions to carbon and oxygen acceptors. The first portion of this study is concerned with the elucidation of the T. pyriformis 2-aminoethylphosphonate (AEP) biosynthetic pathway. The de novo formation of AEP from exogenously added precursors in Tetrahymena cell-free preparations was evaluated by using radioisotopic techniques

1987-01-01

8

Calcineurin-mediated dephosphorylation of eNOS at serine 116 affects eNOS enzymatic activity indirectly by facilitating c-Src binding and tyrosine 83 phosphorylation.  

PubMed

It has been shown previously that phosphorylation of the endothelial nitric oxide synthase (eNOS) at serine 116 (S116) under basal conditions suppresses eNOS enzymatic activity in endothelial cells. It has also been shown that vascular endothelial growth factor (VEGF) treatment of endothelial cells produces a rapid S116 dephosphorylation, which is blocked by the calcineurin inhibitor, cyclosporin A (CsA). In this study, we show that activation of eNOS in response to a variety of other eNOS-activating agonists and the cytosolic calcium-elevating agent, thapsigargin also involves CsA-inhibitable S116 dephosphorylation. Studies with the purified eNOS enzyme also demonstrate that neither mimicking phosphorylation at S116 nor phosphorylation of the purified enzyme at S116 in vitro has any effect on enzymatic activity. Phospho-mimicking, however, does interfere with the interaction of eNOS with c-Src, an interaction which is known to activate eNOS by phosphorylation at tyrosine 83 (Y83). Agonist-stimulated eNOS-Src complex formation, as well as agonist-stimulated Y83 phosphorylation, are blocked by calcineurin inhibition by CsA and by a cell-permeable calcineurin inhibitory peptide. Taken together, these data suggest a mechanism of eNOS regulation whereby calcineurin-mediated dephosphorylation of eNOS at S116 affects eNOS enzymatic activity indirectly, rather than directly, by facilitating c-Src binding and Y83 phosphorylation. PMID:23727078

Ruan, Ling; Torres, Christina M; Buffett, Ryan J; Kennard, Simone; Fulton, David; Venema, Richard C

2013-01-01

9

Calcineurin-mediated Dephosphorylation of eNOS at Serine 116 Affects eNOS Enzymatic Activity Indirectly by Facilitating c-Src Binding and Tyrosine 83 Phosphorylation  

PubMed Central

It has been shown previously that phosphorylation of the endothelial nitric oxide synthase (eNOS) at serine 116 (S116) under basal conditions suppresses eNOS enzymatic activity in endothelial cells. It has also been shown that vascular endothelial growth factor (VEGF) treatment of endothelial cells produces a rapid S116 dephosphorylation, which is blocked by the calcineurin inhibitor, cyclosporin A (CsA). In this study, we show that activation of eNOS in response to a variety of other eNOS-activating agonists and the cytosolic calcium-elevating agent, thapsigargin also involves CsA-inhibitable S116 dephosphorylation. Studies with the purified eNOS enzyme also demonstrate that neither mimicking phosphorylation at S116 nor phosphorylation of the purified enzyme at S116 in vitro has any effect on enzymatic activity. Phospho-mimicking, however, does interfere with the interaction of eNOS with c-Src, an interaction which is known to activate eNOS by phosphorylation at tyrosine 83 (Y83). Agonist-stimulated eNOS-Src complex formation, as well as agonist-stimulated Y83 phosphorylation, are blocked by calcineurin inhibition by CsA and by a cell-permeable calcineurin inhibitory peptide. Taken together, these data suggest a mechanism of eNOS regulation whereby calcineurin-mediated dephosphorylation of eNOS at S116 affects eNOS enzymatic activity indirectly, rather than directly, by facilitating c-Src binding and Y83 phosphorylation. PMID:23727078

Ruan, Ling; Torres, Christina M.; Buffett, Ryan J.; Kennard, Simone; Fulton, David; Venema, Richard C.

2013-01-01

10

Continuous-flow reactor-based enzymatic synthesis of phosphorylated compounds on a large scale.  

PubMed

Acid phosphatase, an enzyme that is able to catalyze the transfer of a phosphate group from cheap pyrophosphate to alcoholic substrates, was covalently immobilized on polymethacrylate beads with an epoxy linker (Immobeads-150 or Sepabeads EC-EP). After immobilization 70% of the activity was retained and the immobilized enzyme was stable for many months. With the immobilized enzyme we were able to produce and prepare D-glucose-6-phosphate, N-acetyl-D-glucosamine-6-phosphate, allyl phosphate, dihydroxyacetone phosphate, glycerol-1-phosphate, and inosine-5'-monophosphate from the corresponding primary alcohol on gram scale using either a fed-batch reactor or a continuous-flow packed-bed reactor. PMID:22505143

Babich, Lara; Hartog, Aloysius F; van der Horst, Michael A; Wever, Ron

2012-05-21

11

Unblocking the Sink: Improved CID-Based Analysis of Phosphorylated Peptides by Enzymatic Removal of the Basic C-Terminal Residue  

NASA Astrophysics Data System (ADS)

A one-step enzymatic reaction for improving the collision-induced dissociation (CID)-based tandem mass spectrometry (MS/MS) analysis of phosphorylated peptides in an ion trap is presented. Carboxypeptidase-B (CBP-B) was used to selectively remove C-terminal arginine or lysine residues from phosphorylated tryptic/Lys-C peptides prior to their MS/MS analysis by CID with a Paul-type ion trap. Removal of this basic C-terminal residue served to limit the extent of gas-phase neutral loss of phosphoric acid (H3PO4), favoring the formation of diagnostic b and y ions as determined by an increase in both the number and relative intensities of the sequence-specific product ions. Such differential fragmentation is particularly valuable when the H3PO4 elimination is so predominant that localizing the phosphorylation site on the peptide sequence is hindered. Improvement in the quality of tandem mass spectral data generated by CID upon CBP-B treatment resulted in greater confidence both in assignment of the phosphopeptide primary sequence and for pinpointing the site of phosphorylation. Higher Mascot ion scores were also generated, combined with lower expectation values and higher delta scores for improved confidence in site assignment; Ascore values also improved. These results are rationalized in accordance with the accepted mechanisms for the elimination of H3PO4 upon low energy CID and insights into the factors dictating the observed dissociation pathways are presented. We anticipate this approach will be of utility in the MS analysis of phosphorylated peptides, especially when alternative electron-driven fragmentation techniques are not available.

Lanucara, Francesco; Chi Hoo Lee, Dave; Eyers, Claire E.

2013-12-01

12

A redox beginning: Which came first phosphoryl, acyl, or electron transfer ?. [Abstract only  

NASA Technical Reports Server (NTRS)

Thermodynamic and kinetic information available on the synthesis of prebiotic monomers and polymers will be examined in order to illuminate the prebiotic plausibility of polymer syntheses based on (a) phosphoryl transfer that yields phosphodiester polymers, (b) acyl transfer that gives polyamides, and (c) electron transfer that produces polydisulfide or poly(thio)ester polymers. New experimental results on the oxidative polymerization of 2,3-dimercaptopropanol by ferric ions on the surface of ferric hydroxide oxide will be discussed as a chemical model of polymerization by electron transfer. This redox polymerization that yields polymers with a polydisulfide backbone was found to give oligomers up to the 15-mer from 1 mM of 2,3-dimercaptopropanol after one day at 25 C. High pressure liquid chromatography (HPLC) analysis of the oligomers was carried out on an Alltech OH-100 column eluted with acetonitrile-water.

Weber, Arthur L.

1994-01-01

13

Enzymatic analysis of isomeric trithymidylates containing ultraviolet light-induced cyclobutane pyrimidine dimers. II. Phosphorylation by phage T4 polynucleotide kinase  

SciTech Connect

Phage T4 polynucleotide kinase proved incapable of catalyzing the phosphorylation of thymidylyl-(3'----5')-thymidine containing either a cis-syn-cyclobutane pyrimidine dimer (d-T less than p greater than T) or a 6-4'-(pyrimidin-2'-one)pyrimidine photoproduct (d-T(p)-T), and similarly the UV-modified compounds of (dT)3 bearing either photoproduct at their 5'-end (d-T less than p greater than TpT and d-T(p)TpT). In contrast, the 3'-structural isomers of these trinucleotides (d-TpT less than p greater than T and d-TpT(p)T) were phosphorylated at the same rate as the parent compound. These phosphorylatable lesion-containing oligonucleotides are quantitatively released from UV-irradiated poly(dA):poly(dT) by enzymatic hydrolysis with snake venom phosphodiesterase and alkaline phosphatase. By combining this digestion regimen with phosphorylation by polynucleotide kinase and (gamma-/sup 32/P)ATP, pyrimidine dimers were quantitated at the fmol level following exposure of poly(dA):poly(dT) and herring sperm DNA to biologically relevant UV fluences. The rate of dimer induction in the synthetic polymer, approximately 10 dimers/10(6) nucleotides/Jm-2, was in close agreement with that obtained by conventional methods. Dimers were induced at one-fourth of this rate in the natural DNA. Further treatment of the phosphorylated oligonucleotides derived from irradiated herring sperm DNA with nuclease P1 released the labeled 5'-nucleotide, thus permitting analysis of the nearest-neighbor bases 5' to the lesions. We observed a ratio for pyrimidine-to-purine bases of almost 6:1, implicating tripyrimidine stretches as hotspots for UV-induced DNA damage.

Weinfeld, M.; Liuzzi, M.; Paterson, M.C.

1989-04-15

14

Application of Electron Transfer Dissociation Mass Spectrometry in Analyses of Non-enzymatically Glycated Peptides  

SciTech Connect

Non-enzymatic glycation of peptides and proteins by D-glucose has important implications in diabetes mellitus research, particularly in the context of development of diabetic complications. The fragmentation behavior of glycated peptides produced from reaction of D-glucose with lysine residues was investigated by electron transfer dissociation (ETD) and collision induced dissociation (CID) tandem mass spectrometry. It was found that high abundance ions corresponding to various degrees of neutral water losses, as well as furylium ion production, dominate the CID spectra, and that the sequence informative b and y ions were rarely observed when Amadori-modified peptides were fragmented. Contrary to what was observed under CID conditions, ions corresponding to neutral losses of water or furylium ion production were not observed in the ETD spectra. Instead, abundant and almost complete series of c and z type ions were observed regardless of whether the modification site was located in the middle of the sequence or close to the N-terminus, greatly facilitating the peptide sequencing. This study strongly suggests that ETD is a better technique for proteomics studies of non-enzymatically glycated peptides and proteins.

Zhang, Qibin; Frolov, Andrej; Tang, Ning; Hoffman, Ralf; van der Goor, Tom; Metz, Thomas O.; Smith, Richard D.

2007-03-15

15

Non-enzymatic synthesis of the coenzymes, uridine diphosphate glucose and cytidine diphosphate choline, and other phosphorylated metabolic intermediates  

NASA Technical Reports Server (NTRS)

Using urea and cyanamide, the two condensing agents considered to have been present on the primitive earth, uridine diphosphate glucose (UDPG), cytidine diphosphate choline (CDP-choline), glucose-1-phosphate (G1P), and glucose-6-phosphate (G6P) were synthesized under simulated prebiotic conditions. The reaction products were separated and identified using paper chromatography, thin layer chromatography, enzymatic analyses, and ion-pair reverse-phase high performance liquid chromatography. The possibility of nonenzymatic synthesis of metabolic intermediates on the primitive earth from simple precursors was thus demonstrated.

Mar, A.; Dworkin, J.; Oro, J.

1987-01-01

16

Transfer of Ser7 phosphorylated CENP-A from centromere to midbody during mitosis in MCF-7 cells.  

PubMed

Serine 7 of centromere protein A (CENP-A) is a very important mitosis-specific phosphorylation site. In this study, we demonstrate the subcellular distribution of Ser7 phosphorylated CENP-A during mitosis in MCF-7 cells. The Ser7 phosphorylation of CENP-A was observed beginning at prophase at centromeres. Upon progression of mitosis, the fluorescence signals emerged in the central region of the metaphase plate and were maintained until anaphase at centromeres. At late anaphase, the fluorescence signals moved to the midzone gradually and transferred from the centromere to the midbody completely at telophase. They were compacted into the centre of the midbody in a thin cylinder consisting of a sandglass-like "mitotic machine" with microtubules and condensed chromosome. We also found that Ser10 phosphorylated H3 and Thr11 phosphorylated H3 were co-localized at the midbody in two bell-like symmetrical bodies with Ser7 phosphorylated CENP-A during the terminal stage of cytokinesis. Midbody isolation and immunoblotting experiments also indicated that Ser7 phosphorylated CENP-A are components of the midbody. These findings suggest that Ser7 phosphorylated CENP-A acts as a chromosomal passenger protein and may play an important role in cytokinesis. PMID:23890477

Liu, R-M; Tian, X-Y; Huang, X-T; Zhou, H

2013-01-01

17

Studies on the mechanisms of phosphorothioyl transfer in enzymatic and nonenzymatic reactions  

SciTech Connect

The stereochemical course of rabbit liver fructose bisphosphatase (E.C.3.1.3.11) was determined by hydrolyzing a substrate analog (Sp)-(1-/sup 18/O)-fructose 1-phosphorothioate 6-phosphate in H/sub 2//sup 17/O, incorporating the chiral, inorganic phosphorothioate product into ATP..beta..S, and analyzing the isotopic distribution of /sup 18/O in ATP..beta..S by /sup 31/P NMR. The results indicate that the 1-phosphoryl group is transferred with inversion of configuration. A series of /sup 18/O-enrichment and exchange, single-turnover experiments rule out an enzyme acylphosphate intermediate in the hydrolysis. Consequently, fructose bisphosphatase catalyzes the hydrolysis of fructose 1,6-bisphosphate via a direct transfer of the phosphoryl moiety to water. To determine whether a monomeric metaphosphorothioate intermediate is formed during the hydrolysis of phosphorothioate monoesters, the stereochemical course of the hydrolysis of chiral (Rp)- and (Sp)-(/sup 18/O) O-p-nitrophenyl phosphorothioate in H/sub 2//sup 17/O was determined as per rabbit liver fructose bisphosphatase. /sup 31/P NMR analysis of the isotopic distribution of the ..beta..-P species of (Rp)-(..beta..-/sup 17/O,..beta..-/sup 18/O) ATP..beta..S for both isomers showed the monoester hydrolysis to proceed with inversion of configuration implying that if the metaphosphorothioate intermediate was formed, it did not exist long enough to become symmetrically solvated and, subsequently, suffered nucleophilic attack on the face opposing that occupied by the leaving group, p-nitrophenol.

Domanico, P.L.

1986-01-01

18

In vitro evidence of chain transfer to tetraethylene glycols in enzymatic polymerization of polyhydroxyalkanoate.  

PubMed

A polyhydroxyalkanoate (PHA) was enzymatically synthesized in vitro, and the end structure of PHA associated with a chain transfer (CT) reaction was investigated. In the CT reaction, PHA chain transfers from PHA synthase (PhaC) to a CT agent, resulting in covalent bonding of CT agent to the PHA chain at its carboxyl end. In vitro CT reaction has never been demonstrated because of relatively low yields of in vitro synthesized poly[(R)-3-hydroxybutyrate)] (P(3HB)), which makes it difficult to characterize the end structures of the polymers by nuclear magnetic resonance (NMR). To overcome these difficulties, a novel in vitro synthesis method that produced relatively larger amounts of P(3HB) was developed by employing PhaCDa from Delftia acidovorans and two enantioselective enoyl-coenzyme A (CoA) hydratases which were R-hydratase (PhaJAc) from Aeromonas caviae and S-hydratase (FadB1x) from Pseudomonas putida KT2440 with ?-butyrolactone and CoA as starting materials. Using this method, P(3HB) synthesis was performed with tetraethylene glycols (TEGs) as a discriminable CT agent, and the resultant P(3HB) was characterized by (1)H-NMR. NMR analysis revealed that the carboxylic end of P(3HB) was covalently linked to TEGs, providing the first direct evidence of in vitro CT reaction. PMID:23474615

Tomizawa, Satoshi; Sato, Shun; Lan, John Chi-Wei; Nakamura, Yoshiyuki; Abe, Hideki; Tsuge, Takeharu

2013-06-01

19

Enzyme orientation for direct electron transfer in an enzymatic fuel cell with alcohol oxidase and laccase electrodes.  

PubMed

A new full enzymatic fuel cell was built and characterized. Both enzymatic electrodes were molecularly oriented to enhance the direct electron transfer between the enzyme active site and the electrode surface. The anode consisted in immobilized alcohol oxidase on functionalized carbon nanotubes with 4-azidoaniline, which acts as active-site ligand to orientate the enzyme molecule. The cathode consisted of immobilized laccase on functionalized graphite electrode with 4-(2-aminoethyl) benzoic acid. The enzymatic fuel cell reaches 0.5 V at open circuit voltage with both, ethanol and methanol, while in short circuit the highest current intensity of 250 ?A cm(-2) was obtained with methanol. Concerning the power density, the methanol was the best substrate reaching 60 ?W cm(-2), while with ethanol 40 ?W cm(-2) was obtained. PMID:24953844

Arrocha, Andrés A; Cano-Castillo, Ulises; Aguila, Sergio A; Vazquez-Duhalt, Rafael

2014-11-15

20

Phosphorylation at 5? end of guanosine stretches inhibits dimerization of G-quadruplexes and formation of a G-quadruplex interferes with the enzymatic activities of DNA enzymes  

PubMed Central

During an analysis of DNA enzymes by gel electrophoresis, we found that some DNA enzymes can adopt more than one conformation. The DNA enzyme Dz31 that formed more than one conformer contained a stretch of G residues. Further investigations, involving kinetic analysis and measurements of circular dichroism, indicated that this DNA enzyme and its derivatives formed G-quadruplexes. Moreover, we found that some derivative oligomers were capable of forming dimeric G-quadruplexes. We also compared the catalytic activities of Dz31 and its mutant derivatives. The present findings suggest that DNA enzymes with five or more continuous G residues are less favorable than those without G5 in the association step in the enzymatic reaction and, thus, the choice of targets that contain a continuous stretch of C residues downstream of the cleavage site should be avoided. In addition, we found that negative charge–charge repulsion disrupted the dimerization of G-quadruplexes when a phosphate group was added directly to the 5?-terminal G of oligomers with continuous guanosine residues. In the case of 5?-phosphorylated G5CTA, direct attachment of a phosphate group to the continuous G5 sequence inhibited dimerization of G-quadruplexes, at least during electrophoresis on a denaturing gel. PMID:15333694

Uddin, M. Khabir; Kato, Yoshio; Takagi, Yasuomi; Mikuma, Toshiyasu; Taira, Kazunari

2004-01-01

21

Physical Properties and Enzymatic Digestibility of Phosphorylated ae, wx , and Normal Maize Starch Prepared at Different pH Levels 1  

Microsoft Academic Search

Cereal Chem. 76(6):938-943 Phosphorylated starches were prepared with sodium tripolyphosphate (STPP) at pH 6, 8, and 10 from waxy (wx, 3.3% amylose), normal (22.4% amylose), and two high-amylose (ae, 47 and 66% amylose) maize starches. After phosphorylation, the gelatinization peak temperature ( Tp) decreased and pasting peak viscosity (PV) increased for all the starches except wx, which showed a slight

Huijun Liu; Lawrence Ramsden; Harold Corke

1999-01-01

22

Cardiac mitochondrial matrix and respiratory complex protein phosphorylation  

PubMed Central

It has become appreciated over the last several years that protein phosphorylation within the cardiac mitochondrial matrix and respiratory complexes is extensive. Given the importance of oxidative phosphorylation and the balance of energy metabolism in the heart, the potential regulatory effect of these classical signaling events on mitochondrial function is of interest. However, the functional impact of protein phosphorylation and the kinase/phosphatase system responsible for it are relatively unknown. Exceptions include the well-characterized pyruvate dehydrogenase and branched chain ?-ketoacid dehydrogenase regulatory system. The first task of this review is to update the current status of protein phosphorylation detection primarily in the matrix and evaluate evidence linking these events with enzymatic function or protein processing. To manage the scope of this effort, we have focused on the pathways involved in energy metabolism. The high sensitivity of modern methods of detecting protein phosphorylation and the low specificity of many kinases suggests that detection of protein phosphorylation sites without information on the mole fraction of phosphorylation is difficult to interpret, especially in metabolic enzymes, and is likely irrelevant to function. However, several systems including protein translocation, adenine nucleotide translocase, cytochrome c, and complex IV protein phosphorylation have been well correlated with enzymatic function along with the classical dehydrogenase systems. The second task is to review the current understanding of the kinase/phosphatase system within the matrix. Though it is clear that protein phosphorylation occurs within the matrix, based on 32P incorporation and quantitative mass spectrometry measures, the kinase/phosphatase system responsible for this process is ill-defined. An argument is presented that remnants of the much more labile bacterial protein phosphoryl transfer system may be present in the matrix and that the evaluation of this possibility will require the application of approaches developed for bacterial cell signaling to the mitochondria. PMID:22886415

Covian, Raul

2012-01-01

23

The stereochemical course of phosphoryl transfer catalysed by Bacillus stearothermophilus and rabbit skeletal-muscle phosphofructokinase with a chiral [16O,17O,18O]phosphate ester.  

PubMed

Bacillus stearothermophilus and rabbit skeletal-muscle phosphofructokinases catalyse the transfer of the chiral [16O,17O,18O]phosphoryl group from D-fructose 1[(S)-16O,17O,18O],6-bisphosphate to ADP with inversion of configuration at the phosphorus atom. D-Fructose 1[(S)-16O,17O,18O],-bisphosphate was synthesized in situ from sn-glycerol 3[(S)-16O,17O,18O]phosphate. The simplest interpretation of these results is that the phosphoryl group is transferred between substrates in the enzyme substrate ternary complexes by an 'in-line' mechanism. PMID:6462132

Jarvest, R L; Lowe, G; Potter, B V

1981-11-01

24

Kinetic Isotope Effects as a Probe of Hydrogen Transfers to and from Common Enzymatic Cofactors  

PubMed Central

Enzymes use a number of common cofactors as sources of hydrogen to drive biological processes, but the physics of the hydrogen transfers to and from these cofactors is not fully understood. Researchers study the mechanistically important contributions from quantum tunneling and enzyme dynamics and connect those processes to the catalytic power of enzymes that use these cofactors. Here we describe some progress that has been made in studying these reactions, particularly through the use of kinetic isotope effects (KIEs). We first discuss the general theoretical framework necessary to interpret experimental KIEs, and then describe practical uses for KIEs in the context of two case studies. The first example is alcohol dehydrogenase, which uses a nicotinamide cofactor to catalyze a hydride transfer, and the second example is thymidylate synthase, which uses a folate cofactor to catalyze both a hydride and a proton transfer. PMID:24161942

Roston, Daniel; Islam, Zahidul; Kohen, Amnon

2013-01-01

25

Two and Three-dimensional Gene Transfer from Enzymatically Degradable Hydrogel Scaffolds  

PubMed Central

The ability to genetically modify mesenchymal stem cells (MSCs) seeded inside synthetic hydrogel scaffolds would offer an alternative approach to guide MSC differentiation. In this report, we explored gene transfer to MSCs seeded on top, or inside matrix metalloproteinase (MMP) degradable hydrogels that were loaded with DNA/poly(ethylene imine) (PEI) polyplexes. DNA/PEI polyplexes were encapsulated inside poly(ethylene glycol) (PEG) hydrogels crosslinked with MMP degradable peptides via Michael Addition chemistry. Gene transfer was visualized and quantified through using a vector encoding for green fluorescent protein and luciferase. We found that gene transfer to MSCs was possible for cells seeded both in two and three dimensions. The amount of luciferase expression was similar for cells seeded in two and three dimensions even though the number of cells in three dimensions is significantly higher, indicating that gene transfer to cells seeded in two dimensions is more efficient than for cells seeded in three dimensions. The use of hydrogel scaffolds that allow cellular infiltration to deliver DNA may result in long lasting signals in vivo, which are essential for the regeneration of functional tissues. PMID:20232458

Lei, Yuguo; Ng, Quinn K. T.; Segura, Tatiana

2010-01-01

26

Peptide-mediated constructs of quantum dot nanocomposites for enzymatic control of nonradiative energy transfer.  

PubMed

A bottom-up approach for constructing colloidal semiconductor quantum dot (QDot) nanocomposites that facilitate nonradiative Fo?rster-type resonance energy transfer (FRET) using polyelectrolyte peptides was proposed and realized. The electrostatic interaction of these polypeptides with altering chain lengths was probed for thermodynamic, structural, and morphological aspects. The resulting nanocomposite film was successfully cut with the protease by digesting the biomimetic peptide layer upon which the QDot assembly was constructed. The ability to control photoluminescence decay lifetime was demonstrated by proteolytic enzyme activity, opening up new possibilities for biosensor applications. PMID:21428276

Seker, Urartu Ozgur Safak; Ozel, Tuncay; Demir, Hilmi Volkan

2011-04-13

27

Lewis acid catalysis of phosphoryl transfer from a copper(II)-NTP complex in a kinase ribozyme  

PubMed Central

The chemical strategies used by ribozymes to enhance reaction rates are revealed in part from their metal ion and pH requirements. We find that kinase ribozyme K28(1-77)C, in contrast with previously characterized kinase ribozymes, requires Cu2+ for optimal catalysis of thiophosphoryl transfer from GTP?S. Phosphoryl transfer from GTP is greatly reduced in the absence of Cu2+, indicating a specific catalytic role independent of any potential interactions with the GTP?S thiophosphoryl group. In-line probing and ATP?S competition both argue against direct Cu2+ binding by RNA; rather, these data establish that Cu2+ enters the active site within a Cu2+•GTP?S or Cu2+•GTP chelation complex, and that Cu2+•nucleobase interactions further enforce Cu2+ selectivity and position the metal ion for Lewis acid catalysis. Replacing Mg2+ with [Co(NH3)6]3+ significantly reduced product yield, but not kobs, indicating that the role of inner-sphere Mg2+ coordination is structural rather than catalytic. Replacing Mg2+ with alkaline earths of increasing ionic radii (Ca2+, Sr2+ and Ba2+) gave lower yields and approximately linear rates of product accumulation. Finally, we observe that reaction rates increased with pH in log-linear fashion with an apparent pKa = 8.0 ± 0.1, indicating deprotonation in the rate-limiting step. PMID:23358821

Biondi, Elisa; Poudyal, Raghav R.; Forgy, Joshua C.; Sawyer, Andrew W.; Maxwell, Adam W. R.; Burke, Donald H.

2013-01-01

28

Enrichment and Analysis of Non-enzymatically Glycated Peptides: Boronate Affinity Chromatography Coupled with Electron Transfer Dissociation Mass Spectrometry  

PubMed Central

Non-enzymatic glycation of peptides and proteins by D-glucose has important implications in the pathogenesis of diabetes mellitus, particularly in the development of diabetic complications. However, no effective high-throughput methods exist for identifying proteins containing this low abundance post-translational modification in bottom-up proteomic studies. In this report, phenylboronate affinity chromatography was used in a two-step enrichment scheme to selectively isolate first glycated proteins and then glycated, tryptic peptides from human serum glycated in vitro. Enriched peptides were subsequently analyzed by alternating electron transfer dissociation (ETD) and collision induced dissociation (CID) tandem mass spectrometry. ETD fragmentation mode permitted identification of a significantly higher number of glycated peptides (87.6% of all identified peptides) versus CID mode (17.0% of all identified peptides), when utilizing enrichment on first the protein and then the peptide level. This study illustrates that phenylboronate affinity chromatography coupled with LC-MS/MS and using ETD as the fragmentation mode is an efficient approach for analysis of glycated proteins and may have broad application in studies of diabetes mellitus. PMID:17488106

Zhang, Qibin; Tang, Ning; Brock, Jonathan W. C.; Mottaz, Heather M.; Ames, Jennifer M.; Baynes, John W.; Smith, Richard D.; Metz, Thomas O.

2008-01-01

29

Miniature direct electron transfer based sulphite/oxygen enzymatic fuel cells.  

PubMed

A direct electron transfer (DET) based sulphite/oxygen biofuel cell is reported that utilises human sulphite oxidase (hSOx) and Myrothecium verrucaria bilirubin oxidase (MvBOx) and nanostructured gold electrodes. For bioanode construction, the nanostructured gold microelectrodes were further modified with 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) to which polyethylene imine was covalently attached. hSOx was adsorbed onto this chemically modified nanostructured electrode with high surface loading of electroactive enzyme and in presence of sulphite high anodic bioelectrocatalytic currents were generated with an onset potential of 0.05V vs. NHE. The biocathode contained MvBOx directly adsorbed to the deposited gold nanoparticles for cathodic oxygen reduction starting at 0.71V vs. NHE. Both enzyme electrodes were integrated to a DET-type biofuel cell. Power densities of 8 and 1?Wcm(-2) were achieved at 0.15V and 0.45V of cell voltages, respectively, with the membrane based biodevices under aerobic conditions. PMID:25460879

Zeng, T; Pankratov, D; Falk, M; Leimkühler, S; Shleev, S; Wollenberger, U

2015-04-15

30

Time-Resolved Fluorescence Energy Transfer Measurements Between Site-Specific Probes On The Ca-Atpase Of Sarcoplasmic Reticulum In Different Enzymatic States  

NASA Astrophysics Data System (ADS)

We have measured resonance energy transfer between two donor-acceptor pairs localized on different domains of the Ca-ATPase of sarcoplasmic reticulum in order to determine whether changes in tertiary structure accompany active calcium transport. Energy transfer was determined from both steady state intensities and time-resolved lifetimes of 5-(2-((acety1)- amino)ethyDaminonaphthalene-l-sulfonic acid (IAEDANS), specifically bound to the B tryptic fragment, using two acceptors: (1) fluorescein 5'-isothiocyanate (FITC), covalently bound at the nucleotide site, also on the B fragment, and (2) 4-dimethylaminophenylazopheny1-4'- maleimide (DABMI), bound on the Al subfragment. Neither binding of calcium to the high affinity sites nor phosphorylation by inorganic phosphate is accompanied by detectable changes in the distance between IAEDANS and FITC, suggesting that the B fragment does not undergo any large-scale (>1 A) physical distortion under these conditions. On the other hand, measurements of energy transfer from IAEDANS to the acceptor DABMI, on the Al subfragment, demonstrate that phosphorylation with inorganic phosphate or addition of pM VO4 results in increased energy transfer, that is reversible with subsequent addition of calcium. Addition of calcium to the nonphosphorylated enzyme results in no detectable change in energy transfer. The presence of the detergent lysolecithin prevents the phosphate dependent increase in fluorescence energy transfer, suggesting that protein-protein interactions may contribute to the observed change in energy transfer. A direct relationship between an increased degree of protein-protein interactions and phosphoenzyme formation is confirmed by investigations using a reconstituted preparation containing a mixed popu Lation of Ca-ATPase polypeptide chains labeled either with IAEDANS or with DABMI. These results suggest a phosphorylation dependent change in either the affinity or orientation of Ca-ATPase polypeptide chains with respect to one another.

Squier, Thomas C.; Bigelow, Diana J.; Garcia de Ancos, Jorge; Bishop, James E.; Inesi, Giuseppe

1988-06-01

31

Semisynthetic aminoglycoside antibiotics: Development and enzymatic modifications  

Microsoft Academic Search

The critical resistance mechanisms of aminoglycoside antibiotics in bacteria of clinical importance are the enzymatic N-acetylation, O-phosphorylation, and O-nucleotidylation that generally result in the inactivation of aminoglycosides. To overcome such resistance mechanisms, dibekacin\\u000a (3?,4?-dideoxykanamycin B) was developed as the first rationally designed semisynthetic aminoglycoside, based on the enzymatic\\u000a 3?-O-phosphorylation of kanamycin. Subsequently, amikacin, netilmicin, and isepamicin were developed by introducing

Shinichi Kondo; Kunimoto Hotta

1999-01-01

32

Vibrational studies of phosphoryl transfer enzymes: ras- p21(*)magnesium-GTP and Myosin S1(*)magnesium-ADP- vanadate  

NASA Astrophysics Data System (ADS)

We have measured the Raman spectra of monophosphate compounds in aqueous solution. The measured frequencies were correlated with P••O valence bond order by using a modification of the Hardcastle- Wachs procedure. The P••O bond order and bond length in phosphates can be determined from vibrational spectra by using the derived bond order/stretching frequency correlation and the bond length/bond order correlation of Brown and Wu. The Raman and infrared spectra of guanosine 5'-diphosphate (GDP) and guanosine 5'-triphosphate (GTP) in aqueous solution were also examined. Frequency shifts were observed as Mg2+ complexes with GDP and GTP in aqueous solution. These results suggested that Mg2+ binds to GDP in a bidentate manner to the ?,? P••O bonds and in a tridentate manner to the ?,? and ? P••O bonds of Mg•GTP . We have analyzed the previously obtained isotope edited Raman difference spectra of 1:1 complexes of Mg•GDP and Mg•GTP in ras-p21. Frequency changes of the phosphate groups were observed when Mg•GDP , Mg•GTP bind to the protein. Employing both the previous empirical relationships between bond orders/lengths and frequencies as well as vibrational analysis from ab initio calculations, the spectral changes can be explained by the change of the Mg2+ binding sites and hydrogen-bonding. Implications of these structural results for the reaction mechanism of GTP hydrolysis catalyzed by the GTPase are discussed. We have analyzed previously obtained isotope edited Raman difference spectra of the non-bridging V••O bonds of vanadates, both in solution, and when bound to the myosin S1•MgADP complex. By use of ab initio calculations on a model of the vanadate binding site in myosin, the angles between the non-bridging V••O bonds and between these bonds and the apical bonds in the myosin S1•MgADP -Vi complex were determined. The summed bond order of the two apical bonds between the attacking and leaving group oxygens with the central vanadium ion in the S1•MgADP -Vi complex was found to increase only slightly compared with the bond order of the ester V-O bond of a monoester vanadate model compound in solution, suggesting an SN2 like mechanism for the phosphoryl transfer reaction catalyzed by myosin.

Wang, Jianghua

1999-07-01

33

J. Am. Chem. SOC.1990, 112, 1951-1956 1951 Nucleophiles of High Reactivity in Phosphoryl Transfer  

E-print Network

Reactions: a-Effect Compounds and Fluoride Ion' Daniel Herschlag and William P. Jencks* Contribution No. I, acetohydroxamate, and fluoride anions with phosphorylated pyridine monoanions (H20,25 O C , ionic strength 1 that influences the stability and structure of the transition state. The observed changes in transition

Herschlag, Dan

34

An enzymatically-sensitized sequential and concentric energy transfer relay self-assembled around semiconductor quantum dots.  

PubMed

The ability to control light energy within de novo nanoscale structures and devices will greatly benefit their continuing development and ultimate application. Ideally, this control should extend from generating the light itself to its spatial propagation within the device along with providing defined emission wavelength(s), all in a stand-alone modality. Here we design and characterize macromolecular nanoassemblies consisting of semiconductor quantum dots (QDs), several differentially dye-labeled peptides and the enzyme luciferase which cumulatively demonstrate many of these capabilities by engaging in multiple-sequential energy transfer steps. To create these structures, recombinantly-expressed luciferase and the dye-labeled peptides were appended with a terminal polyhistidine sequence allowing for controlled ratiometric self-assembly around the QDs via metal-affinity coordination. The QDs serve to provide multiple roles in these structures including as central assembly platforms or nanoscaffolds along with acting as a potent energy harvesting and transfer relay. The devices are activated by addition of coelenterazine H substrate which is oxidized by luciferase producing light energy which sensitizes the central 625 nm emitting QD acceptor by bioluminescence resonance energy transfer (BRET). The sensitized QD, in turn, acts as a relay and transfers the energy to a first peptide-labeled Alexa Fluor 647 acceptor dye displayed on its surface. This dye then transfers energy to a second red-shifted peptide-labeled dye acceptor on the QD surface through a second concentric Förster resonance energy transfer (FRET) process. Alexa Fluor 700 and Cy5.5 are both tested in the role of this terminal FRET acceptor. Photophysical analysis of spectral profiles from the resulting sequential BRET-FRET-FRET processes allow us to estimate the efficiency of each of the transfer steps. Importantly, the efficiency of each step within this energy transfer cascade can be controlled to some extent by the number of enzymes/peptides displayed on the QD. Further optimization of the energy transfer process(es) along with potential applications of such devices are finally discussed. PMID:25804284

Samanta, Anirban; Walper, Scott A; Susumu, Kimihiro; Dwyer, Chris L; Medintz, Igor L

2015-04-24

35

Summarizing lecture: factors influencing enzymatic H-transfers, analysis of nuclear tunnelling isotope effects and thermodynamic versus specific effects  

PubMed Central

In the articles in this Discussion, a wide variety of topics are treated, including reorganization energy, initially introduced for electron transfers (‘environmentally assisted tunnelling’), nuclear tunnelling, H/D and C12/C13 kinetic isotope effects (KIEs), the effect of changes of distal and nearby amino acid residues using site-directed mutagenesis, and dynamics versus statistical effects. A coordinate-free form of semi-classical theory is used to examine topics on data such as tunnelling versus ‘over-the-barrier’ paths and temperature and pressure effects on KIEs. The multidimensional semi-classical theory includes classically allowed and classically forbidden transitions. More generally, we address the question of relating kinetic to thermodynamic factors, as in the electron transfer field, so learning about specific versus thermodynamic effects in enzyme catalysis and KIEs. PMID:16873131

Marcus, R.A

2006-01-01

36

Optimal alignment for enzymatic proton transfer: Structure of the Michaelis complex of triosephosphate isomerase at 1.2-? resolution  

PubMed Central

In enzyme catalysis, where exquisitely positioned functionality is the sine qua non, atomic coordinates for a Michaelis complex can provide powerful insights into activation of the substrate. We focus here on the initial proton transfer of the isomerization reaction catalyzed by triosephosphate isomerase and present the crystal structure of its Michaelis complex with the substrate dihydroxyacetone phosphate at near-atomic resolution. The active site is highly compact, with unusually short and bifurcated hydrogen bonds for both catalytic Glu-165 and His-95 residues. The carboxylate oxygen of the catalytic base Glu-165 is positioned in an unprecedented close interaction with the ketone and the ?-hydroxy carbons of the substrate (C… O ? 3.0 ?), which is optimal for the proton transfer involving these centers. The electrophile that polarizes the substrate, His-95, has close contacts to the substrate's O1 and O2 (N… O ? 3.0 and 2.6 ?, respectively). The substrate is conformationally relaxed in the Michaelis complex: the phosphate group is out of the plane of the ketone group, and the hydroxy and ketone oxygen atoms are not in the cisoid configuration. The ? ammonium group of the electrophilic Lys-12 is within hydrogen-bonding distance of the substrate's ketone oxygen, the bridging oxygen, and a terminal phosphate's oxygen, suggesting a role for this residue in both catalysis and in controlling the flexibility of active-site loop. PMID:12509510

Jogl, Gerwald; Rozovsky, Sharon; McDermott, Ann E.; Tong, Liang

2003-01-01

37

Inhibition of the Conversion of 1-Aminocyclopropane-1-carboxylic Acid to Ethylene by Structural Analogs, Inhibitors of Electron Transfer, Uncouplers of Oxidative Phosphorylation, and Free Radical Scavengers 1  

PubMed Central

Cyclopropane carboxylic acid (CCA) at 1 to 5 millimolar, unlike related cyclopropane ring analogs of 1-aminocyclopropane-1-carboxylic acid (ACC) which were virtually ineffective, inhibited C2H4 production, and this inhibition was nullified by ACC. Inhibition by CCA is not competitive with ACC since there is a decline, rather than an increase, in native endogenous ACC in the presence of CCA. Similarly, short-chain organic acids from acetic to butyric acid and ?-aminoisobutyric acid inhibited C2H4 production at 1 to 5 millimolar and lowered endogenous ACC levels. These inhibitions, like that of CCA, were overcome with ACC. Inhibitors of electron transfer and oxidative phosphorylation effectively inhibited ACC conversion to C2H4 in pea and apple tissues. The most potent inhibitors were 2,4-dinitrophenol (DNP) and carbonyl cyanide m-chlorophenylhydrazone (CCCP) which virtually eliminated ACC-stimulated C2H4 production in both tissues. Still other inhibitors of the conversion of ACC to C2H4 were putative free radical scavengers which reduced chemiluminescence in the free radical-activated luminol reaction. These inhibitor studies suggest the involvement of a free radical in the reaction sequence which converts ACC to C2H4. Additionally, the potent inhibition of this reaction by uncouplers of oxidative phosphorylation (DNP and CCCP) suggest the involvement of ATP or the necessity for an intact membrane for C2H4 production from ACC. In the latter case, CCCP may be acting as a proton ionophore to destroy the membrane integrity necessary for C2H4 production. PMID:16661637

Apelbaum, Akiva; Wang, Shiow Y.; Burgoon, Alan C.; Baker, James E.; Lieberman, Morris

1981-01-01

38

Tapping a bacterial enzymatic pathway for the preparation and manipulation of synthetic nanomaterials.  

PubMed

We present a spherical micelle generated in a three-step sequence in which a farnesyl-pantetheine conjugate is phosphorylated, adenylated, and phosphorylated once more to generate a farnesyl-CoA amphiphile that self-assembles into spherical micelles. A sphere-to-fibril morphological switch is achieved by enzymatically transferring the farnesyl group of the farnesyl-CoA micelle onto a peptide via phosphopantetheinyl transferase to generate a peptide amphiphile. Each step in the sequence is followed with characterization by HPLC, MS, TEM, and DLS. This system offers an entry into cofactor-mediated peptide decoration by extending the principles of bioresponsive polymeric materials to sequential enzyme cascades. PMID:25468257

Ku, Ti-Hsuan; Sahu, Swagat; Kosa, Nicolas M; Pham, Kevin M; Burkart, Michael D; Gianneschi, Nathan C

2014-12-17

39

An insert-based enzymatic cell culture system to rapidly and reversibly induce hypoxia: investigations of hypoxia-induced cell damage, protein expression and phosphorylation in neuronal IMR-32 cells.  

PubMed

Ischemia-reperfusion injury and tissue hypoxia are of high clinical relevance because they are associated with various pathophysiological conditions such as myocardial infarction and stroke. Nevertheless, the underlying mechanisms causing cell damage are still not fully understood, which is at least partially due to the lack of cell culture systems for the induction of rapid and transient hypoxic conditions. The aim of the study was to establish a model that is suitable for the investigation of cellular and molecular effects associated with transient and long-term hypoxia and to gain insights into hypoxia-mediated mechanisms employing a neuronal culture system. A semipermeable membrane insert system in combination with the hypoxia-inducing enzymes glucose oxidase and catalase was employed to rapidly and reversibly generate hypoxic conditions in the culture medium. Hydrogen peroxide assays, glucose measurements and western blotting were performed to validate the system and to evaluate the effects of the generated hypoxia on neuronal IMR-32 cells. Using the insert-based two-enzyme model, hypoxic conditions were rapidly induced in the culture medium. Glucose concentrations gradually decreased, whereas levels of hydrogen peroxide were not altered. Moreover, a rapid and reversible (on-off) generation of hypoxia could be performed by the addition and subsequent removal of the enzyme-containing inserts. Employing neuronal IMR-32 cells, we showed that 3 hours of hypoxia led to morphological signs of cellular damage and significantly increased levels of lactate dehydrogenase (a biochemical marker of cell damage). Hypoxic conditions also increased the amounts of cellular procaspase-3 and catalase as well as phosphorylation of the pro-survival kinase Akt, but not Erk1/2 or STAT5. In summary, we present a novel framework for investigating hypoxia-mediated mechanisms at the cellular level. We claim that the model, the first of its kind, enables researchers to rapidly and reversibly induce hypoxic conditions in vitro without unwanted interference of the hypoxia-inducing agent on the cultured cells. The system could help to further unravel hypoxia-associated mechanisms that are clinically relevant in various tissues and organs. PMID:24046359

Huang, Ying; Zitta, Karina; Bein, Berthold; Steinfath, Markus; Albrecht, Martin

2013-11-01

40

Biofuel Cells: Enhanced Enzymatic Bioelectrocatalysis  

NASA Astrophysics Data System (ADS)

Enzymatic biofuel cells represent an emerging technology that can create electrical energy from biologically renewable catalysts and fuels. A wide variety of redox enzymes have been employed to create unique biofuel cells that can be used in applications such as implantable power sources, energy sources for small electronic devices, self-powered sensors, and bioelectrocatalytic logic gates. This review addresses the fundamental concepts necessary to understand the operating principles of biofuel cells, as well as recent advances in mediated electron transfer- and direct electron transfer-based biofuel cells, which have been developed to create bioelectrical devices that can produce significant power and remain stable for long periods.

Meredith, Matthew T.; Minteer, Shelley D.

2012-07-01

41

Enzymatic hydrolysis of cellulose  

Microsoft Academic Search

This book reviews the theory and application of enzymatic hydrolysis of cellulosic biomass; with implications for genetic engineering techniques. State of the art and potential industrial processes are detailed, including high productivity fermentation systems for the production of ethanol. Contents: Theory of Enzymatic Hydrolysis; Production of Cellulase and Xylanase; Hydrolysis of Agricultural Residues; Enzymatic Hydrolysis Processes; High Productivity Ethanol Fermentation;

1983-01-01

42

Requirements for Phosphorylation of MAP Kinase During Meiosis in Xenopus Oocytes  

Microsoft Academic Search

Mitogen-activated protein (MAP) kinases are activated in response to a variety of extracellular stimuli by phosphorylation on tyrosine and threonine residues. Xp42 is a Xenopus laevis MAP kinase that is activated during oocyte maturation. Modified forms of Xp42 that lacked enzymatic activity or either of the phosphorylation sites were expressed in Xenopus oocytes. When meiotic maturation was induced with progesterone,

James Posada; Jonathan A. Cooper

1992-01-01

43

The Fic protein Doc uses an inverted substrate to phosphorylate and inactivate EF-Tu  

PubMed Central

Fic proteins are ubiquitous in all domains of life and play critical roles in multiple cellular processes through AMPylation of (transfer of AMP to) target proteins. Doc from the doc/phd toxin/antitoxin module is a member of the Fic family and inhibits bacterial translation by an unknown mechanism. Here we show that, in contrast to the predicted AMPylating activity, Doc is a new type of kinase that inhibits bacterial translation by phosphorylating the conserved threonine (Thr382) of the translation elongation factor EF-Tu, rendering it unable to bind aminoacylated tRNAs. We provide evidence that EF-Tu phosphorylation diverged from AMPylation by antiparallel binding of the NTP relative to the catalytic residues of the conserved Fic catalytic core of Doc. The results bring insights into the mechanism and role of phosphorylation of EF-Tu in bacterial physiology as well as represent an example of catalytic plasticity of enzymes and a mechanism for the evolution of new enzymatic activities. PMID:24141193

De Gieter, Steven; van Nuland, Nico A.J.; Loris, Remy; Zenkin, Nikolay

2013-01-01

44

Toward a systems-level view of dynamic phosphorylation networks  

PubMed Central

To better understand how cells sense and respond to their environment, it is important to understand the organization and regulation of the phosphorylation networks that underlie most cellular signal transduction pathways. These networks, which are composed of protein kinases, protein phosphatases and their respective cellular targets, are highly dynamic. Importantly, to achieve signaling specificity, phosphorylation networks must be regulated at several levels, including at the level of protein expression, substrate recognition, and spatiotemporal modulation of enzymatic activity. Here, we briefly summarize some of the traditional methods used to study the phosphorylation status of cellular proteins before focusing our attention on several recent technological advances, such as protein microarrays, quantitative mass spectrometry, and genetically-targetable fluorescent biosensors, that are offering new insights into the organization and regulation of cellular phosphorylation networks. Together, these approaches promise to lead to a systems-level view of dynamic phosphorylation networks. PMID:25177341

Newman, Robert H.; Zhang, Jin; Zhu, Heng

2014-01-01

45

Substrate-dependent control of MAPK phosphorylation in vivo.  

PubMed

Phosphorylation of the mitogen-activated protein kinase (MAPK) is essential for its enzymatic activity and ability to control multiple substrates inside a cell. According to the current models, control of MAPK phosphorylation is independent of its substrates, which are viewed as mere sensors of MAPK activity. Contrary to this modular view of MAPK signaling, our studies in the Drosophila embryo demonstrate that substrates can regulate the level of MAPK phosphorylation in vivo. We demonstrate that a twofold change in the gene dosage of a single substrate can induce a significant change in the phosphorylation level of MAPK and in the conversion of other substrates. Our results support a model where substrates of MAPK counteract its dephosphorylation by phosphatases. Substrate-dependent control of MAPK phosphorylation is a manifestation of a more general retroactive effect that should be intrinsic to all networks with covalent modification cycles. PMID:21283143

Kim, Yoosik; Paroush, Ze'ev; Nairz, Knud; Hafen, Ernst; Jiménez, Gerardo; Shvartsman, Stanislav Y

2011-02-01

46

Suppression of Akt1 phosphorylation by adenoviral transfer of the PTEN gene inhibits hypoxia-induced proliferation of rat pulmonary arterial smooth muscle cells  

SciTech Connect

Recent findings identify the role of proliferation of pulmonary artery smooth muscle cells (PASMCs) in pulmonary vascular remodeling. Phosphoinositide 3 kinase (PI3K) and serine/threonine kinase (Akt) proteins are expressed in vascular smooth muscle cells. In addition, phosphatase and tensin homolog deleted on chromosome 10 (PTEN) has been identified as a negative regulator of cytokine signaling that inhibits the PI3K-Akt pathway. However, little is known about the role of PTEN/Akt signaling in hypoxia-associated vascular remodeling. In this study, we found that hypoxia-induced the expression of Akt1 mRNA and phosphorylated protein by at least twofold in rat PASMCs. Phospho-PTEN significantly decreased in the nuclei of PASMCs after hypoxic stimulation. After forcing over-expression of PTEN by adenovirus-mediated PTEN (Ad-PTEN) transfection, the expression of phospho-Akt1 was significantly suppressed in PASMCs at all time-points measured. Additionally, we showed here that hypoxia increased proliferation of PASMCs by nearly twofold and over-expression of PTEN significantly inhibited hypoxia-induced PASMCs proliferation. These findings suggest that phospho-PTEN loss in the nuclei of PASMCs under hypoxic conditions may be the major cause of aberrant activation of Akt1 and may, therefore, play an important role in hypoxia-associated pulmonary arterial remodeling. Finally, the fact that transfection with Ad-PTEN inhibits the phosphorylation of Akt1 in PASMCs suggests a potential therapeutic effect on hypoxia-associated pulmonary arterial remodeling.

Luo, Chunxia [Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China)] [Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Yi, Bin, E-mail: yibin1974@163.com [Department of Anesthesia, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China) [Department of Anesthesia, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Institute of Respiratory Disease, Xinqiao Hospital, Third Military Medical University, Chongqing 400037 (China); Bai, Li [Institute of Respiratory Disease, Xinqiao Hospital, Third Military Medical University, Chongqing 400037 (China)] [Institute of Respiratory Disease, Xinqiao Hospital, Third Military Medical University, Chongqing 400037 (China); Xia, Yongzhi [Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China)] [Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Wang, Guansong; Qian, Guisheng [Institute of Respiratory Disease, Xinqiao Hospital, Third Military Medical University, Chongqing 400037 (China)] [Institute of Respiratory Disease, Xinqiao Hospital, Third Military Medical University, Chongqing 400037 (China); Feng, Hua [Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China)] [Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China)

2010-07-02

47

cPLA2 is phosphorylated and activated by MAP kinase  

Microsoft Academic Search

Treatment of cells with agents that stimulate the release of arachidonic acid causes increased serine phosphorylation and activation of cytosolic phospholipase A2 (cPLA2). Here we report that cPLA2 is a substrate for mitogen-activated protein (MAP) kinase. Moreover, phosphorylation by MAP kinase increases the enzymatic activity of cPLA2. The site of cPLA2 phosphorylation by MAP kinase, Ser-505, is identical to the

Lih-Ling Lin; Markus Wartmann; Alice Y. Lin; John L. Knop; Alpna Seth; Roger J. Davis

1993-01-01

48

Enzymatic single-molecule kinetic isotope effects.  

PubMed

Ensemble-based measurements of kinetic isotope effects (KIEs) have advanced physical understanding of enzyme-catalyzed reactions, but controversies remain. KIEs are used as reporters of rate-limiting H-transfer steps, quantum mechanical tunnelling, dynamics and multiple reactive states. Single molecule (SM) enzymatic KIEs could provide new information on the physical basis of enzyme catalysis. Here, single pair fluorescence energy transfer (spFRET) was used to measure SM enzymatic KIEs on the H-transfer catalyzed by the enzyme pentaerythritol tetranitrate reductase. We evaluated a range of methods for extracting the SM KIE from single molecule spFRET time traces. The SM KIE enabled separation of contributions from nonenzymatic protein and fluorophore processes and H-transfer reactions. Our work demonstrates SM KIE analysis as a new method for deconvolving reaction chemistry from intrinsic dynamics. PMID:23402437

Pudney, Christopher R; Lane, Richard S K; Fielding, Alistair J; Magennis, Steven W; Hay, Sam; Scrutton, Nigel S

2013-03-13

49

SOLID-PHASE ASSAY FOR THE PHOSPHORYLATION OF PROTEINS BLOTTED ON NITROCELLULOSE MEMBRANE FILTERS  

EPA Science Inventory

A new procedure for the phosphorylation and assay of phosphoproteins is described. Proteins are solubilized from tissue samples, separated by polyacrylamide gel electrophoresis, transferred onto nitrocellulose membrane filters and the blotted polypeptides are phosphorylated with ...

50

Enzymatic synthesis of farnesyl laurate in organic solvent: initial water activity, kinetics mechanism, optimization of continuous operation using packed bed reactor and mass transfer studies.  

PubMed

The influence of water activity and water content was investigated with farnesyl laurate synthesis catalyzed by Lipozyme RM IM. Lipozyme RM IM activity depended strongly on initial water activity value. The best results were achieved for a reaction medium with an initial water activity of 0.11 since it gives the best conversion value of 96.80%. The rate constants obtained in the kinetics study using Ping-Pong-Bi-Bi and Ordered-Bi-Bi mechanisms with dead-end complex inhibition of lauric acid were compared. The corresponding parameters were found to obey the Ordered-Bi-Bi mechanism with dead-end complex inhibition of lauric acid. Kinetic parameters were calculated based on this model as follows: V (max) = 5.80 mmol l(-1) min(-1) g enzyme(-1), K (m,A) = 0.70 mmol l(-1) g enzyme(-1), K (m,B) = 115.48 mmol l(-1) g enzyme(-1), K (i) = 11.25 mmol l(-1) g enzyme(-1). The optimum conditions for the esterification of farnesol with lauric acid in a continuous packed bed reactor were found as the following: 18.18 cm packed bed height and 0.9 ml/min substrate flow rate. The optimum molar conversion of lauric acid to farnesyl laurate was 98.07 ± 0.82%. The effect of mass transfer in the packed bed reactor has also been studied using two models for cases of reaction limited and mass transfer limited. A very good agreement between the mass transfer limited model and the experimental data obtained indicating that the esterification in a packed bed reactor was mass transfer limited. PMID:21327986

Rahman, N K; Kamaruddin, A H; Uzir, M H

2011-08-01

51

Regulation of protein phosphorylation in oat mitochondria  

SciTech Connect

We sought to identify phosphorylated proteins in isolated oat mitocchondria and to characterize the enzymatic and regulatory properties of the protein kinase(s). Mitochondria from oats (Avena sativa L. cv. Garry) were purified on Percoll gradients. Mitochondria were incubated with {sup 32}P-{gamma}-ATP; proteins were separated by SDS-PAGE. A small number of bands was detected on autoradiograms, most prominently at 70 kD and 42 kD; the latter band has been tentatively identified as a subunit of the pyruvate dehydrogenase complex, a well-known phosphoprotein. The protein kinase(s) could also phosphorylate casein, but not histone. Spermine enhanced the phosphorylation of casein and inhibited the phosphorylation of the 42 kD band. These studies were carried out on both intact and burst mitochondria. Control by calcium and other ions was investigated. The question of the action of regulators on protein kinase or protein phosphatase was studied by the use of {sup 35}S-adenosine thiotriphosphate.

Pike, C.; Kopeck, K.; Sceppa, E. (Franklin and Marshall College, Lancaster, PA (USA))

1989-04-01

52

Enzymatic modification of schizophyllan  

Technology Transfer Automated Retrieval System (TEKTRAN)

An enzymatic method was developed for the progressive modification of the polysaccharide schizophyllan. Fungal strains Hypocrea nigricans NRRL 62555, Penicillium crustosum NRRL 62558, and Penicillium simplicissimum NRRL 62550 were previously identified as novel sources of ß-endoglucanase with specif...

53

Enzymatic desulfurization of coal  

SciTech Connect

Our current efforts to develop clean coal technology emphasize the advantages of enzymatic desulfurization techniques and have specifically addressed the potential of using partially-purified extracellular microbial enzymes as well as commercially available enzymes. Our work is focused on the treatment of model'' organic sulfur compounds such as dibenzothiophene (DBT) and ethylphenylsulfide (EPS). Furthermore, we are designing experiments to facilitate the enzymatic process by means of a hydrated organic solvent matrix.

Boyer, Y.N.; Crooker, S.C.; Kitchell, J.P.; Nochur, S.V. (Holometrix, Inc., Cambridge, MA (United States)); Marquis, J.K. (Boston Univ., MA (United States). School of Medicine)

1989-06-16

54

Transfers  

Microsoft Academic Search

In this paper I develop a positive theory of intergenerational transfers. I argue that transfers are a means to induce retirement. that is, to buy the elderly out of the labor force. The reason why societies choose to do such a thing is that aggregate output is higher if the elderly do not work. I model this idea through positive

Xavier Sala-i-Martin

1992-01-01

55

Reduction of Cysteine Sulfinic Acid in Peroxiredoxin by Sulfiredoxin Proceeds Directly Through a Sulfinic Phosphoryl Ester Intermediate  

SciTech Connect

Sulfiredoxin (Srx) catalyzes a novel enzymatic reaction, the reduction of protein cysteine sulfinic acid, Prx-SO{sub 2}{sup -}. This reaction is unique to the typical 2-Cys peroxiredoxins (Prx) and plays a role in peroxide-mediated signaling by regulating the activity of Prxs. Two mechanistic schemes have been proposed that differ regarding the first step of the reaction. This step involves either the direct transfer of the {gamma}-phosphate of ATP to the Prx molecule or through Srx acting as a phosphorylated intermediary. In an effort to clarify this step of the Srx reaction, we have determined the 1.8 Angstroms resolution crystal structure of Srx in complex with ATP and Mg2+. This structure reveals the role of the Mg2+ ion to position the {gamma}-phosphate toward solvent, thus preventing an in-line attack by the catalytic residue Cys-99 of Srx. A model of the quaternary complex is consistent with this proposal. Furthermore, phosphorylation studies on several site-directed mutants of Srx and Prx, including the Prx-Asp mimic of the Prx-SO{sub 2}{sup -} species, support a mechanism where phosphorylation of Prx-SO{sub 2}{sup -} is the first chemical step.

Jonsson,T.; Murray, M.; Johnson, L.; Lowther, W.

2008-01-01

56

Enzymatic synthesis of magnetic nanoparticles.  

PubMed

We report the first in vitro enzymatic synthesis of paramagnetic and antiferromagnetic nanoparticles toward magnetic ELISA reporting. With our procedure, alkaline phosphatase catalyzes the dephosphorylation of l-ascorbic-2-phosphate, which then serves as a reducing agent for salts of iron, gadolinium, and holmium, forming magnetic precipitates of Fe45±14Gd5±2O50±15 and Fe42±4Ho6±4O52±5. The nanoparticles were found to be paramagnetic at 300 K and antiferromagnetic under 25 K. Although weakly magnetic at 300 K, the room-temperature magnetization of the nanoparticles found here is considerably greater than that of analogous chemically-synthesized LnxFeyOz (Ln = Gd, Ho) samples reported previously. At 5 K, the nanoparticles showed a significantly higher saturation magnetization of 45 and 30 emu/g for Fe45±14Gd5±2O50±15 and Fe42±4Ho6±4O52±5, respectively. Our approach of enzymatically synthesizing magnetic labels reduces the cost and avoids diffusional mass-transfer limitations associated with pre-synthesized magnetic reporter particles, while retaining the advantages of magnetic sensing. PMID:25854425

Kolhatkar, Arati G; Dannongoda, Chamath; Kourentzi, Katerina; Jamison, Andrew C; Nekrashevich, Ivan; Kar, Archana; Cacao, Eliedonna; Strych, Ulrich; Rusakova, Irene; Martirosyan, Karen S; Litvinov, Dmitri; Lee, T Randall; Willson, Richard C

2015-01-01

57

NMR of Enzymatically Synthesized Uniformly 13C15N-Labeled DNA Oligonucleotides  

Microsoft Academic Search

A procedure for the enzymatic synthesis of uniformly 13C15N-labeled DNA oligonucleotides in milligram quantities for NMR studies is described. Deoxynucleotides obtained from microorganisms grown on 13C and 15N nutrient sources are enzymatically phosphorylated to dNTPs, and the dNTPs are incorporated into oligonucleotides using a 3'-5' exonuclease-deficient mutant of Klenow fragment of DNA polymerase I and an oligonucleotide template primer designed

Daniel P. Zimmer; Donald M. Crothers

1995-01-01

58

Synthesis of Red-Shifted 8-Hydroxyquinoline Derivatives Using Click Chemistry and Their Incorporation into Phosphorylation Chemosensors  

E-print Network

Protein phosphorylation is a ubiquitous post-translational modification, and protein kinases, the enzymes that catalyze the phosphoryl transfer, are involved in nearly every aspect of normal, as well as aberrant, cell ...

Gonzalez-Vera, Juan A.

59

Bypassing AMPK phosphorylation.  

PubMed

AMP-activated protein kinase (AMPK) functions as a signaling hub to balance energy supply with demand. Phosphorylation of activation loop Thr172 has been considered as an essential step in AMPK activation. In this issue of Chemistry & Biology, Scott and colleagues show that the small molecule direct AMPK activator, A-769662, bypasses this phosphorylation event and acts synergistically with AMP on naive AMPK. PMID:24856137

Viollet, Benoit; Foretz, Marc; Schlattner, Uwe

2014-05-22

60

Enzymatic DNA molecules  

NASA Technical Reports Server (NTRS)

The present invention discloses deoxyribonucleic acid enzymes--catalytic or enzymatic DNA molecules--capable of cleaving nucleic acid sequences or molecules, particularly RNA, in a site-specific manner, as well as compositions including same. Methods of making and using the disclosed enzymes and compositions are also disclosed.

Joyce, Gerald F. (Inventor); Breaker, Ronald R. (Inventor)

1998-01-01

61

[Enzymatic properties in muscle membranes].  

PubMed

A study in the enzymatic properties of muscle membranes established that sarcolemma of the rabbit skeletal muscles contains the Ca2+-ATPase system which does not require Mg2+ for manifestation of ions activity. By some kinetic properties it differs from ATPase of myosin. The complex Ca-ATP2+ is a substrate of Ca2+-ATPase. Ions of a series of bivalent metals inhibit the latter as well as the passive transport of Ca2+, that may evidence for a definite relation of Ca2+-ATPase with Ca+2 transport in skeletal muscles. Acetyl cholinesterase and AMP-aminohydrolase are strongly bound with the sarcolemma. The sarcolemma structural organization is shown to play a certain role in manifestation of their activity. On the basis of the data obtained when studying the activity in the ATPase systems and dynamics of formation and decay of the intermediate phosphorylated product in the microsomal fraction of cow and rabbit myometrium certain peculiarities are established for the active mechanisms of Ca2+ transport in smooth muscles. A problem is under discussion on the possible active participation of sarcolemma in regulation of Ca2+ concentration in the smooth muscle cells. Two ATPase systems, Mg2+-dependent and Mg2+-dependent Ca2+ activated are found in nuclei; the role of lipids of the skeletal muscles in manifestation of their activity is studied. AMP-amino hydrolase properties are characterized for different areas of the sarcoplasmatic reticulum membranes. The model of E-avitaminous muscular distrophy was used to show disturbances in the structure of sarcolemma and membranes of the sarcoplasmatic reticulum which are accompanied by changes in their ATPase and Ca2+-transporting properties. PMID:128174

Kursky, M D; Grigoryeva, V A

1975-01-01

62

Enzymatic desulfurization of coal  

SciTech Connect

The overall objective of this program was to investigate the feasibility of an enzymatic desulfurization process specifically intended for organic sulfur removal from coal. Toward that end, a series of specific objectives were defined: (1) establish the feasibility of (bio)oxidative pretreatment followed by biochemical sulfate cleavage for representative sulfur-containing model compounds and coals using commercially-available enzymes; (2) investigate the potential for the isolation and selective use of enzyme preparations from coal-utilizing microbial systems for desulfurization of sulfur-containing model compounds and coals; and (3) develop a conceptual design and economic analysis of a process for enzymatic removal of organic sulfur from coal. Within the scope of this program, it was proposed to carry out a portion of each of these efforts concurrently. (VC)

Boyer, Y.N.; Crooker, S.C.; Kitchell, J.P.; Nochur, S.V.

1991-05-16

63

Enzymatic and mitochondrial responses to 5 months of aerial exposure in the slender lungfish  

E-print Network

Enzymatic and mitochondrial responses to 5 months of aerial exposure in the slender lungfish control aquatic slender lungfish Protopterus dolloi, and those exposed to air for 5 months. Activities; ornithine-urea cycle; oxidative phosphorylation. INTRODUCTION The habitat of the African slender lungfish

McClelland, Grant B.

64

Graphene based enzymatic bioelectrodes and biofuel cells.  

PubMed

The excellent electrical conductivity and ease of functionalization make graphene a promising material for use in enzymatic bioelectrodes and biofuel cells. Enzyme based biofuel cells have attracted substantial interest due to their potential to harvest energy from organic materials. This review provides an overview of the functional properties and applications of graphene in the construction of biofuel cells as alternative power sources. The review covers the current state-of-the-art research in graphene based nanomaterials (physicochemical properties and surface functionalities), the role of these parameters in enhancing electron transfer, the stability and activity of immobilized enzymes, and how enhanced power density can be achieved. Specific examples of enzyme immobilization methods, enzyme loading, stability and function on graphene, functionalized graphene and graphene based nanocomposite materials are discussed along with their advantages and limitations. Finally, a critical evaluation of the performance of graphene based enzymatic biofuel cells, the current status, challenges and future research needs are provided. PMID:25832672

Karimi, Anahita; Othman, Ali; Uzunoglu, Aytekin; Stanciu, Lia; Andreescu, Silvana

2015-04-01

65

Struvite and prebiotic phosphorylation.  

NASA Technical Reports Server (NTRS)

Struvite rather than apatite or amorphous calcium phosphate is precipitated when phosphate is added to seawater containing more than 0.01M NH4+ ions. Struvite may have precipitated from evaporating seawater on the primitive earth, and may have been important for prebiotic phosphorylation.

Handschuh, G. J.; Orgel, L. E.

1973-01-01

66

Maturation of the yeast plasma membrane [H+]ATPase involves phosphorylation during intracellular transport  

PubMed Central

In this study we show that the plasma membrane [H+]ATPase of Saccharomyces cerevisiae is phosphorylated on multiple Ser and Thr residues in vivo. Phosphorylation occurs during the movement of newly synthesized ATPase from the ER to the cell surface, as revealed by the analysis of temperature-sensitive sec mutants blocked at successive steps of the secretory pathway. Two-dimensional phosphopeptide analysis of the ATPase indicates that, although most sites are phosphorylated at or before arrival in secretory vesicles, some phosphopeptides are unique to the plasma membrane. Phosphorylation of plasma membrane- specific site(s) is associated with increased ATPase activity during growth on glucose. Upon glucose starvation, dephosphorylation occurs concomitantly with a decrease in enzymatic activity, and both are rapidly reversed (within 2 min) upon readdition of glucose. We suggest that reversible, site-specific phosphorylation serves to adjust ATPase activity in response to nutritional signals. PMID:1833410

1991-01-01

67

Oxidative phosphorylation revisited.  

PubMed

The fundamentals of oxidative phosphorylation and photophosphorylation are revisited. New experimental data on the involvement of succinate and malate anions respectively in oxidative phosphorylation and photophosphorylation are presented. These new data offer a novel molecular mechanistic explanation for the energy coupling and ATP synthesis carried out in mitochondria and chloroplast thylakoids. The mechanism does not suffer from the flaws in Mitchell's chemiosmotic theory that have been pointed out in many studies since its first appearance 50 years ago, when it was hailed as a ground-breaking mechanistic explanation of what is perhaps the most important process in cellular energetics. The new findings fit very well with the predictions of Nath's torsional mechanism of energy transduction and ATP synthesis. It is argued that this mechanism, based on at least 15 years of experimental and theoretical work by Sunil Nath, constitutes a fundamentally different theory of the energy conversion process that eliminates all the inconsistencies in Mitchell's chemiosmotic theory pointed out by other authors. It is concluded that the energy-transducing complexes in oxidative phosphorylation and photosynthesis are proton-dicarboxylic acid anion cotransporters and not simply electrogenic proton translocators. These results necessitate revision of previous theories of biological energy transduction, coupling, and ATP synthesis. The novel molecular mechanism is extended to cover ATP synthesis in prokaryotes, in particular to alkaliphilic and haloalkaliphilic bacteria, essentially making it a complete theory addressing mechanistic, kinetic, and thermodynamic details. Finally, based on the new interpretation of oxidative phosphorylation, quantitative values for the P/O ratio, the amount of ATP generated per redox package of the reduced substrates, are calculated and compared with experimental values for fermentation on different substrates. It is our hope that the presentation of oxidative phosphorylation and photophosphorylation from a wholly new perspective will rekindle scientific discussion of a key process in bioenergetics and catalyze new avenues of research in a truly interdisciplinary field. PMID:25384602

Nath, Sunil; Villadsen, John

2015-03-01

68

Determining in vivo Phosphorylation Sites using Mass Spectrometry  

PubMed Central

Phosphorylation is the most studied protein post-translational modification (PTM) in biological systems since it controls cell growth, proliferation, survival, etc. High resolution/high mass accuracy mass spectrometers are used to identify protein phosphorylation sites due to their speed, sensitivity, selectivity and throughput. The protocol described here focuses on two common strategies: 1) Identifying phosphorylation sites from individual proteins and small protein complexes, and 2) Identifying global phosphorylation sites from whole cell and tissue extracts. For the first, endogenous or epitope tagged proteins are typically immunopurified (IP) from cell lysates, purified via gel electrophoresis or precipitation and enzymatically digested into peptides. Samples can be optionally enriched for phosphopeptides using immobilized metal affinity chromatography (IMAC) or titanium dioxide (TiO2) and then analyzed by microcapillary liquid chromatography/tandem mass spectrometry (LC-MS/MS). Global phosphorylation site analyses that capture pSer/pThr/pTyr sites from biological sources sites are more resource and time-consuming and involve digesting the whole cell lysate, followed by peptide fractionation by strong cation exchange chromatography (SCX), phosphopeptide enrichment by IMAC or TiO2 and LC-MS/MS. Alternatively, one can fractionate the protein lysate by SDS-PAGE, followed by digestion, phosphopeptide enrichment and LC-MS/MS. One can also IP only phospho-tyrosine peptides using a pTyr antibody followed by LC-MS/MS. PMID:22470061

Breitkopf, Susanne B.; Asara, John M.

2012-01-01

69

Phosphorylating enzymes involved in glucose fermentation of Actinomyces naeslundii.  

PubMed Central

Enzymatic activities involved in glucose fermentation of Actinomyces naeslundii were studied with glucose-grown cells from batch cultures. Glucose could be phosphorylated to glucose 6-phosphate by a glucokinase that utilized polyphosphate and GTP instead of ATP as a phosphoryl donor. Glucose 6-phosphate was further metabolized to the end products lactate, formate, acetate, and succinate through the Embden-Meyerhof-Parnas pathway. The phosphoryl donor for phosphofructokinase was only PPi. Phosphoglycerate kinase, pyruvate kinase, and acetate kinase coupled GDP as well as ADP, but P(i) compounds were not their phosphoryl acceptor. Cell extracts showed GDP-dependent activity of phosphoenolpyruvate carboxykinase, which assimilates bicarbonate and phosphoenolpyruvate into oxaloacetate, a precursor of succinate. Considerable amounts of GTP, polyphosphate, and PPi were found in glucose-fermenting cells, indicating that these compounds may serve as phosphoryl donors or acceptors in Actinomyces cells. PPi could be generated from UTP and glucose 1-phosphate through catalysis of UDP-glucose synthase, which provides UDP-glucose, a precursor of glycogen. PMID:7592327

Takahashi, N; Kalfas, S; Yamada, T

1995-01-01

70

Enzymatic cascade bioreactor  

DOEpatents

Disclosed is an apparatus and method for continuously converting sucrose to .beta.-D-glucose. The method comprises a three stage enzymatic reactor in which an aqueous solution of sucrose is first converted into a solution of fructose and .alpha.-D-glucose by passing it through a porous, packed column containing an inert media on which invertase is immobilized. This solution is then sent through a second packed column containing glucose isomerase and finally a third packed column containing mutarotase. Solution temperature and pH are adjusted to maximize glucose output.

Simmons, Blake A. (San Francisco, CA); Volponi, Joanne V. (Livermore, CA); Ingersoll, David (Albuquerque, NM); Walker, Andrew (Woodinville, WA)

2007-09-04

71

Enzymatic route to preparative-scale synthesis of UDP–GlcNAc\\/GalNAc, their analogues and GDP–fucose  

Microsoft Academic Search

Enzymatic synthesis using glycosyltransferases is a powerful approach to building polysaccharides with high efficiency and selectivity. Sugar nucleotides are fundamental donor molecules in enzymatic glycosylation reactions by Leloir-type glycosyltransferases. The applications of these donors are restricted by their limited availability. In this protocol, N-acetylglucosamine (GlcNAc)\\/N-acetylgalactosamine (GalNAc) are phosphorylated by N-acetylhexosamine 1-kinase (NahK) and subsequently pyrophosphorylated by N-acetylglucosamine uridyltransferase (GlmU) to

Guohui Zhao; Wanyi Guan; Li Cai; Peng George Wang

2010-01-01

72

Enzymatic modification of schizophyllan.  

PubMed

An enzymatic method was developed for the progressive modification of the polysaccharide schizophyllan. Fungal strains Hypocrea nigricans NRRL 62555, Penicillium crustosum NRRL 62558, and Penicillium simplicissimum NRRL 62550 were previously identified as novel sources of ?-endoglucanase with specificity towards schizophyllan. Concentrated enzyme preparations from these strains showed specific activities of 1.7-4.3 U ?-glucanase/mg protein. Using dilutions of these enzymes in time course digestions, schizophyllan was progressively modified to reduced molecular weight species. Glucose and oligosaccharides were found only in the more complete digestions, and thus modified schizophyllan can be produced quantitatively, without loss, to small molecules. Permethylation analysis confirmed that modified schizophyllan retains the fundamental linkage structure of native schizophyllan. Modified schizophyllan species showed progressively reduced viscosity profiles, and all exhibited pseudoplasticity in response to shear thinning. PMID:25335747

Leathers, Timothy D; Sutivisedsak, Nongnuch; Nunnally, Melinda S; Price, Neil P J; Stanley, April M

2015-03-01

73

Enzymatic deglycosylation of glycoproteins.  

PubMed

Recombinant protein expression using eukaryotic expression systems has certain advantages, such as addition of posttranslational modifications that help protein stability and activity. Asparagine-linked sugar attachment is one of the most common posttranslation modifications. However, sugar modification can impede the growth of high-quality protein crystals for structural studies using X-ray crystallography. To overcome this problem, consensus sites of N-linked attachments can be mutated into other similar residues, such as aspartic acid. Alternatively, enzymatic deglycosylation can be used to remove sugars. Peptide-N-Glycosidase F (PNGase F; EC 3.5.1.52) and Endoglycosidase H (Endo H; EC 3.2.1.96) are the most popular enzymes for this purpose. PMID:24182931

Kim, Min-Sung; Leahy, Dan

2013-01-01

74

Phosphorylation by PINK1 Releases the UBL Domain and Initializes the Conformational Opening of the E3 Ubiquitin Ligase Parkin  

PubMed Central

Loss-of-function mutations in PINK1 or PARKIN are the most common causes of autosomal recessive Parkinson's disease. Both gene products, the Ser/Thr kinase PINK1 and the E3 Ubiquitin ligase Parkin, functionally cooperate in a mitochondrial quality control pathway. Upon stress, PINK1 activates Parkin and enables its translocation to and ubiquitination of damaged mitochondria to facilitate their clearance from the cell. Though PINK1-dependent phosphorylation of Ser65 is an important initial step, the molecular mechanisms underlying the activation of Parkin's enzymatic functions remain unclear. Using molecular modeling, we generated a complete structural model of human Parkin at all atom resolution. At steady state, the Ub ligase is maintained inactive in a closed, auto-inhibited conformation that results from intra-molecular interactions. Evidently, Parkin has to undergo major structural rearrangements in order to unleash its catalytic activity. As a spark, we have modeled PINK1-dependent Ser65 phosphorylation in silico and provide the first molecular dynamics simulation of Parkin conformations along a sequential unfolding pathway that could release its intertwined domains and enable its catalytic activity. We combined free (unbiased) molecular dynamics simulation, Monte Carlo algorithms, and minimal-biasing methods with cell-based high content imaging and biochemical assays. Phosphorylation of Ser65 results in widening of a newly defined cleft and dissociation of the regulatory N-terminal UBL domain. This motion propagates through further opening conformations that allow binding of an Ub-loaded E2 co-enzyme. Subsequent spatial reorientation of the catalytic centers of both enzymes might facilitate the transfer of the Ub moiety to charge Parkin. Our structure-function study provides the basis to elucidate regulatory mechanisms and activity of the neuroprotective Parkin. This may open up new avenues for the development of small molecule Parkin activators through targeted drug design. PMID:25375667

Moussaud-Lamodičre, Elisabeth L.; Dourado, Daniel F. A. R.; Flores, Samuel C.; Springer, Wolfdieter

2014-01-01

75

Anesthesia Induces Phosphorylation of Tau  

PubMed Central

Abnormal hyperphosphorylation and aggregation of microtubule-associated protein tau play a crucial role in neurodegeneration of Alzheimer’s disease (AD). Anesthesia has been associated with cognitive impairment and the risk for AD. Here we investigated the effects of anesthesia on site-specific tau phosphorylation and the possible mechanisms. We found that anesthesia for short periods (30 sec to 5 min) induced tau phosphorylation at Thr181, Ser199, Thr205, Thr212, Ser262, and Ser404 to small, but significant, extents, which appeared to result from anesthesia-induced activation of stress-activated protein kinases. Anesthesia for a longer time (1 h) induced much more dramatic phosphorylation of tau at the above sites, and the further phosphorylation may be associated with hypothermia induced by anesthesia. Anesthesia-induced tau phosphorylation appears to be specific because the increased phosphorylation was only seen at half of the tau phosphorylation sites studied and was not observed in global brain proteins. These studies clarified the dynamic changes of tau phosphorylation at various sites and, thus, served as a fundamental guide for future studies on tau phosphorylation by using brains of anesthetized experimental animals. Our findings also provide a possible mechanism by which anesthesia may cause postoperative cognitive impairment and increase the risk for AD. PMID:19276556

Run, Xiaoqin; Liang, Zhihou; Zhang, Lan; Iqbal, Khalid; Grundke-Iqbal, Inge; Gong, Cheng-Xin

2010-01-01

76

Ribonucleotide reductase and thymidine phosphorylation: two potential targets of azodicarbonamide.  

PubMed

Azodicarbonamide tested as an anti-HIV agent was reported to expulse zinc from viral zinc-cysteine factors and to inhibit calcium mobilization machinery. It has structural analogy with hydroxyurea that inhibits ribonucleotide reductase and could also act on this target. Azodicarbonamide was therefore tested for its capacity to modulate deoxyribonucleotides triphosphate pools alone or in combination with other agents in the lymphoblastic SUP-T1 cell line susceptible to HIV infection. The deoxyribonucleotides triphosphate were evaluated by an enzymatic assay using sequenase. Two hours exposure of SUP-T1 cells to 100 microM azodicarbonamide induced a 50% reduction of each deoxyribonucleotide triphosphate. Among other inhibitors of nucleotide metabolism (hydroxyurea, methotrexate and thymidine), hydroxyurea only reproduces the effect of azodicarbonamide. This suggests, but does not demonstrate directly, that azodicarbonamide inhibits ribonucleotide reductase activity. The combination of azodicarbonamide with each of these inhibitors affected particularly the dCTP pool. During this study it was also suggested that azodicarbonamide could interfere with thymidine phosphorylation. Thymidine phosphorylating activity was measured with 3H-thymidine as substrate. In acellular preparations, azodicarbonamide also non-competitively inhibits thymidine phosphorylating activity. This effect was not reproduced by hydroxyurea. Thus, in vitro azodicarbonamide decreases the intracellular pool of deoxyribonucleotide and thymidine phosphorylation. PMID:12147296

Fagny, Christine; Vandevelde, Michel; Svoboda, Michal; Robberecht, Patrick

2002-08-01

77

Cytochrome c Is Tyrosine 97 Phosphorylated by Neuroprotective Insulin Treatment  

PubMed Central

Recent advancements in isolation techniques for cytochrome c (Cytc) have allowed us to discover post-translational modifications of this protein. We previously identified two distinct tyrosine phosphorylated residues on Cytc in mammalian liver and heart that alter its electron transfer kinetics and the ability to induce apoptosis. Here we investigated the phosphorylation status of Cytc in ischemic brain and sought to determine if insulin-induced neuroprotection and inhibition of Cytc release was associated with phosphorylation of Cytc. Using an animal model of global brain ischemia, we found a ?50% decrease in neuronal death in the CA1 hippocampal region with post-ischemic insulin administration. This insulin-mediated increase in neuronal survival was associated with inhibition of Cytc release at 24 hours of reperfusion. To investigate possible changes in the phosphorylation state of Cytc we first isolated the protein from ischemic pig brain and brain that was treated with insulin. Ischemic brains demonstrated no detectable tyrosine phosphorylation. In contrast Cytc isolated from brains treated with insulin showed robust phosphorylation of Cytc, and the phosphorylation site was unambiguously identified as Tyr97 by immobilized metal affinity chromatography/nano-liquid chromatography/electrospray ionization mass spectrometry. We next confirmed these results in rats by in vivo application of insulin in the absence or presence of global brain ischemia and determined that Cytc Tyr97-phosphorylation is strongly induced under both conditions but cannot be detected in untreated controls. These data suggest a mechanism whereby Cytc is targeted for phosphorylation by insulin signaling, which may prevent its release from the mitochondria and the induction of apoptosis. PMID:24223835

Pecina, Petr; Ji, Qinqin; Yu, Kebing; Sinkler, Christopher; Varughese, Ashwathy; Kumar, Rita; Bukowski, Melissa J.; Tousignant, Renee N.; Salomon, Arthur R.; Lee, Icksoo; Hüttemann, Maik

2013-01-01

78

How Phosphotransferase System-Related Protein Phosphorylation Regulates Carbohydrate Metabolism in Bacteria†  

PubMed Central

The phosphoenolpyruvate(PEP):carbohydrate phosphotransferase system (PTS) is found only in bacteria, where it catalyzes the transport and phosphorylation of numerous monosaccharides, disaccharides, amino sugars, polyols, and other sugar derivatives. To carry out its catalytic function in sugar transport and phosphorylation, the PTS uses PEP as an energy source and phosphoryl donor. The phosphoryl group of PEP is usually transferred via four distinct proteins (domains) to the transported sugar bound to the respective membrane component(s) (EIIC and EIID) of the PTS. The organization of the PTS as a four-step phosphoryl transfer system, in which all P derivatives exhibit similar energy (phosphorylation occurs at histidyl or cysteyl residues), is surprising, as a single protein (or domain) coupling energy transfer and sugar phosphorylation would be sufficient for PTS function. A possible explanation for the complexity of the PTS was provided by the discovery that the PTS also carries out numerous regulatory functions. Depending on their phosphorylation state, the four proteins (domains) forming the PTS phosphorylation cascade (EI, HPr, EIIA, and EIIB) can phosphorylate or interact with numerous non-PTS proteins and thereby regulate their activity. In addition, in certain bacteria, one of the PTS components (HPr) is phosphorylated by ATP at a seryl residue, which increases the complexity of PTS-mediated regulation. In this review, we try to summarize the known protein phosphorylation-related regulatory functions of the PTS. As we shall see, the PTS regulation network not only controls carbohydrate uptake and metabolism but also interferes with the utilization of nitrogen and phosphorus and the virulence of certain pathogens. PMID:17158705

Deutscher, Josef; Francke, Christof; Postma, Pieter W.

2006-01-01

79

Microtubule depolymerization and tau phosphorylation.  

PubMed

Inge Grundke-Iqbal and Khalid Iqbal found a connection between microtubule associated tau and Alzheimer's disease. They described that abnormally phosphorylated tau is a component of the paired helical filaments found in the disease. Afterwards they described that tau hyperphosphorylation prevents microtubule assembly. Now trying to complement the relationship between microtubules and tau phosphorylation, we have commented on the effect of microtubule disassembly on tau phosphorylation. In this study, we investigated the role of microtubule depolymerization induced by nocodazole on tau phosphorylation in human neuroblastoma SH-SY5Y cells. Our results indicate that nocodazole provokes tau phosphorylation mediated by GSK3, as determined by using AT-8 or Tau-1 antibodies. Interestingly, total GSK3? and GSK3? phosphorylation on Ser-9 are not altered during nocodazole treatment. In addition, microtubule stabilization with taxol had similar effects, likely because taxol and tau compete for the same binding sites on microtubules, and in the presence of taxol, tau could be detached from microtubules. Thus, unbound tau from microtubles can be phosphorylated by GSK3, even if the activity of GSK3 is not altered, probably because tau unbound to microtubules could be a better substrate for the kinase than microtubule-associated tau. These findings suggest that microtubule depolymerization can be a primary event in neurodegenerative disorders like Alzheimer's disease and that tau phosphorylation takes place afterwards. PMID:23948896

Hernández, Félix; García-García, Esther; Avila, Jesús

2013-01-01

80

Phosphorylation of chicken growth hormone  

SciTech Connect

The possibility that chicken growth hormone (cGH) can be phosphorylated has been examined. Both native and biosynthetic cGH were phosphorylated by cAMP-dependent protein kinase (and {gamma}-{sup 32}P-ATP). The extent of phosphorylation was however less than that observed with ovine prolactin. Under the conditions employed, glycosylated cGH was not phosphorylated. Chicken anterior pituitary cells in primary culture were incubated in the presence of {sup 32}P-phosphate. Radioactive phosphate was incorporated in vitro into the fraction immunoprecipitable with antisera against cGH. Incorporation was increased with cell number and time of incubation. The presence of GH releasing factor (GRF) increased the release of {sup 32}P-phosphate labeled immunoprecipitable GH into the incubation media but not content of immunoprecipitable GH in the cells. The molecular weight of the phosphorylated immunoreactive cGH in the cells corresponded to cGH dimer.

Aramburo, C.; Montiel, J.L. (Universidad Nacional Autonoma de Mexico (Mexico)); Donoghue, D.; Scanes, C.G. (Rutgers Univ., New Brunswick, NJ (USA)); Berghman, L.R. (Laboratory for Neuroendocrinology and Immunological Biotechnology, Louvain (Belgium))

1990-01-01

81

Electron transfer and protein engineering studies of the soluble methane monooxygenase from Methylococcus capsulatus (Bath)  

E-print Network

Chapter 1. Introduction: Electron Transfer in Biological Systems In many biological processes, including oxidative phosphorylation and photosynthesis, electron transfer reactions play vital roles. Electrons must be transported ...

Blazyk, Jessica L. (Jessica Lee), 1974-

2003-01-01

82

Direct transfer of the phosphoryl moiety of mannitol 1-phosphate to [14C]mannitol catalyzed by the enzyme II complexes of the phosphoenolpyruvate: mannitol phosphotransferase systems in Spirochaeta aurantia and Salmonella typhimurium.  

PubMed

Spirochaeta aurantia possesses a phosphoenolpyruvate:mannitol phosphotransferase system which catalyzes the transmembrane transport and phosphorylation of mannitol. In vitro studies showed that both phosphoenolpyruvate and mannitol 1-phosphate could serve as phosphate donors. The phosphoenolpyruvate-dependent reaction required two soluble proteins, Enzyme SI and HPr, and an integral membrane complex, Enzyme SII. Only Enzyme SII was required for the mannitol 1-phosphate-dependent reaction. Enzyme II-dependent transphosphorylation of sugars was also demonstrated in eubacterial extracts. The results lead to the suggestion that the Enzyme II complexes of bacterial phosphotransferase systems possess nonoverlapping binding sites for sugar and sugar phosphate. PMID:819432

Saier, M H; Newman, M J

1976-06-25

83

Phosphorylation of lymphocyte myosin catalyzed in vitro and in intact cells  

PubMed Central

Myosin has been isolated from guinea pig B-lymphocytic leukemia cells (L2C). The myosin has been enzymatically phosphorylated and dephosphorylated in vitro using both heterologous and lymphocyte- derived enzymes. Both the heavy chain and 20,000-dalton light chain of lymphocyte myosin are phosphorylated in vitro. Phosphorylation of myosin enhances actin-activated ATPase activity. Phosphorylation of myosin in murine lymphocytes was analyzed by use of a novel technique for rapid immunoprecipitation of myosin from cell extracts. Both the heavy chain and 20,000-dalton light chain of myosin are phosphorylated in intact cells. Addition of antibody reactive with cell-surface immunoglobulin to lymphocyte populations enriched for B cells stimulates locomotion of these cells and also increases the quantity of 32P isolated in association with the 20,000-dalton light chain of lymphocyte myosin, when 32Pi was present in the medium. In addition, an unidentified, phosphorylated polypeptides with a molecular mass of 22,000 daltons is co-isolated with myosin from cells by rapid immunoprecipitation. These results are consistent with the hypothesis that phosphorylation of myosin may contribute to regulation of movements performed by lymphocytes which are related to their participation in immunologic reactions. PMID:6212588

1982-01-01

84

Phosphorylation of Two Serine Residues Regulates Human T-Cell Leukemia Virus Type 2 Rex Function  

PubMed Central

The function of the human T-cell leukemia virus (HTLV) Rex phosphoprotein is to increase the level of the viral structural and enzymatic gene products expressed from the incompletely spliced viral RNAs containing the Rex-responsive element. The phosphorylation of HTLV type 2 Rex (Rex-2), predominantly on serine residues, correlates with an altered conformation, as detected by a gel mobility shift, and is required for specific binding to its viral RNA target sequence. Thus, the phosphorylation state of Rex in the infected cell may be a switch that determines whether the virus exists in a latent or a productive state. A mutational analysis of Rex-2 that focused on serine and threonine residues was performed to identify regions or domains within Rex-2 important for function, with a specific emphasis on identifying Rex-2 phosphorylation mutants. We identified mutations near the carboxy terminus that disrupted a novel region or domain and abrogated Rex-2 function. Mutant M17 (with S151A and S153A mutations) displayed reduced phosphorylation that correlated with reduced function. Replacement of both serine residues 151 and 153 with phosphomimetic aspartic acid restored Rex-2 function and locked Rex-2 in a phosphorylated active conformation. A mutant containing threonine residues at positions 151 and 153 displayed a phenotype indistinguishable from that of wild-type Rex. Furthermore, this same mutant showed increased threonine phosphorylation and decreased serine phosphorylation, providing conclusive evidence that one or both of these residues are phosphorylated in vivo. Our results provide the first direct evidence that the phosphorylation of Rex-2 is important for function. Further understanding of HTLV Rex phosphorylation will provide insight into the regulatory control of HTLV replication and ultimately the pathobiology of HTLV. PMID:11507189

Narayan, Murli; Kusuhara, Koichi; Green, Patrick L.

2001-01-01

85

Solid-phase assay for the phosphorylation of proteins blotted on nitrocellulose membrane filters  

SciTech Connect

A new procedure for the phosphorylation and assay of phosphoproteins is described. Proteins are solubilized from tissue samples, separated by polyacrylamide gel electrophoresis, transferred onto nitrocellulose membrane filters, and the blotted polypeptides are phyosphorylated with the catalytic subunit of cyclic AMP (adenosine 3':5'-monophosphate)-dependent protein kinase. The method was developed for the assay of dephosphosynapsin I, but it has also proven suitable for the phosphorylation of other proteins. The patterns of phosphorylation of tissue samples phosphorylated using the new method are similar to those obtained using the conventional test tube assay. Once phosphorylated, the adsorbed proteins can be digested with proteases and subjected to phosphopeptide mapping. The phosphorylated blotted proteins can also be analyzed by overlay techniques for the immunological detection of polypeptides.

Valtorta, F.; Schiebler, W.; Jahn, R.; Ceccarelli, B.; Greengard, P.

1986-10-01

86

Enzymatic Hydrolysis of Cellulosic Biomass  

SciTech Connect

Biological conversion of cellulosic biomass to fuels and chemicals offers the high yields to products vital to economic success and the potential for very low costs. Enzymatic hydrolysis that converts lignocellulosic biomass to fermentable sugars may be the most complex step in this process due to substrate-related and enzyme-related effects and their interactions. Although enzymatic hydrolysis offers the potential for higher yields, higher selectivity, lower energy costs, and milder operating conditions than chemical processes, the mechanism of enzymatic hydrolysis and the relationship between the substrate structure and function of various glycosyl hydrolase components are not well understood. Consequently, limited success has been realized in maximizing sugar yields at very low cost. This review highlights literature on the impact of key substrate and enzyme features that influence performance to better understand fundamental strategies to advance enzymatic hydrolysis of cellulosic biomass for biological conversion to fuels and chemicals. Topics are summarized from a practical point of view including characteristics of cellulose (e.g., crystallinity, degree of polymerization, and accessible surface area) and soluble and insoluble biomass components (e.g., oligomeric xylan, lignin, etc.) released in pretreatment, and their effects on the effectiveness of enzymatic hydrolysis. We further discuss the diversity, stability, and activity of individual enzymes and their synergistic effects in deconstructing complex lignocellulosic biomass. Advanced technologies to discover and characterize novel enzymes and to improve enzyme characteristics by mutagenesis, post-translational modification, and over-expression of selected enzymes and modifications in lignocellulosic biomass are also discussed.

Yang, Bin; Dai, Ziyu; Ding, Shi-You; Wyman, Charles E.

2011-08-22

87

Oxidative and Photosynthetic Phosphorylation Mechanisms  

ERIC Educational Resources Information Center

Proposes a molecular mechanism for the coupling of phosphorylation to electron transport in both mitochondria and chloroplasts. Justifies the proposed reaction schemes in terms of thermodynamics and biochemical data. Suggests how areobic respiration could have evolved. (EB)

Wang, Jui H.

1970-01-01

88

Creatine kinase increases the solubility and enzymatic activity of pyruvate kinase by means of diazymatic coupling  

Microsoft Academic Search

Five separate methods, paper chromatography, ethanol solubility, pH dependence, enzymatic activity, and NMR saturation transfer, were used to study the coupling of pyruvate kinase (PK) and creatine kinase (CK). Each method demonstrated specific coupling of the two proteins. The coupling with CK showed that PK had increased ethanol solubility, enzymatic activity, pH-dependent aqueous solubility, and ability to receive ATP directly

P. F. Dillon; M. K. Weberling; S. M. Letarte; J. F. Clark; P. R. Sears; R. S. Root-Bernstein

1995-01-01

89

Herpes simplex virus 2 VP22 phosphorylation induced by cellular and viral kinases does not influence intracellular localization  

SciTech Connect

Phosphorylation of the herpes simplex virus (HSV) VP22 protein is regulated by cellular kinases and the UL13 viral kinase, but the sites at which these enzymes induce phosphorylation of HSV-2 VP22 are not known. Using serine-to-alanine mutants to map phosphorylation sites on HSV-2 VP22 in cells, we made three major observations. First, phosphorylation by a cellular kinase mapped to serines 70, 71, and/or 72 within CKII consensus sites analogous to previously identified phosphorylation sites in HSV-1 VP22. Second, we mapped UL13-mediated phosphorylation of HSV-2 VP22 to serines 28 and 34, describing for the first time UL13-dependent phosphorylation sites on VP22. Third, previously identified VP22-associated cellular kinase sites in HSV-1 VP22 (serines 292 and 294) were not phosphorylated in HSV-2 VP22 (serines 291 and 293). VP22 expressed alone accumulated in the cytoplasm and to a lesser extent in the nucleus. Phosphorylation by endogenous cellular kinase(s) did not alter the localization of VP22. Co-expression of HSV-2 VP22 with active UL13, but not with enzymatically inactive UL13, resulted in nuclear accumulation of VP22 and altered nuclear morphology. Surprisingly, redistribution of VP22 to the nucleus occurred independently of UL13-induced phosphorylation of VP22. The altered nuclear morphology of UL13-expressing cells was not due to apoptosis. These results demonstrate that phosphorylation of HSV-2 VP22 at multiple serine residues is induced by UL13 and cellular kinase(s), and that the nuclear/cytoplasmic distribution of VP22 is independent of its phosphorylation status but is controlled indirectly by UL13 kinase activity.

Geiss, Brian J. [Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, MO 63104-1083 (United States); Cano, Gina L. [Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, MO 63104-1083 (United States); Tavis, John E. [Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, MO 63104-1083 (United States); Morrison, Lynda A. [Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, MO 63104-1083 (United States)]. E-mail: morrisla@slu.edu

2004-12-05

90

Accelerated Articles Enzymatically Amplified Surface Plasmon  

E-print Network

such as an ELISA sandwich assay are used after target adsorption.10,11 Unfortunately, both of these enzymatic, and the enzymatic product detected in ELISA measurements is a solution species that can diffuse into adjacent array

91

Bioluminescence methods for enzymatic determinations  

DOEpatents

An enzymatic method for continuous, on-line and rapid detection of diagnostically useful biomarkers, which are symptomatic of disease or trauma-related tissue damage, is disclosed. The method is characterized by operability on authentic samples of complex biological fluids which contain the biomarkers.

Bostick, William D. (Oak Ridge, TN); Denton, Mark S. (Clinton, TN); Dinsmore, Stanley R. (Norris, TN)

1982-01-01

92

Non-enzymatic oxidation of NADH by quinones  

NASA Astrophysics Data System (ADS)

Non-enzymatic oxidation of NADH by a large number of different quinones has been explored both theoretically and experimentally. It is concluded that the smaller benzo- and naphtho-quinones are capable of oxidising NADH in aqueous solution, whereas the larger anthraquinone is not. The mechanisms of stepwise electron and proton transfers are explored, and ruled out in favour of direct hydride transfer. For menadione (2-methyl-1,4-naphthoquinone), no reaction is observed experimentally; theoretically we find that there is a very close balance between the energetic cost of hydride removal from NADH and the energy gain of formation of the menadione semiquinone radical anion.

Scherbak, Nikolai; Strid, Ĺke; Eriksson, Leif A.

2005-10-01

93

New methods based on capillary electrophoresis for in vitro evaluation of protein tau phosphorylation by glycogen synthase kinase 3-?.  

PubMed

The hyperphosphorylation of tau protein is associated with the development of the neuronal pathology of Alzheimer's disease. As most conventional methods study only particular phosphorylation sites of tau, it is necessary to develop a simple and reliable assay to determine the phosphorylation of tau at multiple sites. Capillary electrophoresis (CE)-based enzymatic assays are not yet used to monitor tau phosphorylation. The present work aims to develop CE-based assays to evaluate tau phosphorylation by the glycogen synthase kinase 3-? (GSK3?). A novel pre-capillary CE assay was first developed. An in-capillary CE-based enzymatic assay was also used since this approach is known to be time- and cost- effective. The enzymatic reaction was monitored by quantifying the product adenosine 5'- diphosphate (ADP). The influence of two classes of glycosaminoglycan (GAG), namely heparin and heparan sulfate, on the phosphorylation reaction was also assessed. Results obtained by both CE approaches were comparable and in excellent agreement with those reported in the literature using conventional radiometric and immunoblotting methods. In fact, CE results confirmed the inductory effect of the sulfated sugars heparin and heparan sulfate on tau hyperphosphorylation, probably because of the exposition of new sites phosphorylatable by GSK3?. This study shows that simple (no-labeling), rapid (less than 30 min per assay), and eco-friendly (no-radioactivity) CE-based kinase assays can give insight into the abnormal phosphorylation of tau. They can be extended to screen different modulators of tau phosphorylation to highlight their function and to develop effective drugs for neurodegenerative disease treatments. PMID:25711986

Nehmé, Hala; Chantepie, Sandrine; Defert, Justine; Morin, Philippe; Papy-Garcia, Dulce; Nehmé, Reine

2015-04-01

94

Inhibition of CtBP1 activity by Akt-mediated phosphorylation  

PubMed Central

Pc2 (Cbx4) is a member of the chromobox family of polycomb proteins, and is a SUMO E3 ligase for the transcriptional corepressor, CtBP1. Here we show that both CtBP1 and Pc2 are phosphorylated by the kinase Akt1, which is activated by growth factor signaling via the PI3-kinase pathway. In the presence of Pc2, phosphorylation of CtBP1 is increased, and this requires interaction of both CtBP1 and Akt1 with Pc2. Pc2 promotes CtBP1 phosphorylation by recruiting Akt1, and in part by preventing de-phosphorylation of activated Akt1. Alteration of the Akt-phosphorylated residue in CtBP1 to a phosphomimetic results in decreased CtBP1 dimerization, but does not prevent interaction with other transcriptional regulators. The phosphomimetic mutant of CtBP1 is expressed at a lower level than the wild type protein, resulting in decreased transcriptional repression. We show that this CtBP1 mutant is targeted for poly-ubiquitylation and is less stable than the wild type protein. Coexpression of Pc2 and Akt1 together results in both phosphorylation and ubiquitylation of CtBP1, thereby targeting CtBP1 for degradation. This work suggests that Pc2 may coordinate multiple enzymatic activities to regulate CtBP1 function. PMID:20361981

Merrill, Jacqueline C.; Kagey, Michael H.; Melhuish, Tiffany A.; Powers, Shannon E.; Zerlanko, Brad J.; Wotton, David

2010-01-01

95

Click Conjugation of a Binuclear Terbium(III) Complex for Real-Time Detection of Tyrosine Phosphorylation.  

PubMed

Phosphorylation of proteins is closely associated with various diseases, and, therefore, its detection is vitally important in molecular biology and drug discovery. Previously, we developed a binuclear Tb(III) complex, which emits notable luminescence only in the presence of phosphotyrosine. In this study, we conjugated a newly synthesized binuclear Tb(III) complex to substrate peptides by using click chemistry. Using these conjugates, we were able to detect tyrosine phosphorylation in real time. These conjugates were superior to nonconjugated Tb(III) complexes for the detection of tyrosine phosphorylation, especially when the substrate peptides used were positively charged. Luminescence intensity upon phosphorylation was enhanced 10-fold, making the luminescence intensity of this system one of the largest among lanthanide luminescence-based systems. We also determined Michaelis-Menten parameters for the phosphorylation of various kinase/peptide combinations and quantitatively analyzed the effects of mutations in the peptide substrates. Furthermore, we successfully monitored the inhibition of enzymatic phosphorylation by inhibitors in real time. Advantageously, this system detects only the phosphorylation of tyrosine (phosphorylated serine and threonine are virtually silent) and is applicable to versatile peptide substrates. Our study thus demonstrates the applicability of this system for the analysis of kinase activity, which could lead to drug discovery. PMID:25757507

Akiba, Hiroki; Sumaoka, Jun; Tsumoto, Kouhei; Komiyama, Makoto

2015-04-01

96

Interphase phosphorylation of lamin A.  

PubMed

Nuclear lamins form the major structural elements that comprise the nuclear lamina. Loss of nuclear structural integrity has been implicated as a key factor in the lamin A/C gene mutations that cause laminopathies, whereas the normal regulation of lamin A assembly and organization in interphase cells is still undefined. We assumed phosphorylation to be a major determinant, identifying 20 prime interphase phosphorylation sites, of which eight were high-turnover sites. We examined the roles of these latter sites by site-directed mutagenesis, followed by detailed microscopic analysis - including fluorescence recovery after photobleaching, fluorescence correlation spectroscopy and nuclear extraction techniques. The results reveal three phosphorylation regions, each with dominant sites, together controlling lamin A structure and dynamics. Interestingly, two of these interphase sites are hyper-phosphorylated in mitotic cells and one of these sites is within the sequence that is missing in progerin of the Hutchinson-Gilford progeria syndrome. We present a model where different phosphorylation combinations yield markedly different effects on the assembly, subunit turnover and the mobility of lamin A between, and within, the lamina, the nucleoplasm and the cytoplasm of interphase cells. PMID:24741066

Kochin, Vitaly; Shimi, Takeshi; Torvaldson, Elin; Adam, Stephen A; Goldman, Anne; Pack, Chan-Gi; Melo-Cardenas, Johanna; Imanishi, Susumu Y; Goldman, Robert D; Eriksson, John E

2014-06-15

97

The Enzymatic Oxidation of Graphene Oxide  

PubMed Central

Two-dimensional graphitic carbon is a new material with many emerging applications, and studying its chemical properties is an important goal. Here, we reported a new phenomenon – the enzymatic oxidation of a single layer of graphitic carbon by horseradish peroxidase (HRP). In the presence of low concentrations of hydrogen peroxide (~40 µM), HRP catalyzed the oxidation of graphene oxide, which resulted in the formation of holes on its basal plane. During the same period of analysis, HRP failed to oxidize chemically reduced graphene oxide (RGO). The enzymatic oxidation was characterized by Raman, UV-Vis, EPR and FT-IR spectroscopy, TEM, AFM, SDS-PAGE, and GC-MS. Computational docking studies indicated that HRP was preferentially bound to the basal plane rather than the edge for both graphene oxide and RGO. Due to the more dynamic nature of HRP on graphene oxide, the heme active site of HRP was in closer proximity to graphene oxide compared to RGO, thereby facilitating the oxidation of the basal plane of graphene oxide. We also studied the electronic properties of the reduced intermediate product, holey reduced graphene oxide (hRGO), using field-effect transistor (FET) measurements. While RGO exhibited a V-shaped transfer characteristic similar to a single layer of graphene that was attributed to its zero band gap, hRGO demonstrated a p-type semiconducting behavior with a positive shift in the Dirac points. This p-type behavior rendered hRGO, which can be conceptualized as interconnected graphene nanoribbons, as a potentially attractive material for FET sensors. PMID:21344859

Kotchey, Gregg P.; Allen, Brett L.; Vedala, Harindra; Yanamala, Naveena; Kapralov, Alexander A.; Tyurina, Yulia Y.; Klein-Seetharaman, Judith; Kagan, Valerian E.; Star, Alexander

2011-01-01

98

Assay development for the determination of phosphorylation stoichiometry using multiple reaction monitoring methods with and without phosphatase treatment: application to breast cancer signaling pathways.  

PubMed

We have developed a phosphatase-based phosphopeptide quantitation (PPQ) method for determining phosphorylation stoichiometry in complex biological samples. This PPQ method is based on enzymatic dephosphorylation, combined with specific and accurate peptide identification and quantification by multiple reaction monitoring (MRM) with stable-isotope-labeled standard peptides. In contrast with classical MRM methods for the quantitation of phosphorylation stoichiometry, the PPQ-MRM method needs only one nonphosphorylated SIS (stable isotope-coded standard) and two analyses (one for the untreated sample and one for the phosphatase-treated sample), from which the expression and modification levels can accurately be determined. From these analyses, the percent phosphorylation can be determined. In this manuscript, we compare the PPQ-MRM method with an MRM method without phosphatase and demonstrate the application of these methods to the detection and quantitation of phosphorylation of the classic phosphorylated breast cancer biomarkers (ERalpha and HER2), and for phosphorylated RAF and ERK1, which also contain phosphorylation sites of biological importance. Using synthetic peptides spiked into a complex protein digest, we were able to use our PPQ-MRM method to accurately determine the total phosphorylation stoichiometry on specific peptides as well as the absolute amount of the peptide and phosphopeptide present. Analyses of samples containing ERalpha protein revealed that the PPQ-MRM method is capable of determining phosphorylation stoichiometry in proteins from cell lines, and is in good agreement with determinations obtained using the direct MRM approach in terms of phosphorylation and total protein amount. PMID:20524616

Domanski, Dominik; Murphy, Leigh C; Borchers, Christoph H

2010-07-01

99

Substitutions of Aspartate 378 in the Phosphorylation Domain of the Yeast PMA1 H -ATPase Disrupt Protein  

E-print Network

Substitutions of Aspartate 378 in the Phosphorylation Domain of the Yeast PMA1 H -ATPase Disrupt Verjovski-Almeida§, Kenneth E. Allen, Anthony Ambesi, Rajini Rao¶, and Carolyn W. Slayman From, the -phosphoryl group of ATP is transferred to an as- partyl residue embedded in a strongly conserved sequence mo

Rao, Rajini

100

Nucleoside phosphorylation by phosphate minerals.  

PubMed

In the presence of formamide, crystal phosphate minerals may act as phosphate donors to nucleosides, yielding both 5'- and, to a lesser extent, 3'-phosphorylated forms. With the mineral Libethenite the formation of 5'-AMP can be as high as 6% of the adenosine input and last for at least 10(3) h. At high concentrations, soluble non-mineral phosphate donors (KH(2)PO(4) or 5'-CMP) afford 2'- and 2':3'-cyclic AMP in addition to 5'-and 3'-AMP. The phosphate minerals analyzed were Herderite Ca[BePO(4)F], Hureaulite Mn(2+)(5)(PO(3)(OH)(2)(PO(4))(2)(H(2)O)(4), Libethenite Cu(2+)(2)(PO(4))(OH), Pyromorphite Pb(5)(PO(4))(3)Cl, Turquoise Cu(2+)Al(6)(PO(4))(4)(OH)(8)(H(2)O)(4), Fluorapatite Ca(5)(PO(4))(3)F, Hydroxylapatite Ca(5)(PO(4))(3)OH, Vivianite Fe(2+)(3)(PO(4))(2)(H(2)O)(8), Cornetite Cu(2+)(3)(PO(4))(OH)(3), Pseudomalachite Cu(2+)(5)(PO(4))(2)(OH)(4), Reichenbachite Cu(2+)(5)(PO(4))(2)(OH)(4), and Ludjibaite Cu(2+)(5)(PO(4))(2)(OH)(4)). Based on their behavior in the formamide-driven nucleoside phosphorylation reaction, these minerals can be characterized as: 1) inactive, 2) low level phosphorylating agents, or 3) active phosphorylating agents. Instances were detected (Libethenite and Hydroxylapatite) in which phosphorylation occurs on the mineral surface, followed by release of the phosphorylated compounds. Libethenite and Cornetite markedly protect the beta-glycosidic bond. Thus, activated nucleic monomers can form in a liquid non-aqueous environment in conditions compatible with the thermodynamics of polymerization, providing a solution to the standard-state Gibbs free energy change (DeltaG degrees ') problem, the major obstacle for polymerizations in the liquid phase in plausible prebiotic scenarios. PMID:17412692

Costanzo, Giovanna; Saladino, Raffaele; Crestini, Claudia; Ciciriello, Fabiana; Di Mauro, Ernesto

2007-06-01

101

Enzymatic transesterification for biodiesel production.  

PubMed

Biodiesel consists monoalkyl esters of long chain fatty acids. It is produced from vegetable oils or fats either by chemical transesterification or by lipase-catalyzed transesterification with methanol or ethanol. Biodiesel is a green fuel and can be used as a blend with diesel or alone. Either way, it does not require any modification in engine design or storage facilities. The enzymatic process offers several advantages over the chemical routes. The handicap of increase in process cost because of the cost of the enzyme can be overcome by using efficient production process for enzyme and using reusable derivatives of enzymes, such as immobilized enzyme. Numerous strategies available in the area of non-aqueous enzymology can be exploited during the enzymatic alcoholysis for biodiesel production. Some of the technical challenges and their possible solutions are also discussed. PMID:22900366

Shah, Shweta; Sharma, Shweta; Gupta, M N

2003-12-01

102

Oxidative Phosphorylation at the fin de siècle  

NSDL National Science Digital Library

Mitochondria produce most of the energy in animal cells by a process called oxidative phosphorylation. Electrons are passed along a series of respiratory enzyme complexes located in the inner mitochondrial membrane, and the energy released by this electron transfer is used to pump protons across the membrane. The resultant electrochemical gradient enables another complex, adenosine 5â?˛-triphosphate (ATP) synthase, to synthesize the energy carrier ATP.

Matti Saraste (European Molecular Biology Laboratory; )

1999-03-05

103

Single-Molecule Enzymatic Dynamics  

Microsoft Academic Search

Enzymatic turnovers of single cholesterol oxidase molecules are observed in real time by monitoring the emission from the enzyme's fluorescent active site, flavin adenine dinucleotide (FAD). Although chemical kinetics, the Michaelis-Menten mechanism in particular, holds as a good approximation, statistical analyses of single-molecule trajectories reveal fluctuations in the rate of the activation step in the Michaelis-Menten mechanism. There exists a

H. Peter Lu; Luying Xun; Xiaoliang Xie

1998-01-01

104

Recent developments in enzymatic chlorination.  

PubMed

While the existence of chlorinated natural products has been known for over 100 years, our understanding of the enzymology of biological chlorination reactions has been limited to chloroperoxidases, which are now known not to play a significant role in chlorometabolite biosynthesis. The discoveries of new classes of halogenases, described in this Highlight, have shed new light on the mechanisms of enzymatic chlorination of aromatic and aliphatic compounds. PMID:16572225

Murphy, Cormac D

2006-04-01

105

SYMPOSIUM ON PLANT PROTEIN PHOSPHORYLATION  

SciTech Connect

Protein phosphorylation and dephosphorylation play key roles in many aspects of plant biology, including control of cell division, pathways of carbon and nitrogen metabolism, pattern formation, hormonal responses, and abiotic and biotic responses to environmental signals. A Symposium on Plant Protein Phosphorylation was hosted on the Columbia campus of the University of Missouri from May 26-28, 2010. The symposium provided an interdisciplinary venue at which scholars studying protein modification, as it relates to a broad range of biological questions and using a variety of plant species, presented their research. It also provided a forum where current international challenges in studies related to protein phosphorylation could be examined. The symposium also stimulated research collaborations through interactions and networking among those in the research community and engaged students and early career investigators in studying issues in plant biology from an interdisciplinary perspective. The proposed symposium, which drew 165 researchers from 13 countries and 21 States, facilitated a rapid dissemination of acquired knowledge and technical expertise regarding protein phosphorylation in plants to a broad range of plant biologists worldwide.

JOHN C WALKER

2011-11-01

106

Physiological consequences of the complete loss of phosphoryl-transfer proteins HPr and FPr of the phosphoenolpyruvate:sugar phosphotransferase system and analysis of fructose (fru) operon expression in Salmonella typhimurium.  

PubMed Central

Mutants of Salmonella typhimurium defective in the proteins of the fructose operon [fruB(MH)KA], the fructose repressor (fruR), the energy-coupling enzymes of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) (ptsH and ptsI), and the proteins of cyclic AMP action (cya and crp) were analyzed for their effects on cellular physiological processes and expression of the fructose operon. The fru operon consists of three structural genes: fruB(MH), which encodes the enzyme IIIFru-modulator-FPr tridomain fusion protein of the PTS; fruK, which encodes fructose-1-phosphate kinase; and fruA, which encodes enzyme IIFru of the PTS. Among the mutants analyzed were Tn10 insertion mutants and lacZ transcriptional fusion mutants. It was found that whereas a fruR::Tn10 insertion mutant, several fruB(MH)::Mu dJ and fruK::Mu dJ fusion mutants, and several ptsHI deletion mutants expressed the fru operon and beta-galactosidase at high constitutive levels, ptsH point mutants and fruA::Mu dJ fusion mutants retained inducibility. Inclusion of the wild-type fru operon in trans did not restore fructose-inducible beta-galactosidase expression in the fru::Mu dJ fusion mutants. cya and crp mutants exhibited reduced basal activities of all fru regulon enzymes, but inducibility was not impaired. Surprisingly, fruB::Mu dJ crp or cya double mutants showed over 10-fold inducibility of the depressed beta-galactosidase activity upon addition of fructose, even though this activity in the fruB::Mu dJ fusion mutants that contained the wild-type cya and crp alleles was only slightly inducible. By contrast, beta-galactosidase activity in a fruK::Mu dJ fusion mutant, which was similarly depressed by introduction of a crp or cya mutation, remained constitutive. Other experiments indicated that sugar uptake via the PTS can utilize either FPr-P or HPr-P as the phosphoryl donor, but that FPr is preferred for fructose uptake whereas HPr is preferred for uptake of the other sugars. Double mutants lacking both proteins were negative for the utilization of all sugar substrates of the PTS, were negative for the utilization of several gluconeogenic carbon sources, exhibited greatly reduced adenylate cyclase activity, and were largely nonmotile. These phenotypic properties are more extreme than those observed for tight ptsH and ptsI mutants, including mutants deleted for these genes. A biochemical explanation for this fact is proposed. PMID:2203752

Feldheim, D A; Chin, A M; Nierva, C T; Feucht, B U; Cao, Y W; Xu, Y F; Sutrina, S L; Saier, M H

1990-01-01

107

Physicochemical mechanisms of protein regulation by phosphorylation  

PubMed Central

Phosphorylation offers a dynamic way to regulate protein activity and subcellular localization, which is achieved through its reversibility and fast kinetics. Adding or removing a dianionic phosphate group somewhere on a protein often changes the protein’s structural properties, its stability and dynamics. Moreover, the majority of signaling pathways involve an extensive set of protein–protein interactions, and phosphorylation can be used to regulate and modulate protein–protein binding. Losses of phosphorylation sites, as a result of disease mutations, might disrupt protein binding and deregulate signal transduction. In this paper we focus on the effects of phosphorylation on protein stability, dynamics, and binding. We describe several physico-chemical mechanisms of protein regulation through phosphorylation and pay particular attention to phosphorylation in protein complexes and phosphorylation in the context of disorder–order and order–disorder transitions. Finally we assess the role of multiple phosphorylation sites in a protein molecule, their possible cooperativity and function. PMID:25147561

Nishi, Hafumi; Shaytan, Alexey; Panchenko, Anna R.

2014-01-01

108

Photoinitiated proton-coupled electron transfer and radical transport kinetics in class la ribonucleotide reductase  

E-print Network

Proton-coupled electron transfer (PCET) is a critical mechanism in biology, underpinning key processes such as radical transport, energy transduction, and enzymatic substrate activation. Ribonucleotide reductases (RNRs) ...

Pizano, Arturo A. (Arturo Alejandro)

2013-01-01

109

Large-scale determination of absolute phosphorylation stoichiometries in human cells by motif-targeting quantitative proteomics  

PubMed Central

Our ability to model the dynamics of signal transduction networks will depend on accurate methods to quantify levels of protein phosphorylation on a global scale. Here we describe a motif-targeting quantitation method for phosphorylation stoichiometry typing. Proteome-wide phosphorylation stoichiometry can be obtained by a simple phosphoproteomic workflow integrating dephosphorylation and isotope tagging with enzymatic kinase reaction. Proof-of-concept experiments using CK2-, MAPK- and EGFR-targeting assays in lung cancer cells demonstrate the advantage of kinase-targeted complexity reduction, resulting in deeper phosphoproteome quantification. We measure the phosphorylation stoichiometry of >1,000 phosphorylation sites including 366 low-abundance tyrosine phosphorylation sites, with high reproducibility and using small sample sizes. Comparing drug-resistant and sensitive lung cancer cells, we reveal that post-translational phosphorylation changes are significantly more dramatic than those at the protein and messenger RNA levels, and suggest potential drug targets within the kinase–substrate network associated with acquired drug resistance. PMID:25814448

Tsai, Chia-Feng; Wang, Yi-Ting; Yen, Hsin-Yung; Tsou, Chih-Chiang; Ku, Wei-Chi; Lin, Pei-Yi; Chen, Hsuan-Yu; Nesvizhskii, Alexey I.; Ishihama, Yasushi; Chen, Yu-Ju

2015-01-01

110

Large-scale determination of absolute phosphorylation stoichiometries in human cells by motif-targeting quantitative proteomics.  

PubMed

Our ability to model the dynamics of signal transduction networks will depend on accurate methods to quantify levels of protein phosphorylation on a global scale. Here we describe a motif-targeting quantitation method for phosphorylation stoichiometry typing. Proteome-wide phosphorylation stoichiometry can be obtained by a simple phosphoproteomic workflow integrating dephosphorylation and isotope tagging with enzymatic kinase reaction. Proof-of-concept experiments using CK2-, MAPK- and EGFR-targeting assays in lung cancer cells demonstrate the advantage of kinase-targeted complexity reduction, resulting in deeper phosphoproteome quantification. We measure the phosphorylation stoichiometry of >1,000 phosphorylation sites including 366 low-abundance tyrosine phosphorylation sites, with high reproducibility and using small sample sizes. Comparing drug-resistant and sensitive lung cancer cells, we reveal that post-translational phosphorylation changes are significantly more dramatic than those at the protein and messenger RNA levels, and suggest potential drug targets within the kinase-substrate network associated with acquired drug resistance. PMID:25814448

Tsai, Chia-Feng; Wang, Yi-Ting; Yen, Hsin-Yung; Tsou, Chih-Chiang; Ku, Wei-Chi; Lin, Pei-Yi; Chen, Hsuan-Yu; Nesvizhskii, Alexey I; Ishihama, Yasushi; Chen, Yu-Ju

2015-01-01

111

Prediction of phosphorylation sites using SVMs  

Microsoft Academic Search

Motivation: Phosphorylation is involved in diverse signal transduction pathways. By predicting phosphorylation sites and their kinases from primary protein sequences, we can obtain much valuable information that can form the basis for further research. Using support vector machines, we attemp- ted to predict phosphorylation sites and the type of kinase that acts at each site. Results: Our prediction system was

Jong-hun Kim; Juyoung Lee; Oh Bermseok; Kuchan Kimm; Insong Koh

2004-01-01

112

Global analysis of protein phosphorylation in yeast  

Microsoft Academic Search

Protein phosphorylation is estimated to affect 30% of the proteome and is a major regulatory mechanism that controls many basic cellular processes. Until recently, our biochemical understanding of protein phosphorylation on a global scale has been extremely limited; only one half of the yeast kinases have known in vivo substrates and the phosphorylating kinase is known for less than 160

Jason Ptacek; Geeta Devgan; Gregory Michaud; Heng Zhu; Xiaowei Zhu; Joseph Fasolo; Hong Guo; Ghil Jona; Ashton Breitkreutz; Richelle Sopko; Rhonda R. McCartney; Martin C. Schmidt; Najma Rachidi; Soo-Jung Lee; Angie S. Mah; Lihao Meng; Michael J. R. Stark; David F. Stern; Claudio de Virgilio; Mike Tyers; Brenda Andrews; Mark Gerstein; Barry Schweitzer; Paul F. Predki; Michael Snyder

2005-01-01

113

The semi-phosphorylative Entner–Doudoroff pathway in hyperthermophilic archaea: a re-evaluation  

PubMed Central

Biochemical studies have suggested that, in hyperthermophilic archaea, the metabolic conversion of glucose via the ED (Entner–Doudoroff) pathway generally proceeds via a non-phosphorylative variant. A key enzyme of the non-phosphorylating ED pathway of Sulfolobus solfataricus, KDG (2-keto-3-deoxygluconate) aldolase, has been cloned and characterized previously. In the present study, a comparative genomics analysis is described that reveals conserved ED gene clusters in both Thermoproteus tenax and S. solfataricus. The corresponding ED proteins from both archaea have been expressed in Escherichia coli and their specificity has been identified, revealing: (i) a novel type of gluconate dehydratase (gad gene), (ii) a bifunctional 2-keto-3-deoxy-(6-phospho)-gluconate aldolase (kdgA gene), (iii) a 2-keto-3-deoxygluconate kinase (kdgK gene) and, in S. solfataricus, (iv) a GAPN (non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase; gapN gene). Extensive in vivo and in vitro enzymatic analyses indicate the operation of both the semi-phosphorylative and the non-phosphorylative ED pathway in T. tenax and S. solfataricus. The existence of this branched ED pathway is yet another example of the versatility and flexibility of the central carbohydrate metabolic pathways in the archaeal domain. PMID:15869466

2005-01-01

114

Aluminum interaction with human brain tau protein phosphorylation by various kinases  

SciTech Connect

Phosphorylation is an indispensable process for energy and signal transduction in biological systems. AlCl[sub 3] at 10 nM to 10 uM range activated in-vitro [[gamma]-[sup 32]P] ATP phosphorylation of the brain (tau) [Tau] protein in both normal human or E. coli expressed [Tau] forms; in the presence of the kinases P34, PKP, and PKC to a maximum at 1 mM level. AlCl[sub 3] at 100 uM to 500 uM range induced non-enzymatic phosphorylation of [Tau] with [gamma]-ATP, [gamma]-GTP, and [alpha]-GTP, and [alpha]-GTP. AlCl[sub 3] activated histone phosphorylation by P34 in a similar pattern. The hyperphosphorylation of [Tau] with [gamma]-ATP, [gamma]-GTP, and [alpha]-GTP. AlCl[sub 3] activated histone phosphorylation by P34 in a similar pattern. The hyperphosphorylation of [Tau] by Al[sup 3+] was accompanied by molecular shift and mobility retardation in SDS-PAGE. This may demonstrate the mechanism of the longterm neurological effect of Al[sup 3+] in human brain leading to the formation of the neurofibrillary tangles related to Alzeheimer's disease.

El-Sebae, A.H.; Zeid, M.M.A.; Saleh, M.A. (Texas Southern Univ., Houston, TX (United States). Environmental Chemistry and Toxicology Lab.); Abdel-Ghany, M.E.; Shalloway, D. (Cornell Univ., Ithaca, NY (United States)); Blancato, J. (Environmental Protect Agency, Las Vegas, NV (United States). Environmental Monitoring Systems Lab.)

1993-01-01

115

Aluminum interaction with human brain tau protein phosphorylation by various kinases  

SciTech Connect

Phosphorylation is an indispensable process for energy and signal transduction in biological systems. AlCl[sub 3] at 10 nM to 10 [mu]M range activated in-vitro [[gamma][sup [minus]32]P]ATP phosphorylation of the brain ([tau]) [Gamma] protein in both normal human or E.coli expressed [Gamma] forms; in the presence of the kinases P34,PKP, and PKC. However, higher concentrations of AlCl[sub 3] inhibited the [Gamma] phosphorylation with P34, PKP, and PKC to a maximum at 1 mM level. AlCl[sub 3] at 100 [mu]M to 500 [mu]M range induced non-enzymatic phosphorylation of [Gamma] with [gamma]-ATP, [gamma]-GTP, and [alpha]-GRP. AlCl[sub 3] activated histone phosphorylation by P34 in a similar pattern. The hyperphosphorylation of [Gamma] by Al[sup 3+] was accompanied in molecular shift and mobility retardation in SDS-PAGE. This may demonstrate the mechanism of the long term neurological effect of Al[sub 3+] in human brain leading to the formation of the neutrofibrillary tangles related to Alzeheimer's disease.

El-Sebae; Abou Zeid, M.M.; Saleh, M.A. (Texas Southern Univ., Houston, TX (United States). Environmental Chemistry and Toxicology Lab.); Abdel-Ghany, M.E.; Shalloway, D. (Cornell Univ., Ithaca, NY (United States). Section of Biochemistry, Mol, and Cell Biology); Blancato, J. (US EPA, Las Vegas, NV (United States). Environmental Monit. Systems Lab.)

1993-01-01

116

Enzymatic reaction paths as determined by transition path sampling  

NASA Astrophysics Data System (ADS)

Enzymes are biological catalysts capable of enhancing the rates of chemical reactions by many orders of magnitude as compared to solution chemistry. Since the catalytic power of enzymes routinely exceeds that of the best artificial catalysts available, there is much interest in understanding the complete nature of chemical barrier crossing in enzymatic reactions. Two specific questions pertaining to the source of enzymatic rate enhancements are investigated in this work. The first is the issue of how fast protein motions of an enzyme contribute to chemical barrier crossing. Our group has previously identified sub-picosecond protein motions, termed promoting vibrations (PVs), that dynamically modulate chemical transformation in several enzymes. In the case of human heart lactate dehydrogenase (hhLDH), prior studies have shown that a specific axis of residues undergoes a compressional fluctuation towards the active site, decreasing a hydride and a proton donor--acceptor distance on a sub-picosecond timescale to promote particle transfer. To more thoroughly understand the contribution of this dynamic motion to the enzymatic reaction coordinate of hhLDH, we conducted transition path sampling (TPS) using four versions of the enzymatic system: a wild type enzyme with natural isotopic abundance; a heavy enzyme where all the carbons, nitrogens, and non-exchangeable hydrogens were replaced with heavy isotopes; and two versions of the enzyme with mutations in the axis of PV residues. We generated four separate ensembles of reaction paths and analyzed each in terms of the reaction mechanism, time of barrier crossing, dynamics of the PV, and residues involved in the enzymatic reaction coordinate. We found that heavy isotopic substitution of hhLDH altered the sub-picosecond dynamics of the PV, changed the favored reaction mechanism, dramatically increased the time of barrier crossing, but did not have an effect on the specific residues involved in the PV. In the mutant systems, we observed changes in the reaction mechanism and altered contributions of the mutated residues to the enzymatic reaction coordinate, but we did not detect a substantial change in the time of barrier crossing. These results confirm the importance of maintaining the dynamics and structural scaffolding of the hhLDH PV in order to facilitate facile barrier passage. We also utilized TPS to investigate the possible role of fast protein dynamics in the enzymatic reaction coordinate of human dihydrofolate reductase (hsDHFR). We found that sub-picosecond dynamics of hsDHFR do contribute to the reaction coordinate, whereas this is not the case in the E. coli version of the enzyme. This result indicates a shift in the DHFR family to a more dynamic version of catalysis. The second inquiry we addressed in this thesis regarding enzymatic barrier passage concerns the variability of paths through reactive phase space for a given enzymatic reaction. We further investigated the hhLDH-catalyzed reaction using a high-perturbation TPS algorithm. Though we saw that alternate reaction paths were possible, the dominant reaction path we observed corresponded to that previously elucidated in prior hhLDH TPS studies. Since the additional reaction paths we observed were likely high-energy, these results indicate that only the dominant reaction path contributes significantly to the overall reaction rate. In conclusion, we show that the enzymes hhLDH and hsDHFR exhibit paths through reactive phase space where fast protein motions are involved in the enzymatic reaction coordinate and exhibit a non-negligible contribution to chemical barrier crossing.

Masterson, Jean Emily

117

Enzymatic transglycosylation for glycoconjugate synthesis  

PubMed Central

Summary Remarkable advances have been made in recent years in exploiting the transglycosylation activity of glycosidases and glycosynthase mutants for oligosaccharide and glycoconjugate synthesis. New glycosynthases were generated from retaining glycosidases, inverting glycosidases, and those that proceed in a mechanism of substrate-assisted catalysis. Directed evolution coupled with elegant screening methods has led to the discovery of an expanding number of glycosynthase mutants that show improved catalytic activity and/or altered substrate specificity. In particular, enzymatic transglycosylation strategy has been recently extended to the synthesis of complex glycoconjugates, including glycosphingolipids, N-glycoproteins, and other glycosylated natural products. PMID:19766528

Wang, Lai-Xi; Huang, Wei

2009-01-01

118

Method for the enzymatic production of hydrogen  

DOEpatents

The present invention is an enzymatic method for producing hydrogen comprising the steps of: a) forming a reaction mixture within a reaction vessel comprising a substrate capable of undergoing oxidation within a catabolic reaction, such as glucose, galactose, xylose, mannose, sucrose, lactose, cellulose, xylan and starch. The reaction mixture further comprises an amount of glucose dehydrogenase in an amount sufficient to catalyze the oxidation of the substrate, an amount of hydrogenase sufficient to catalyze an electron-requiring reaction wherein a stoichiometric yield of hydrogen is produced, an amount of pH buffer in an amount sufficient to provide an environment that allows the hydrogenase and the glucose dehydrogenase to retain sufficient activity for the production of hydrogen to occur and also comprising an amount of nicotinamide adenine dinucleotide phosphate sufficient to transfer electrons from the catabolic reaction to the electron-requiring reaction; b) heating the reaction mixture at a temperature sufficient for glucose dehydrogenase and the hydrogenase to retain sufficient activity and sufficient for the production of hydrogen to occur, and heating for a period of time that continues until the hydrogen is no longer produced by the reaction mixture, wherein the catabolic reaction and the electron-requiring reactions have rates of reaction dependent upon the temperature; and c) detecting the hydrogen produced from the reaction mixture.

Woodward, Jonathan (Kingston, TN); Mattingly, Susan M. (State College, PA)

1999-01-01

119

Method for the enzymatic production of hydrogen  

DOEpatents

The present invention is an enzymatic method for producing hydrogen comprising the steps of: (a) forming a reaction mixture within a reaction vessel comprising a substrate capable of undergoing oxidation within a catabolic reaction, such as glucose, galactose, xylose, mannose, sucrose, lactose, cellulose, xylan and starch; the reaction mixture also comprising an amount of glucose dehydrogenase in an amount sufficient to catalyze the oxidation of the substrate, an amount of hydrogenase sufficient to catalyze an electron-requiring reaction wherein a stoichiometric yield of hydrogen is produced, an amount of pH buffer in an amount sufficient to provide an environment that allows the hydrogenase and the glucose dehydrogenase to retain sufficient activity for the production of hydrogen to occur and also comprising an amount of nicotinamide adenine dinucleotide phosphate sufficient to transfer electrons from the catabolic reaction to the electron-requiring reaction; (b) heating the reaction mixture at a temperature sufficient for glucose dehydrogenase and the hydrogenase to retain sufficient activity and sufficient for the production of hydrogen to occur, and heating for a period of time that continues until the hydrogen is no longer produced by the reaction mixture, wherein the catabolic reaction and the electron-requiring reactions have rates of reaction dependent upon the temperature; and (c) detecting the hydrogen produced from the reaction mixture. 8 figs.

Woodward, J.; Mattingly, S.M.

1999-08-24

120

In vivo and in vitro phosphorylation of membrane and soluble forms of soybean nodule sucrose synthase.  

PubMed

Sucrose synthase (SS) is a known phosphoserine (SerP)-containing enzyme in a variety of plant "sink" organs, including legume root nodules, where it is phosphorylated primarily at Ser-11. Using immunofluorescence confocal microscopy, we documented that part of the total SS (nodulin-100) pool in mature soybean (Glycine max) nodules is apparently associated with the plasma membrane in situ, and we report that this association is very "tight," as evidenced by a variety of chemical and enzymatic pretreatments of the isolated microsomal fraction. To investigate the in situ and in planta phosphorylation state of the membrane (m) and soluble (s) forms of nodule SS, three complementary approaches were used. First, excised nodules were radiolabeled in situ with [(32)P]Pi for subsequent analysis of phosphorylated m- and s-SS; second, immunopurified s- and m-SS were used as substrate in "on-bead" assays of phosphorylation by nodule Ca(2+)-dependent protein kinase; and third, SS-Ser-11(P) phosphopeptide-specific antibodies were developed and used. The collective results provide convincing evidence that microsomal nodulin-100 is phosphorylated in mature nodules, and that it is hypophosphorylated relative to s-SS (on an equivalent SS protein basis) in attached, unstressed nodules. Moreover, the immunological data and related phosphopeptide mapping analyses indicate that a homologous N-terminal seryl-phosphorylation domain and site reside in microsomal nodulin-100. We also observed that mild, short-term inorganic nitrogen and salt stresses have a significant negative impact on the content and N-terminal phosphorylation state of nodule m- and s-SS, with the former being the more sensitive of the two SS forms. PMID:12177479

Komina, Olga; Zhou, You; Sarath, Gautam; Chollet, Raymond

2002-08-01

121

Enzymatic Synthesis of Glycosaminoglycan Heparin  

PubMed Central

Heparin and its low molecular weight heparin derivatives, widely used as clinical anticoagulants, are acidic polysaccharide members of a family of biomacromolecules called glycosaminoglycans (GAGs). Heparin and the related heparan sulfate are biosynthesized in the Golgi apparatus of eukaryotic cells. Heparin is a polycomponent drug that currently is prepared for clinical use by extraction from animal tissues. A heparin pentasaccharide, fondaparinux, has also been prepared through chemical synthesis for use as a homogenous anticoagulant drug. Recent enabling technologies suggest that it may now be possible to synthesize heparin and its derivatives enzymatically. Moreover, new technologies including advances in synthetic carbohydrate synthesis, enzyme-based GAG synthesis, micro- and nano-display of GAGs, rapid on-line structural analysis, and microarray/microfluidic technologies might be applied to the enzymatic synthesis of heparins with defined structures and exhibiting selected activities. The advent of these new technologies also makes it possible to consider the construction of an artificial Golgi to increase our understanding of the cellular control of GAG biosyntheses in this organelle. PMID:17629842

Linhardt, Robert J.; Dordick, Jonathan S.; Deangelis, Paul L.; Liu, Jian

2014-01-01

122

Tyrosine phosphorylation and bacterial virulence  

PubMed Central

Protein phosphorylation on tyrosine has emerged as a key device in the control of numerous cellular functions in bacteria. In this article, we review the structure and function of bacterial tyrosine kinases and phosphatases. Phosphorylation is catalyzed by autophosphorylating adenosine triphosphate-dependent enzymes (bacterial tyrosine (BY) kinases) that are characterized by the presence of Walker motifs. The reverse reaction is catalyzed by three classes of enzymes: the eukaryotic-like phosphatases (PTPs) and dual-specific phosphatases; the low molecular weight protein-tyrosine phosphatases (LMW-PTPs); and the polymerase–histidinol phosphatases (PHP). Many BY kinases and tyrosine phosphatases can utilize host cell proteins as substrates, thereby contributing to bacterial pathogenicity. Bacterial tyrosine phosphorylation/dephosphorylation is also involved in biofilm formation and community development. The Porphyromonas gingivalis tyrosine phosphatase Ltp1 is involved in a restraint pathway that regulates heterotypic community development with Streptococcus gordonii. Ltp1 is upregulated by contact with S. gordonii and Ltp1 activity controls adhesin expression and levels of the interspecies signal AI-2. PMID:22388693

Whitmore, Sarah E; Lamont, Richard J

2012-01-01

123

Enzymatic synthesis of DNA on glycerol nucleic acid templates without stable duplex formation between  

E-print Network

Enzymatic synthesis of DNA on glycerol nucleic acid templates without stable duplex formation for review May 8, 2007) Glycerol nucleic acid (GNA) is an interesting alternative base- pairing system based is not required for template-dependent polymerization. information transfer polymerase Nucleic acid analogs

Heller, Eric

124

Monitoring enzymatic ATP hydrolysis by EPR spectroscopy.  

PubMed

An adenosine triphosphate (ATP) analogue modified with two nitroxide radicals is developed and employed to study its enzymatic hydrolysis by electron paramagnetic resonance spectroscopy. For this application, we demonstrate that EPR holds the potential to complement fluorogenic substrate analogues in monitoring enzymatic activity. PMID:24872080

Hacker, Stephan M; Hintze, Christian; Marx, Andreas; Drescher, Malte

2014-07-14

125

The biochemistry and control of enzymatic browning  

Microsoft Academic Search

Half of the world's fruit and vegetable crops is lost due to postharvest deteriorative reactions. Polyphenol oxidase (PPO), found in most fruit and vegetables, is responsible for enzymatic browning of fresh horticultural products, following bruising, cutting or other damage to the cell. Chemical methods for controlling enzymatic browning include the use of sodium bisulfite, ascorbic acid and\\/or packaging under controlled

M. Victoria Martinez; John R. Whitaker

1995-01-01

126

Ethanol from biomass by enzymatic hydrolysis  

Microsoft Academic Search

Enzymes are biological catalysts that generally are designed to do one job well, but to do one job only. Therefore, the enzymes that catalyze the hydrolysis of cellulose to sugar do not break down the sugars. Thus, enzymatic processes are capable of yields approaching 100%. Enzymatic hydrolysis processes have been under development for only 10 years. Although improvements have been

1988-01-01

127

Oxidative Phosphorylation at the fin de siècle  

NSDL National Science Digital Library

Mitochondria produce most of the energy in animal cells by a process called oxidative phosphorylation. Electrons are passed along a series of respiratory enzyme complexes located in the inner mitochondrial membrane, and the energy released by this electron transfer is used to pump protons across the membrane. The resultant electrochemical gradient enables another complex, adenosine 5â?˛-triphosphate (ATP) synthase, to synthesize the energy carrier ATP. Important new mechanistic insights into oxidative phosphorylation have emerged from recent three-dimensional structural analyses of ATP synthase and two of the respiratory enzyme complexes, cytochrome bc1 and cytochrome c oxidase. This work, and new enzymological studies of ATP synthase's unusual catalytic mechanism, are reviewed here.

Matti Saraste (European Molecular Biology Laboratory; )

1999-03-05

128

Applying the Brakes to Multi-Site SR Protein Phosphorylation: Substrate-Induced Effects on the Splicing Kinase SRPK1†  

PubMed Central

To investigate how a protein kinase interacts with its protein substrate during extended, multi-site phosphorylation, the kinetic mechanism of a protein kinase involved in mRNA splicing control was investigated using rapid quench flow techniques. The protein kinase SRPK1 phosphorylates approximately 10 serines in the arginine-serine-rich domain (RS domain) of the SR protein SRSF1 in a C-to-N-terminal direction, a modification that directs this essential splicing factor from the cytoplasm to the nucleus. Transient-state kinetic experiments illustrate that the first phosphate is added rapidly onto the RS domain of SRSF1 (t1/2 = 0.1 sec) followed by slower, multi-site phosphorylation at the remaining serines (t1/2 = 15 sec). Mutagenesis experiments suggest that efficient phosphorylation rates are maintained by an extensive hydrogen bonding and electrostatic network between the RS domain of the SR protein and the active site and docking groove of the kinase. Catalytic trapping and viscosometric experiments demonstrate that while the phosphoryl transfer step is fast, ADP release limits multi-site phosphorylation. By studying phosphate incorporation into selectively pre-phosphorylated forms of the enzyme-substrate complex, the kinetic mechanism for site-specific phosphorylation along the reaction coordinate was assessed. The binding affinity of the SR protein, the phosphoryl transfer rate and ADP exchange rate were found to decline significantly as a function of progressive phosphorylation in the RS domain. These findings indicate that the protein substrate actively modulates initiation, extension and termination events associated with prolonged, multi-site phosphorylation. PMID:21728354

Aubol, Brandon E.; Adams, Joseph A.

2011-01-01

129

A mitotic kinase TOPK enhances Cdk1/cyclin B1-dependent phosphorylation of PRC1 and promotes cytokinesis.  

PubMed

A MAPKK-like mitotic kinase, TOPK, implies the formation of mitotic spindles and spindle midzone and accomplishing cytokinesis, however, its underlying mechanism remains unclear. A microtubule bundling protein, PRC1, plays a pivotal role in the formation of mitotic spindles and spindle midzone. Because of their functional resemblance, we attempted to clarify the links between these two molecules. TOPK supported mitotic advance via the cdk1/cyclin B1-dependent phosphorylation of PRC1. TOPK induced the phosphorylation of PRC1 at T481 in vivo, however, TOPK did not phosphorylate PRC1 in vitro. TOPK induced the phosphorylation of PRC1 at T481 only when the cdk1/cyclin B1 existed simultaneously in vitro. Both the enzymatic activity of TOPK and association competence of TOPK with PRC1 were mandatory for this phosphorylation. TOPK binds to cdk1/cyclin B1, microtubules and PRC1 via its unique region near the C terminus. TOPK co-localized closely with cdk1 throughout the cell cycle in vivo. Collectively, these data indicate that TOPK, which makes a kinase-substrate complex with cdk1/cyclin B1 and PRC1 on microtubules during mitosis, enhances the cdk1/cyclin B1-dependent phosphorylation of PRC1 and thereby strongly promotes cytokinesis. PMID:17512944

Abe, Yasuhito; Takeuchi, Takashi; Kagawa-Miki, Lisa; Ueda, Norifumi; Shigemoto, Kazuhiro; Yasukawa, Masaki; Kito, Katsumi

2007-07-01

130

Multisite phosphorylation of oxysterol-binding protein regulates sterol binding and activation of sphingomyelin synthesis  

PubMed Central

The endoplasmic reticulum (ER)-Golgi sterol transfer activity of oxysterol-binding protein (OSBP) regulates sphingomyelin (SM) synthesis, as well as post-Golgi cholesterol efflux pathways. The phosphorylation and ER-Golgi localization of OSBP are correlated, suggesting this modification regulates the directionality and/or specificity of transfer activity. In this paper, we report that phosphorylation on two serine-rich motifs, S381-S391 (site 1) and S192, S195, S200 (site 2), specifically controls OSBP activity at the ER. A phosphomimetic of the SM/cholesterol-sensitive phosphorylation site 1 (OSBP-S5E) had increased in vitro cholesterol and 25-hydroxycholesterol–binding capacity, and cholesterol extraction from liposomes, but reduced transfer activity. Phosphatidylinositol 4-phosphate (PI(4)P) and cholesterol competed for a common binding site on OSBP; however, direct binding of PI(4)P was not affected by site 1 phosphorylation. Individual site 1 and site 2 phosphomutants supported oxysterol activation of SM synthesis in OSBP-deficient CHO cells. However, a double site1/2 mutant (OSBP-S381A/S3D) was deficient in this activity and was constitutively colocalized with vesicle-associated membrane protein–associated protein A (VAP-A) in a collapsed ER network. This study identifies phosphorylation regulation of sterol and VAP-A binding by OSBP in the ER, and PI(4)P as an alternate ligand that could be exchanged for sterol in the Golgi apparatus. PMID:22875984

Goto, Asako; Liu, Xinwei; Robinson, Carolyn-Ann; Ridgway, Neale D.

2012-01-01

131

Salt stress-induced protein phosphorylation  

SciTech Connect

Protein phosphorylation induced by salt stress in tomato germinating seeds were investigated by two-dimensional polyacrilamide gel electrophoresis of proteins labeled in vivo with ({sup 32}P)-Phosphate. NaCl induced the phosphorylation of a 14 Kd polypeptide. Pulse-chase experiments revealed that the phosphorylated molecules of this polypeptide are only stable while the stress is present. Phosphorylated 14 Kd polypeptides could be detected in radicles of salt-shocked seedlings after 6 hours stress period. 14 Kd polypeptide phosphorylation was also observed in seeds germinating in the presence of abscisic acid (ABA). The amount of phosphorylated 14 Kd polypeptide was significantly increased in seeds treated simultaneously with NaCl and ABA.

Godoy, J.A.; Torres-Schumann, S.; Llobell, A.; Pintor-Toro, J.A.

1989-04-01

132

Recent advances in carbon nanotube-based enzymatic fuel cells.  

PubMed

This review summarizes recent trends in the field of enzymatic fuel cells. Thanks to the high specificity of enzymes, biofuel cells can generate electrical energy by oxidation of a targeted fuel (sugars, alcohols, or hydrogen) at the anode and reduction of oxidants (O2, H2O2) at the cathode in complex media. The combination of carbon nanotubes (CNT), enzymes and redox mediators was widely exploited to develop biofuel cells since the electrons involved in the bio-electrocatalytic processes can be efficiently transferred from or to an external circuit. Original approaches to construct electron transfer based CNT-bioelectrodes and impressive biofuel cell performances are reported as well as biomedical applications. PMID:25386555

Cosnier, Serge; Holzinger, Michael; Le Goff, Alan

2014-01-01

133

Recent Advances in Carbon Nanotube-Based Enzymatic Fuel Cells  

PubMed Central

This review summarizes recent trends in the field of enzymatic fuel cells. Thanks to the high specificity of enzymes, biofuel cells can generate electrical energy by oxidation of a targeted fuel (sugars, alcohols, or hydrogen) at the anode and reduction of oxidants (O2, H2O2) at the cathode in complex media. The combination of carbon nanotubes (CNT), enzymes and redox mediators was widely exploited to develop biofuel cells since the electrons involved in the bio-electrocatalytic processes can be efficiently transferred from or to an external circuit. Original approaches to construct electron transfer based CNT-bioelectrodes and impressive biofuel cell performances are reported as well as biomedical applications. PMID:25386555

Cosnier, Serge; Holzinger, Michael; Le Goff, Alan

2014-01-01

134

Correlation between persistent forms of zeaxanthin-dependent energy dissipation and thylakoid protein phosphorylation.  

PubMed

High light stress induced not only a sustained form of xanthophyll cycle-dependent energy dissipation but also sustained thylakoid protein phosphorylation. The effect of protein phosphatase inhibitors (fluoride and molybdate ions) on recovery from a 1-h exposure to a high PFD was examined in leaf discs of Parthenocissus quinquefolia (Virginia creeper). Inhibition of protein dephosphorylation induced zeaxanthin retention and sustained energy dissipation (NPQ) upon return to low PFD for recovery, but had no significant effects on pigment and Chl fluorescence characteristics under high light exposure. In addition, whole plants of Monstera deliciosa and spinach grown at low to moderate PFDs were transferred to high PFDs, and thylakoid protein phosphorylation pattern (assessed with anti-phosphothreonine antibody) as well as pigment and Chl fluorescence characteristics were examined over several days. A correlation was obtained between dark-sustained D1/D2 phosphorylation and dark-sustained zeaxanthin retention and maintenance of PS II in a state primed for energy dissipation in both species. The degree of these dark-sustained phenomena was more pronounced in M. deliciosa compared with spinach. Moreover, M. deliciosa but not spinach plants showed unusual phosphorylation patterns of Lhcb proteins with pronounced dark-sustained Lhcb phosphorylation even under low PFD growth conditions. Subsequent to the transfer to a high PFD, dark-sustained Lhcb protein phosphorylation was further enhanced. Thus, phosphorylation patterns of D1/D2 and Lhcb proteins differed from each other as well as among plant species. The results presented here suggest an association between dark-sustained D1/D2 phosphorylation and sustained retention of zeaxanthin and energy dissipation (NPQ) in light-stressed, and particularly 'photoinhibited', leaves. Functional implications of these observations are discussed. PMID:16228317

Ebbert, V; Demmig-Adams, B; Adams, W W; Mueh, K E; Staehelin, L A

2001-01-01

135

Regulation of Smad Function by Phosphorylation  

Microsoft Academic Search

Phosphorylation is a dynamic and reversible post-translational modification which has a strong impact on structural features\\u000a of proteins. All Smad proteins have been reported as phosphoproteins. Phosphorylation of receptor-activated Smad proteins\\u000a by type I receptors initiates TGF-? family signaling. Phosphorylation of Smads by a number of other kinases is a mechanism\\u000a of cross-talk between Smads and other signaling pathways. Smad

Ihor Yakymovych; Serhiy Souchelnytskyi

136

Proline-Directed Androgen Receptor Phosphorylation  

PubMed Central

The androgen receptor (AR) has been identified for decades and mediates essential steroid functions. Like most of biological molecules, AR functional activities are modulated by post-translational modifications. This review is focused on the reported activities and significance of AR phosphorylation, with particular emphasis on proline-directed serine/threonine phosphorylation that occurs predominantly on the receptor. The marked enrichment of AR phosphorylation in the most diverse N-terminal domain suggests that targeting AR phosphorylation can be synergistic to antagonizing the C-terminal domain by clinical antiandrogens.

Gao, Yanfei; Chen, Shaoyong

2015-01-01

137

Phosphorylation-mediated inactivation of coactivator-associated arginine methyltransferase 1.  

PubMed

Multiple protein arginine methyltransferases are involved in transcriptional activation of nuclear receptors. Coactivator-associated arginine methyltransferase 1 (CARM1)-mediated histone methylation has been shown to activate nuclear receptor-dependent transcription; however, little is known about the regulation of its enzymatic activity. Here, we report that the methyltransferase activity of CARM1 is negatively regulated through phosphorylation at a conserved serine residue. When the serine residue is mutated to glutamic acid, which mimics the phosphorylated serine residue, the mutant CARM1 exhibits diminished ability to bind the methyl donor adenosylmethionine and diminished histone methylation activity. Moreover, such mutation leads to the inhibition of CARM1 transactivation of estrogen receptor-dependent transcription. Our results provide an example for the regulation of protein arginine methyltransferase activity by phosphorylation. As CARM1 is a potent transcriptional coactivator of estrogen receptor, our results suggest that phosphorylation of CARM1 serves as a unique mechanism for inactivating CARM1-regulated estrogen-dependent gene expression. PMID:17640894

Higashimoto, Ken; Kuhn, Peter; Desai, Dhaval; Cheng, Xiaodong; Xu, Wei

2007-07-24

138

Chaperon-like Activation of Serum-Inducible Tryptophanyl-tRNA Synthetase Phosphorylation through Refolding as a Tool for Analysis of Clinical Samples1  

PubMed Central

Tryptophanyl-tRNA synthetase (TrpRS) expression alters in colorectal (CRC), pancreatic (PC), and cervical (CC) cancers. Here, phosphorylation of unfolded TrpRS and its fragments is stimulated by human cancer sera (CS; n = 13) and serum of rabbit tumor induced by Rous sarcoma virus, unaffected by donor sera (NS; 11/15) and abolished by alkaline phosphatase. At 20 years of follow-up, serum-inducible TrpRS phosphorylation found years before healthy donors (3/15) diagnosed with PC, CRC, or leukemia. I have examined a specificity of serum-inducible TrpRS phosphorylation and found, surprisingly, that serine phosphorylation of unfolded TrpRS is stimulated by anti-TrpRS rabbit antisera but is unaffected by rabbit nonimmune sera and antisera to other antigens. Anti-TrpRS immunoglobulin G (IgG) inhibits phosphorylation of full-length TrpRS and stimulates phosphorylation of its 20-kDa fragment. Phosphorylation of this fragment is stimulated also by CS but not NS. 2-Mercaptoethanol and cyclic AMP exerted synergistic inhibitory effect on TrpRS phosphorylation. Anti-TrpRS sera and casein act as chaperones increasing TrpRS phosphorylation through refolding. Histone-specific protein kinase activity in CS (n = 44) and anti-TrpRS sera was lower than that in NS (n = 11), rabbit nonimmune sera and antisera to other antigens. TrpRS inhibitors, tryptamine, and tryptophanol stimulate in vivo accumulation of enzymatically inactive, nonphosphorylated, aggregated and anti-TrpRS IgG refoldable TrpRS. Phosphorylation of postsurgical tissues (n = 18) reveals TrpRS in ovarian cancer (OVC) and CC but not in normal placenta and liver. In OVC, TrpRS phosphorylation increase correlates with elevated tryptophan-dependent ATP-inorganic pyrophosphate exchange. Although not inducing cancer, TrpRS triggers signaling concomitant with cancer. PMID:22191002

Paley, Elena L

2011-01-01

139

Extracellular Phosphorylation and Phosphorylated Proteins: Not Just Curiosities But Physiologically Important  

NSDL National Science Digital Library

With 3 figures, 1 table, and 221 references plus 2 supplementary figures and 1 supplementary table, this Review describes the evidence supporting physiological and pathological functions of phosphorylated extracellular proteins. In addition, evidence for extracellular phosphorylation in various contexts and tissues is also presented. To facilitate the study of the extracellular phosphoproteome, annotation of the phosphorylated proteins found in proteomic databases is supplied.

Garif Yalak (ETH Zurich; Department of Health Sciences and Technology REV)

2012-12-18

140

Relationships between histone phosphorylation and cell proliferation  

SciTech Connect

From studies with various Peromyscus cell lines, correlations were made which led to the proposal that H2A phosphorylation is most active in constitutive heterochromatin. Recent studies on the two H2A variants found in these cells have revealed that the high level of H2A phosphorylation associated with heterochromatin is not the result of an increase in H2A phosphorylation rate or an increase in the number of phosphorylation sites, but rather, is due to an increase in the proportion of one of the H2A variants which is more highly phosphorylated than the other. If H2A phosphorylation is necessary for the constitutive heterochromatin state, it is reasonable that the cell would accomplish the generation of this structure by permanently installing a more highly phosphorylated H2A in the heterochromatin nucleosome rather than by trying to modulate the phosphorylation rate in such a condensed structure. The proposal that histone phosphorylation is involved with the condensed structures of chromatin is based primarily on correlations between histone phosphorylation measurements and cellular phenomena. One proof that this concept is correct ultimately rests in the ability to demonstrate these correlations in isolated chromosomes and chromatin fractions. This demonstration is presently limited by the excessive dephosphorylation of histones which occurs during the isolation of chromosomes and chromatin fractions. Thus, the demonstration of an effective inhibitor of histone dephosphorylation which is compatible with the isolation of nuclear structures and chromatin fractions having native morphologies is essential for future studies on the biological function of histone phosphorylation. (ERB)

Gurley, L.R.; D'Anna, J.A.; Halleck, M.S.; Barham, S.S.; Walters, R.A.; Jett, J.H.; Tobey, R.A.

1980-01-01

141

Analysis of protein phosphorylation using mass spectrometry: deciphering the phosphoproteome  

Microsoft Academic Search

In signal transduction in eukaryotes, protein phosphorylation is a key event. To understand signaling processes, we must first acquire an inventory of phosphoproteins and their phosphorylation sites under different conditions. Because phosphorylation is a dynamic process, elucidation of signaling networks also requires quantitation of these phosphorylation events. In this article, we outline several methods for enrichment of phosphorylated proteins and

Matthias Mann; Shao-En Ong; Mads Grřnborg; Hanno Steen; Ole N. Jensen; Akhilesh Pandey

2002-01-01

142

IMPORTANCE OF ENZYMATIC BIOTRANSFORMATION IN IMMUNOTOXICOLOGY  

EPA Science Inventory

Many immunotoxic compounds, such as benzene and other organic solvents, pesticides, mycotoxins and polycyclic aromatic hydrocarbons, can alter immune function only after undergoing enzyme-mediated reactions within various tissues. In the review that follows, the role of enzymatic...

143

Enzymatic degradation of thiolated chitosan.  

PubMed

The objective of this study was to evaluate the biodegradability of thiolated chitosans in comparison to unmodified chitosan. Mediated by carbodiimide, thioglycolic acid (TGA) and mercaptonicotinic acid (MNA) were covalently attached to chitosan via formation an amide bond. Applying two different concentrations of carbodiimide 50 and 100?mM, two chitosan TGA conjugates (TGA A and TGA B) were obtained. According to chitosan solution (3% m/v) thiomer solutions were prepared and chitosanolytic enzyme solutions were added. Lysozyme, pectinase and cellulase were examined in chitosan degrading activity. The enzymatic degradability of these thiomers was investigated by viscosity measurements with a plate-plate viscometer. The obtained chitosan TGA conjugate A displayed 267.7 µmol and conjugate B displayed 116.3 µmol of immobilized thiol groups. With 325.4 µmol immobilized thiol groups, chitosan MNA conjugate displayed the most content of thiol groups. In rheological studies subsequently the modification proved that chitosan TGA conjugates with a higher coupling rate of thiol groups were not only degraded to a lesser extent by 20.9-26.4% but also more slowly. Chitosan mercaptonicotinic acid was degraded by 31.4-50.1% depending the investigated enzyme and even faster than unmodified chitosan. According to these results the biodegradability can be influenced by various modifications of the polymer which showed in particular that the rate of biodegradation is increased when MNA is the ligand, whereas the degradation is hampered when TGA is used as ligand for chitosan. PMID:23057506

Laffleur, Flavia; Hintzen, Fabian; Rahmat, Deni; Shahnaz, Gul; Millotti, Gioconda; Bernkop-Schnürch, Andreas

2013-10-01

144

Phosphorylation of the multidrug resistance associated glycoprotein  

SciTech Connect

Drug-resistant cell lines derived from the mouse macrophage-like cell line J774.2 express the multidrug resistant phenotype which includes the overexpression of a membrane glycoprotein (130-140 kilodaltons). Phosphorylation of this resistant-specific glycoprotein (P-glycoprotein) in intact cells and in cell-free membrane fractions has been studied. The phosphorylated glycoprotein can be immunoprecipitated by a rabbit polyclonal antibody specific for the glycoprotein. Phosphorylation studies done with partially purified membrane fractions derived from colchicine-resistant cells indicated that (a) phosphorylation of the glycoprotein in 1 mM MgCl/sub 2/ was enhanced a minimum of 2-fold by 10 ..mu..M cAMP and (b) the purified catalytic subunit of the cAMP-dependent protein kinase (protein kinase A) phosphorylated partially purified glycoprotein that was not phosphorylated by (..gamma..-/sup 32/P)ATP alone, suggesting that autophosphorylation was not involved. These results indicate that the glycoprotein is a phosphoprotein and that at least one of the kinases responsible for its phosphorylation is a membrane-associated protein kinase A. The state of phosphorylation of the glycoprotein, which is a major component of the multidrug resistance phenotype, may be related to the role of the glycoprotein in maintaining drug resistance.

Mellado, W.; Horwitz, S.B.

1987-11-03

145

Intramolecular domaindomain association/ dissociation and phosphoryl transfer in the mannitol  

E-print Network

of active catalysis. Thus, on average, 80 association/ dissociation events are required to effect a single used to study dynamics of enzyme function and protein folding on milli- to microsecond time scales (2 are directly linked to catalysis (5, 7, 8). For adenylate kinase, the rate of lid opening, which involves large

Clore, G. Marius

146

Modulation of P1798 lymphosarcoma proliferation by protein phosphorylation  

SciTech Connect

The role of protein kinases in modulating cell proliferation was examined. Studies characterized the regulation of cell proliferation by adenosine 3':5'-monophosphate-dependent protein kinase (cA-Pk). Calcium/calmodulin-dependent myosin light chain kinase (MLCK) was isolated and examined as a potential substrate regulated by cA-PK in the rapidly proliferating P1798 lymphosarcoma. Modulation of cell proliferation by cA-PK was characterized by quantitating cell division by (methyl-/sup 3/H) thymidine ((/sup 3/H)-dT) incorporation into DNA, cAMP accumulations, and activation of cA-PK using P1798 lymphosarcoma cells. Epinephrine and prostaglandin E/sub 1/ (PGE/sub 1/) were demonstrated to suppress (/sup 3/H)-dT incorporation into DNA, to stimulate cAMP accumulation, and to activate cA-PK with dose-dependency. Calcium/calmodulin-dependent MLCK was partially purified from P1798 lymphosarcoma. P1798 MLCK phosphorylated myosin regulatory light chains (P-LC) from thymus, cardiac and skeletal muscles. One mol (/sup 32/Pi) was transferred into one mol cardiac or skeletal P-LC by P1798 MLCK. Apparent Km values of 65 ..mu..M and 51 ..mu..M were determined for ATP and cardiac P-LC, respectively. The apparent molecular weight of P1798 MLCK was 135,000. P1798 MLCK was phosphorylated by cA-PK. Phosphorylated MLCK showed a 41% decrease in calcium-dependent activity. Two additional protein kinases from P1798 lymphosarcoma phosphorylated cardiac and skeletal light chains (MLC).

Michnoff, C.A.H.

1983-01-01

147

The impact of N-terminal phosphorylation on LHCII conformation in state transition  

NASA Astrophysics Data System (ADS)

State transition is an important protection mechanism of plants for maintaining optimal efficiency through redistributing unbalanced excitation energy between photo-system II (PSII) and photosystem I (PSI). This process depends on the reversible phosphorylation/dephosphorylation of the major light-harvesting complex II (LHCII) and its bi-directional migration between PSII and PSI. But it remains unclear how phosphorylation/dephosphorylation modulates the LHCII conformation and further regulates its reversible migration. Here molecular dynamics simulations (MDS) were employed to elucidate the impact of phosphorylation on LHCII conformation. The results indicated that N-terminal phosphorylation loosened LHCII trimer with decreased hydrogen bond (H-bond) interactions and extended the distances between neighboring monomers, which stemmed from the conformational adjustment of each monomer itself. Global conformational change of LHCII monomer started from its stromal Nterminal (including the phosphorylation sites) by enhancing its interaction to lipid membrane and by adjusting the interaction network with surrounded inter-monomer and intra-monomer transmembrane helixes of B, C, and A, and finally triggered the reorientation of transmembrane helixes and transferred the conformational change to luminal side helixes and loops. These results further our understanding in molecular mechanism of LHCII migration during state transition from the phosphorylation-induced microstructural feature of LHCII.

Ding, Jin-Hong; Li, Ning; Wang, Man-Liu; Zhang, Yan; Lü, Shou-Qin; Long, Mian

2014-06-01

148

Lignin hydrolysis and phosphorylation mechanism during phosphoric acid-acetone pretreatment: a DFT study.  

PubMed

The study focused on the structural sensitivity of lignin during the phosphoric acid-acetone pretreatment process and the resulting hydrolysis and phosphorylation reaction mechanisms using density functional theory calculations. The chemical stabilities of the seven most common linkages (?-O-4, ?-?, 4-O-5, ?-1, 5-5, ?-O-4, and ?-5) of lignin in H3PO4, CH3COCH3, and H2O solutions were detected, which shows that ?-O-4 linkage and ?-O-4 linkage tend to break during the phosphoric acid-acetone pretreatment process. Then ?-O-4 phosphorylation and ?-O-4 phosphorylation follow a two-step reaction mechanism in the acid treatment step, respectively. However, since phosphorylation of ?-O-4 is more energetically accessible than phosphorylation of ?-O-4 in phosphoric acid, the phosphorylation of ?-O-4 could be controllably realized under certain operational conditions, which could tune the electron and hole transfer on the right side of ?-O-4 in the H2PO4- functionalized lignin. The results provide a fundamental understanding for process-controlled modification of lignin and the potential novel applications in lignin-based imprinted polymers, sensors, and molecular devices. PMID:25529020

Qin, Wu; Wu, Lingnan; Zheng, Zongming; Dong, Changqing; Yang, Yongping

2014-01-01

149

Affinity-based SDS PAGE identification of phosphorylated Arabidopsis MAPKs and substrates by acrylamide pendant Phos-Tag™.  

PubMed

Protein phosphorylation is the most abundant and best studied protein posttranslational modification, dedicated to the regulation of protein function and subcellular localization as well as to protein-protein interactions. Identification and quantitation of the dynamic, conditional protein phosphorylation can be achieved by either metabolic labeling of the protein of interest with (32)P-labeled ATP followed by autoradiographic analysis, the use of specific monoclonal or polyclonal antibodies against the phosphorylated protein species and finally by phosphoproteome delineation using mass spectrometry.Hereby we present a fourth alternative which relies on the enforced-affinity-based-electrophoretic separation of phosphorylated from non-phosphorylated protein species by standard SDS-PAGE systems co-polymerized with Phos-Tag™ and Mn(2+) or Zn(2+) cations. Phosphate groups of phosphorylated Ser, Thr, and Tyr residues form complexes with Mn(2+) and Zn(2+) cations with polyacrylamide immobilized Phos-Tag™. Following appropriate treatment of the gels, separated proteins can be quantitatively transferred to PVDF or nitrocellulose membranes and probed with common-not phosphorylation state specific-antibodies and delineate the occurrence of a certain phosphoprotein species against its non-phosphorylated counterpart. PMID:24908119

Komis, George; Taká?, Tomáš; Bekešová, Slávka; Vadovi?, Pavol; Samaj, Jozef

2014-01-01

150

Histone H1 Phosphorylation in Breast Cancer  

PubMed Central

Breast cancer is the second leading cause of cancer-related deaths in women. The need for new clinical biomarkers in breast cancer is necessary to further predict prognosis and therapeutic response. In this article, the LC-MS histone H1 phosphorylation profiles were established for three distinct breast cancer cell lines. The results show that the extent of H1 phosphorylation can distinguish between the different cell lines. The histone H1 from the metastatic cell line, MDA-MB-231, was subjected to chemical derivitization and LC-MS/MS analysis. The results suggest that the phosphorylation at threonine 146 is found on both histone H1.2 and histone H1.4. Cell lines were then treated with an extracellular stimulus, estradiol or kinase inhibitor LY294002, to monitor changes in histone H1 phosphorylation. The data show that histone H1 phosphorylation can increase and decrease in response to extracellular stimuli. Finally, primary breast tissues were stained for the histone H1 phosphorylation at threonine 146. Variable staining patterns across tumor grades and subtypes were observed with pT146 labeling correlating with tumor grade. These results establish the potential for histone H1 phosphorylation at threonine 146 as a clinical biomarker in breast cancer. PMID:24601643

2015-01-01

151

Histone H1 phosphorylation in breast cancer.  

PubMed

Breast cancer is the second leading cause of cancer-related deaths in women. The need for new clinical biomarkers in breast cancer is necessary to further predict prognosis and therapeutic response. In this article, the LC-MS histone H1 phosphorylation profiles were established for three distinct breast cancer cell lines. The results show that the extent of H1 phosphorylation can distinguish between the different cell lines. The histone H1 from the metastatic cell line, MDA-MB-231, was subjected to chemical derivitization and LC-MS/MS analysis. The results suggest that the phosphorylation at threonine 146 is found on both histone H1.2 and histone H1.4. Cell lines were then treated with an extracellular stimulus, estradiol or kinase inhibitor LY294002, to monitor changes in histone H1 phosphorylation. The data show that histone H1 phosphorylation can increase and decrease in response to extracellular stimuli. Finally, primary breast tissues were stained for the histone H1 phosphorylation at threonine 146. Variable staining patterns across tumor grades and subtypes were observed with pT146 labeling correlating with tumor grade. These results establish the potential for histone H1 phosphorylation at threonine 146 as a clinical biomarker in breast cancer. PMID:24601643

Harshman, Sean W; Hoover, Michael E; Huang, Chengsi; Branson, Owen E; Chaney, Sarah B; Cheney, Carolyn M; Rosol, Thomas J; Shapiro, Charles L; Wysocki, Vicki H; Huebner, Kay; Freitas, Michael A

2014-05-01

152

The negative impact of ?-ketoglutarate dehydrogenase complex deficiency on matrix substrate-level phosphorylation  

PubMed Central

A decline in ?-ketoglutarate dehydrogenase complex (KGDHC) activity has been associated with neurodegeneration. Provision of succinyl-CoA by KGDHC is essential for generation of matrix ATP (or GTP) by substrate-level phosphorylation catalyzed by succinyl-CoA ligase. Here, we demonstrate ATP consumption in respiration-impaired isolated and in situ neuronal somal mitochondria from transgenic mice with a deficiency of either dihydrolipoyl succinyltransferase (DLST) or dihydrolipoyl dehydrogenase (DLD) that exhibit a 20–48% decrease in KGDHC activity. Import of ATP into the mitochondrial matrix of transgenic mice was attributed to a shift in the reversal potential of the adenine nucleotide translocase toward more negative values due to diminished matrix substrate-level phosphorylation, which causes the translocase to reverse prematurely. Immunoreactivity of all three subunits of succinyl-CoA ligase and maximal enzymatic activity were unaffected in transgenic mice as compared to wild-type littermates. Therefore, decreased matrix substrate-level phosphorylation was due to diminished provision of succinyl-CoA. These results were corroborated further by the finding that mitochondria from wild-type mice respiring on substrates supporting substrate-level phosphorylation exhibited ?30% higher ADP-ATP exchange rates compared to those obtained from DLST+/? or DLD+/? littermates. We propose that KGDHC-associated pathologies are a consequence of the inability of respiration-impaired mitochondria to rely on “in-house” mitochondrial ATP reserves.—Kiss, G., Konrad, C., Doczi, J., Starkov, A. A., Kawamata, H., Manfredi, G., Zhang, S. F., Gibson, G. E., Beal, M. F., Adam-Vizi, V., Chinopoulos, C. The negative impact of ?-ketoglutarate dehydrogenase complex deficiency on matrix substrate-level phosphorylation. PMID:23475850

Kiss, Gergely; Konrad, Csaba; Doczi, Judit; Starkov, Anatoly A.; Kawamata, Hibiki; Manfredi, Giovanni; Zhang, Steven F.; Gibson, Gary E.; Beal, M. Flint; Adam-Vizi, Vera; Chinopoulos, Christos

2013-01-01

153

In the Beginning, There Was Protein Phosphorylation  

PubMed Central

The importance of reversible protein phosphorylation to cellular regulation cannot be overstated. In eukaryotic cells, protein kinase/phosphatase signaling pathways regulate a staggering number of cellular processes, including cell proliferation, cell death (apoptosis, necroptosis, necrosis), metabolism (at both the cellular and organismal levels), behavior and neurological function, development, and pathogen resistance. Although protein phosphorylation as a mode of eukaryotic cell regulation is familiar to most biochemists, many are less familiar with protein kinase/phosphatase signaling networks that function in prokaryotes. In this thematic minireview series, we present four minireviews that cover the important field of prokaryotic protein phosphorylation. PMID:24554697

Kyriakis, John M.

2014-01-01

154

Review: Enzymatic Hydrolysis of Cellulosic Biomass  

SciTech Connect

Biological conversion of cellulosic biomass to fuels and chemicals offers the high yields to products vital to economic success and the potential for very low costs. Enzymatic hydrolysis that converts lignocellulosic biomass to fermentable sugars may be the most complex step in this process due to substrate-related and enzyme-related effects and their interactions. Although enzymatic hydrolysis offers the potential for higher yields, higher selectivity, lower energy costs, and milder operating conditions than chemical processes, the mechanism of enzymatic hydrolysis and the relationship between the substrate structure and function of various glycosyl hydrolase components are not well understood. Consequently, limited success has been realized in maximizing sugar yields at very low cost. This review highlights literature on the impact of key substrate and enzyme features that influence performance to better understand fundamental strategies to advance enzymatic hydrolysis of cellulosic biomass for biological conversion to fuels and chemicals. Topics are summarized from a practical point of view including characteristics of cellulose (e.g., crystallinity, degree of polymerization, and accessible surface area) and soluble and insoluble biomass components (e.g., oligomeric xylan, lignin, etc.) released in pretreatment, and their effects on the effectiveness of enzymatic hydrolysis. We further discuss the diversity, stability, and activity of individual enzymes and their synergistic effects in deconstructing complex lignocellulosic biomass. Advanced technologies to discover and characterize novel enzymes and to improve enzyme characteristics by mutagenesis, post-translational modification, and over-expression of selected enzymes and modifications in lignocellulosic biomass are also discussed.

Yang, Bin; Dai, Ziyu; Ding, Shi-You; Wyman, Charles E.

2011-07-16

155

In Vivo and in Vitro Phosphorylation of Membrane and Soluble Forms of Soybean Nodule Sucrose Synthase1  

PubMed Central

Sucrose synthase (SS) is a known phosphoserine (SerP)-containing enzyme in a variety of plant “sink” organs, including legume root nodules, where it is phosphorylated primarily at Ser-11. Using immunofluorescence confocal microscopy, we documented that part of the total SS (nodulin-100) pool in mature soybean (Glycine max) nodules is apparently associated with the plasma membrane in situ, and we report that this association is very “tight,” as evidenced by a variety of chemical and enzymatic pretreatments of the isolated microsomal fraction. To investigate the in situ and in planta phosphorylation state of the membrane (m) and soluble (s) forms of nodule SS, three complementary approaches were used. First, excised nodules were radiolabeled in situ with [32P]Pi for subsequent analysis of phosphorylated m- and s-SS; second, immunopurified s- and m-SS were used as substrate in “on-bead” assays of phosphorylation by nodule Ca2+-dependent protein kinase; and third, SS-Ser-11(P) phosphopeptide-specific antibodies were developed and used. The collective results provide convincing evidence that microsomal nodulin-100 is phosphorylated in mature nodules, and that it is hypophosphorylated relative to s-SS (on an equivalent SS protein basis) in attached, unstressed nodules. Moreover, the immunological data and related phosphopeptide mapping analyses indicate that a homologous N-terminal seryl-phosphorylation domain and site reside in microsomal nodulin-100. We also observed that mild, short-term inorganic nitrogen and salt stresses have a significant negative impact on the content and N-terminal phosphorylation state of nodule m- and s-SS, with the former being the more sensitive of the two SS forms. PMID:12177479

Komina, Olga; Zhou, You; Sarath, Gautam; Chollet, Raymond

2002-01-01

156

Increased phospholipase A2 activity with phosphorylation of peroxiredoxin 6 requires a conformational change in the protein  

PubMed Central

We have shown previously and confirmed in the present study that the phospholipase A2 (PLA2) activity of peroxiredoxin 6 (Prdx6) is markedly increased by phosphorylation. This report evaluated the conformation and thermodynamic stability of Prdx6 protein after phosphorylation to understand the physical basis for increased activity. Phosphorylation resulted in decreased negative far-UV CD, increased ANS binding, and lack of rigid tertiary structure, compatible with a change in conformation to that of a molten globule. The ?GDo was 3.3 ± 0.3 kcal mol-1 for Prdx6 and 1.7 ± 0.7 kcal mol-1 for pPrdx6 suggesting that phosphorylation destabilizes the protein. Phosphorylation of Prdx6 changed the conformation of the N-terminal domain exposing Trp 33, as determined by tryptophan fluorescence and NaI fluorescence quenching. The kinetics of interaction of proteins with unilamellar liposomes (DPPC/egg PC/cholesterol/PG; 50:25:15:10, mol/mol) was evaluated with tryptophan fluorescence. pPrdx6 bound to liposomes with higher affinity (Kd, 5.6 ± 1.2 ?M) in comparison to Prdx6 (Kd, 24.9 ± 4.5 ?M). By isothermal titration calorimetry, pPrdx6 bound to liposomes with a large exothermic heat loss (?H = -31.49 ± 0.22 kcal mol-1). Correlating our conformation studies with the published crystal structure of oxidized Prdx6 suggests that phosphorylation results in exposure of hydrophobic residues, thereby providing accessibility to the sites for liposome binding. Because binding of the enzyme to the phospholipid substrate interface is a requirement for PLA2 activity, these results indicate that a change in the conformation of Prdx6 upon its phosphorylation is the basis for enhancement of PLA2 enzymatic activity. PMID:22663767

Rahaman, Hamidur; Zhou, Suiping; Dodia, Chandra; Feinstein, Sheldon I.; Huang, Shaohui; Speicher, David; Fisher, Aron B.

2012-01-01

157

ATM-mediated phosphorylation of the chromatin remodeling enzyme BRG1 modulates DNA double-strand break repair.  

PubMed

ATP-dependent chromatin remodeling complexes such as SWI/SNF (SWItch/Sucrose NonFermentable) have been implicated in DNA double-strand break (DSB) repair and damage responses. However, the regulatory mechanisms that control the function of chromatin remodelers in DNA damage response are largely unknown. Here, we show that ataxia telangiectasia mutated (ATM) mediates the phosphorylation of BRG1, the catalytic ATPase of the SWI/SNF complex that contributes to DSB repair by binding ?-H2AX-containing nucleosomes via interaction with acetylated histone H3 and stimulating ?-H2AX formation, at Ser-721 in response to DNA damage. ATM-mediated phosphorylation of BRG1 occurs rapidly and transiently after DNA damage. Phosphorylated BRG1 binds ?-H2AX-containing nucleosomes to form the repair foci. The Ser-721 phosphorylation of BRG1 is critical for binding ?-H2AX-containing nucleosomes and stimulating ?-H2AX formation and DSB repair. BRG1 binds to acetylated H3 peptides much better after phosphorylation at Ser-721 by DNA damage. However, the phosphorylation of Ser-721 does not significantly affect the ATPase and transcriptional activities of BRG1. These results, establishing BRG1 as a novel and functional ATM substrate, suggest that the ATM-mediated phosphorylation of BRG1 facilitates DSB repair by stimulating the association of this remodeler with ?-H2AX nucleosomes via enhancing the affinity to acetylated H3. Our work also suggests that the mechanism of BRG1 stimulation of DNA repair is independent of the remodeler's enzymatic or transcriptional activities. PMID:24413084

Kwon, S-J; Park, J-H; Park, E-J; Lee, S-A; Lee, H-S; Kang, S W; Kwon, J

2015-01-15

158

An infrared radiation based thermal biosensor for enzymatic biochemical reactions.  

PubMed

In this paper, a thermal biosensor based on the infrared radiation energy is proposed for calorimetric measurement of biochemical reactions. Having a good structure design combined with MEMS technology as well as employing the Si /SiGe quantum well sensing material with a high TCR and low 1/f noise, the sensor shows potentials to be high sensitive and real-time. The urea enzymatic reaction was tested to verify the performance of sensor, which demonstrates a linear detection range from 0.5mM to 150mM and a relative standard deviation less than 1%. For the sensor fabrication, wafer-level transfer bonding is a key process, which makes the integration of quantum well material and a free standing structure possible. It reduces the heat loss from the sensor to the surrounding environment. PMID:23365944

Zhang, Lei; Dong, Tao; Zhao, Xinyan; Yang, Zhaochu; Pires, Nuno M M

2012-01-01

159

Efficient enzymatic acrylation through transesterification at controlled water activity.  

PubMed

Enzymatic acrylation is a process of potentially strong interest to the chemical industry. Direct esterification involving acrylic acid is unfortunately rather slow, with inhibition phenomena appearing at high acid concentrations. In the present study the acrylation of 1-octanol catalyzed by immobilized Candida antarctica lipase B (Novozym 435) was shown to be as much as an order of magnitude faster when ethyl acrylate served as the donor of the acrylic group. Water activity is a key parameter for optimizing the rate of ester synthesis. The optimum water activity for the esterification of octanol by acrylic acid was found to be 0.75, that for its esterification by propionic acid to be 0.45 and the transesterification involving ethyl acrylate to be fastest at a water activity of 0.3. The reasons for these differences in optimum water activity are discussed in terms of enzyme specificity, substrate solvation, and mass transfer effects. PMID:17969140

Nordblad, Mathias; Adlercreutz, Patrick

2008-04-15

160

Enzymatic enantioselective decarboxylative protonation of heteroaryl malonates.  

PubMed

The enzyme aryl/alkenyl malonate decarboxylase (AMDase) catalyses the enantioselective decarboxylative protonation (EDP) of a range of disubstituted malonic acids to give homochiral carboxylic acids that are valuable synthetic intermediates. AMDase exhibits a number of advantages over the non-enzymatic EDP methods developed to date including higher enantioselectivity and more environmentally benign reaction conditions. In this report, AMDase and engineered variants have been used to produce a range of enantioenriched heteroaromatic ?-hydroxycarboxylic acids, including pharmaceutical precursors, from readily accessible ?-hydroxymalonates. The enzymatic method described here represents an improvement upon existing synthetic chemistry methods that have been used to produce similar compounds. The relationship between the structural features of these new substrates and the kinetics associated with their enzymatic decarboxylation is explored, which offers further insight into the mechanism of AMDase. PMID:25766433

Lewin, Ross; Goodall, Mark; Thompson, Mark L; Leigh, James; Breuer, Michael; Baldenius, Kai; Micklefield, Jason

2015-04-20

161

Expression and phosphorylation of TOPK during spermatogenesis.  

PubMed

Among normal organs and tissues, the MAPKK-like mitotic protein kinase TOPK is expressed exclusively in the testis. We analyzed the expression and phosphorylation of TOPK to address the functional role of this kinase during spermatogenesis. TOPK protein is expressed mainly in the cytosol of spermatocytes and spermatids, but not in spermatids and spermatogonia in situ. TOPK-Thr-9, a cdk1/cyclin B target residue, was specifically phosphorylated during mitotic and meiotic phases, while TOPK-Thr-198, a key amino acid for the ATP pocket, was constantly phosphorylated irrespective of the cell cycle. These data indicate that spermatogenic germ cells with vital proliferation activity express TOPK. As TOPK-Thr-9 was phosphorylated during both mitosis and meiosis, TOPK was indicted to play a role in cytokinesis and/or chromosomal segregation but not in DNA replication. PMID:16316408

Fujibuchi, Taketsugu; Abe, Yasuhito; Takeuchi, Takashi; Ueda, Norifumi; Shigemoto, Kazuhiro; Yamamoto, Haruyasu; Kito, Katsumi

2005-12-01

162

Phosphorylation based insulation devices design and implementation  

E-print Network

This thesis presents the analysis of a phosphorylation based insulation device implemented in Saccharomyces cerevisae and the minimization of the retroactivity to the input and retroactivity to the output of a single cycle ...

Rivera Ortiz, Phillip M. (Phillip Michael)

2013-01-01

163

Structural Perspective on Enzymatic Halogenation  

PubMed Central

Simple halogen substituents frequently afford key structural features that account for the potency and selectivity of natural products, including antibiotics and hormones. For example, when a single chlorine atom on the antibiotic vancomycin is replaced by hydrogen, the resulting antibacterial activity decreases by up to 70% (HarrisC. M.; KannanR.; KopeckaH.; HarrisT. M.J. Am. Chem. Soc.1985, 107, 6652?6658). This Account analyzes how structure underlies mechanism in halogenases, the molecular machines designed by nature to incorporate halogens into diverse substrates. Traditional synthetic methods of integrating halogens into complex molecules are often complicated by a lack of specificity and regioselectivity. Nature, however, has developed a variety of elegant mechanisms for halogenating specific substrates with both regio- and stereoselectivity. An improved understanding of the biological routes toward halogenation could lead to the development of novel synthetic methods for the creation of new compounds with enhanced functions. Already, researchers have co-opted a fluorinase from the microorganism Streptomyces cattleya to produce 18F-labeled molecules for use in positron emission tomography (PET) (DengH.; CobbS. L.; GeeA. D.; LockhartA.; MartarelloL.; McGlincheyR. P.; O’HaganD.; OnegaM.Chem. Commun.2006, 652?654). Therefore, the discovery and characterization of naturally occurring enzymatic halogenation mechanisms has become an active area of research. The catalogue of known halogenating enzymes has expanded from the familiar haloperoxidases to include oxygen-dependent enzymes and fluorinases. Recently, the discovery of a nucleophilic halogenase that catalyzes chlorinations has expanded the repertoire of biological halogenation chemistry (DongC.; HuangF.; DengH.; SchaffrathC.; SpencerJ. B.; O’HaganD.; NaismithJ. H.Nature2004, 427, 561?56514765200). Structural characterization has provided a basis toward a mechanistic understanding of the specificity and chemistry of these enzymes. In particular, the latest crystallographic snapshots of active site architecture and halide binding sites have provided key insights into enzyme catalysis. Herein is a summary of the five classes of halogenases, focusing on the three most recently discovered: flavin-dependent halogenases, non-heme iron-dependent halogenases, and nucleophilic halogenases. Further, the potential roles of halide-binding sites in determining halide selectivity are discussed, as well as whether or not binding-site composition is always a seminal factor for selectivity. Expanding our understanding of the basic chemical principles that dictate the activity of the halogenases will advance both biology and chemistry. A thorough mechanistic analysis will elucidate the biological principles that dictate specificity, and the application of those principles to new synthetic techniques will expand the utility of halogenations in small-molecule development. PMID:18774824

2008-01-01

164

Hormonal regulation of mitochondrial oxidative phosphorylation  

E-print Network

'g~ (Member) May 1969 ABSTRACT Hormonal Regulation of Mitochondrial Oxidative Phosphorylation (May 1969) Gholam Reza Djavadi, B. A. Johns Hopkins University Directed by: Dr. Igor V. Sarkissian Mitochondria were isolated from 2-1/2 day old wheat shoot...- chondrial oxidative phosphorylation. ACKNOWLEDGMENTS I would like to express my sincere gratitude to the Chairman of my Committee& Dr. Igor V. Sarkissian, under whose direction this research was carried out. I am grateful to him for reasons too many...

Djavadi, Gholam Reza

1969-01-01

165

Enzymatic route to preparative-scale synthesis of UDP-GlcNAc/GalNAc, their analogues and GDP-fucose.  

PubMed

Enzymatic synthesis using glycosyltransferases is a powerful approach to building polysaccharides with high efficiency and selectivity. Sugar nucleotides are fundamental donor molecules in enzymatic glycosylation reactions by Leloir-type glycosyltransferases. The applications of these donors are restricted by their limited availability. In this protocol, N-acetylglucosamine (GlcNAc)/N-acetylgalactosamine (GalNAc) are phosphorylated by N-acetylhexosamine 1-kinase (NahK) and subsequently pyrophosphorylated by N-acetylglucosamine uridyltransferase (GlmU) to give UDP-GlcNAc/GalNAc. Other UDP-GlcNAc/GalNAc analogues can also be prepared depending on the tolerance of these enzymes to the modified sugar substrates. Starting from L-fucose, GDP-fucose is constructed by one bifunctional enzyme L-fucose pyrophosphorylase (FKP) via two reactions. PMID:20224564

Zhao, Guohui; Guan, Wanyi; Cai, Li; Wang, Peng George

2010-04-01

166

Enzymatic route to preparative-scale synthesis of UDP–GlcNAc/GalNAc, their analogues and GDP–fucose  

PubMed Central

Enzymatic synthesis using glycosyltransferases is a powerful approach to building polysaccharides with high efficiency and selectivity. Sugar nucleotides are fundamental donor molecules in enzymatic glycosylation reactions by Leloir-type glycosyltransferases. The applications of these donors are restricted by their limited availability. In this protocol, N-acetylglucosamine (GlcNAc)/N-acetylgalactosamine (GalNAc) are phosphorylated by N-acetylhexosamine 1-kinase (NahK) and subsequently pyrophosphorylated by N-acetylglucosamine uridyltransferase (GlmU) to give UDP–GlcNAc/GalNAc. Other UDP–GlcNAc/GalNAc analogues can also be prepared depending on the tolerance of these enzymes to the modified sugar substrates. Starting from l-fucose, GDP–fucose is constructed by one bifunctional enzyme l-fucose pyrophosphorylase (FKP) via two reactions. PMID:20224564

Zhao, Guohui; Guan, Wanyi; Cai, Li; Wang, Peng George

2010-01-01

167

Protein phosphorylation in neurodegeneration: friend or foe?  

PubMed Central

Protein misfolding and aggregation is a common hallmark in neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), and fronto-temporal dementia (FTD). In these disorders, the misfolding and aggregation of specific proteins occurs alongside neuronal degeneration in somewhat specific brain areas, depending on the disorder and the stage of the disease. However, we still do not fully understand the mechanisms governing protein aggregation, and whether this constitutes a protective or detrimental process. In PD, alpha-synuclein (aSyn) forms protein aggregates, known as Lewy bodies, and is phosphorylated at serine 129. Other residues have also been shown to be phosphorylated, but the significance of phosphorylation in the biology and pathophysiology of the protein is still controversial. In AD and in FTD, hyperphosphorylation of tau protein causes its misfolding and aggregation. Again, our understanding of the precise consequences of tau phosphorylation in the biology and pathophysiology of the protein is still limited. Through the use of a variety of model organisms and technical approaches, we are now gaining stronger insight into the effects of phosphorylation in the behavior of these proteins. In this review, we cover recent findings in the field and discuss how targeting phosphorylation events might be used for therapeutic intervention in these devastating diseases of the nervous system. PMID:24860424

Tenreiro, Sandra; Eckermann, Katrin; Outeiro, Tiago F.

2014-01-01

168

Phosphorylation of human skeletal muscle myosin  

SciTech Connect

Phosphorylation of the P-light chains (phosphorylatable light chains) in human skeletal muscle myosin was studied in vitro and in vivo under resting an d contracted conditions. biopsy samples from rested vastus lateralis muscle of male and female subjects were incubated in oxygenated physiological solution at 30/sup 0/C. Samples frozen following a quiescent period showed the presence of only unphosphorylated P-light chains designated LC2f (light chain two of fast myosin) CL2s and LC2s'(light chains two of slow myosin). Treatment with caffeine (10 mM) or direct electrical stimulation resulted in the appearance of three additional bands which were identified as the phosphorylated forms of the P-light chains i.e. LC2f-P, LC2s-P and LC2s'-P. The presence of phosphate was confirmed by prior incubation with (/sup 30/P) orthophosphate. Muscle samples rapidly frozen from resting vastus lateralis muscle revealed the presence of unphosphorylated and phosphorylated P-light chains in approximately equal ratios. Muscle samples rapidly frozen following a maximal 10 second isometric contraction showed virtually only phosphorylated fast and slow P-light chains. These results reveal that the P-light chains in human fast and slow myosin may be rapidly phosphorylated, but the basal level of phosphorylation in rested human muscle considerably exceeds that observed in animal muscles studied in vitro or in situ.

Houston, M.E.; Lingley, M.D.; Stuart, D.S.; Hoffman-Goetz, L.

1986-03-01

169

Phosphorylation meets nuclear import: a review  

PubMed Central

Phosphorylation is the most common and pleiotropic modification in biology, which plays a vital role in regulating and finely tuning a multitude of biological pathways. Transport across the nuclear envelope is also an essential cellular function and is intimately linked to many degeneration processes that lead to disease. It is therefore not surprising that phosphorylation of cargos trafficking between the cytoplasm and nucleus is emerging as an important step to regulate nuclear availability, which directly affects gene expression, cell growth and proliferation. However, the literature on phosphorylation of nucleocytoplasmic trafficking cargos is often confusing. Phosphorylation, and its mirror process dephosphorylation, has been shown to have opposite and often contradictory effects on the ability of cargos to be transported across the nuclear envelope. Without a clear connection between attachment of a phosphate moiety and biological response, it is difficult to fully understand and predict how phosphorylation regulates nucleocytoplasmic trafficking. In this review, we will recapitulate clue findings in the field and provide some general rules on how reversible phosphorylation can affect the nuclear-cytoplasmic localization of substrates. This is only now beginning to emerge as a key regulatory step in biology. PMID:21182795

2010-01-01

170

Protein phosphorylation: Localization in regenerating optic axons  

SciTech Connect

A number of axonal proteins display changes in phosphorylation during goldfish optic nerve regeneration. (1) To determine whether the phosphorylation of these proteins was closely linked to their synthesis in the retinal ganglion cell body, cycloheximide was injected intraocularly into goldfish whose optic nerves had been regenerating for 3 weeks. Cycloheximide reduced the incorporation of (3H)proline and 32P orthophosphate into total nerve protein by 84% and 46%, respectively. Of the 20 individual proteins examined, 17 contained less than 15% of the (3H)proline label measured in corresponding controls, whereas 18 proteins contained 50% or more of the 32P label, suggesting that phosphorylation was largely independent of synthesis. (2) To determine whether the proteins were phosphorylated in the ganglion cell axons, axonal transport of proteins was blocked by intraocular injection of vincristine. Vincristine reduced (3H)proline labeling of total protein by 88% and 32P labeling by 49%. Among the individual proteins (3H)proline labeling was reduced by 90% or more in 18 cases but 32P labeling was reduced only by 50% or less. (3) When 32P was injected into the cranial cavity near the ends of the optic axons, all of the phosphoproteins were labeled more intensely in the optic tract than in the optic nerve. These results suggest that most of the major phosphoproteins that undergo changes in phosphorylation in the course of regeneration are phosphorylated in the optic axons.

Larrivee, D. (Cornell Univ. Medical College, New York, NY (USA))

1990-09-01

171

Visualizing an ultra-weak protein-protein interaction in phosphorylation signaling.  

PubMed

Proteins interact with each other to fulfill their functions. The importance of weak protein-protein interactions has been increasingly recognized. However, owing to technical difficulties, ultra-weak interactions remain to be characterized. Phosphorylation can take place via a K(D)?25?mM interaction between two bacterial enzymes. Using paramagnetic NMR spectroscopy and with the introduction of a novel Gd(III)-based probe, we determined the structure of the resulting complex to atomic resolution. The structure accounts for the mechanism of phosphoryl transfer between the two enzymes and demonstrates the physical basis for their ultra-weak interaction. Further, molecular dynamics (MD) simulations suggest that the complex has a lifetime in the micro- to millisecond regimen. Hence such interaction is termed a fleeting interaction. From mathematical modeling, we propose that an ultra-weak fleeting interaction enables rapid flux of phosphoryl signal, providing a high effective protein concentration. PMID:25131700

Xing, Qiong; Huang, Peng; Yang, Ju; Sun, Jian-Qiang; Gong, Zhou; Dong, Xu; Guo, Da-Chuan; Chen, Shao-Min; Yang, Yu-Hong; Wang, Yan; Yang, Ming-Hui; Yi, Ming; Ding, Yi-Ming; Liu, Mai-Li; Zhang, Wei-Ping; Tang, Chun

2014-10-20

172

Phosphorylation of Tau by Fyn: Implications for Alzheimer's Disease  

Microsoft Academic Search

The abnormal phosphorylation of tau protein on serines and threonines is a hallmark characteristic of the neurofibrillary tangles of Alzheimer's disease (AD). The discovery that tau could be phosphorylated on tyrosine and evidence that A signal transduction involved tyrosine phosphorylation led us to question whether tyrosine phosphorylation of tau occurred during the neurodegenerative process. In this study we determined that

Gloria Lee; Ramasamy Thangavel; Vandana M. Sharma; Joel M. Litersky; Kiran Bhaskar; Sandy M. Fang; Lana H. Do; Athena Andreadis; Gary Van Hoesen; Hanna Ksiezak-Reding

2004-01-01

173

Caught in the act: the structure of phosphorylated beta-phosphoglucomutase from Lactococcus lactis.  

PubMed

Phosphoglucomutases catalyze the interconversion of D-glucose 1-phosphate and D-glucose 6-phosphate, a reaction central to energy metabolism in all cells and to the synthesis of cell wall polysaccharides in bacterial cells. Two classes of phosphoglucomutases (alpha-PGM and beta-PGM) are distinguished on the basis of their specificity for alpha- and beta-glucose-1-phosphate. beta-PGM is a member of the haloacid dehalogenase (HAD) superfamily, which includes the sarcoplasmic Ca(2+)-ATPase, phosphomannomutase, and phosphoserine phosphatase. beta-PGM is unusual among family members in that the common phosphoenzyme intermediate exists as a stable ground-state complex in this enzyme. Herein we report, for the first time, the three-dimensional structure of a beta-PGM and the first view of the true phosphoenzyme intermediate in the HAD superfamily. The crystal structure of the Mg(II) complex of phosphorylated beta-phosphoglucomutase (beta-PGM) from Lactococcus lactis has been determined to 2.3 A resolution by multiwavelength anomalous diffraction (MAD) phasing on selenomethionine, and refined to an R(cryst) = 0.24 and R(free) = 0.28. The active site of beta-PGM is located between the core and the cap domain and is freely solvent accessible. The residues within a 6 A radius of the phosphorylated Asp8 include Asp10, Thr16, Ser114, Lys145, Glu169, and Asp170. The cofactor Mg(2+) is liganded with octahedral coordination geometry by the carboxylate side chains of Asp8, Glu169, Asp170, and the backbone carbonyl oxygen of Asp10 along with one oxygen from the Asp8-phosphoryl group and one water ligand. The phosphate group of the phosphoaspartyl residue, Asp8, interacts with the side chains of Ser114 and Lys145. The absence of a base residue near the aspartyl phosphate group accounts for the persistence of the phosphorylated enzyme under physiological conditions. Substrate docking shows that glucose-6-P can bind to the active site of phosphorylated beta-PGM in such a way as to position the C(1)OH near the phosphoryl group of the phosphorylated Asp8 and the C(6) phosphoryl group near the carboxylate group of Asp10. This result suggests a novel two-base mechanism for phosphoryl group transfer in a phosphorylated sugar. PMID:12081483

Lahiri, Sushmita D; Zhang, Guofeng; Dunaway-Mariano, Debra; Allen, Karen N

2002-07-01

174

Exploring Potential Energy Surfaces for Enzymatic Reactions  

E-print Network

Exploring Potential Energy Surfaces for Enzymatic Reactions Using QM/MM Calculations Prof. H, and wound healing Related to cancer, inflammation and connective tissue diseases Zinc dependent #12;MMP2. B 2010, 114, 1030 S C O HCCH2 S HH O * #12;Exploring the Potential Energy Surface for KDO8P Synthase

Schlegel, H. Bernhard

175

Heavy metal pollution and soil enzymatic activity  

Microsoft Academic Search

The activity of hydrolytic soil enzymes was studied on spruce mor, polluted with Cu and Zn from a brass foundry in Sweden. Approximately straight regression lines were obtained between enzymatic activity or respiration rate and log Cu+Zn concentration, with highly significant negative regression coefficients for urease and acid phosphatase activity as well as respiration rate, whereas ß-glucosidase activity was not

Germund Tyler

1974-01-01

176

Ultrasonic acceleration of enzymatic processing of cotton  

Technology Transfer Automated Retrieval System (TEKTRAN)

Enzymatic bio-processing of cotton generates significantly less hazardous wastewater effluents, which are readily biodegradable, but it also has several critical shortcomings that impede its acceptance by industries: expensive processing costs and slow reaction rates. It has been found that the intr...

177

Enzymatic hydrolysis of cellulose: theory and applications  

Microsoft Academic Search

A large amount of research has been published on the theory of enzymatic hydrolysis and the various microbial, and other, sources of the enzymes. The present report endeavors to supplement this information by emphasizing insofar as possible the status of the technology and of potential industrial processes for production of sugars from cellulose. A substantial research effort on cellulose conversion

C. R. Wilke; B. Maiorella; A. Sciamanna; K. Tangnu; D. Wiley; H. Wong

1980-01-01

178

Frank Westheimer's Early Demonstration of Enzymatic Specificity  

ERIC Educational Resources Information Center

In this article I review one of the most significant accomplishments of Frank H. Westheimer, one of the most respected chemists of the 20th century. This accomplishment was a series of stereospecific enzymatic oxidation and reduction experiments that led chemists to recognize what we now call the enantiotopic and diastereotopic relationships of…

Ault, Addison

2008-01-01

179

Ethanol from biomass by enzymatic hydrolysis  

SciTech Connect

Enzymes are biological catalysts that generally are designed to do one job well, but to do one job only. Therefore, the enzymes that catalyze the hydrolysis of cellulose to sugar do not break down the sugars. Thus, enzymatic processes are capable of yields approaching 100%. Enzymatic hydrolysis processes have been under development for only 10 years. Although improvements have been made in enzymatic technology, more are both possible and necessary. The important research issues include understanding the processes necessary to render the crystalline cellulose easily digestible, understanding and improving the basic mechanisms in the hydrolysis step, and developing better and less expensive enzymes. The hemicellulose fraction (25%) is primarily composed of xylan, which is simple to convert to the simple sugar xylose, but the xylose is difficult to ferment to ethanol. There were no practical systems for xylose fermentation 10 years ago. Today, methods have been identified using new yeasts, fungi, bacteria, and processes combining enzymes and yeasts. Although none of the fermentations is yet ready for commercial use, considerable progress has been made. The following sections describe current research efforts in each of the major areas (cellulose hydrolysis, xylose fermentation, and lignin conversion), with an emphasis on enzymatic hydrolysis using fungal enzymes.

Wright, J.D.

1988-08-01

180

Phosphorylation of Lipin 1 and Charge on the Phosphatidic Acid Head Group Control Its Phosphatidic Acid Phosphatase Activity and Membrane Association*  

PubMed Central

The lipin gene family encodes a class of Mg2+-dependent phosphatidic acid phosphatases involved in the de novo synthesis of phospholipids and triglycerides. Unlike other enzymes in the Kennedy pathway, lipins are not integral membrane proteins, and they need to translocate from the cytosol to intracellular membranes to participate in glycerolipid synthesis. The movement of lipin 1 within the cell is closely associated with its phosphorylation status. Although cellular analyses have demonstrated that highly phosphorylated lipin 1 is enriched in the cytosol and dephosphorylated lipin 1 is found on membranes, the effects of phosphorylation on lipin 1 activity and binding to membranes has not been recapitulated in vitro. Herein we describe a new biochemical assay for lipin 1 using mixtures of phosphatidic acid (PA) and phosphatidylethanolamine that reflects its physiological activity and membrane interaction. This depends on our observation that lipin 1 binding to PA in membranes is highly responsive to the electrostatic charge of PA. The studies presented here demonstrate that phosphorylation regulates the ability of the polybasic domain of lipin 1 to recognize di-anionic PA and identify mTOR as a crucial upstream signaling component regulating lipin 1 phosphorylation. These results demonstrate how phosphorylation of lipin 1 together with pH and membrane phospholipid composition play important roles in the membrane association of lipin 1 and thus the regulation of its enzymatic activity. PMID:23426360

Eaton, James M.; Mullins, Garrett R.; Brindley, David N.; Harris, Thurl E.

2013-01-01

181

Tyrosine Phosphorylation Modifies Protein Kinase C ?-dependent Phosphorylation of Cardiac Troponin I*  

PubMed Central

Our study identifies tyrosine phosphorylation as a novel protein kinase C? (PKC?) activation mechanism that modifies PKC?-dependent phosphorylation of cardiac troponin I (cTnI), a myofilament regulatory protein. PKC? phosphorylates cTnI at Ser23/Ser24 when activated by lipid cofactors; Src phosphorylates PKC? at Tyr311 and Tyr332 leading to enhanced PKC? autophosphorylation at Thr505 (its activation loop) and PKC?-dependent cTnI phosphorylation at both Ser23/Ser24 and Thr144. The Src-dependent acquisition of cTnI-Thr144 kinase activity is abrogated by Y311F or T505A substitutions. Treatment of detergent-extracted single cardiomyocytes with lipid-activated PKC? induces depressed tension at submaximum but not maximum [Ca2+] as expected for cTnI-Ser23/Ser24 phosphorylation. Treatment of myocytes with Src-activated PKC? leads to depressed maximum tension and cross-bridge kinetics, attributable to a dominant effect of cTnI-Thr144 phosphorylation. Our data implicate PKC?-Tyr311/Thr505 phosphorylation as dynamically regulated modifications that alter PKC? enzymology and allow for stimulus-specific control of cardiac mechanics during growth factor stimulation and oxidative stress. PMID:18550549

Sumandea, Marius P.; Rybin, Vitalyi O.; Hinken, Aaron C.; Wang, Chaojian; Kobayashi, Tomoyoshi; Harleton, Erin; Sievert, Gail; Balke, C. William; Feinmark, Steven J.; Solaro, R. John; Steinberg, Susan F.

2008-01-01

182

The Abnormal Phosphorylation of Tau Protein at Ser202 in Alzheimer Disease Recaptitulates Phosphorylation During Development  

Microsoft Academic Search

Tau is a neuronal phosphoprotein whose expression is developmentally regulated. A single tau isoform is expressed in fetal human brain but six isoforms are expressed in adult brain, with the fetal isoform corresponding to the shortest of the adult isoforms. Phosphorylation of tau is also developmentally regulated, as fetal tau is phosphorylated at more sites than adult tau. In Alzheimer

M. Goedert; R. Jakes; R. A. Crowther; U. Lubke; M. Vandermeeren; P. Cras; J. Q. Trojanowski; V. M.-Y. Lee

1993-01-01

183

Identification of a glucokinase that generates a major glucose phosphorylation activity in the cyanobacterium Synechocystis sp. PCC 6803.  

PubMed

In silico analysis of genome of the cyanobacterium Synechocystis sp. PCC 6803 identified two genes, slr0329 and sll0593, that might participate in glucose (Glc) phosphorylation (www.kazusa.or.jp/cyano). In order to determine the functions of these two genes, we generated deletion mutants, and analyzed their phenotypes and enzymatic activities. In the presence of 10 mM Glc, wild-type (WT) and slr0329 defective strain (M1) grew fast with increased respiratory activity and NADPH production, whereas the sll0593 deletion mutant (M2) failed to show any of the Glc responses. WT and M1 were not significantly different in their glucokinase activity, but M2 had 90% less activity. Therefore, we propose that Sll0593 plays a major role in the phosphorylation of glucose in Synechocystis cells. PMID:15879711

Lee, Jung-Mi; Ryu, Jee-Youn; Kim, Hyong-Ha; Choi, Sang-Bong; de Marsac, Nicole Tandeau; Park, Youn-Il

2005-04-30

184

Nucleotide Release Sequences in the Protein Kinase SRPK1 Accelerate Substrate Phosphorylation  

PubMed Central

Protein kinases are essential signaling enzymes that transfer phosphates from bound ATP to select amino acids in protein targets. For most kinases, the phosphoryl transfer step is highly efficient while the rate-limiting step for substrate processing involves slow release of the product ADP. It is generally thought that structural factors intrinsic to the kinase domain and the nucleotide-binding pocket control this step and consequently the efficiency of protein phosphorylation for these cases. However, the kinase domains of protein kinases are commonly flanked by sequences that regulate catalytic function. To address whether such sequences could alter nucleotide exchange and, thus, regulate protein phosphorylation, the presence of activating residues external to the kinase domain was probed in the serine protein kinase SRPK1. Deletion analyses indicate that a small segment of a large spacer insert domain and a portion of an N-terminal extension function cooperatively to increase nucleotide exchange. The data point to a new mode of protein kinase regulation in which select sequences outside the kinase domain constitute a nucleotide release factor that likely interacts with the small lobe of the kinase domain and enhances protein substrate phosphorylation through increases in ADP dissociation rate. PMID:22839969

Aubol, Brandon E.; Plocinik, Ryan M.; McGlone, Maria L.; Adams, Joseph A.

2012-01-01

185

Protein phosphorylation systems in postmortem human brain  

SciTech Connect

Protein phosphorylation systems regulated by cyclic adenosine 3',5'-monophosphate (cyclic AMP), or calcium in conjunction with calmodulin or phospholipid/diacylglycerol, have been studied by phosphorylation in vitro of particulate and soluble fractions from human postmortem brain samples. One-dimensional or two-dimensional gel electrophoretic protein separations were used for analysis. Protein phosphorylation catalyzed by cyclic AMP-dependent protein kinase was found to be highly active in both particulate and soluble preparations throughout the human CNS, with groups of both widely distributed and region-specific substrates being observed in different brain nuclei. Dopamine-innervated parts of the basal ganglia and cerebral cortex contained the phosphoproteins previously observed in rodent basal ganglia. In contrast, calcium/phospholipid-dependent and calcium/calmodulin-dependent protein phosphorylation systems were less prominent in human postmortem brain than in rodent brain, and only a few widely distributed substrates for these protein kinases were found. Protein staining indicated that postmortem proteolysis, particularly of high-molecular-mass proteins, was prominent in deeply located, subcortical regions in the human brain. Our results indicate that it is feasible to use human postmortem brain samples, when obtained under carefully controlled conditions, for qualitative studies on brain protein phosphorylation. Such studies should be of value in studies on human neurological and/or psychiatric disorders.

Walaas, S.I.; Perdahl-Wallace, E.; Winblad, B.; Greengard, P. (Rockefeller Univ., New York, NY (USA))

1989-01-01

186

Signaling pathways regulating murine cardiac CREB phosphorylation.  

PubMed

Using the mouse Langendorff heart perfusion model, the signaling pathways that regulate cardiac CREB-S133 phosphorylation have been defined. In mouse hearts stimulated with isoproterenol (ISO) (10(-8) M), endothelin-1 (ET-1) (10(-8) M), and phorbol 12-myristate 13-acetate (TPA) (10(-7) M), CREB-S133 phosphorylation was attained only by TPA-treatment. Activation of protein kinase A (PKA) was achieved by ISO. ISO- and ET-1-stimulation activated Ca2+/calmodulin-dependent kinase II (CaMKII). Protein kinase C (PKC) and p90(RSK) were activated with all three stimuli. Inhibition of ERK1/2 with PD98059 (10(-5) M) completely inhibited the activation of p90(RSK), but did not block CREB-S133 phosphorylation in TPA-perfused heart, indicating that PKA, CaMKII, and p90(RSK) do not phosphorylate CREB-S133 in the murine heart. PKC activation is signal specific. Analyses of PKC isoforms suggest that CREB phosphorylation is mediated by PKC epsilon translocating into nucleus only with TPA stimulation. These results, unlike those reported in other tissues, demonstrate that cardiac CREB is not a multi-signal target. PMID:16996475

Li, Bailing; Kaetzel, Marcia A; Dedman, John R

2006-11-10

187

Systematic Discovery of In Vivo Phosphorylation Networks  

PubMed Central

Summary Protein kinases control cellular decision processes by phosphorylating specific substrates. Proteome-wide mapping has identified thousands of in vivo phosphorylation sites. However, systematically resolving which kinase targets each site is presently infeasible, due to the limited specificity of consensus motifs and the potential influence of contextual factors, such as protein scaffolds, localisation and expression, on cellular substrate specificity. We have therefore developed a computational method, NetworKIN, that augments motifs with context for kinases and phosphoproteins. This can pinpoint individual kinases responsible for specific in vivo phosphorylation events and yields a 2.5-fold improvement in the accuracy with which phosphorylation networks can be constructed. We show that context provides 60–80% of the computational capability to assign in vivo substrate specificity. Applying this approach to a DNA damage signalling network, we extend its cell-cycle regulation by showing that 53BP1 is a CDK1 substrate, show that Rad50 is phosphorylated by ATM kinase under genotoxic stress, and suggest novel roles of ATM in apoptosis. Finally, we present a scalable strategy to validate our predictions and use it to support the prediction that BCLAF1 is a GSK3 substrate. PMID:17570479

Linding, Rune; Jensen, Lars Juhl; Ostheimer, Gerard J.; van Vugt, Marcel A.T.M.; Jřrgensen, Claus; Miron, Ioana M.; Diella, Francesca; Colwill, Karen; Taylor, Lorne; Elder, Kelly; Metalnikov, Pavel; Nguyen, Vivian; Pasculescu, Adrian; Jin, Jing; Park, Jin Gyoon; Samson, Leona D.; Woodgett, James R.; Russell, Robert B.; Bork, Peer; Yaffe, Michael B.; Pawson, Tony

2009-01-01

188

Systematic discovery of in vivo phosphorylation networks.  

PubMed

Protein kinases control cellular decision processes by phosphorylating specific substrates. Thousands of in vivo phosphorylation sites have been identified, mostly by proteome-wide mapping. However, systematically matching these sites to specific kinases is presently infeasible, due to limited specificity of consensus motifs, and the influence of contextual factors, such as protein scaffolds, localization, and expression, on cellular substrate specificity. We have developed an approach (NetworKIN) that augments motif-based predictions with the network context of kinases and phosphoproteins. The latter provides 60%-80% of the computational capability to assign in vivo substrate specificity. NetworKIN pinpoints kinases responsible for specific phosphorylations and yields a 2.5-fold improvement in the accuracy with which phosphorylation networks can be constructed. Applying this approach to DNA damage signaling, we show that 53BP1 and Rad50 are phosphorylated by CDK1 and ATM, respectively. We describe a scalable strategy to evaluate predictions, which suggests that BCLAF1 is a GSK-3 substrate. PMID:17570479

Linding, Rune; Jensen, Lars Juhl; Ostheimer, Gerard J; van Vugt, Marcel A T M; Jřrgensen, Claus; Miron, Ioana M; Diella, Francesca; Colwill, Karen; Taylor, Lorne; Elder, Kelly; Metalnikov, Pavel; Nguyen, Vivian; Pasculescu, Adrian; Jin, Jing; Park, Jin Gyoon; Samson, Leona D; Woodgett, James R; Russell, Robert B; Bork, Peer; Yaffe, Michael B; Pawson, Tony

2007-06-29

189

Synthesis and enzymatic properties of deoxyribooligonucleotides containing methyl and phenylphosphonate linkages.  

PubMed Central

Chemical methods for the synthesis of short deoxyribooligonucleotides containing methyl and phenylphosphonodiester linkages have been developed. The interaction of two such nonionic dinucleotide analogs, T(pCH3)T and T(pC6H5)T, with several enzymes has been investigated. Because of the phosphonate linkage each dinucleotide exists as a diastereomeric pair as shown by thin layer chromatography and enzymatic studies. Both isomers of each dinucleotide can be phosphorylated by T4-polynucleotide kinase in the presence of [gamma-32P]ATP. Only one of the diastereoisomers of each dinucleotide is slowly hydrolyzed by snake venom phosphodiesterase and acts as an inhibitor of the enzyme-catalyzed hydrolysis of 5'-labeled oligothymidylic acid. Both isomers of each dinucleotide analog are completely resistant to hydrolysis by spleen phosphodiesterase. Images PMID:226943

Agarwal, K L; Riftina, F

1979-01-01

190

Transfer form  

Cancer.gov

10/02 Transfer Investigational Agent Form This form is to be used for an intra-institutional transfer, one transfer/form. Division of Cancer Prevention National Cancer Institute National Institutes of Health TRANSFER FROM: Investigator transferring agent:

191

Focus Issue: Systems Analysis of Protein Phosphorylation  

NSDL National Science Digital Library

Kinases and phosphatases are key regulatory molecules that participate in most cell signaling pathways. Systems-level analyses are providing new insights into phosphorylation sites and kinase specificity, and phosphoproteomic analyses are creating not just a wealth of data, but are also revealing rich revelations about cellular behavior, cellular responses to changing environmental conditions, and mechanisms of disease. Phosphatases are not merely signal terminators, but play active roles in signal transduction and are especially important in redox signaling. In this Focus Issue, Science Signaling highlights protein phosphorylation as the center of the signaling universe.

Nancy R. Gough (American Association for the Advancement of Science; Science Signaling REV)

2010-08-31

192

Studies on the Relationship Between Cerebral Glucose Transport and Phosphorylation Using 2Deoxyglucose  

Microsoft Academic Search

Summary: Regional rates of blood-brain glucose transfer and phosphorylation have been measured in anaesthetized fasted and conscious fed and fasted rats using a dual-label 2-deoxyglucose technique that exploits differences in the early-time distribution of analogue and native glucose between blood and brain. Regional cerebral blood flow was also measured in comparable groups of rats. Estimates of glucose influx in the

Richard J. Hargreaves; Anna M. Planas; Jill E. Cremer; Vincent J. Cunningham

1986-01-01

193

Dynamic Simulation of Mitochondrial Respiration and Oxidative Phosphorylation: Comparison with Experimental Results  

Microsoft Academic Search

Hypoxia hampers ATP production and threatens cell survival. Since cellular energetics tightly controls cell responses and\\u000a fate, ATP levels and dynamics are of utmost importance. An integrated mathematical model of ATP synthesis by the mitochondrial\\u000a oxidative phosphorylation\\/electron transfer chain system has been recently published (Beard, PLoS Comput Biol 1(4):e36, 2005).\\u000a This model was validated under static conditions. To evaluate its

François Guillaud; Patrick Hannaert

2008-01-01

194

Biofunctional Properties of Enzymatic Squid Meat Hydrolysate  

PubMed Central

Squid is one of the most important commercial fishes in the world and is mainly utilized or consumed as sliced raw fish or as processed products. The biofunctional activities of enzymatic squid meat hydrolysate were determined to develop value-added products. Enzymatic squid hydrolysate manufactured by Alcalase effectively quenched 1,1-diphenyl-2-picrylhydrazyl radical, hydroxyl radical, and hydrogen peroxide radical with IC50 values of 311, 3,410, and 111.5 ?g/mL, respectively. Angiotensin I-converting enzyme inhibitory activity of squid hydrolysate was strong with an IC50 value of 145.1 ?g/mL, while tyrosinase inhibitory activity with an IC50 value of 4.72 mg/mL was moderately low. Overall, squid meat hydrolysate can be used in food or cosmetic industries as a bioactive ingredient and possibly be used in the manufacture of seasoning, bread, noodle, or cosmetics.

Choi, Joon Hyuk; Kim, Kyung-Tae; Kim, Sang Moo

2015-01-01

195

Enzymatic intracrine regulation of white adipose tissue  

PubMed Central

Abdominal fat formation has become a permanent risk factor for metabolic syndrome and various cancers in one-third of the world's population of obese and even lean patients. Formation of abdominal fat involves additional mechanisms beyond an imbalance in energy intake and expenditure, which explains systemic obesity. In this review, we briefly summarized autonomous regulatory circuits that locally produce hormones from inactive precursors or nutrients for intra-/auto-/paracrine signaling in white adipose depots. Enzymatic pathways activating steroid and thyroid hormones in adipose depots were compared with enzymatic production of retinoic acid from vitamin A. We discussed the role of intracrine circuits in fat-depot functions and strategies to reduce abdominal adiposity through thermogenic adipocytes with interrupted generation of retinoic acid. PMID:25390015

DiSilvestro, David; Petrosino, Jennifer; Aldoori, Ayat; Melgar-Bermudez, Emiliano; Wells, Alexandra; Ziouzenkova, Ouliana

2015-01-01

196

Biofunctional properties of enzymatic squid meat hydrolysate.  

PubMed

Squid is one of the most important commercial fishes in the world and is mainly utilized or consumed as sliced raw fish or as processed products. The biofunctional activities of enzymatic squid meat hydrolysate were determined to develop value-added products. Enzymatic squid hydrolysate manufactured by Alcalase effectively quenched 1,1-diphenyl-2-picrylhydrazyl radical, hydroxyl radical, and hydrogen peroxide radical with IC50 values of 311, 3,410, and 111.5 ?g/mL, respectively. Angiotensin I-converting enzyme inhibitory activity of squid hydrolysate was strong with an IC50 value of 145.1 ?g/mL, while tyrosinase inhibitory activity with an IC50 value of 4.72 mg/mL was moderately low. Overall, squid meat hydrolysate can be used in food or cosmetic industries as a bioactive ingredient and possibly be used in the manufacture of seasoning, bread, noodle, or cosmetics. PMID:25866752

Choi, Joon Hyuk; Kim, Kyung-Tae; Kim, Sang Moo

2015-03-01

197

Enzymatically Triggered Actuation of Miniaturized Tools  

PubMed Central

We demonstrate a methodology that utilizes the specificity of enzyme-substrate biomolecular interactions to trigger miniaturized tools under biocompatible conditions. Miniaturized grippers were constructed using multilayer hinges that employed intrinsic strain energy and biopolymer triggers, as well as ferromagnetic elements. This composition obviated the need for external energy sources, and allowed for remote manipulation of the tools. Selective enzymatic degradation of biopolymer hinge components triggered closing of the grippers; subsequent reopening was achieved with an orthogonal enzyme. We highlight the utility of these enzymatically triggered tools by demonstrating the biopsy of liver tissue from a model organ system and gripping and releasing an alginate bead. This strategy suggests an approach for the development of smart materials and devices that autonomously reconfigure in response to extremely specific biological environments. PMID:20849106

Bassik, Noy; Brafman, Alla; Zarafshar, Aasiyeh M.; Jamal, Mustapha; Luvsanjav, Delgermaa; Selaru, Florin M.; Gracias, David H.

2010-01-01

198

Structural characterization of cellulose with enzymatic treatment  

NASA Astrophysics Data System (ADS)

Different cellulosic materials were treated with different extraceller microbial enzymes. Changes in structure and properties of the cellulose caused by enzymatic treatment depend on the composition, the type of enzyme and the type of cellulosic materials. Both endoglucanase and crude cellulase have pronounced effects on the degree of polymerization and the structure of cellulose. The variation of supramolecular structure was found to wide variations in conformation caused by the change of the hydrogen bonding energy.

Cao, Yu; Tan, Huimin

2004-11-01

199

Effects of agitation on particle-size distribution and enzymatic hydrolysis of pretreated spruce and giant reed  

PubMed Central

Background Mixing is an energy demanding process which has been previously shown to affect enzymatic hydrolysis. Concentrated biomass slurries are associated with high and non-Newtonian viscosities and mixing in these systems is a complex task. Poor mixing can lead to mass and/or heat transfer problems as well as inhomogeneous enzyme distribution, both of which can cause possible yield reduction. Furthermore the stirring energy dissipation may impact the particle size which in turn may affect the enzymatic hydrolysis. The objective of the current work was to specifically quantify the effects of mixing on particle-size distribution (PSD) and relate this to changes in the enzymatic hydrolysis. Two rather different materials were investigated, namely pretreated Norway spruce and giant reed. Results Changes in glucan hydrolysis and PSD were measured as a function of agitation during enzymatic hydrolysis at fiber loadings of 7 or 13% water-insoluble solids (WIS). Enzymatic conversion of pretreated spruce was strongly affected by agitation rates at the higher WIS content. However, at low WIS content the agitation had almost no effect on hydrolysis. There was some effect of agitation on the hydrolysis of giant reed at high WIS loading, but it was smaller than that for spruce, and there was no measurable effect at low WIS loading. In the case of spruce, intense agitation clearly affected the PSD and resulted in a reduced mean particle size, whereas for giant reed the decrease in particle size was mainly driven by enzymatic action. However, the rate of enzymatic hydrolysis was not increased after size reduction by agitation. Conclusions The impact of agitation on the enzymatic hydrolysis clearly depends not only on feedstock but also on the solids loading. Agitation was found to affect the PSD differently for the examined pretreated materials spruce and giant reed. The fact that the reduced mean particle diameter could not explain the enhanced hydrolysis rates found for spruce at an elevated agitation suggests that mass transfer at sustained high viscosities plays an important role in determining the rate of enzymatic hydrolysis. PMID:24920958

2014-01-01

200

Enzymatic transformation of nonfood biomass to starch.  

PubMed

The global demand for food could double in another 40 y owing to growth in the population and food consumption per capita. To meet the world's future food and sustainability needs for biofuels and renewable materials, the production of starch-rich cereals and cellulose-rich bioenergy plants must grow substantially while minimizing agriculture's environmental footprint and conserving biodiversity. Here we demonstrate one-pot enzymatic conversion of pretreated biomass to starch through a nonnatural synthetic enzymatic pathway composed of endoglucanase, cellobiohydrolyase, cellobiose phosphorylase, and alpha-glucan phosphorylase originating from bacterial, fungal, and plant sources. A special polypeptide cap in potato alpha-glucan phosphorylase was essential to push a partially hydrolyzed intermediate of cellulose forward to the synthesis of amylose. Up to 30% of the anhydroglucose units in cellulose were converted to starch; the remaining cellulose was hydrolyzed to glucose suitable for ethanol production by yeast in the same bioreactor. Next-generation biorefineries based on simultaneous enzymatic biotransformation and microbial fermentation could address the food, biofuels, and environment trilemma. PMID:23589840

You, Chun; Chen, Hongge; Myung, Suwan; Sathitsuksanoh, Noppadon; Ma, Hui; Zhang, Xiao-Zhou; Li, Jianyong; Zhang, Y-H Percival

2013-04-30

201

Enzymatic transformation of nonfood biomass to starch  

PubMed Central

The global demand for food could double in another 40 y owing to growth in the population and food consumption per capita. To meet the world’s future food and sustainability needs for biofuels and renewable materials, the production of starch-rich cereals and cellulose-rich bioenergy plants must grow substantially while minimizing agriculture’s environmental footprint and conserving biodiversity. Here we demonstrate one-pot enzymatic conversion of pretreated biomass to starch through a nonnatural synthetic enzymatic pathway composed of endoglucanase, cellobiohydrolyase, cellobiose phosphorylase, and alpha-glucan phosphorylase originating from bacterial, fungal, and plant sources. A special polypeptide cap in potato alpha-glucan phosphorylase was essential to push a partially hydrolyzed intermediate of cellulose forward to the synthesis of amylose. Up to 30% of the anhydroglucose units in cellulose were converted to starch; the remaining cellulose was hydrolyzed to glucose suitable for ethanol production by yeast in the same bioreactor. Next-generation biorefineries based on simultaneous enzymatic biotransformation and microbial fermentation could address the food, biofuels, and environment trilemma. PMID:23589840

You, Chun; Chen, Hongge; Myung, Suwan; Sathitsuksanoh, Noppadon; Ma, Hui; Zhang, Xiao-Zhou; Li, Jianyong; Zhang, Y.-H. Percival

2013-01-01

202

Dynamics of human keratin 18 phosphorylation: polarized distribution of phosphorylated keratins in simple epithelial tissues  

PubMed Central

Phosphorylation of keratin polypeptides 8 and 18 (K8/18) and other intermediate filament proteins results in their reorganization in vitro and in vivo. In order to study functional aspects of human K18 phosphorylation, we generated and purified a polyclonal antibody (termed 3055) that specifically recognizes a major phosphorylation site (ser52) of human K18 but not dephosphorylated K18 or a ser52-->ala K18 mutant. Pulse-chase experiments followed by immunoprecipitation and peptide mapping of in vivo 32PO4-labeled K8/18 indicated that the overall phosphorylation turnover rate is faster for K18 versus K8, and that ser52 of K18 is a highly dynamic phosphorylation site. Isoelectric focusing of 32PO4 labeled K18 followed by immunoblotting with 3055 showed that the major phosphorylated K18 species contain ser52 phosphorylation but that some K18 molecules exist that are preferentially phosphorylated on K18 sites other than ser52. Immunoblotting of total cell lysates obtained from cells at different stages of the cell cycle showed that ser52 phosphorylation increases three to fourfold during the S and G2/M phases of the cell cycle. Immunofluorescence staining of cells at different stages of mitosis, using 3055 or other antibodies that recognize the total keratin pool, resulted in preferential binding of the 3055 antibody to the reorganized keratin fraction. Staining of human tissues or tissues from transgenic mice that express human K18 showed that the phospho-ser52 K18 species are located preferentially in the basolateral and apical domains in the liver and pancreas, respectively, but no preferential localization was noted in other simple epithelial organs examined. Our results support a model whereby phosphorylated intermediate filaments are localized in specific cellular domains depending on the tissue type and site(s) of phosphorylation. In addition, ser52 of human K18 is a highly dynamic phosphorylation site that undergoes modulation during the S and G2/M phases of the cell cycle in association with filament reorganization. PMID:8522590

1995-01-01

203

Kinetics of PCr to ATP and ?-ATP to ?-ADP phosphoryl conversion are modified in working rat skeletal muscle after training  

Microsoft Academic Search

Kinetics of phosphoryl transfers from PCr to ?-ATP and from ?-ATP to ?-ADP were measured by magnetization transfer in an in\\u000a vivo31P NMR experiment in working rat skeletal hind leg muscles. Two groups were examined. One group was submitted to a 6-week training\\u000a program of treadmill running. The other group was composed of sedentary animals. Metabolic oxidative capacity and mechanical

Xavier Ravalec; Nathalie Le Tallec; François Carré; Jacques D. de Certaines; Elisabeth Le Rumeur

1999-01-01

204

Herpes Simplex Virus 1 Protein Kinase Us3 Phosphorylates Viral dUTPase and Regulates Its Catalytic Activity in Infected Cells  

PubMed Central

Us3 is a serine-threonine protein kinase encoded by herpes simplex virus 1 (HSV-1). In this study, a large-scale phosphoproteomic analysis of titanium dioxide affinity chromatography-enriched phosphopeptides from HSV-1-infected cells using high-accuracy mass spectrometry (MS) and subsequent analyses showed that Us3 phosphorylated HSV-1-encoded dUTPase (vdUTPase) at serine 187 (Ser-187) in HSV-1-infected cells. Thus, the following observations were made. (i) In in vitro kinase assays, Ser-187 in the vdUTPase domain was specifically phosphorylated by Us3. (ii) Phosphorylation of vdUTPase Ser-187 in HSV-1-infected cells was detected by phosphate-affinity polyacrylamide gel electrophoresis analyses and was dependent on the kinase activity of Us3. (iii) Replacement of Ser-187 with alanine (S187A) in vdUTPase and an amino acid substitution in Us3 that inactivated its kinase activity significantly downregulated the enzymatic activity of vdUTPase in HSV-1-infected cells, whereas a phosphomimetic substitution at vdUTPase Ser-187 restored the wild-type enzymatic activity of vdUTPase. (iv) The vdUTPase S187A mutation as well as the kinase-dead mutation in Us3 significantly reduced HSV-1 replication in human neuroblastoma SK-N-SH cells at a multiplicity of infection (MOI) of 5 but not at an MOI of 0.01, whereas the phosphomimetic substitution at vdUTPase Ser-187 restored the wild-type viral replication at an MOI of 5. In contrast, these mutations had no effect on HSV-1 replication in Vero and HEp-2 cells. Collectively, our results suggested that Us3 phosphorylation of vdUTPase Ser-187 promoted HSV-1 replication in a manner dependent on cell types and MOIs by regulating optimal enzymatic activity of vdUTPase. PMID:24173231

Kato, Akihisa; Tsuda, Shumpei; Liu, Zhuoming; Kozuka-Hata, Hiroko; Oyama, Masaaki

2014-01-01

205

A quantitative method for measuring protein phosphorylation  

Microsoft Academic Search

We have developed a novel method for quantitating protein phosphorylation by a variety of protein kinases. It can be used with purified kinases and their substrates in vitro or in combination with cell extracts. The method is based on the knowledge that protein kinase C (PKC) adds three phosphates to each molecule of its preferred substrate, myelin basic protein (MBP).

J. Andres Mckenzie; Phyllis R. Strauss

2003-01-01

206

APP processing is regulated by cytoplasmic phosphorylation  

Microsoft Academic Search

myloid- ? peptide (A ? ) aggregate in senile plaque is a key characteristic of Alzheimer's disease (AD). Here, we show that phosphorylation of amyloid precursor protein (APP) on threonine 668 (P-APP) may play a role in APP metabolism. In AD brains, P-APP accumulates in large vesicular structures in afflicted hippocampal pyramidal neurons that costain with antibodies against endosome markers

Ming-Sum Lee; Shih-Chu Kao; Cynthia A. Lemere; Weiming Xia; Huang-Chun Tseng; Ying Zhou; Rachael Neve; Michael K. Ahlijanian; Li-Huei Tsai

2003-01-01

207

Dynamics of protein phosphorylation during meiotic maturation  

PubMed Central

Purpose To ask whether distinct kinase signaling pathways mediate cytoplasmic or nuclear maturation of mouse oocytes and if in vitro maturation influences the distribution and timing of these phosphorylation events. Methods Mouse cumulus oocyte complexes (COCs) were matured under conditions known to influence oocyte quality (basal or supplemented media) and assayed with epitope specific antibodies that would distinguish between Cdk1 or tyrosine kinase targets at 0, 2, 4, 8, and 16 hrs. Semi-quantitative image analysis was used to assess the topographical patterns of protein phosphorylation during in vitro maturation. In vitro fertization and embryo culture were used to examine the effects of culture conditions on developmental potential. Results Protein tyrosine phosphorylation increased during meiotic progression from methaphase-I to metaphase-II. Levels were significantly higher in the oocyte cortex. Levels of cortical staining are enhanced in oocytes matured in supplemented media that displayed higher developmental competence. In contrast, bulk substrates for Cdk1 kinase localize to the meiotic spindle while cytoplasmic levels of kinase activity increase throughout meiotic progression; culture media had no measurable effect. Ablation of the tyrosine kinase Fyn significantly reduced cortical levels of tyrosine phosphorylation. Conclusions The findings indicate that distinct signaling pathways mediate nuclear and cytoplasmic maturation during in vitro maturation in a fashion consistent with a role for tyrosine kinases in cortical maturation and oocyte quality. PMID:20174967

Albertini, David F.

2010-01-01

208

Phosphorylation of FMRP inhibits association with Dicer.  

PubMed

Fragile X syndrome is caused by an absence of the protein product of the fragile X mental retardation gene (FMR1). The fragile X mental retardation protein (FMRP) is an RNA-binding protein that regulates translation of associated mRNAs; however, the mechanism for this regulation remains unknown. Constitutively, phosphorylated FMRP (P-FMRP) is found associated with stalled untranslating polyribosomes, and translation of at least one mRNA is down-regulated when FMRP is phosphorylated. Based on our hypothesis that translational regulation by P-FMRP is accomplished through association with the microRNA (miRNA) pathway, we developed a phospho-specific antibody to P-FMRP and showed that P-FMRP associates with increased amounts of precursor miRNAs (pre-miRNA) compared with total FMRP. Furthermore, P-FMRP does not associate with Dicer or Dicer-containing complexes in coimmunoprecipitation experiments or in an in vitro capture assay using a P-FMRP peptide sequence bound to agarose beads. These data show that Dicer-containing complexes bind FMRP at amino acids 496-503 and that phosphorylation disrupts this association with a consequent increase in association with pre-miRNAs. In sum, we propose that in addition to regulating translation, phosphorylation of FMRP regulates its association with the miRNA pathway by modulating association with Dicer. PMID:19155329

Cheever, Anne; Ceman, Stephanie

2009-03-01

209

Phosphorylation of FMRP inhibits association with Dicer  

PubMed Central

Fragile X syndrome is caused by an absence of the protein product of the fragile X mental retardation gene (FMR1). The fragile X mental retardation protein (FMRP) is an RNA-binding protein that regulates translation of associated mRNAs; however, the mechanism for this regulation remains unknown. Constitutively, phosphorylated FMRP (P-FMRP) is found associated with stalled untranslating polyribosomes, and translation of at least one mRNA is down-regulated when FMRP is phosphorylated. Based on our hypothesis that translational regulation by P-FMRP is accomplished through association with the microRNA (miRNA) pathway, we developed a phospho-specific antibody to P-FMRP and showed that P-FMRP associates with increased amounts of precursor miRNAs (pre-miRNA) compared with total FMRP. Furthermore, P-FMRP does not associate with Dicer or Dicer-containing complexes in coimmunoprecipitation experiments or in an in vitro capture assay using a P-FMRP peptide sequence bound to agarose beads. These data show that Dicer-containing complexes bind FMRP at amino acids 496–503 and that phosphorylation disrupts this association with a consequent increase in association with pre-miRNAs. In sum, we propose that in addition to regulating translation, phosphorylation of FMRP regulates its association with the miRNA pathway by modulating association with Dicer. PMID:19155329

Cheever, Anne; Ceman, Stephanie

2009-01-01

210

RESEARCH COMMUNICATION Phosphorylation of histone H3  

E-print Network

and control of gene expression contain domains that se- lectively bind covalently modified histone N). The expression of a large number of genes from organisms across the phylogenetic scale correlates with histone histone acetylation and phosphorylation in Dro- sophila transgenes activated by the yeast Gal4 transcrip

211

Mitochondrial DNA & Oxidative Phosphorylation ATP SYNTHASE  

E-print Network

Mitochondrial DNA & Oxidative Phosphorylation 2 proteins ATP SYNTHASE COMPLEX IV COMPLEX IIICOMPLEX II COMPLEX I 1 protein 3 proteins Human mitochondrial DNA 7 proteins #12;Replication Organisation Segregation The mtDNA Troika #12;Replication Organisation Segregation The mtDNA Troika #12;Mitochondrial (DNA

Schnaufer, Achim

212

FADD phosphorylation impaired islet morphology and function.  

PubMed

Previous studies have indicated that Fas-FasL pathway and its downstream caspase-8 can regulate islet mass and insulin secretion. As a classical adaptor in Fas-FasL signaling, Fas-associated death domain-containing protein (FADD) takes part in many non-apoptosis processes regulated by its phosphorylation. However, its role in islets has not been evaluated to date. Here, through comparative proteomics and bioinformatic analysis on FADD phosphorylated (FADD-D) and wild-type (WT) MEFs, we found three proteins involved in islet differentiation and function were dysregulated due to FADD phosphorylation. The mouse model of FADD-D, which mimics constitutive phosphorylated FADD expression in mice, was further analyzed to address this issue. We confirmed the proteomic results by immunohistological analyses on pancreatic islets. In addition, we found that FADD-D mice displayed decreased islet area, and the glucose stimulated insulin secretion (GSIS) of FADD-D islets was impaired. These data suggest a novel role of FADD in islet development and insulin secretion. J. Cell. Physiol. 230: 1448-1456, 2015. © 2015 Wiley Periodicals, Inc., A Wiley Company. PMID:25641109

Yao, Chun; Zhuang, Hongqin; Cheng, Wei; Lin, Yan; Du, Pan; Yang, Bingya; Huang, Xiaofeng; Chen, Sheng; Hu, Qingang; Hua, Zi-Chun

2015-07-01

213

Post-Translational Phosphorylation of Serine 74 of Human Deoxycytidine Kinase Favors the Enzyme Adopting the Open Conformation Making It Competent for Nucleoside Binding and Release  

SciTech Connect

Deoxycytidine kinase (dCK) uses either ATP or UTP as a phosphoryl donor to catalyze the phosphorylation of nucleoside acceptors. The kinetic properties of human dCK are modulated in vivo by phosphorylation of serine 74. This residue is a part of the insert region and is distant from the active site. Replacing the serine with a glutamic acid (S74E variant) can mimic phosphorylation of Ser74. To understand how phosphorylation affects the catalytic properties of dCK, we examined the S74E variant of dCK both structurally and kinetically. We observe that the presence of a glutamic acid at position 74 favors the adoption by the enzyme of the open conformation. Glu74 stabilizes the open conformation by directly interacting with the indole side chain of Trp58, a residue that is in the proximity of the base of the nucleoside substrate. The open dCK conformation is competent for the binding of nucleoside but not for phosphoryl transfer. In contrast, the closed conformation is competent for phosphoryl transfer but not for product release. Thus, dCK must make the transition between the open and closed states during the catalytic cycle. We propose a reaction scheme for dCK that incorporates the transition between the open and closed states, and this serves to rationalize the observed kinetic differences between wild-type dCK and the S74E variant.

Hazra, Saugata; Szewczak, Andrzej; Ort, Stephan; Konrad, Manfred; Lavie, Arnon (UIC); (MXPL-G)

2012-03-26

214

Bacillus subtilis Two-Component System Sensory Kinase DegS Is Regulated by Serine Phosphorylation in Its Input Domain  

PubMed Central

Bacillus subtilis two-component system DegS/U is well known for the complexity of its regulation. The cytosolic sensory kinase DegS does not receive a single predominant input signal like most two-component kinases, instead it integrates a wide array of metabolic inputs that modulate its activity. The phosphorylation state of the response regulator DegU also does not confer a straightforward “on/off” response; it is fine-tuned and at different levels triggers different sub-regulons. Here we describe serine phosphorylation of the DegS sensing domain, which stimulates its kinase activity. We demonstrate that DegS phosphorylation can be carried out by at least two B. subtilis Hanks-type kinases in vitro, and this stimulates the phosphate transfer towards DegU. The consequences of this process were studied in vivo, using phosphomimetic (Ser76Asp) and non-phosphorylatable (Ser76Ala) mutants of DegS. In a number of physiological assays focused on different processes regulated by DegU, DegS S76D phosphomimetic mutant behaved like a strain with intermediate levels of DegU phosphorylation, whereas DegS S76A behaved like a strain with lower levels of DegU phophorylation. These findings suggest a link between DegS phosphorylation at serine 76 and the level of DegU phosphorylation, establishing this post-translational modification as an additional trigger for this two-component system. PMID:21304896

Jers, Carsten; Kobir, Ahasanul; Sřndergaard, Elsebeth Oline; Jensen, Peter Ruhdal; Mijakovic, Ivan

2011-01-01

215

Functional Interplay between Caspase Cleavage and Phosphorylation Sculpts  

E-print Network

Resource Functional Interplay between Caspase Cleavage and Phosphorylation Sculpts the Apoptotic proteolysis. We find that caspase cleavage can expose new sites for phosphorylation, and, conversely, that phosphor- ylation at the +3 position of cleavage sites can directly promote substrate proteolysis

Cravatt, Benjamin

216

Protein Synthesis Initiation Factors: Phosphorylation and Regulation  

SciTech Connect

The initiation of the synthesis of proteins is a fundamental process shared by all living organisms. Each organism has both shared and unique mechanisms for regulation of this vital process. Higher plants provide for a major amount of fixation of carbon from the environment and turn this carbon into food and fuel sources for our use. However, we have very little understanding of how plants regulate the synthesis of the proteins necessary for these metabolic processes. The research carried out during the grant period sought to address some of these unknowns in the regulation of protein synthesis initiation. Our first goal was to determine if phosphorylation plays a significant role in plant initiation of protein synthesis. The role of phosphorylation, although well documented in mammalian protein synthesis regulation, is not well studied in plants. We showed that several of the factors necessary for the initiation of protein synthesis were targets of plant casein kinase and showed differential phosphorylation by the plant specific isoforms of this kinase. In addition, we identified and confirmed the phosphorylation sites in five of the plant initiation factors. Further, we showed that phosphorylation of one of these factors, eIF5, affected the ability of the factor to participate in the initiation process. Our second goal was to develop a method to make initiation factor 3 (eIF3) using recombinant methods. To date, we successfully cloned and expressed 13/13 subunits of wheat eIF3 in E. coli using de novo gene construction methods. The final step in this process is to place the subunits into three different plasmid operons for co-expression. Successful completion of expression of eIF3 will be an invaluable tool to the plant translation community.

Karen S. Browning

2009-06-15

217

Recycling of platelet phosphorylation and cytoskeletal assembly.  

PubMed

The shape change and aggregation of washed platelets induced by 10 microM arachidonic acid (AA) can be reversed by 20 ng/ml prostacyclin (PGI2), but these platelets can be reactivated by treatment with 30 microM epinephrine and subsequent addition of 10 microM AA mixture. These events may be modulated by cAMP since 2 mM dibutyryl cAMP also reversed activation without reactivation by epinephrine and AA. We examined protein phosphorylation and formation of cytoskeletal cores resistant to 1% Triton X-100 extraction of these platelets and correlated these processes with aggregation, fibrinogen binding, and changes in ultrastructure. Unactivated platelet cores contained less than 15% of the total actin and no detectable myosin or actin-binding protein. AA-induced cytoskeletal cores, which contained 60-80% of the total actin, myosin, and actin-binding protein as the major components, were disassembled back to unactivated levels by PGI2 and then fully reassembled by epinephrine and AA. Phosphorylation of myosin light chain and a 40,000-dalton protein triggered by AA (two- to fivefold) was reversed to basal levels by PGI2 but was completely restored to peak levels upon addition of the epinephrine and AA mixture. The reversibility of actin-binding protein phosphorylation could not be established clearly because both PGI2 and dibutyryl cAMP caused its phosphorylation independent of activation. With this possible exception, cytoskeletal assembly with associated protein phosphorylation, aggregation, fibrinogen binding, and changes in ultrastructure triggered by activation are readily and concertedly recyclable. PMID:6423649

Cox, A C; Carroll, R C; White, J G; Rao, G H

1984-01-01

218

PKA regulates calcineurin function through the phosphorylation of RCAN1: Identification of a novel phosphorylation site.  

PubMed

Calcineurin is a calcium/calmodulin-dependent phosphatase that has been implicated in T cell activation through the induction of nuclear factors of activated T cells (NFAT). We have previously suggested that endogenous regulator of calcineurin (RCAN1, also known as DSCR1) is targeted by protein kinase A (PKA) for the control of calcineurin activity. In the present study, we characterized the PKA-mediated phosphorylation site in RCAN1 by mass spectrometric analysis and revealed that PKA directly phosphorylated RCAN1 at the Ser 93. PKA-induced phosphorylation and the increase in the half-life of the RCAN1 protein were prevented by the substitution of Ser 93 with Ala (S93A). Furthermore, the PKA-mediated phosphorylation of RCAN1 at Ser 93 potentiated the inhibition of calcineurin-dependent pro-inflammatory cytokine gene expression by RCAN1. Our results suggest the presence of a novel phosphorylation site in RCAN1 and that its phosphorylation influences calcineurin-dependent inflammatory target gene expression. PMID:25753203

Kim, Seon Sook; Lee, Eun Hye; Lee, Kooyeon; Jo, Su-Hyun; Seo, Su Ryeon

2015-04-17

219

Regulation of Sprouty Stability by Mnk1Dependent Phosphorylation  

Microsoft Academic Search

Sprouty (Spry) proteins are negative feedback modulators of receptor tyrosine kinase pathways in Drosophila melanogaster and mammals. Mammalian Spry proteins have been shown to undergo tyrosine and serine phosphorylation in response to growth factor stimulation. While several studies have addressed the function of tyrosine phosphorylation of Spry, little is known about the significance of Spry serine phosphorylation. Here we identify

John DaSilva; Lizhong Xu; Hong Joo Kim; W. Todd Miller; Dafna Bar-Sagi

2006-01-01

220

Dysfunctional conformational dynamics of protein kinase A induced by a lethal mutant of phospholamban hinder phosphorylation.  

PubMed

The dynamic interplay between kinases and substrates is crucial for the formation of catalytically committed complexes that enable phosphoryl transfer. However, a clear understanding on how substrates modulate kinase structural dynamics to control catalytic efficiency is still missing. Here, we used solution NMR spectroscopy to study the conformational dynamics of two complexes of the catalytic subunit of the cAMP-dependent protein kinase A with WT and R14 deletion phospholamban, a lethal human mutant linked to familial dilated cardiomyopathy. Phospholamban is a central regulator of heart muscle contractility, and its phosphorylation by protein kinase A constitutes a primary response to ?-adrenergic stimulation. We found that the single deletion of arginine in phospholamban's recognition sequence for the kinase reduces its binding affinity and dramatically reduces phosphorylation kinetics. Structurally, the mutant prevents the enzyme from adopting conformations and motions committed for catalysis, with concomitant reduction in catalytic efficiency. Overall, these results underscore the importance of a well-tuned structural and dynamic interplay between the kinase and its substrates to achieve physiological phosphorylation levels for proper Ca(2+) signaling and normal cardiac function. PMID:25775607

Kim, Jonggul; Masterson, Larry R; Cembran, Alessandro; Verardi, Raffaello; Shi, Lei; Gao, Jiali; Taylor, Susan S; Veglia, Gianluigi

2015-03-24

221

Enzymatic Catalytic Beds For Oxidation Of Alcohols  

NASA Technical Reports Server (NTRS)

Modules containing beds of enzymatic material catalyzing oxidation of primary alcohols and some other organic compounds developed for use in wastewater-treatment systems of future spacecraft. Designed to be placed downstream of multifiltration modules, which contain filters and sorbent beds removing most of non-alcoholic contaminants but fail to remove significant amounts of low-molecular-weight, polar, nonionic compounds like alcohols. Catalytic modules also used on Earth to oxidize primary alcohols and other compounds in wastewater streams and industrial process streams.

Jolly, Clifford D.; Schussel, Leonard J.

1993-01-01

222

Enzymatic surface modification of acrylonitrile fibers  

NASA Astrophysics Data System (ADS)

The surface of polyacrylonitrile polymer (containing 10% acetate groups) as fibers and finely ground powder have been modified by enzymatic treatment. The enzyme used was a nitrile hydratase, member of the class of nitrile converting enzymes, present in the microorganisms Brevibacterium imperiale and Corynebacterium nitrilophilus. The pendant nitrile groups were selectively converted into the corresponding amides as assessed by XPS analysis. As indicated by the increase of the O/C atomic ratio, the fiber surface showed a significant increase in hydrophilicity. The newly formed amide groups were then able to react with the acid dyes typically used to stain natural fibers, conferring the coloring properties to the otherwise inert polymer surface.

Battistel, Ezio; Morra, Marco; Marinetti, Massimo

2001-06-01

223

Phosphorylation of Kraft fibers with phosphate esters.  

PubMed

Phosphate esters, derived from two different long-chain aliphatic alcohols, were used as phosphorylating reagents for Kraft pulp fibers. High phosphorus contents and almost non-degraded fibers were obtained by following this pathway. The phosphorylation efficiency was influenced by the alkyl chain length of PEs since the phosphorus content in modified fibers was higher for the shorter chain reagent. Due to the heterogeneous reaction environment, the amount of grafted phosphorus was found to be almost three times higher at the surface than in the bulk of the fibers. Analyses also indicated that the phosphorus was bonded to fibers as a phosphate-like structure. Furthermore, the situation seemed to be different for the fiber surface where significant amounts of phosphorus were present in more complex structures like pyrophosphate or even oligo-phosphate. PMID:24721058

Shi, Ying; Belosinschi, Dan; Brouillette, François; Belfkira, Ahmed; Chabot, Bruno

2014-06-15

224

Subcellular Clustering of the Phosphorylated WspR Response Regulator Protein Stimulates Its Diguanylate Cyclase Activity  

PubMed Central

ABSTRACT WspR is a hybrid response regulator-diguanylate cyclase that is phosphorylated by the Wsp signal transduction complex in response to growth of Pseudomonas aeruginosa on surfaces. Active WspR produces cyclic di-GMP (c-di-GMP), which in turn stimulates biofilm formation. In previous work, we found that when activated by phosphorylation, yellow fluorescent protein (YFP)-tagged WspR forms clusters that are visible in individual cells by fluorescence microscopy. Unphosphorylated WspR is diffuse in cells and not visible. Thus, cluster formation is an assay for WspR signal transduction. To understand how and why WspR forms subcellular clusters, we analyzed cluster formation and the enzymatic activities of six single amino acid variants of WspR. In general, increased cluster formation correlated with increased in vivo and in vitro diguanylate cyclase activities of the variants. In addition, WspR specific activity was strongly concentration dependent in vitro, and the effect of the protein concentration on diguanylate cyclase activity was magnified when WspR was treated with the phosphor analog beryllium fluoride. Cluster formation appears to be an intrinsic property of phosphorylated WspR (WspR-P). These results support a model in which the formation of WspR-P subcellular clusters in vivo in response to a surface stimulus is important for potentiating the diguanylate cyclase activity of WspR. Subcellular cluster formation appears to be an additional means by which the activity of a response regulator protein can be regulated. PMID:23653447

Huangyutitham, Varisa; Güvener, Zehra Tüzün; Harwood, Caroline S.

2013-01-01

225

Regulation of Rad51 function by phosphorylation  

Microsoft Academic Search

Rad51 is a key enzyme involved in DNA double-strand break repair by homologous recombination. Here, we show that in response to DNA damage, budding yeast Rad51 is phosphorylated on Ser 192 in a manner that is primarily mediated by the DNA-damage-responsive protein kinase Mec1. We show that mutating Rad51 Ser 192 to Ala or Glu confers hypersensitivity to DNA damage

Sonja Flott; Youngho Kwon; Ying Zhang Pigli; Phoebe A Rice; Patrick Sung; Stephen P Jackson

2011-01-01

226

Solid polymer electrolyte from phosphorylated chitosan  

SciTech Connect

Recently, the need of secondary battery application continues to increase. The secondary battery which using a liquid electrolyte was indicated had some weakness. A solid polymer electrolyte is an alternative electrolytes membrane which developed in order to replace the liquid electrolyte type. In the present study, the effect of phosphorylation on to polymer electrolyte membrane which synthesized from chitosan and lithium perchlorate salts was investigated. The effect of the component’s composition respectively on the properties of polymer electrolyte, was carried out by analyzed of it’s characterization such as functional groups, ion conductivity, and thermal properties. The mechanical properties i.e tensile resistance and the morphology structure of membrane surface were determined. The phosphorylation processing of polymer electrolyte membrane of chitosan and lithium perchlorate was conducted by immersing with phosphoric acid for 2 hours, and then irradiated on a microwave for 60 seconds. The degree of deacetylation of chitosan derived from shrimp shells was obtained around 75.4%. Relative molecular mass of chitosan was obtained by viscometry method is 796,792 g/mol. The ionic conductivity of chitosan membrane was increase from 6.33 × 10{sup ?6} S/cm up to 6.01 × 10{sup ?4} S/cm after adding by 15 % solution of lithium perchlorate. After phosphorylation, the ionic conductivity of phosphorylated lithium chitosan membrane was observed 1.37 × 10{sup ?3} S/cm, while the tensile resistance of 40.2 MPa with a better thermal resistance. On the strength of electrolyte membrane properties, this polymer electrolyte membrane was suggested had one potential used for polymer electrolyte in field of lithium battery applications.

Fauzi, Iqbal, E-mail: arcana@chem.itb.ac.id; Arcana, I Made, E-mail: arcana@chem.itb.ac.id [Inorganic and Physical Chemistry Research Groups, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia)

2014-03-24

227

Phosphorylation network rewiring by gene duplication  

PubMed Central

Elucidating how complex regulatory networks have assembled during evolution requires a detailed understanding of the evolutionary dynamics that follow gene duplication events, including changes in post-translational modifications. We compared the phosphorylation profiles of paralogous proteins in the budding yeast Saccharomyces cerevisiae to that of a species that diverged from the budding yeast before the duplication of those genes. We found that 100 million years of post-duplication divergence are sufficient for the majority of phosphorylation sites to be lost or gained in one paralog or the other, with a strong bias toward losses. However, some losses may be partly compensated for by the evolution of other phosphosites, as paralogous proteins tend to preserve similar numbers of phosphosites over time. We also found that up to 50% of kinase–substrate relationships may have been rewired during this period. Our results suggest that after gene duplication, proteins tend to subfunctionalize at the level of post-translational regulation and that even when phosphosites are preserved, there is a turnover of the kinases that phosphorylate them. PMID:21734643

Freschi, Luca; Courcelles, Mathieu; Thibault, Pierre; Michnick, Stephen W; Landry, Christian R

2011-01-01

228

Phosphorylation Stoichiometries of Human Eukaryotic Initiation Factors  

PubMed Central

Eukaryotic translation initiation factors are the principal molecular effectors regulating the process converting nucleic acid to functional protein. Commonly referred to as eIFs (eukaryotic initiation factors), this suite of proteins is comprised of at least 25 individual subunits that function in a coordinated, regulated, manner during mRNA translation. Multiple facets of eIF regulation have yet to be elucidated; however, many of the necessary protein factors are phosphorylated. Herein, we have isolated, identified and quantified phosphosites from eIF2, eIF3, and eIF4G generated from log phase grown HeLa cell lysates. Our investigation is the first study to globally quantify eIF phosphosites and illustrates differences in abundance of phosphorylation between the residues of each factor. Thus, identification of those phosphosites that exhibit either high or low levels of phosphorylation under log phase growing conditions may aid researchers to concentrate their investigative efforts to specific phosphosites that potentially harbor important regulatory mechanisms germane to mRNA translation. PMID:24979134

Andaya, Armann; Villa, Nancy; Jia, Weitao; Fraser, Christopher S.; Leary, Julie A.

2014-01-01

229

Enzymatic characterization of Chlamydophila pneumoniae phospholipase D.  

PubMed

Chlamydophila pneumoniae, an aetiological agent of respiratory infection, is also thought to play an immuno-pathogenetic role in atherosclerosis by contributing to inflammation and plaque instability. Phospholipase D (PLD) is an enzyme involved in lipid metabolism and may have a direct or indirect impact on virulence and the inflammatory response. Some aspects of the developmental cycle of C. pneumoniae suggest a direct implication of its PLD (CpPLD) in the pathogenesis, specifically by affecting the regulation of lipid metabolism and lipid exchange between C. pneumoniae and host cells. Our previous studies disclosed a specific anti-CpPLD antibody response in patients with acute coronary syndromes chronically infected with C. pneumoniae, and demonstrated that this antigen is a factor able to drive the inflammatory process in atherosclerosis. Due to the intriguing aspects of the CpPLD, the present study investigated CpPLD enzymatic activity of the protein and the two domains that include one HKD motif each polypeptide. Our results showed that CpPLD was able to synthesize the cardiolipin (CL) but unable to hydrolyze phospholipids. It was also observed that each single HKD motif has an independent CL synthetase activity. This enzymatic activity of CpPLD could be important in the inflammatory process within the atherothrombotic events. PMID:25742148

Mancini, Fabiola; Ciervo, Alessandra

2015-01-01

230

Probing Enzymatic Activity Inside Single Cells  

PubMed Central

We report a novel approach for determining the enzymatic activity within a single suspended cell. Using a steady-state microfluidic delivery device, and timed exposure to the pore-forming agent digitonin, we controlled the plasma membrane permeation of individual NG108-15 cells. Mildly permeabilized cells (~100 pores) were exposed to a series of concentrations of fluorescein diphosphate (FDP), a fluorogenic alkaline phosphatase substrate, with and without levamisole, an alkaline phosphatase inhibitor. We generated quantitative estimates for intracellular enzyme activity, and were able to construct both dose-response and dose-inhibition curves, at the single-cell level, resulting in an apparent Michaelis contant Km of 15.3 ?M ± 1.02 (mean ± standard error of the mean (SEM), n=16), and an inhibition constant Ki of 0.59 mM ± 0.07 (mean ± SEM, n=14). Enzymatic activity could be monitored just 40 s after permeabilization, and 5 point dose-inhibition curves could be obtained within 150 s. This rapid approach offers a new methodology for characterizing enzyme activity within single cells. PMID:24003961

Olofsson, Jessica; Xu, Shijun; Jeffries, Gavin D. M.; Jesorka, Aldo; Bridle, Helen; Isaksson, Ida; Weber, Stephen G; Orwar, Owe

2013-01-01

231

Enzymatic deconstruction of xylan for biofuel production  

PubMed Central

The combustion of fossil-derived fuels has a significant impact on atmospheric carbon dioxide (CO2) levels and correspondingly is an important contributor to anthropogenic global climate change. Plants have evolved photosynthetic mechanisms in which solar energy is used to fix CO2 into carbohydrates. Thus, combustion of biofuels, derived from plant biomass, can be considered a potentially carbon neutral process. One of the major limitations for efficient conversion of plant biomass to biofuels is the recalcitrant nature of the plant cell wall, which is composed mostly of lignocellulosic materials (lignin, cellulose, and hemicellulose). The heteropolymer xylan represents the most abundant hemicellulosic polysaccharide and is composed primarily of xylose, arabinose, and glucuronic acid. Microbes have evolved a plethora of enzymatic strategies for hydrolyzing xylan into its constituent sugars for subsequent fermentation to biofuels. Therefore, microorganisms are considered an important source of biocatalysts in the emerging biofuel industry. To produce an optimized enzymatic cocktail for xylan deconstruction, it will be valuable to gain insight at the molecular level of the chemical linkages and the mechanisms by which these enzymes recognize their substrates and catalyze their reactions. Recent advances in genomics, proteomics, and structural biology have revolutionized our understanding of the microbial xylanolytic enzymes. This review focuses on current understanding of the molecular basis for substrate specificity and catalysis by enzymes involved in xylan deconstruction. PMID:20431716

DODD, DYLAN; CANN, ISAAC K. O.

2010-01-01

232

Recycling of cellulosic fibers by enzymatic process.  

PubMed

In this research, enzymatic treatment as an environmental friendly process has been used for recycling process of old cellulosic wastes such as cotton, viscose, and lyocell. Cellulase hydrolyses cellulosic chains and shortens cellulosic fibers. This study investigates to detect the optimum enzyme concentration and time of treatments for suitable changes of length and weight loss. The main purposes of this article are shortening of cellulosic fibers and evaluating of enzymatic treatment in different kind of cellulosic fibers. According to the data of experiments, with the increase of enzyme concentration and the treatment time, the length and weight loss percentage of the cellulosic fibers has been decreased. The length and weight loss percentage of treated viscose is more than that of lyocell and cotton fibers. Optimized condition, reaction time, and enzyme concentration have been determined by mean length of treated cellulosic samples. Suitable longitudinal distribution of fiber for papermaking industries is in the range of 0 to 4 mm. Optimum enzyme concentration and treatment time for recycling cotton, lyocell, and viscose fibers are 2% and 48 h for cotton and lyocell and 0.5% and 48 h for viscose, respectively. According to the data of experiment, the length of treated fibers is appropriate for its usage as a raw material in papermaking industries. PMID:22161212

Shojaei, K M; Dadashian, F; Montazer, M

2012-02-01

233

Enzymatic synthesis of inulin-containing hydrogels.  

PubMed

The Bacillus subtilis protease Proleather FG-F catalyzed the transesterification of inulin with vinyl acrylate (VA) in dimethylformamide (DMF). The reaction conversion for different VA concentrations was greater than 57% after 96 h at 50 degrees C. The degree of substitution (DS, defined as the amount of acrylate groups per 100 inulin fructofuranoside residues) with acrylate moieties can be controlled by varying the molar ratio of VA to inulin. Reasonable yields were obtained (44-51%, 2 days) using a two-step purification methodology. Inulin derivatized with VA (Inul-VA) was characterized by gel permeation chromatography, and its structure was established by (1)H, (13)C, and (1)H-(1)H correlation spectroscopy and (1)H-(13)C heteronuclear multiple quantum coherence NMR. The main positional isomer was at the 6 position of the fructofuranoside residue and two other minor isomers were observed at the 3 and 4 positions. Thus, the enzymatic reaction was largely regioselective. Furthermore, the inulin fructose residues were monosubstituted. Gels with swelling ratios at equilibrium of up to ca. 20 were prepared by free radical polymerization of aqueous solutions of Inul-VA with different DS and monomer concentrations. Gel pore sizes were calculated from swelling experiments and range from 19 to 57 A. To our knowledge, this work reports the first successful enzymatic modification of a polysaccharide solubilized in 100% DMF solution. PMID:11888320

Ferreira, Lino; Carvalho, Rui; Gil, Maria H; Dordick, Jonathan S

2002-01-01

234

Mapping the Reaction Coordinates of Enzymatic Defluorination  

SciTech Connect

The carbon-fluorine bond is the strongest covalent bond in organic chemistry, yet fluoroacetate dehalogenases can readily hydrolyze this bond under mild physiological conditions. Elucidating the molecular basis of this rare biocatalytic activity will provide the fundamental chemical insights into how this formidable feat is achieved. Here, we present a series of high-resolution (1.15-1.80 {angstrom}) crystal structures of a fluoroacetate dehalogenase, capturing snapshots along the defluorination reaction: the free enzyme, enzyme-fluoroacetate Michaelis complex, glycolyl-enzyme covalent intermediate, and enzyme-product complex. We demonstrate that enzymatic defluorination requires a halide pocket that not only supplies three hydrogen bonds to stabilize the fluoride ion but also is finely tailored for the smaller fluorine halogen atom to establish selectivity toward fluorinated substrates. We have further uncovered dynamics near the active site which may play pivotal roles in enzymatic defluorination. These findings may ultimately lead to the development of novel defluorinases that will enable the biotransformation of more complex fluorinated organic compounds, which in turn will assist the synthesis, detoxification, biodegradation, disposal, recycling, and regulatory strategies for the growing markets of organofluorines across major industrial sectors.

Chan, Peter W.Y.; Yakunin, Alexander F.; Edwards, Elizabeth A.; Pai, Emil F. (Toronto)

2011-09-28

235

Enzymatic and bacterial conversions during sourdough fermentation.  

PubMed

Enzymatic and microbial conversion of flour components during bread making determines bread quality. Metabolism of sourdough microbiota and the activity of cereal enzymes are interdependent. Acidification, oxygen consumption, and thiols accumulation by microbial metabolism modulate the activity of cereal enzymes. In turn, cereal enzymes provide substrates for bacterial growth. This review highlights the role of cereal enzymes and the metabolism of lactic acid bacteria in conversion of carbohydrates, proteins, phenolic compounds and lipids. Heterofermentative lactic acid bacteria prevailing in wheat and rye sourdoughs preferentially metabolise sucrose and maltose; the latter is released by cereal enzymes during fermentation. Sucrose supports formation of acetate by heterofermentative lactobacilli, and the formation of exopolysaccharides. The release of maltose and glucose by cereal enzymes during fermentation determines the exopolysaccharide yield in sourdough fermentations. Proteolysis is dependent on cereal proteases. Peptidase activities of sourdough lactic acid bacteria determine the accumulation of (bioactive) peptides, amino acids, and amino acid metabolites in dough and bread. Enzymatic conversion and microbial metabolism of phenolic compounds is relevant in sorghum and millet containing high levels of phenolic compounds. The presence of phenolic compounds with antimicrobial activity in sorghum selects for fermentation microbiota that are resistant to the phenolic compounds. PMID:24230468

Gänzle, Michael G

2014-02-01

236

Effects of enzymatic hydrolysis on lentil allergenicity.  

PubMed

Enzymatic hydrolysis and further processing are commonly used to produce hypoallergenic dietary products derived from different protein sources, such as cow's milk. Lentils and chickpeas seem to be an important cause of IgE-mediated hypersensitivity in the Mediterranean area and India. Some studies have investigated the effects of enzymatic treatments on the in vitro immunological reactivity of members of the Leguminosae family, such as soybean, chickpea, lentil, and lupine. Nevertheless, there are only a few studies carried out to evaluate the effect on IgE reactivity of these food-hydrolysis products with sera from patients with well-documented allergy to these foods. In this study, lentil protein extract was hydrolyzed by sequential action of an endoprotease (Alcalase) and an exoprotease (Flavourzyme). Immunoreactivity to raw and hydrolyzed lentil extract was evaluated by means of IgE immunoblotting and ELISA using sera from five patients with clinical allergy to lentil. The results indicated that sequential hydrolysis of lentil results in an important proteolytic destruction of IgE-binding epitopes shown by in vitro experiments. However, some allergenic proteins were still detected by sera from four out of five patients in the last step of sequential hydrolyzation. PMID:20306474

Cabanillas, Beatriz; Pedrosa, Mercedes M; Rodríguez, Julia; González, Angela; Muzquiz, Mercedes; Cuadrado, Carmen; Crespo, Jesús F; Burbano, Carmen

2010-09-01

237

Sensitive Electrochemical Detection of Enzymatically-generated Thiocholine at Carbon Nanotube Modified Glassy Carbon Electrode  

SciTech Connect

A carbon nanotube modified glassy-carbon (CNT/GC) electrode was used for enhancing the sensitivity of electrochemical measurements of enzymatically-generated thiocholine. Cyclic voltammetric and amperometric characteristics of thiocholine at CNT/GC, glassy carbon, carbon paste, and gold electrodes were compared. The CNT layer leads to a greatly improved anodic detection of enzymatically generated thiocholine product including lower oxidation overpotential (0.15 V) and higher sensitivity because of its electrocatalytic activity, fast electron transfer and large surface area. The sensor performance was optimized with respect to the operating conditions. Under the optimal batch conditions, a detection limit of 5 ?10 -6 mol/L was obtained with good precision (RSD = 5.2%, n=10). Furthermore, the attractive response of thiocholine on a CNT/GC electrode has allowed it to be used for constant-potential flow injection analysis. The detection limit was greatly improved to 0.3 ?10-6 mol/L. The high sensitivity electrochemical detection of enzymatically generated thiocholine with a CNT sensing platform holds great promise to prepare an acetylcholinesterase biosensor for monitoring organophosphate pesticides and nerve agents.

Liu, Guodong; Riechers, Shawn L.; Mellen, Maria C.; Lin, Yuehe

2005-11-01

238

High throughput, high resolution enzymatic lithography process: effect of crystallite size, moisture, and enzyme concentration.  

PubMed

By bringing enzymes into contact with predefined regions of a surface, a polymer film can be selectively degraded to form desired patterns that find a variety of applications in biotechnology and electronics. This so-called "enzymatic lithography" is an environmentally friendly process as it does not require actinic radiation or synthetic chemicals to develop the patterns. A significant challenge to using enzymatic lithography has been the need to restrict the mobility of the enzyme in order to maintain control of feature sizes. Previous approaches have resulted in low throughput and were limited to polymer films only a few nanometers thick. In this paper, we demonstrate an enzymatic lithography system based on Candida antartica lipase B (CALB) and poly(?-caprolactone) (PCL) that can resolve fine-scale features, (<1 ?m across) in thick (0.1-2.0 ?m) polymer films. A Polymer Pen Lithography (PPL) tool was developed to deposit an aqueous solution of CALB onto a spin-cast PCL film. Immobilization of the enzyme on the polymer surface was monitored using fluorescence microscopy by labeling CALB with FITC. The crystallite size in the PCL films was systematically varied; small crystallites resulted in significantly faster etch rates (20 nm/min) and the ability to resolve smaller features (as fine as 1 ?m). The effect of printing conditions and relative humidity during incubation is also presented. Patterns formed in the PCL film were transferred to an underlying copper foil demonstrating a "Green" approach to the fabrication of printed circuit boards. PMID:25346335

Mao, Zhantong; Ganesh, Manoj; Bucaro, Michael; Smolianski, Igor; Gross, Richard A; Lyons, Alan M

2014-12-01

239

The enzymatic reaction-induced configuration change of the prosthetic group PQQ of methanol dehydrogenase.  

PubMed

Methanol dehydrogenase is a heterotetrameric enzyme containing the prosthetic group pyrroloquinoline quinone (PQQ), which catalyzes the oxidation of methanol to formaldehyde. The crystal structure of methanol dehydrogenase from Methylophilus W3A1, previously determined at high resolution, exhibits a non-planar configuration of the PQQ ring system and lends support for a hydride transfer mechanism of the enzymatic reaction catalyzed by the enzyme. To investigate why PQQ is in the C5-reduced form and to better understand the catalytic mechanism of the enzyme, three structures of this enzyme in a new crystal form have been determined at higher resolution. Two of the three crystals were grown in the presence of 1 and 50 mM methanol, respectively, both structures of which show non-planar configurations of the PQQ ring system, confirming the previous conclusion; the other was crystallized in the presence of 50 mM ethanol, the structure of which displays a planar ring system for PQQ. Comparison of these structures reveals that the configuration change of PQQ is induced by the enzymatic reaction. The reaction takes place and the C5-reduced PQQ intermediate is produced when the enzyme co-crystallizes with methanol, but the enzymatic reaction does not take place and the PQQ ring retains a planar configuration of the oxidized orthoquinone form when ethanol instead of methanol is present in the crystallization solution. PMID:21356200

Li, Jie; Gan, Jian-Hua; Mathews, F Scott; Xia, Zong-Xiang

2011-03-25

240

In Plants, 3-O-Methylglucose Is Phosphorylated by Hexokinase But Not Perceived as a Sugar1  

PubMed Central

In plants, sugars are the main respiratory substrates and important signaling molecules in the regulation of carbon metabolism. Sugar signaling studies suggested that sugar sensing involves several key components, among them hexokinase (HXK). Although the sensing mechanism of HXK is unknown, several experiments support the hypothesis that hexose phosphorylation is a determining factor. Glucose (Glc) analogs transported into cells but not phosphorylated are frequently used to test this hypothesis, among them 3-O-methyl-Glc (3-OMG). The aim of the present work was to investigate the effects and fate of 3-OMG in heterotrophic plant cells. Measurements of respiration rates, protein and metabolite contents, and protease activities and amounts showed that 3-OMG is not a respiratory substrate and does not contribute to biosynthesis. Proteolysis and lipolysis are induced in 3-OMG-fed maize (Zea mays L. cv DEA) roots in the same way as in sugar-starved organs. However, contrary to the generally accepted idea, phosphorous and carbon nuclear magnetic resonance experiments and enzymatic assays prove that 3-OMG is phosphorylated to 3-OMG-6-phosphate, which accumulates in the cells. Insofar as plant HXK is involved in sugar sensing, these findings are discussed on the basis of the kinetic properties because the catalytic efficiency of HXK isolated from maize root tips is five orders of magnitude lower for 3-OMG than for Glc and Man. PMID:12586906

Cortčs, Sandra; Gromova, Marina; Evrard, Adeline; Roby, Claude; Heyraud, Alain; Rolin, Dominique B.; Raymond, Philippe; Brouquisse, Renaud M.

2003-01-01

241

MORC2 signaling integrates phosphorylation-dependent, ATPase-coupled chromatin remodeling during the DNA damage response.  

PubMed

Chromatin dynamics play a central role in maintaining genome integrity, but how this is achieved remains largely unknown. Here, we report that microrchidia CW-type zinc finger 2 (MORC2), an uncharacterized protein with a derived PHD finger domain and a conserved GHKL-type ATPase module, is a physiological substrate of p21-activated kinase 1 (PAK1), an important integrator of extracellular signals and nuclear processes. Following DNA damage, MORC2 is phosphorylated on serine 739 in a PAK1-dependent manner, and phosphorylated MORC2 regulates its DNA-dependent ATPase activity to facilitate chromatin remodeling. Moreover, MORC2 associates with chromatin and promotes gamma-H2AX induction in a PAK1 phosphorylation-dependent manner. Consequently, cells expressing MORC2-S739A mutation displayed a reduction in DNA repair efficiency and were hypersensitive to DNA-damaging agent. These findings suggest that the PAK1-MORC2 axis is critical for orchestrating the interplay between chromatin dynamics and the maintenance of genomic integrity through sequentially integrating multiple essential enzymatic processes. PMID:23260667

Li, Da-Qiang; Nair, Sujit S; Ohshiro, Kazufumi; Kumar, Anupam; Nair, Vasudha S; Pakala, Suresh B; Reddy, Sirigiri Divijendra Natha; Gajula, Rajendra P; Eswaran, Jeyanthy; Aravind, L; Kumar, Rakesh

2012-12-27

242

MORC2 Signaling Facilitates Phosphorylation-dependent, ATPase-coupled Chromatin Remodeling during the DNA Damage Response  

PubMed Central

SUMMARY Chromatin dynamics play a central role in maintaining genome integrity, but how this is achieved remains largely unknown. Here, we report that microrchidia CW-type zinc finger 2 (MORC2), an uncharacterized protein with a derived PHD finger domain and a conserved GHKL-type ATPase module, is a physiological substrate of p21-activated kinase 1 (PAK1), an important integrator of extracellular signals and nuclear processes. Following DNA damage, MORC2 is phosphorylated on serine 739 in a PAK1 dependent manner, and phosphorylated MORC2 regulates its DNA-dependent ATPase activity to facilitate chromatin remodeling. Moreover, MORC2 associates with chromatin and promotes gamma-H2AX induction in a PAK1 phosphorylation-dependent manner. Consequently, cells expressing MORC2-S739A mutation displayed a reduction in DNA repair efficiency and were hypersensitive to DNA-damaging agent. These findings suggest that the PAK1-MORC2 axis is critical for orchestrating the interplay between chromatin dynamics and the maintenance of genomic integrity through sequentially integrating multiple essential enzymatic processes. PMID:23260667

Li, Da-Qiang; Nair, Sujit S.; Ohshiro, Kazufumi; Kumar, Anupam; Nair, Vasudha S.; Pakala, Suresh B.; Reddy, Sirigiri Divijendra Natha; Gajula, Rajendra P.; Eswaran, Jeyanthy; Aravind, L.; Kumar, Rakesh

2013-01-01

243

Phosphorylation of Tip60 Tyrosine 327 by Abl Kinase Inhibits HAT Activity through Association with FE65  

PubMed Central

The transfer of acetyl groups from acetyl coenzyme A to the ? amino group of internal lysine residues is catalyzed by Tip60, which is in the MYST family of nuclear histone acetyltransferases (HATs). The tyrosine phosphorylation of Tip60 seems to be a unique modification. We present evidence that Tip60 is modified on tyrosine 327 by Abl kinase. We show that this causes functional changes in HAT activity and the subcellular localization of TIP60, which forms a complex with Abl kinase. The Tip60 mutation Y327F abolished tyrosine phosphorylation, reduced the inhibition of Tip60 HAT activity, and caused G0-G1 arrest and association with FE65. Thus, our findings for the first time suggested a novel regulation mechanism of Tip60. Regulation was through phosphorylation of tyrosine 327 by Abl tyrosine kinase and depended on environmental conditions, suggesting that the tyrosine residue of Tip60 is important for the activation process. PMID:24044023

Shin, Sung Hwa; Kang, Sang Sun

2013-01-01

244

Phosphorylation of Tip60 Tyrosine 327 by Abl Kinase Inhibits HAT Activity through Association with FE65.  

PubMed

The transfer of acetyl groups from acetyl coenzyme A to the ? amino group of internal lysine residues is catalyzed by Tip60, which is in the MYST family of nuclear histone acetyltransferases (HATs). The tyrosine phosphorylation of Tip60 seems to be a unique modification. We present evidence that Tip60 is modified on tyrosine 327 by Abl kinase. We show that this causes functional changes in HAT activity and the subcellular localization of TIP60, which forms a complex with Abl kinase. The Tip60 mutation Y327F abolished tyrosine phosphorylation, reduced the inhibition of Tip60 HAT activity, and caused G0-G1 arrest and association with FE65. Thus, our findings for the first time suggested a novel regulation mechanism of Tip60. Regulation was through phosphorylation of tyrosine 327 by Abl tyrosine kinase and depended on environmental conditions, suggesting that the tyrosine residue of Tip60 is important for the activation process. PMID:24044023

Shin, Sung Hwa; Kang, Sang Sun

2013-01-01

245

Inhibition of Phosphorylation of Na+,K+-ATPase by Mutations Causing Familial Hemiplegic Migraine*  

PubMed Central

The neurological disorder familial hemiplegic migraine type II (FHM2) is caused by mutations in the ?2-isoform of the Na+,K+-ATPase. We have studied the partial reaction steps of the Na+,K+-pump cycle in nine FHM2 mutants retaining overall activity at a level still compatible with cell growth. Although it is believed that the pathophysiology of FHM2 results from reduced extracellular K+ clearance and/or changes in Na+ gradient-dependent transport processes in neuroglia, a reduced affinity for K+ or Na+ is not a general finding with the FHM2 mutants. Six of the FHM2 mutations markedly affect the maximal rate of phosphorylation from ATP leading to inhibition by intracellular K+, thereby likely compromising pump function under physiological conditions. In mutants R593W, V628M, and M731T, the defective phosphorylation is caused by local perturbations within the Rossmann fold, possibly interfering with the bending of the P-domain during phosphoryl transfer. In mutants V138A, T345A, and R834Q, long range effects reaching from as far away as the M2 transmembrane helix perturb the function of the catalytic site. Mutant E700K exhibits a reduced rate of E2P dephosphorylation without effect on phosphorylation from ATP. An extremely reduced vanadate affinity of this mutant indicates that the slow dephosphorylation reflects a destabilization of the phosphoryl transition state. This seems to be caused by insertion of the lysine between two other positively charged residues of the Rossmann fold. In mutants R202Q and T263M, effects on the A-domain structure are responsible for a reduced rate of the E1P to E2P transition. PMID:22117059

Schack, Vivien Rodacker; Holm, Rikke; Vilsen, Bente

2012-01-01

246

Effect of phosphorylation on alpha B-crystallin: differences in stability, subunit exchange and chaperone activity of homo and mixed oligomers of alpha B-crystallin and its phosphorylation-mimicking mutant.  

PubMed

Phosphorylation appears to be one of the modulators of chaperone functions of small heat shock proteins. However, the role of phosphorylation is not completely understood. We have investigated the structural and functional consequences of a phosphorylation-mimicking mutation in alpha B-crystallin, a small heat shock protein with chaperone activity. We have used a phosphorylation-mimicking mutant, 3D alpha B-crystallin, in which all the three phosphorylatable serine residues are replaced with aspartic acid. 3D alpha B-Crystallin showed enhanced chaperone-like activity towards DTT-induced aggregation of insulin, heat-induced aggregation of citrate synthase and SDS-induced amyloid fibril formation of alpha-synuclein. Fluorescence and circular dichroism spectroscopic studies showed that 3D alpha B-crystallin exhibits lower stability towards urea-induced denaturation compared to alpha B-crystallin. Subunit exchange studies using fluorescence resonance energy transfer showed that 3D alpha B-crystallin exhibits an observable increase in subunit exchange compared to alpha B-crystallin. Since only part of alpha B-crystallin is phosphorylated in vivo, our subunit exchange studies indicate that formation of mixed oligomers between the unphosphorylated and phosphorylated subunits are likely to play a role in vivo. Our study shows that mixed-oligomer formation modulates the chaperone-like activity. We propose that the degree of phosphorylation of the alpha B-crystallin oligomers and temperature are key modulators to achieve a wide range of chaperone capabilities of the small heat shock protein, alpha -crystallin. PMID:18061612

Ahmad, Md Faiz; Raman, Bakthisaran; Ramakrishna, Tangirala; Rao, Ch Mohan

2008-01-25

247

Use of enzymatic cleaners on US Navy ships. Research report  

Microsoft Academic Search

The Naval Surface Warfare Center, Carderock Division, conducted a study to determine the feasibility of using enzymatic and bacterial products in cleaning applications aboard U.S. Navy ships. A review of the most recent technical literature and a survey of potential suppliers were conducted. In addition, shipboard systems, subsystems and housekeeping processes were evaluated to identify suitable applications for enzymatic and

Venkatachalam

1996-01-01

248

Effect of Homeopathic Dilutions on Subcellular Enzymatic Activity  

Microsoft Academic Search

The activity of various inhibitors on several subcellular enzymes was studied. First we determined the inhibitory concentration required to reduce maximum enzymatic activity by 50%, then the effect of various hahnemannian dilutions of the same inhibitory agent was tested. Seven inhibitory agents were tested in this way on seven different enzymatic systems. No effects of these hahnemannian dilutions were shown.

C. Petit; P. Belon; R. Got

1989-01-01

249

RESEARCH Open Access Comparison of enzymatic reactivity of corn stover  

E-print Network

RESEARCH Open Access Comparison of enzymatic reactivity of corn stover solids prepared by dilute liquid (IL) thermochemical pretreatments of corn stover were followed over time for the same range. Results: Corn stover solids from pretreatment by DA, AFEX, and IL were enzymatically digested over a range

California at Riverside, University of

250

Enzymatic treatment of peanut kernels to reduce allergen levels  

Microsoft Academic Search

This study investigated the use of enzymatic treatment to reduce peanut allergens in peanut kernels as affected by processing conditions. Two major peanut allergens, Ara h 1 and Ara h 2, were used as indicators of process effectiveness. Enzymatic treatment effectively reduced Ara h 1 and Ara h 2 in roasted peanut kernels by up to 100% under optimal conditions.

Jianmei Yu; Mohamed Ahmedna; Ipek Goktepe; Hsiaopo Cheng; Soheila Maleki

2011-01-01

251

Enzymatic browning and its control in fresh-cut produce  

Technology Transfer Automated Retrieval System (TEKTRAN)

Enzymatic browning of damaged tissues of fruits and vegetables during postharvest handling and processing degrades the sensory properties and nutritional value and discourages the consumer purchase of fresh-cut products. Consequently, enzymatic browning results in significant economic losses for the...

252

ESTIMATION OF UPPER BOUNDS FOR THE RATES OF ENZYMATIC REACTIONS  

Microsoft Academic Search

A general methodology that allows the estimation of maximum rates of enzymatic reactions is described. For a typical mechanism of an enzymatic reaction, the rate is a function of kinetic parameters which are unknown but required to obey certain constraints. Specifically, the ratio of forward to backward rate constants must be consistent with the equilibrium constant, and the rate of

MICHAEL L. MAVROVOUNIOTIS; GEORGE STEPHANOPOULOS; GREGORY STEPHANOPOULOS

1990-01-01

253

Enzymatic Products from Modified Soybean Oil Containing Hydrazinoester  

Technology Transfer Automated Retrieval System (TEKTRAN)

We use soybean oil to produce new, non-petroleum based products. The starting material is the ene reaction product of soybean oil and diethyl azodicarboxylate (DEAD), which can then be hydrolyzed chemically and enzymatically. Chemical hydrolysis gives hydrazino-fatty acids, whereas enzymatic hydro...

254

Enzymatically cross-linked hydrogels and their adhesive  

E-print Network

), and as surgical sealants and adhesives (4­6). An emerging approach to formation of hydrogels relies on enzymaticEnzymatically cross-linked hydrogels and their adhesive strength to biosurfaces B-H Hu PB-linked hydrogels were compared with commercial fibrin tissue adhesive. Outcome Measure ­ The shear strength between

255

Serine-727 Phosphorylation Activates Hypothalamic STAT-3 Independently From Tyrosine-705 Phosphorylation.  

PubMed

Transcriptional activity of signal transducer and activator of transcription-3 (STAT-3) is a key element in the central regulation of appetite and energy homeostasis. Activation of hypothalamic STAT-3 has been attributed to cytokine-promoted phosphorylation at tyrosine-705 (Tyr-705). In nonhypothalamic cells, STAT-3 is also phosphorylated at serine-727 (Ser-727), but the functional significance of Ser-727 in the regulation of hypothalamic STAT-3 is not known. We used 2 hypothalamic cell lines and analyzed the effects of various hormones on STAT-3-dependent reporter gene activity and observed that IFN-?, epidermal growth factor (EGF), and bradykinin (BK) induce similar STAT-3 reporter activation. EGF and BK solely increased Ser-727 and IFN-? increased Tyr-705 phosphorylation of STAT-3. Specific inhibition of ERK-1/2 activity blocked EGF- and BK-induced STAT-3 activation and Ser-727 phosphorylation. BK-induced ERK-1/2 activation occurred via EGF receptor transactivation. Consequently, the BK-mediated effects on STAT-3 were blocked by a specific EGF receptor antagonist. Next, we analyzed the effects of IFN-? and EGF on the expression of the STAT-3-dependent genes thyroliberin-releasing hormone and suppressors of cytokine signaling-3. EGF but not IFN-? enhanced thyroliberin-releasing hormone expression via STAT-3. With regard to suppressors of cytokine signaling-3, we observed prolonged expression induced by IFN-? and a transient effect of EGF that required coactivation of the activator protein-1. Thus, EGF-promoted Ser-727 phosphorylation by ERK-1/2 is not only sufficient to fully activate hypothalamic STAT-3, but, in terms of targeted genes and required cofactors, entails distinct modes of STAT-3 actions compared with IFN-?-induced Tyr-705 phosphorylation. PMID:25584415

Breit, Andreas; Besik, Valeria; Solinski, Hans Jürgen; Muehlich, Susanne; Glas, Evi; Yarwood, Stephen J; Gudermann, Thomas

2015-03-01

256

Pretreatment and enzymatic hydrolysis of lignocellulosic biomass  

NASA Astrophysics Data System (ADS)

The performance of soybean hulls and forage sorghum as feedstocks for ethanol production was studied. The main goal of this research was to increase fermentable sugars' yield through high-efficiency pretreatment technology. Soybean hulls are a potential feedstock for production of bio-ethanol due to their high carbohydrate content (?50%) of nearly 37% cellulose. Soybean hulls could be the ideal feedstock for fuel ethanol production, because they are abundant and require no special harvesting and additional transportation costs as they are already in the plant. Dilute acid and modified steam-explosion were used as pretreatment technologies to increase fermentable sugars yields. Effects of reaction time, temperature, acid concentration and type of acid on hydrolysis of hemicellulose in soybean hulls and total sugar yields were studied. Optimum pretreatment parameters and enzymatic hydrolysis conditions for converting soybean hulls into fermentable sugars were identified. The combination of acid (H2SO4, 2% w/v) and steam (140°C, 30 min) efficiently solubilized the hemicellulose, giving a pentose yield of 96%. Sorghum is a tropical grass grown primarily in semiarid and dry parts of the world, especially in areas too dry for corn. The production of sorghum results in about 30 million tons of byproducts mainly composed of cellulose, hemicellulose, and lignin. Forage sorghum such as brown midrib (BMR) sorghum for ethanol production has generated much interest since this trait is characterized genetically by lower lignin concentrations in the plant compared with conventional types. Three varieties of forage sorghum and one variety of regular sorghum were characterized and evaluated as feedstock for fermentable sugar production. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-Ray diffraction were used to determine changes in structure and chemical composition of forage sorghum before and after pretreatment and enzymatic hydrolysis process. Up to 72% of hexose yield and 94% of pentose yield were obtained using "modified" steam explosion with 2% sulfuric acid at 140°C for 30 min and enzymatic hydrolysis with cellulase (15 FPU/g cellulose) and beta-glucosidase (50 CBU/g cellulose).

Corredor, Deisy Y.

257

Mitotic phosphorylation of histone H3 threonine 80  

PubMed Central

The onset and regulation of mitosis is dependent on phosphorylation of a wide array of proteins. Among the proteins that are phosphorylated during mitosis is histone H3, which is heavily phosphorylated on its N-terminal tail. In addition, large-scale mass spectrometry screens have revealed that histone H3 phosphorylation can occur at multiple sites within its globular domain, yet detailed analyses of the functions of these phosphorylations are lacking. Here, we explore one such histone H3 phosphorylation site, threonine 80 (H3T80), which is located on the nucleosome surface. Phosphorylated H3T80 (H3T80ph) is enriched in metazoan cells undergoing mitosis. Unlike H3S10 and H3S28, H3T80 is not phosphorylated by the Aurora B kinase. Further, mutations of T80 to either glutamic acid, a phosphomimetic, or to alanine, an unmodifiable residue, result in an increase in cells in prophase and an increase in anaphase/telophase bridges, respectively. SILAC-coupled mass spectrometry shows that phosphorylated H3T80 (H3T80ph) preferentially interacts with histones H2A and H4 relative to non-phosphorylated H3T80, and this result is supported by increased binding of H3T80ph to histone octamers in vitro. These findings support a model where H3T80ph, protruding from the nucleosome surface, promotes interactions between adjacent nucleosomes to promote chromatin compaction during mitosis in metazoan cells. PMID:24275038

Hammond, Sharra L; Byrum, Stephanie D; Namjoshi, Sarita; Graves, Hillary K; Dennehey, Briana K; Tackett, Alan J; Tyler, Jessica K

2014-01-01

258

Roles of subunit phosphorylation in regulating glutamate receptor function.  

PubMed

Protein phosphorylation is an important mechanism for regulating ionotropic glutamate receptors (iGluRs). Early studies have established that major iGluR subtypes, including ?-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors and N-methyl-d-aspartate (NMDA) receptors, are subject to phosphorylation. Multiple serine, threonine, and tyrosine residues predominantly within the C-terminal regions of AMPA receptor and NMDA receptor subunits have been identified as sensitive phosphorylation sites. These distinct sites undergo either constitutive phosphorylation or activity-dependent phosphorylation induced by changing cellular and synaptic inputs. An increasing number of synapse-enriched protein kinases have been found to phosphorylate iGluRs The common kinases include protein kinase A, protein kinase C, Ca(2+)/calmodulin-dependent protein kinase II, Src/Fyn non-receptor tyrosine kinases, and cyclin dependent kinase-5. Regulated phosphorylation plays a well-documented role in modulating the biochemical, biophysical, and functional properties of the receptor. In the future, identifying the precise mechanisms how phosphorylation regulates iGluR activities and finding the link between iGluR phosphorylation and the pathogenesis of various brain diseases, including psychiatric and neurodegenerative diseases, chronic pain, stroke, Alzheimer's disease and substance addiction, will be hot topics and could contribute to the development of novel pharmacotherapies, by targeting the defined phosphorylation process, for suppressing iGluR-related disorders. PMID:24291102

Wang, John Q; Guo, Ming-Lei; Jin, Dao-Zhong; Xue, Bing; Fibuch, Eugene E; Mao, Li-Min

2014-04-01

259

Regulation of renal fibrosis by Smad3 Thr388 phosphorylation.  

PubMed

Transforming growth factor-? (TGF-?) promotes tissue fibrosis via receptor-mediated phosphorylation of the receptor-activated Smad2/3, together with Smad4. Of these, Smad3 plays a major profibrotic role in mouse models of tissue fibrosis. Transcriptional activity of the Smad3 protein is regulated by phosphorylation of residues in the C-terminal domain and the linker region. Herein, we examined the role of a novel phosphorylation site within the MH2 domain (T388) in the regulation of Smad3 activity. Confocal microscopy using an Smad3 phosphorylated T388-specific antibody identified phosphorylation of Smad3 T388 in myofibroblasts and tubular epithelial cells in human focal and segmental glomerulosclerosis and mouse models of unilateral ureteric obstruction and diabetic nephropathy, whereas phosphorylated T388 was largely absent in normal kidney. In vitro, TGF-?1 induced phosphorylation of Smad3 T388 in a biphasic pattern. A point mutation of T388/V in an Smad3 construct demonstrated that phosphorylation of T388 promotes Smad3 binding to Smad4 and CDK8, but was not necessary for nuclear translocation. Furthermore, T388 phosphorylation was required for TGF-?-induced collagen I gene promoter activity and extracellular matrix production in cultured fibroblasts. In conclusion, our study identifies phosphorylation of T388 in the Smad3 MH2 domain as an important mechanism that regulates the profibrotic TGF-?/Smad3 signaling pathway, which has direct relevance to human and experimental fibrotic kidney disease. PMID:24485922

Qu, Xinli; Li, Xueling; Zheng, Yaowu; Ren, Yi; Puelles, Victor G; Caruana, Georgina; Nikolic-Paterson, David J; Li, Jinhua

2014-04-01

260

Constitutive phosphorylation of the Parkinson's disease associated alpha-synuclein.  

PubMed

alpha-Synuclein has been implicated in the pathogenesis of Parkinson's disease, since rare autosomal dominant mutations are associated with early onset of the disease and alpha-synuclein was found to be a major constituent of Lewy bodies. We have analyzed alpha-synuclein expression in transfected cell lines. In pulse-chase experiments alpha-synuclein appeared to be stable over long periods (t((1)/(2)) 54 h) and no endoproteolytic processing was observed. alpha-Synuclein was constitutively phosphorylated in human kidney 293 cells as well as in rat pheochromocytoma PC12 cells. In both cell lines phosphorylation was highly sensitive to phosphatases, since okadaic acid markedly stabilized phosphate incorporation. Phosphoamino acid analysis revealed that phosphorylation occurred predominantly on serine. Using site-directed mutagenesis we have identified a major phosphorylation site at serine 129 within the C-terminal domain of alpha-synuclein. An additional site, which was phosphorylated less efficiently, was mapped to serine 87. The major phosphorylation site was located within a consensus recognition sequence of casein kinase 1 (CK-1). In vitro experiments and two-dimensional phosphopeptide mapping provided further evidence that serine 129 was phosphorylated by CK-1 and CK-2. Moreover, phosphorylation of serine 129 was reduced in vivo upon inhibition of CK-1 or CK-2. These data demonstrate that alpha-synuclein is constitutively phosphorylated within its C terminus and may indicate that the function of alpha-synuclein is regulated by phosphorylation/dephosphorylation. PMID:10617630

Okochi, M; Walter, J; Koyama, A; Nakajo, S; Baba, M; Iwatsubo, T; Meijer, L; Kahle, P J; Haass, C

2000-01-01

261

Differential effects of an O-GlcNAcase inhibitor on tau phosphorylation.  

PubMed

Abnormal hyperphosphorylation of microtubule-associated protein tau plays a crucial role in neurodegeneration in Alzheimer's disease (AD). The aggregation of hyperphosphorylated tau into neurofibrillary tangles is also a hallmark brain lesion of AD. Tau phosphorylation is regulated by tau kinases, tau phosphatases, and O-GlcNAcylation, a posttranslational modification of proteins on the serine or threonine residues with ?-N-acetylglucosamine (GlcNAc). O-GlcNAcylation is dynamically regulated by O-GlcNAc transferase, the enzyme catalyzing the transfer of GlcNAc to proteins, and N-acetylglucosaminidase (OGA), the enzyme catalyzing the removal of GlcNAc from proteins. Thiamet-G is a recently synthesized potent OGA inhibitor, and initial studies suggest it can influence O-GlcNAc levels in the brain, allowing OGA inhibition to be a potential route to altering disease progression in AD. In this study, we injected thiamet-G into the lateral ventricle of mice to increase O-GlcNAcylation of proteins and investigated the resulting effects on site-specific tau phosphorylation. We found that acute thiamet-G treatment led to a decrease in tau phosphorylation at Thr181, Thr212, Ser214, Ser262/Ser356, Ser404 and Ser409, and an increase in tau phosphorylation at Ser199, Ser202, Ser396 and Ser422 in the mouse brain. Investigation of the major tau kinases showed that acute delivery of a high dose of thiamet-G into the brain also led to a marked activation of glycogen synthase kinase-3? (GSK-3?), possibly as a consequence of down-regulation of its upstream regulating kinase, AKT. However, the elevation of tau phosphorylation at the sites above was not observed and GSK-3? was not activated in cultured adult hippocampal progenitor cells or in PC12 cells after thiamet-G treatment. These results suggest that acute high-dose thiamet-G injection can not only directly antagonize tau phosphorylation, but also stimulate GSK-3? activity, with the downstream consequence being site-specific, bi-directional regulation of tau phosphorylation in the mammalian brain. PMID:22536363

Yu, Yang; Zhang, Lan; Li, Xiaojing; Run, Xiaoqin; Liang, Zhihou; Li, Yi; Liu, Ying; Lee, Moon H; Grundke-Iqbal, Inge; Iqbal, Khalid; Vocadlo, David J; Liu, Fei; Gong, Cheng-Xin

2012-01-01

262

Differential Effects of an O-GlcNAcase Inhibitor on Tau Phosphorylation  

PubMed Central

Abnormal hyperphosphorylation of microtubule-associated protein tau plays a crucial role in neurodegeneration in Alzheimer's disease (AD). The aggregation of hyperphosphorylated tau into neurofibrillary tangles is also a hallmark brain lesion of AD. Tau phosphorylation is regulated by tau kinases, tau phosphatases, and O-GlcNAcylation, a posttranslational modification of proteins on the serine or threonine residues with ?-N-acetylglucosamine (GlcNAc). O-GlcNAcylation is dynamically regulated by O-GlcNAc transferase, the enzyme catalyzing the transfer of GlcNAc to proteins, and N-acetylglucosaminidase (OGA), the enzyme catalyzing the removal of GlcNAc from proteins. Thiamet-G is a recently synthesized potent OGA inhibitor, and initial studies suggest it can influence O-GlcNAc levels in the brain, allowing OGA inhibition to be a potential route to altering disease progression in AD. In this study, we injected thiamet-G into the lateral ventricle of mice to increase O-GlcNAcylation of proteins and investigated the resulting effects on site-specific tau phosphorylation. We found that acute thiamet-G treatment led to a decrease in tau phosphorylation at Thr181, Thr212, Ser214, Ser262/Ser356, Ser404 and Ser409, and an increase in tau phosphorylation at Ser199, Ser202, Ser396 and Ser422 in the mouse brain. Investigation of the major tau kinases showed that acute delivery of a high dose of thiamet-G into the brain also led to a marked activation of glycogen synthase kinase-3? (GSK-3?), possibly as a consequence of down-regulation of its upstream regulating kinase, AKT. However, the elevation of tau phosphorylation at the sites above was not observed and GSK-3? was not activated in cultured adult hippocampal progenitor cells or in PC12 cells after thiamet-G treatment. These results suggest that acute high-dose thiamet-G injection can not only directly antagonize tau phosphorylation, but also stimulate GSK-3? activity, with the downstream consequence being site-specific, bi-directional regulation of tau phosphorylation in the mammalian brain. PMID:22536363

Li, Xiaojing; Run, Xiaoqin; Liang, Zhihou; Li, Yi; Liu, Ying; Lee, Moon H.; Grundke-Iqbal, Inge; Iqbal, Khalid; Vocadlo, David J.; Liu, Fei; Gong, Cheng-Xin

2012-01-01

263

Analog Noise Reduction in Enzymatic Logic Gates  

E-print Network

In this work we demonstrate both experimentally and theoretically that the analog noise generation by a single enzymatic logic gate can be dramatically reduced to yield gate operation with virtually no input noise amplification. This is achieved by exploiting the enzyme's specificity when using a co-substrate that has a much lower affinity than the primary substrate. Under these conditions, we obtain a negligible increase in the noise output from the logic gate as compared to the input noise level. Experimental realizations of the AND logic gate with the enzyme horseradish peroxidase using hydrogen peroxide and two different co-substrates, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and ferrocyanide, with vastly different rate constants confirmed our general theoretical conclusions.

Dmitriy Melnikov; Guinevere Strack; Marcos Pita; Vladimir Privman; Evgeny Katz

2009-05-17

264

Fungal biodegradation and enzymatic modification of lignin  

PubMed Central

Lignin, the most abundant aromatic biopolymer on Earth, is extremely recalcitrant to degradation. By linking to both hemicellulose and cellulose, it creates a barrier to any solutions or enzymes and prevents the penetration of lignocellulolytic enzymes into the interior lignocellulosic structure. Some basidiomycetes white-rot fungi are able to degrade lignin efficiently using a combination of extracellular ligninolytic enzymes, organic acids, mediators and accessory enzymes. This review describes ligninolytic enzyme families produced by these fungi that are involved in wood decay processes, their molecular structures, biochemical properties and the mechanisms of action which render them attractive candidates in biotechnological applications. These enzymes include phenol oxidase (laccase) and heme peroxidases [lignin peroxidase (LiP), manganese peroxidase (MnP) and versatile peroxidase (VP)]. Accessory enzymes such as H2O2-generating oxidases and degradation mechanisms of plant cell-wall components in a non-enzymatic manner by production of free hydroxyl radicals (·OH) are also discussed. PMID:21968746

Dashtban, Mehdi; Schraft, Heidi; Syed, Tarannum A.; Qin, Wensheng

2010-01-01

265

Pretreatment and enzymatic hydrolysis of corn fiber  

SciTech Connect

Corn fiber is a co-product of the corn wet milling industry which is usually marketed as a low value animal feed ingredient. Approximately 1.2 x 10{sup 6} dry tons of this material are produced annually in the United States. The fiber is composed of kernel cell wall fractions and a residual starch which can all be potentially hydrolyzed to a mixture of glucose, xylose, arabinose and galactose. We have investigated a sequential saccharification of polysaccharides in corn fiber by a treatment with dilute sulfuric acid at 100 to 160{degrees}C followed by partial neutralization and enzymatic hydrolysis with mixed cellulose and amyloglucosidase enzymes at 45{degrees}C. The sequential treatment achieved a high (approximately 85%) conversion of all polysaccharides in the corn fiber to monomeric sugars, which were in most cases fermentable to ethanol by the recombinant bacterium Escherichia coli KOll.

Grohmann, K. [USDA Citrus and Subtropical Products Research Labs., Winter Haven, CT (United States); Bothast, R.J. [National Center for Agricultural Utilization Research, Peoria, IL (United States)

1996-10-01

266

Cascade enzymatic reactions for efficient carbon sequestration.  

PubMed

Thermochemical processes developed for carbon capture and storage (CCS) offer high carbon capture capacities, but are generally hampered by low energy efficiency. Reversible cascade enzyme reactions are examined in this work for energy-efficient carbon sequestration. By integrating the reactions of two key enzymes of RTCA cycle, isocitrate dehydrogenase and aconitase, we demonstrate that intensified carbon capture can be realized through such cascade enzymatic reactions. Experiments show that enhanced thermodynamic driving force for carbon conversion can be attained via pH control under ambient conditions, and that the cascade reactions have the potential to capture 0.5mol carbon at pH 6 for each mole of substrate applied. Overall it manifests that the carbon capture capacity of biocatalytic reactions, in addition to be energy efficient, can also be ultimately intensified to approach those realized with chemical absorbents such as MEA. PMID:25708541

Xia, Shunxiang; Zhao, Xueyan; Frigo-Vaz, Benjamin; Zheng, Wenyun; Kim, Jungbae; Wang, Ping

2015-04-01

267

Enzymatic production of glycerol acetate from glycerol.  

PubMed

In this study, we report the enzymatic production of glycerol acetate from glycerol and methyl acetate. Lipases are essential for the catalysis of this reaction. To find the optimum conditions for glycerol acetate production, sequential experiments were designed. Type of lipase, lipase concentration, molar ratio of reactants, reaction temperature and solvents were investigated for the optimum conversion of glycerol to glycerol acetate. As the result of lipase screening, Novozym 435 (Immobilized Candida antarctica lipase B) was turned out to be the optimal lipase for the reaction. Under the optimal conditions (2.5 g/L of Novozym 435, 1:40 molar ratio of glycerol to methyl acetate, 40 °C and tert-butanol as the solvent), glycerol acetate production was achieved in 95.00% conversion. PMID:25640720

Oh, Seokhyeon; Park, Chulhwan

2015-02-01

268

Analysis of mutations that uncouple transport from phosphorylation in enzyme IIGlc of the Escherichia coli phosphoenolpyruvate-dependent phosphotransferase system.  

PubMed Central

Mutations that uncouple glucose transport from phosphorylation were isolated in plasmid-encoded Escherichia coli enzyme IIGlc of the phosphoenolpyruvate-dependent phosphotransferase system (PTS). The uncoupled enzymes IIGlc were able to transport glucose in the absence of the general phosphoryl-carrying proteins of the PTS, enzyme I and HPr, although with relatively low affinity. Km values of the uncoupled enzymes IIGlc for glucose ranged from 0.5 to 2.5 mM, 2 orders of magnitude higher than the value of normal IIGlc. Most of the mutant proteins were still able to phosphorylate glucose and methyl alpha-glucoside (a non-metabolizable glucose analog specific for IIGlc), indicating that transport and phosphorylation are separable functions of the enzyme. Some of the uncoupled enzymes IIGlc transported glucose with a higher rate and lower apparent Km in a pts+ strain than in a delta ptsHI strain lacking the general proteins enzyme I and HPr. Since the properties of these uncoupled enzymes IIGlc in the presence of PTS-mediated phosphoryl transfer resembled those of wild-type IIGlc, these mutants appeared to be conditionally uncoupled. Sequencing of the mutated ptsG genes revealed that all amino acid substitutions occurred in a hydrophilic segment within the hydrophobic N-terminal part of IIGlc. These results suggest that this hydrophilic loop is involved in binding and translocation of the sugar substrate. Images PMID:1569016

Ruijter, G J; van Meurs, G; Verwey, M A; Postma, P W; van Dam, K

1992-01-01

269

Enhanced detection and identification of multiply phosphorylated peptides using TiO2 enrichment in combination with MALDI TOF/TOF MS.  

PubMed

The analysis of PTMs such as phosphorylation has become an important field in MS because they can directly indicate protein states and interactions. Whereas the characterization of singly and doubly phosphorylated peptides has almost become routine, identifying phosphorylation events at multiple residues within a small region of a protein is still problematic. The identification of multiple modifications can be further hampered by low sequence information due to multiple neutral losses from phosphorylated side chains. Here we present a strategy for the analysis of complex phosphopeptides that combines peptide enrichment by titanium dioxide, separation by RP separation on monolithic columns and MS using high energy HE-CAD in a MALDI TOF/TOF analyser. Using synthetic phosphopeptides our approach is compared to multistage activation (MSA) MS/MS and the recently described electron transfer dissociation (ETD) method using an ESI-LTQ mass spectrometer. PMID:18972529

Schmidt, Andreas; Csaszar, Edina; Ammerer, Gustav; Mechtler, Karl

2008-11-01

270

Mechanistic and physiological consequences of HPr(ser) phosphorylation on the activities of the phosphoenolpyruvate:sugar phosphotransferase system in gram-positive bacteria: studies with site-specific mutants of HPr.  

PubMed Central

The bacterial phosphotransferase system (PTS) catalyzes the transport and phosphorylation of its sugar substrates. The protein-kinase-catalyzed phosphorylation of serine 46 in the phosphocarrier protein, HPr, inhibits PTS activity, but neither the mechanism of this inhibition nor its physiological significance is known. Site-specific HPr mutants were constructed in which serine 46 was replaced by alanine (S46A), threonine (S46T), tyrosine (S46Y) or aspartate (S46D). The purified S46D protein exhibited markedly lower Vmax and higher Km values than the wild-type, S46T or S46A protein for the phosphoryl transfer reactions involving HPr(His approximately P). Interactions of HPr with the enzymes catalyzing phosphoryl transfer to and from HPr regulated the kinase-catalyzed reaction. These results establish the inhibitory effect of a negative charge at position 46 on PTS-mediated phosphoryl transfer and suggest that HPr is phosphorylated on both histidyl and seryl residues by enzymes that recognize its tertiary rather than its primary structure. In vivo studies showed that a negative charge on residue 46 of HPr strongly inhibits PTS-mediated sugar uptake, but that competition of two PTS permeases for HPr(His approximately P) is quantitatively more important to the regulation of PTS function than serine 46 phosphorylation. Images PMID:2507315

Reizer, J; Sutrina, S L; Saier, M H; Stewart, G C; Peterkofsky, A; Reddy, P

1989-01-01

271

The UL12 Protein of Herpes Simplex Virus 1 Is Regulated by Tyrosine Phosphorylation  

PubMed Central

ABSTRACT The herpes simplex virus 1 (HSV-1) UL12 protein (pUL12) is a nuclease that is critical for viral replication in vitro and neurovirulence in vivo. In this study, mass spectrometric analysis of pUL12 and phosphate-affinity SDS-polyacrylamide gel electrophoresis analysis identified tyrosine at pUL12 residue 371 (Tyr-371) as a pUL12 phosphorylation site: Tyr-371 is conserved in pUL12 homologs in herpesviruses in all Herpesviridae subfamilies. Replacement of Tyr-371 with phenylalanine (Y371F) in pUL12 (i) abolished its exonuclease activity in HSV-1-infected Vero, HEL, and A549 cells, (ii) reduced viral replication, cell-cell spread, and pUL12 expression in infected cells in a cell type-dependent manner, (iii) led to aberrant subcellular localization of pUL12 in infected cells in a cell type-dependent manner, and (iv) reduced HSV-1 neurovirulence in mice. The effects of the pUL12 Y371F mutation in cell cultures and mice were similar to those of a nuclease-dead double mutation in pUL12, although the Y371F mutation reduced viral replication severalfold more than the nuclease-dead double mutation in a cell type- and multiplicity-of-infection-dependent manner. Replacement of Tyr-371 with glutamic acid, which mimics constitutive phosphorylation, restored the wild-type phenotype in cell cultures and mice. These results suggested that phosphorylation of pUL12 Tyr-371 was essential for pUL12 to express its nuclease activity in HSV-1-infected cells and that this phosphorylation promoted viral replication and cell-cell spread in cell cultures and neurovirulence in mice mainly by upregulating pUL12 nuclease activity and, in part, by regulating the subcellular localization and expression of pUL12 in HSV-1-infected cells. IMPORTANCE Herpesviruses encode a considerable number of enzymes for their replication. Like cellular enzymes, the viral enzymes need to be properly regulated in infected cells. Although the functional aspects of herpesvirus enzymes have gradually been clarified, information on how most of these enzymes are regulated in infected cells is lacking. In the present study, we report that the enzymatic activity of the herpes simplex virus 1 alkaline nuclease pUL12 was regulated by phosphorylation of pUL12 Tyr-371 in infected cells and that this phosphorylation promoted viral replication and cell-cell spread in cell cultures and neurovirulence in mice, mainly by upregulating pUL12 nuclease activity. Interestingly, pUL12 and tyrosine at pUL12 residue 371 appeared to be conserved in all herpesviruses in the family Herpesviridae, raising the possibility that the herpesvirus pUL12 homologs may also be regulated by phosphorylation of the conserved tyrosine residue. PMID:24991005

Fujii, Hikaru; Kato, Akihisa; Mugitani, Michio; Kashima, Yukie; Oyama, Masaaki; Kozuka-Hata, Hiroko; Arii, Jun

2014-01-01

272

Can You Hear Me Now? Regulating Transcriptional Activators by Phosphorylation  

NSDL National Science Digital Library

Extracellular signals often modulate the expression of specific genetic programs by triggering the phosphorylation of relevant transcription factors (TFs). Phosphorylation in turn regulates such TFs by altering their cellular localization, DNA binding affinity, or transcriptional activity. Structural approaches have revealed how phosphorylation turns some TFs on or off; but less is known about how phosphorylation regulates other transcription factors in a graded manner that depends on signal intensity. A recent paper by Graves and colleagues reveals how a group of phosphorylation sites in Ets-1 regulates its DNA binding activity. Their studies provide new insight into the importance of multisite phosphorylation for the graded regulation of transcription and highlight the involvement of allosteric mechanisms in this process.

Kevin H. Gardner (University of Texas Southwestern Medical Center; Departments of Biochemistry and Pharmacology REV)

2005-09-13

273

Regulation of type II PIP kinase by PKD phosphorylation  

Microsoft Academic Search

The type II PIP kinases phosphorylate the poorly understood inositol lipid PtdIns5P, producing the multi-functional lipid product PtdIns(4,5)P2. To investigate the regulation of these enzymes by phosphorylation, we partially purified a protein kinase from pig platelets that phosphorylated type II? PIP kinase on an activation loop threonine residue, T376. Pharmacological studies suggested this protein kinase was protein kinase D (PKD),

Katherine A. Hinchliffe; Robin F. Irvine

2006-01-01

274

Tip60 Acetyltransferase Activity Is Controlled by Phosphorylation  

Microsoft Academic Search

Here we show that the phosphorylation of histone acetyltransferase Tip60, a target of human immunodeficiency virus, type 1-encoded transactivator Tat, plays a crucial role in the control of its catalytic activity. Baculovirus-based expression and purification of Tip60 combined with mass spectrometry allowed the identification of serines 86 and 90 as two major sites of phosphorylation in vivo. The phosphorylation of

Claudie Lemercier; Gaëlle Legube; Cécile Caron; Mathilde Louwagie; Jérôme Garin; Didier Trouche; Saadi Khochbin

2003-01-01

275

High-yield enzymatic bioconversion of hydroquinone to ?-arbutin, a powerful skin lightening agent, by amylosucrase.  

PubMed

?-Arbutin (?-Ab) is a powerful skin whitening agent that blocks epidermal melanin biosynthesis by inhibiting the enzymatic oxidation of tyrosine and L-3,4-dihydroxyphenylalanine (L-DOPA). ?-Ab was effectively synthesized from hydroquinone (HQ) by enzymatic biotransformation using amylosucrase (ASase). The ASase gene from Deinococcus geothermalis (DGAS) was expressed and efficiently purified from Escherichia coli using a constitutive expression system. The expressed DGAS was functional and performed a glycosyltransferase reaction using sucrose as a donor and HQ as an acceptor. The presence of a single HQ bioconversion product was confirmed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). The HQ bioconversion product was isolated by silica gel open column chromatography and its chemical structure determined by 1H and 13C nuclear magnetic resonance (NMR). The product was determined to be hydroquinone-O-?-D-glucopyranoside with a glucose molecule linked to HQ through an ?-glycosidic bond. However, the production yield of the transfer reaction was significantly low (1.3%) due to the instability of HQ in the reaction mixture. The instability of HQ was considerably improved by antioxidant agents, particularly ascorbic acid, implying that HQ is labile to oxidation. A maximum yield of HQ transfer product of 90% was obtained at a 10:1 molar ratio of donor (sucrose) and acceptor (HQ) molecules in the presence of 0.2 mM ascorbic acid. PMID:22314516

Seo, Dong-Ho; Jung, Jong-Hyun; Ha, Suk-Jin; Cho, Hyun-Kug; Jung, Dong-Hyun; Kim, Tae-Jip; Baek, Nam-In; Yoo, Sang-Ho; Park, Cheon-Seok

2012-06-01

276

Impact of mass transport on the enzymatic hydrolysis of rapeseed oil.  

PubMed

In order to assess the capillary segmented flow reactor as a potentially appropriate reactor device for the enzymatic hydrolysis of vegetable oils, a study was made to reveal the impact of incident mass transfer processes on the hydrolysis rate. As demonstrated by means of experiments performed in a modified Lewis-cell type contactor, which allows the independent adjustment of flow rates for both phases, the enzymatic hydrolysis rate of rapeseed oil is strongly governed by mass transport processes taking place in both phases. In the oil phase, any increase in convective mass transfer results in an enhancement of hydrolysis rate due to facilitated removal of fatty acids from interface layer which is known to inhibit the activity of the enzyme adsorbed at the interface. At asynchronous condition when solely the water phase is agitated, however, convective mass transport in the interface layer has an inverse effect on the hydrolysis rate due to the generation of considerable shear stress in the vicinity of the interface unfavorable for the performance of the enzymes. By operating at synchronous agitation conditions, the shear stress can considerably be reduced. Generally, the positive effect of mass transport in the oil phase compensates the negative one in the aqueous phase thus resulting in an overall increase in hydrolysis rate of 57% with increasing stirrer rates. The results can be applied to the operation of segmented-flow capillary reactors by choosing the oil phase as disperse phase and the water phase as continuous phase, respectively. PMID:25007743

Schröter, Sandra; Stahmann, Klaus-Peter; Schnitzlein, Klaus

2015-01-01

277

Complex formation of EphB1/Nck/Caskin1 leads to tyrosine phosphorylation and structural changes of the Caskin1 SH3 domain  

PubMed Central

Background Scaffold proteins have an important role in the regulation of signal propagation. These proteins do not possess any enzymatic activity but can contribute to the formation of multiprotein complexes. Although scaffold proteins are present in all cell types, the nervous system contains them in the largest amount. Caskin proteins are typically present in neuronal cells, particularly, in the synapses. However, the signaling mechanisms by which Caskin proteins are regulated are largely unknown. Results Here we demonstrate that EphB1 receptor tyrosine kinase can recruit Caskin1 through the adaptor protein Nck. Upon activation of the receptor kinase, the SH2 domain of Nck binds to one of its tyrosine residues, while Nck SH3 domains interact with the proline-rich domain of Caskin1. Complex formation of the receptor, adaptor and scaffold proteins results in the tyrosine phosphorylation of Caskin1 on its SH3 domain. The phosphorylation sites were identified by mass-spectrometry as tyrosines 296 and 336. To reveal the structural consequence of this phosphorylation, CD spectroscopy was performed. This measurement suggests that upon tyrosine phosphorylation the structure of the Caskin1 SH3 domain changes significantly. Conclusion Taken together, we propose that the scaffold protein Caskin1 can form a complex with the EphB1 tyrosine kinase via the Nck protein as a linker. Complex formation results in tyrosine phosphorylation of the Caskin1 SH3 domain. Although we were not able to identify any physiological partner of the SH3 domain so far, we could demonstrate that phosphorylation on conserved tyrosine residues results in marked changes in the structure of the SH3 domain. PMID:23181695

2012-01-01

278

Differential VASP phosphorylation controls remodeling of the actin cytoskeleton  

PubMed Central

Summary Proteins of the Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) family link signal transduction pathways to actin cytoskeleton dynamics. VASP is substrate of cAMP-dependent, cGMP-dependent and AMP-activated protein kinases that primarily phosphorylate the sites S157, S239 and T278, respectively. Here, we systematically analyzed functions of VASP phosphorylation patterns for actin assembly and subcellular targeting in vivo and compared the phosphorylation effects of Ena/VASP family members. Methods used were the reconstitution of VASP-null cells with `locked' phosphomimetic VASP mutants, actin polymerization of VASP mutants in vitro and in living cells, site-specific kinase-mediated VASP phosphorylation, and analysis of the endogenous protein with phosphorylation-status-specific antibodies. Phosphorylation at S157 influenced VASP localization, but had a minor impact on F-actin assembly. Phosphorylation of the S157-equivalent site in the Ena/VASP family members Mena and EVL had no effect on the ratio of cellular F-actin to G-actin. By contrast, VASP phosphorylation at S239 (and the equivalent site in Mena) or T278 impaired VASP-driven actin filament formation. The data show that VASP functions are precisely regulated by differential phosphorylation and provide new insights into cytoskeletal control by serine/threonine kinase-dependent signaling pathways. PMID:19825941

Benz, Peter M.; Blume, Constanze; Seifert, Stefanie; Wilhelm, Sabine; Waschke, Jens; Schuh, Kai; Gertler, Frank; Münzel, Thomas; Renné, Thomas

2009-01-01

279

Effect of caspase cleavage-site phosphorylation on proteolysis.  

PubMed Central

Caspases are important mediators of apoptotic cell death. Several cellular protein substrates of caspases contain potential phosphorylation site(s) at the cleavage-site region, and some of these sites have been verified to be phosphorylated. Since phosphorylation may affect substantially the substrate susceptibility towards proteolysis, phosphorylated, non-phosphorylated and substituted oligopeptides representing such cleavage sites were studied as substrates of apoptotic caspases 3, 7 and 8. Peptides containing phosphorylated serine residues at P4 and P1' positions were found to be substantially less susceptible towards proteolysis as compared with the serine-containing analogues, while phosphoserine at P3 did not have a substantial effect. P1 serine as well as P1-phosphorylated, serine-containing analogues of an oligopeptide representing the poly(ADP-ribose) polymerase cleavage site of caspase-3 were not hydrolysed by any of these enzymes, whereas the P1 aspartate-containing peptides were efficiently hydrolysed. These findings were interpreted with the aid of molecular modelling. Our results suggest that cleavage-site phosphorylation in certain positions could be disadvantageous or detrimental with respect to cleavability by caspases. Cleavage-site phosphorylation may therefore provide a regulatory mechanism to protect substrates from caspase-mediated degradation. PMID:12589706

Tözsér, József; Bagossi, Péter; Zahuczky, Gábor; Specht, Suzanne I; Majerova, Eva; Copeland, Terry D

2003-01-01

280

Tropomyosin Ser-283 pseudo-phosphorylation slows myofibril relaxation  

PubMed Central

Tropomyosin (Tm) is a central protein in the Ca2+ regulation of striated muscle. The Tm isoform undergoes phosphorylation at serine residue 283. While the biochemical and steady-state muscle function of muscle purified Tm phosphorylation have been explored, the effects of Tm phosphorylation on the dynamic properties of muscle contraction and relaxation are unknown. To investigate the kinetic regulatory role of Tm phosphorylation we expressed and purified native N-terminal acetylated Ser-283 wild-type, S283A phosphorylation null and S283D pseudo-phosphorylation Tm mutants from insect cells. Purified Tm’s regulate thin filaments similar to that reported for muscle purified Tm. Steady-state Ca2+ binding to troponin C (TnC) in reconstituted thin filaments did not differ between the 3 Tm’s, however disassociation of Ca2+ from filaments containing pseudo-phosphorylated Tm was slowed compared to WT Tm. Replacement of pseudo-phosphorylated Tm into myofibrils similarly prolonged the slow phase of relaxation and decreased the rate of the fast phase without altering activation kinetics. These data demonstrate that Tm pseudo-phosphorylation slows deactivation of the thin filament and muscle force relaxation dynamics in the absence of dynamic and steady-state effects on muscle activation. This supports a role for Tm as a key protein in the regulation of muscle relaxation dynamics. PMID:23232082

Nixon, Benjamin R.; Liu, Bin; Scellini, Beatrice; Tesi, Chiara; Piroddi, Nicoletta; Ogut, Ozgur; Solaro, R. John; Ziolo, Mark T.; Janssen, Paul M.L.; Davis, Jonathan P.; Poggesi, Corrado; Biesiadecki, Brandon J.

2012-01-01

281

Tropomyosin Ser-283 pseudo-phosphorylation slows myofibril relaxation.  

PubMed

Tropomyosin (Tm) is a central protein in the Ca(2+) regulation of striated muscle. The ?Tm isoform undergoes phosphorylation at serine residue 283. While the biochemical and steady-state muscle function of muscle purified Tm phosphorylation have been explored, the effects of Tm phosphorylation on the dynamic properties of muscle contraction and relaxation are unknown. To investigate the kinetic regulatory role of ?Tm phosphorylation we expressed and purified native N-terminal acetylated Ser-283 wild-type, S283A phosphorylation null and S283D pseudo-phosphorylation Tm mutants in insect cells. Purified Tm's regulate thin filaments similar to that reported for muscle purified Tm. Steady-state Ca(2+) binding to troponin C (TnC) in reconstituted thin filaments did not differ between the 3 Tm's, however disassociation of Ca(2+) from filaments containing pseudo-phosphorylated Tm was slowed compared to wild-type Tm. Replacement of pseudo-phosphorylated Tm into myofibrils similarly prolonged the slow phase of relaxation and decreased the rate of the fast phase without altering activation kinetics. These data demonstrate that Tm pseudo-phosphorylation slows deactivation of the thin filament and muscle force relaxation dynamics in the absence of dynamic and steady-state effects on muscle activation. This supports a role for Tm as a key protein in the regulation of muscle relaxation dynamics. PMID:23232082

Nixon, Benjamin R; Liu, Bin; Scellini, Beatrice; Tesi, Chiara; Piroddi, Nicoletta; Ogut, Ozgur; Solaro, R John; Ziolo, Mark T; Janssen, Paul M L; Davis, Jonathan P; Poggesi, Corrado; Biesiadecki, Brandon J

2013-07-01

282

Phosphorylation of Adenosine with Trimetaphosphate Under Simulated Prebiotic Conditions  

NASA Astrophysics Data System (ADS)

The phosphorylation of adenosine with trimetaphosphate in solution, in solid phase and using wet-dry cycles was carried out and it was found that wet-dry cycles were the most efficient. The catalytic effects of some metal ions on the phosphorylation were also studied and it was discovered that Ni(II) is the most effective. The combination of wet-dry cycles (4 cycles) and catalysis by Ni(II) led to an unprecedented high conversion of adenosine to phosphorylated products (30%) near neutral pH. The main phosphorylated products were 2', 3'-cyclic AMP (10.4%) and 5'-ATP (13.0%).

Cheng, Changmei; Fan, Chang; Wan, Rong; Tong, Chunyuan; Miao, Zhiwei; Chen, Jing; Zhao, Yufen

2002-06-01

283

Regulation of cardiac C-protein phosphorylation  

SciTech Connect

Molecular mechanisms of cardiac sympathetic and parasympathetic responses were addressed by studying subcellular changes in protein phosphorylation, cAMP-dependent protein kinase activity and protein phosphatase activity in frog hearts. B-adrenergic agonists increased and muscarinic cholinergic agonists decreased (/sup 32/P)phosphate incorporation into C-protein, a thick filament component. Regulation of protein phosphatase activity by Iso and methacholine (MCh) was assayed using extracts of drug treated frog hearts and (/sup 32/P)phospho-C-protein as substrate. Total phosphatase activity decreased 21% in extracts from hearts perfused with 0.1 ..mu..M Iso and 17% in hearts exposed to Iso plus 1 ..mu..M methacholine. This decrease reflected decreased phosphatase-2A activity. No changes in total phosphatase activity were measurable in broken cells treated with Iso or MCh. The results suggest adrenergic stimulation changes contractile activity in frog hearts by activating cAMP-dependent protein kinase associated with particulate cellular elements and inactivating soluble protein phosphatase-2A. This is the first demonstration of coordinated regulation of these enzymes by B-adrenergic agonists favoring phosphorylation of effector proteins. Coordinated regulation by methacholine in the presence of Iso was not observed.

Titus, F.L.

1985-01-01

284

Effect of Ultrasonic Frequency on Enzymatic Hydrolysis of Cellulose  

NASA Astrophysics Data System (ADS)

The effect of ultrasonic frequency on the enzymatic hydrolysis of cellulose was examined. As the cellulose and enzyme, needle unbleached kraft pulp and cellulase were used. In the cases of the horn-type transducer at 20 kHz and the plate-type transducer at 28 kHz, the enzymatic hydrolysis was accelerated by ultrasonic irradiation. Total sugar concentration linearly increased with ultrasonic intensity. On the other hand, in the case of the plate-type transducer at 500 kHz, the enzymatic hydrolysis was inhibited. Total sugar concentration decreased with increasing ultrasonic intensity.

Yasuda, Keiji; Kato, Daiki; Xu, Zheng; Sakka, Makiko; Sakka, Kazuo

2010-07-01

285

Hits, Fhits and Nits: beyond enzymatic function.  

PubMed

We have briefly summarized what is known about these proteins, but in closing wish to feature the outstanding questions. Hint1 was discovered mistakenly as an inhibitor of Protein Kinase C and designated Pkci, a designation that still confuses the literature. The other Hint family members were discovered by homology to Hint1. Aprataxin was discovered as a result of the hunt for a gene responsible for AOA1. Fhit was discovered through cloning of a familial chromosome translocation breakpoint on chromosome 3 that interrupts the large FHIT gene within an intron, in the FRA3B chromosome region (Ohta et al., 1996), now known to be the region of the human genome most susceptible to DNA damage due to replication stress (Durkin et al., 2008). The NitFhit fusion genewas discovered during searches for Fhit homologs in flies and worms because the fly/worm Nit polypeptide is fused to the 5'-end of the Fhit gene; the mammalian Nit gene family was discovered because of the NitFhit fusion gene, in searches for homologs to the Nit polypeptide of the NitFhit gene. Each of the Hit family member proteins is reported to have enzymatic activities toward putative substrates involving nucleosides or dinucleosides. Most surprisingly, each of the Hit family proteins discussed has been implicated in important DNA damage response pathways and/or tumor suppression pathways. And for each of them it has been difficult to assign definite substrates, to know if the substrates and catalytic products have biological functions, to know if that function is related to the DNA damage response and suppressor functions, and to precisely define the pathways through which tumor suppression occurs. When the fly Nit sequence was found at the 5'-end of the fly Fhit gene, this gene was hailed as a Rosetta stone gene/protein that would help in discovery of the function of Fhit, because the Nit protein should be in the same signal pathway (Pace et al., 2000). However, the mammalian Nit family proteins have turned out to be at least as mysterious as the Fhit proteins, with the Nit1 substrate still unknown and the surprising finding that Nit proteins also appear to behave as tumor suppressor proteins. Whether the predicted enzymatic functions of these proteins are relevant to the observed biological functions, remain among the outstanding unanswered puzzles and raise the question: have these mammalian proteins evolved beyond the putative original enzymatic purpose, such that the catalytic function is now vestigial and subservient to signal pathways that use the protein-substrate complexes in pathways that signal apoptosis or DNA damage response? Or can these proteins be fulfilling catalytic functions independently but in parallel with signal pathway functions, as perhaps observed for Aprataxin? Or is the catalytic function indeed part of the observed biological functions, such as apoptosis and tumor suppression? Perhaps the recent, post-genomic focus on metabolomics and genome-wide investigations of signal pathway networks will lead to answers to some of these outstanding questions. PMID:21035495

Huebner, Kay; Saldivar, Joshua C; Sun, Jin; Shibata, Hidetaka; Druck, Teresa

2011-01-01

286

Enzymatic treatment of duck hepatitis B virus: Topology of the surface proteins for virions and noninfectious subviral particles  

SciTech Connect

The large surface antigen L of duck hepatitis B virus exhibits a mixed topology with the preS domains of the protein alternatively exposed to the particles' interior or exterior. After separating virions from subviral particles (SVPs), we compared their L topologies and showed that both particle types exhibit the same amount of L with the following differences: 1-preS of intact virions was enzymatically digested with chymotrypsin, whereas in SVPs only half of preS was accessible, 2-phosphorylation of L at S118 was completely removed by phosphatase treatment only in virions, 3-iodine-125 labeling disclosed a higher ratio of exposed preS to S domains in virions compared to SVPs. These data point towards different surface architectures of virions and SVPs. Because the preS domain acts in binding to a cellular receptor of hepatocytes, our findings implicate the exclusion of SVPs as competitors for the receptor binding and entry of virions.

Franke, Claudia [Heinrich-Pette-Institut fuer Experimentelle Virologie und Immunologie an der Universitaet Hamburg, Martinistrasse 52, D-20251 Hamburg (Germany); Matschl, Urte [Heinrich-Pette-Institut fuer Experimentelle Virologie und Immunologie an der Universitaet Hamburg, Martinistrasse 52, D-20251 Hamburg (Germany); Bruns, Michael [Heinrich-Pette-Institut fuer Experimentelle Virologie und Immunologie an der Universitaet Hamburg, Martinistrasse 52, D-20251 Hamburg (Germany)]. E-mail: mbruns@hpi.uni-hamburg.de

2007-03-01

287

Effects of targeted phosphorylation site mutations in the DNA-PKcs phosphorylation domain on low and high LET radiation sensitivity  

PubMed Central

The present study investigated the effect of targeted mutations in the DNA-dependent protein kinase catalytic subunit and phosphorylation domains on the survival of cells in response to different qualities of ionizing radiation. Mutated Chinese hamster ovary V3 cells were exposed to 500 MeV/nucleon initial energy and 200 keV/?m monoenergetic Fe ions; 290 MeV/nucleon initial energy and average 50 keV/?m spread-out Bragg peak C ions; 70 MeV/nucleon initial energy and 1 keV/?m monoenergetic protons; and 0.663 MeV initial energy and 0.3 keV/?m Cs137 ? radiation. The results demonstrated that sensitivity to high linear energy transfer radiation is increased when both S2056 and T2609 clusters each contain a point mutation or multiple mutations are present in either cluster, whereas the phosphoinositide 3 kinase cluster only requires a single mutation to induce the sensitized phenotype of V3 cells. Additionally, the present study demonstrated that sensitivity to DNA cross-linking damage by cisplatin only requires a single mutation in one of the three clusters and that additional point mutations do not increase cell sensitivity. PMID:25789011

CARTWRIGHT, IAN M.; BELL, JUSTIN J.; MAEDA, JUNKO; GENET, MATTHEW D.; ROMERO, ASHLEY; FUJII, YOSHIHIRO; FUJIMORI, AKIRA; KITAMUTA, HISASHI; KAMADA, TADASHI; CHEN, DAVID J.; KATO, TAKAMITSU A.

2015-01-01

288

Enzymatic detection of troponin C and melittin bee  

NASA Astrophysics Data System (ADS)

One of the major goals of biosensor technology is to detect and quantify in detail analytes with very high accuracy. To achieve this, much of the emphasis in sensor fabrication has been laid on antibody-antigen interaction. The consequence of this focus of enzyme biosensor studies is the development of critical techniques which can be extended in the detection of Acute Myocardial Infarction (AMI). Biosensors for AMI have attracted considerable interest in the last few years since the monitoring of a specific substance is central in enzymatic reactions. This interest has led to the investigation of biochemical markers of myocardial injury. These biomarkers facilitate the diagnosis and treatment of patients with AMI. Serial measurements of biochemical markers are now universally accepted as an important determinant in AMI diagnosis. Due to their high sensitivity and specificity over other biomarkers, the troponins are the markers of choice for the diagnosis or exclusion of AMI. The present techniques used in the identification of the troponins are lengthy and require large amount of specimen solution. The present research is directed towards the identification of optical detection procedures that are compatible to the miniaturization. In the present study an effort has been made to study the antigen-antibody reaction of rabbit skeletal muscle troponin C (TnC) and bee venom melittin (ME). Fluorescence energy transfer experiments were done to investigate the Ca 2+ -dependant interaction of TnC-ME in a 1:1 complex. Experiments were also conducted on TnC-ME binding at different ratios. These results validate the biosensor technology and illustrate how a biosensor can be developed based on the study of interaction between monoclonal antibody and antigen reaction in real time. The reported experimental results provide valuable information that will be useful in the development of a biosensor for the detection of AMI.

Jeetender, Amritsar; Stiharu, Ion; Packirisamy, Muthukumaran

2005-04-01

289

A Grammar Inference Approach for Predicting Kinase Specific Phosphorylation Sites  

PubMed Central

Kinase mediated phosphorylation site detection is the key mechanism of post translational mechanism that plays an important role in regulating various cellular processes and phenotypes. Many diseases, like cancer are related with the signaling defects which are associated with protein phosphorylation. Characterizing the protein kinases and their substrates enhances our ability to understand the mechanism of protein phosphorylation and extends our knowledge of signaling network; thereby helping us to treat such diseases. Experimental methods for predicting phosphorylation sites are labour intensive and expensive. Also, manifold increase of protein sequences in the databanks over the years necessitates the improvement of high speed and accurate computational methods for predicting phosphorylation sites in protein sequences. Till date, a number of computational methods have been proposed by various researchers in predicting phosphorylation sites, but there remains much scope of improvement. In this communication, we present a simple and novel method based on Grammatical Inference (GI) approach to automate the prediction of kinase specific phosphorylation sites. In this regard, we have used a popular GI algorithm Alergia to infer Deterministic Stochastic Finite State Automata (DSFA) which equally represents the regular grammar corresponding to the phosphorylation sites. Extensive experiments on several datasets generated by us reveal that, our inferred grammar successfully predicts phosphorylation sites in a kinase specific manner. It performs significantly better when compared with the other existing phosphorylation site prediction methods. We have also compared our inferred DSFA with two other GI inference algorithms. The DSFA generated by our method performs superior which indicates that our method is robust and has a potential for predicting the phosphorylation sites in a kinase specific manner. PMID:25886273

Datta, Sutapa; Mukhopadhyay, Subhasis

2015-01-01

290

Isomerization of 1-O-indol-3-ylacetyl-beta-D-glucose. Enzymatic hydrolysis of 1-O, 4-O, and 6-O-indol-3-ylacetyl-beta-D-glucose and the enzymatic synthesis of indole-3-acetyl glycerol by a hormone metabolizing complex  

NASA Technical Reports Server (NTRS)

The first compound in the series of reactions leading to the ester conjugates of indole-3-acetic acid (IAA) in kernels of Zea mays sweet corn is the acyl alkyl acetal, 1-O-indol-3-ylacetyl-beta-D-glucose (1-O-IAGlu). The enzyme catalyzing the synthesis of this compound is UDP-glucose:indol-3-ylacetate glucosyl-transferase (IAGlu synthase). The IAA moiety of the high energy compound 1-O-IAGlu may be enzymatically transferred to myo-inositol or to glycerol or the 1-O-IAGlu may be enzymatically hydrolyzed. Alternatively, nonenzymatic acyl migration may occur to yield the 2-O, 4-O, and 6-O esters of IAA and glucose. The 4-O and 6-O esters may then be enzymatically hydrolyzed to yield free IAA and glucose. This work reports new enzymatic activities, the transfer of IAA from 1-O-IAGlu to glycerol, and the enzyme-catalyzed hydrolysis of 4-O and 6-O-IAGlu. Data is also presented on the rate of non-enzymatic acyl migration of IAA from the 1-O to the 4-O and 6-O positions of glucose. We also report that enzymes catalyzing the synthesis of 1-O-IAGlu and the hydrolysis of 1-O, 4-O, and 6-O-IAGlu fractionate as a hormone metabolizing complex. The association of synthetic and hydrolytic capabilities in enzymes which cofractionate may have physiological significance.

Kowalczyk, S.; Bandurski, R. S.

1990-01-01

291

Convergent evolution of similar enzymatic function on different protein folds: the hexokinase, ribokinase, and galactokinase families of sugar kinases.  

PubMed Central

Kinases that catalyze phosphorylation of sugars, called here sugar kinases, can be divided into at least three distinct nonhomologous families. The first is the hexokinase family, which contains many prokaryotic and eukaryotic sugar kinases with diverse specificities, including a new member, rhamnokinase from Salmonella typhimurium. The three-dimensional structure of hexokinase is known and can be used to build models of functionally important regions of other kinases in this family. The second is the ribokinase family, of unknown three-dimensional structure, and comprises pro- and eukaryotic ribokinases, bacterial fructokinases, the minor 6-phosphofructokinase 2 from Escherichia coli, 6-phosphotagatokinase, 1-phosphofructokinase, and, possibly, inosine-guanosine kinase. The third family, also of unknown three-dimensional structure, contains several bacterial and yeast galactokinases and eukaryotic mevalonate and phosphomevalonate kinases and may have a substrate binding region in common with homoserine kinases. Each of the three families of sugar kinases appears to have a distinct three-dimensional fold, since conserved sequence patterns are strikingly different for the three families. Yet each catalyzes chemically equivalent reactions on similar or identical substrates. The enzymatic function of sugar phosphorylation appears to have evolved independently on the three distinct structural frameworks, by convergent evolution. In addition, evolutionary trees reveal that (1) fructokinase specificity has evolved independently in both the hexokinase and ribokinase families and (2) glucose specificity has evolved independently in different branches of the hexokinase family. These are examples of independent Darwinian adaptation of a structure to the same substrate at different evolutionary times. The flexible combination of active sites and three-dimensional folds observed in nature can be exploited by protein engineers in designing and optimizing enzymatic function. PMID:8382990

Bork, P.; Sander, C.; Valencia, A.

1993-01-01

292

MICROCHIP ENZYMATIC ASSAY OF ORGANOPHOSPHATE NERVE AGENTS. (R830900)  

EPA Science Inventory

An on-chip enzymatic assay for screening organophosphate (OP) nerve agents, based on a pre-column reaction of organophosphorus hydrolase (OPH), electrophoretic separation of the phosphonic acid products, and their contactless-conductivity detection, is described. Factors affec...

293

Enzymatic properties of transplanted glomerulosa cells.  

PubMed

There are several theories about the physiologic regeneration of adrenals and maintenance of physiologic steroid secretion after subtotal loss of adrenal cortical cells. According to the cell migration theory, adrenocytes from the zona glomerulosa migrate centripetally toward the medulla. This theory is opposed by the zonal theory according to which each zone resplenishes its cells independently. What these theories have in common is that they are based on data from the intact adrenal gland. We transplanted purified glomerulosa cells under the kidney's capsule of Lewis rats. The tissue was removed 30, 60, 90, and 150 days after transplantation to investigate the presence of two specific enzymes that are responsible for the secretion of aldosterone and corticosterone. Cytochrome p-450as is specific for glomerulosa cells producing aldosterone, and cytochrome p-45011beta is specific for fasciculata cells producing corticosterone. After sequencing the genetic code of these enzymes it became possible to demonstrate expression of the enzymes by in situ hybridization. The transplanted glomerulosa cells turned their enzymatic property to fasciculata cells expressing cytochrome p-45011beta. Our results suggest that glomerulosa cells are able to take over the physiologic function of a whole adrenal cortex in the absence of fasciculata cells, and that they are sufficient to maintain the function of the adrenal cortex. PMID:8678974

Scheumann, G F; Heitmann, P; Teebken, O E; Mössinger, E; Mellon, S H; Pichlmayr, R

1996-09-01

294

Ecological and enzymatic responses to petroleum contamination.  

PubMed

The changes in microbial ecology interpreted from taxonomic and functional genes and biological functions represented by urease and dehydrogenase activities were monitored in soil contaminated with different petroleum hydrocarbons including crude oil, diesel, n-hexadecane and poly-aromatic hydrocarbons (PAHs). It was shown that the presence of n-hexadecane stimulated the activity of indigenous microorganisms, especially alkane degrading bacteria, and led to over 20% degradation of n-hexadecane within one month. No obvious degradation of the other three types of petroleum hydrocarbons was observed. The stimulation effect was most marked in the soil spiked with a medium concentration (2500 mg kg(-1) dry soil) of n-hexadecane. However, the presence of PAHs completely inhibited the previously-mentioned bioactivities of the soil. The content of PAH degrading bacteria, however, increased more than 10-fold, indicating the selection effect of PAHs on soil bacteria. The impacts of diesel and crude oil on the microbial ecology and biological functions varied significantly with their concentration. The disclosure of the ecological and enzymatic responses could be helpful in soil bioremediation. PMID:24765642

Wu, Binbin; Lan, Tian; Lu, Diannan; Liu, Zheng

2014-05-01

295

Nanostructured Organometallic Polymers for Enzymatic Bioenergy  

NASA Astrophysics Data System (ADS)

The development of efficient enzymatic biofuel cell is a subject of considerable studies in past decades for potential applications such as biomedical devices and microchip systems. One of the key challenges in advancing the technology lies in the power densities of the system. Limitations have been arisen from the buried redox active sites within enzyme structure and poor interplay between redox reactions. In present study, a glucose oxidase is employed as a model enzyme and ferrocene-containing organometallic block copolymers are chosen for the electron mediators. Wiring of glucose oxidase into electrode surface was successfully achieved by cross-linked networks of organometallic polymers and remarkably, catalytic current densities of the fabricated electrodes have proven be a sensitive function of the morphologies of electron mediators. Different nanoscale morphologies, i.e., bicontinous structure, nanowires, and nanoparticles, have been derived and the use of bicontinous morphology confirms 2-50 times improved catalytic current response than the values obtained from other morphologies. The bio-sensing ability of the fabricated electrode with structural optimization was also exploited and good sensitivity is obtained at the physiological concentration of glucose in blood.

Park, Moon Jeong; Lee, Jungphil

2012-02-01

296

Natural Product Sugar Biosynthesis and Enzymatic Glycodiversification**  

PubMed Central

Many biologically active small molecule natural products produced by microorganisms derive their activities from sugar substituents. Changing the structures of these sugars can have a profound impact on the biological properties of the parent compounds. This realization has inspired attempts to derivatize the sugar moieties of these natural products through exploitation of the sugar biosynthetic machinery. This approach requires an understanding of the biosynthetic pathway of each target sugar and detailed mechanistic knowledge of the key enzymes. Scientists have begun to unravel the biosynthetic logic behind the assembly of many glycosylated natural products, and have found that a core set of enzyme activities is mixed and matched to synthesize the diverse sugar structures observed in nature. Remarkably, many of these sugar biosynthetic enzymes and glycosyltransferases also exhibit relaxed substrate specificity. The promiscuity of these enzymes has prompted efforts to modify the sugar structures and/or alter the glycosylation patterns of natural products via metabolic pathway engineering and/or enzymatic glycodiversification. In applied biomedical research, these studies will enable the development of new glycosylation tools and generate novel glycoforms of secondary metabolites with useful biological activity. PMID:19058170

Thibodeaux, Christopher J.; Melançon, Charles E.; Liu, Hung-wen

2009-01-01

297

Enzymatically Degradable Mussel-Inspired Adhesive Hydrogel  

PubMed Central

Mussel-inspired adhesive hydrogels represent innovative candidate medical sealants or glues. In the present work, we describe an enzyme-degradable mussel-inspired adhesive hydrogel formulation, achieved by incorporating minimal elastase substrate peptide Ala-Ala into the branched poly(ethylene glycol) (PEG) macromonomer structure. The system takes advantage of neutrophil elastase expression upregulation and secretion from neutrophils upon recruitment to wounded or inflamed tissue. By integrating adhesive degradation behaviors that respond to cellular cues, we expand the functional range of our mussel-inspired adhesive hydrogel platforms. Rapid (<1 min) and simultaneous gelation and adhesion of the proteolytically active, catechol-terminated precursor macromonomer was achieved by addition of sodium periodate oxidant. Rheological analysis and equilibrium swelling studies demonstrated that the hydrogel is appropriate for soft tissue-contacting applications. Notably, hydrogel storage modulus (G?) achieved values on the order of 10 kPa, and strain at failure exceeded 200% strain. Lap shear testing confirmed the material’s adhesive behavior (shear strength: 30.4 ± 3.39 kPa). Although adhesive hydrogel degradation was not observed during short-term (27 h) in vitro treatment with neutrophil elastase, in vivo degradation proceeded over several months following dorsal subcutaneous implantation in mice. This work represents the first example of an enzymatically degradable mussel-inspired adhesive and expands the potential biomedical applications of this family of materials. PMID:22059927

2011-01-01

298

Enzymatic production of hydrogen from glucose  

SciTech Connect

The objective of this research is to optimize conditions for the enzymatic production of hydrogen gas from biomass-derived glucose. This new project is funded at 0.5 PY level of effort for FY 1995. The rationale for the work is that cellulose is, potentially, a vast source of hydrogen and that enzymes offer a specific and efficient method for its extraction with minimal environmental impact. This work is related to the overall hydrogen program goal of technology development and validation. The approach is based on knowledge that glucose is oxidized by the NADP{sup +} requiring enzyme glucose dehydrogenase (GDH) and that the resulting NADPH can donate its electrons to hydrogenase (H{sub 2}ase) which catalyzes the evolution of H{sub 2}. Thus hydrogen production from glucose was achieved using calf liver GDH and Pyrococcus furiosus H{sub 2}ase yielding 17% of theoretical maximum expected. The cofactor NADP{sup +} for this reaction was regenerated and recycled. Current and future work includes understanding the rate limiting steps of this process and the stabilization/immobilization of the enzymes for long term hydrogen production. Cooperative interactions with the Universities of Georgia and Bath for obtaining thermally stable enzymes are underway.

Woodward, J. [Oak Ridge National Lab., TN (United States); Mattingly, S.M.

1995-06-01

299

Enzymatic hydrolysis of spent coffee ground.  

PubMed

Spent coffee ground (SCG) is the main residue generated during the production of instant coffee by thermal water extraction from roasted coffee beans. This waste is composed mainly of polysaccharides such as cellulose and galactomannans that are not solubilised during the extraction process, thus remaining as unextractable, insoluble solids. In this context, the application of an enzyme cocktail (mannanase, endoglucanase, exoglucanase, xylanase and pectinase) with more than one component that acts synergistically with each other is regarded as a promising strategy to solubilise/hydrolyse remaining solids, either to increase the soluble solids yield of instant coffee or for use as raw material in the production of bioethanol and food additives (mannitol). Wild fungi were isolated from both SCG and coffee beans and screened for enzyme production. The enzymes produced from the selected wild fungi and recombinant fungi were then evaluated for enzymatic hydrolysis of SCG, in comparison to commercial enzyme preparations. Out of the enzymes evaluated on SCG, the application of mannanase enzymes gave better yields than when only cellulase or xylanase was utilised for hydrolysis. The recombinant mannanase (Man1) provided the highest increments in soluble solids yield (17 %), even when compared with commercial preparations at the same protein concentration (0.5 mg/g SCG). The combination of Man1 with other enzyme activities revealed an additive effect on the hydrolysis yield, but not synergistic interaction, suggesting that the highest soluble solid yields was mainly due to the hydrolysis action of mannanase. PMID:23436225

Jooste, T; García-Aparicio, M P; Brienzo, M; van Zyl, W H; Görgens, J F

2013-04-01

300

Enzymatic analysis of UDP-N-acetylglucosamine  

PubMed Central

The Methanococcus maripaludis MMP0352 protein belongs to an oxidoreductase family that has been proposed to catalyze the NAD+-dependent oxidation of the 3?-position of uridine diphosphate N-acetyl-d-glucosamine (UDP-GlcNAc), forming a 3-hexulose sugar nucleotide. The heterologously expressed MMP0352 protein was purified and shown to efficiently catalyze UDP-GlcNAc oxidation forming one NADH equivalent. This enzyme was used to develop a fixed endpoint fluorometric method to analyze UDP-GlcNAc. The enzyme is highly specific for this acetamido sugar nucleotide, and the procedure had a detection limit of 0.2 ?M UDP-GlcNAc in a 1-ml sample. Using the method of standard addition, UDP-GlcNAc concentrations were measured in deproteinized extracts of Escherichia coli, Saccharomyces cerevisiae and HeLa carcinoma cells. Equivalent concentrations were determined by both enzymatic and chromatographic analyses, validating this method. This procedure can be adapted for the high-throughput analysis of changes in cellular UDP-GlcNAc concentrations during time series experiments or inhibitor screens. PMID:18634748

Namboori, Seema C.; Graham, David E.

2008-01-01

301

The role of tau phosphorylation in transfected COS1 cells  

Microsoft Academic Search

Tau cDNAs from each of the six human isoforms were transfected into COS- 1 cells and, in every case, more than one peptide was observed. The diversity of expressed isoforms was due to different levels of tau phosphorylation. Tau phosphorylation results in a decrease of the protein electrophoretic mobility. The major contribution to this mobility shift is due to the

M. Medina; E. Montejo de Garcini; J. Avila

1995-01-01

302

Sequence, Structure, and Network Evolution of Protein Phosphorylation  

NSDL National Science Digital Library

With the increasing amount of information about the phosphoproteomes of diverse organisms, it is now possible to begin to evaluate this information in the context of evolution. Work described at the inaugural Keystone Symposium on “The Evolution of Protein Phosphorylation” covered a wide range of eukaryotic and prokaryotic organisms, revealing insights into the evolution of protein phosphorylation at the sequence, network, and structural levels.

Chris Soon Heng Tan (Mount Sinai Hospital; Samuel Lunenfeld Research Institute REV)

2011-07-19

303

Phosphorylation alters backbone conformational preferences of serine and threonine peptides.  

PubMed

Despite the notion that a control of protein function by phosphorylation works mainly by inducing its conformational changes, the phosphorylation effects on even small peptide conformation have not been fully understood yet. To study its possible effects on serine and threonine peptide conformations, we recently carried out pH- and temperature-dependent circular dichroism (CD) as well as (1)H NMR studies of the phosphorylated serine and threonine peptides and compared them with their unphosphorylated analogs. In the present article, by performing the self-consistent singular value decomposition analysis of the temperature-dependent CD spectra and by analyzing the (3)J(H(N),H(?)) coupling constants extracted from the NMR spectra, the populations of the polyproline II (PPII) and ?-strand conformers of the phosphorylated Ser and Thr peptides are determined. As temperature is increased, the ?-strand populations of both phosphorylated serine and threonine peptides increase. However, the dependences of PPII/?-strand population ratio on pH are different for these two cases. The phosphorylation of the serine peptide enhances the PPII propensity, whereas that of the threonine peptide has the opposite effect. This suggests that the serine and threonine phosphorylations can alter the backbone conformational propensity via direct but selective intramolecular hydrogen-bonding interactions with the peptide N--H groups. This clearly indicates that the phosphoryl group actively participates in modulating the peptide backbone conformations. PMID:21989936

Kim, Su-Yeon; Jung, Youngae; Hwang, Geum-Sook; Han, Hogyu; Cho, Minhaeng

2011-11-01

304

Tyrosine phosphorylation enhances activity of pneumococcal autolysin LytA.  

PubMed

Tyrosine phosphorylation has long been recognized as a crucial post-translational regulatory mechanism in eukaryotes. However, only in the past decade has recognition been given to the crucial importance of bacterial tyrosine phosphorylation as an important regulatory feature of pathogenesis. This study describes the effect of tyrosine phosphorylation on the activity of a major virulence factor of the pneumococcus, the autolysin LytA, and a possible connection to the Streptococcus pneumoniae capsule synthesis regulatory proteins (CpsB, CpsC and CpsD). We show that in vitro pneumococcal tyrosine kinase, CpsD, and the protein tyrosine phosphatase, CpsB, act to phosphorylate and dephosphorylate LytA. Furthermore, this modulates LytA function in vitro with phosphorylated LytA binding more strongly to the choline analogue DEAE. A phospho-mimetic (Y264E) mutation of the LytA phosphorylation site displayed similar phenotypes as well as an enhanced dimerization capacity. Similarly, tyrosine phosphorylation increased LytA amidase activity, as evidenced by a turbidometric amidase activity assay. Similarly, when the phospho-mimetic mutation was introduced in the chromosomal lytA of S. pneumoniae, autolysis occurred earlier and at an enhanced rate. This study thus describes, to our knowledge, the first functional regulatory effect of tyrosine phosphorylation on a non-capsule-related protein in the pneumococcus, and suggests a link between the regulation of LytA-dependent autolysis of the cell and the biosynthesis of capsular polysaccharide. PMID:25288646

Standish, Alistair J; Whittall, Jonathan J; Morona, Renato

2014-12-01

305

Michael Lampson, Research Proposal Measuring phosphorylation dynamics in living cells  

E-print Network

Michael Lampson, Research Proposal 1 Measuring phosphorylation dynamics in living cells: from local. Measurements of phosphorylation dynamics in living cells can provide a powerful representation of the state of localized peptide substrates in living cells. This proposal is motivated by specific questions related

Kim, Junhyong

306

Developmental regulation of tau phosphorylation, tau kinases, and tau phosphatases  

PubMed Central

Tau is a neuronal microtubule-associated protein. Its hyperphosphorylation plays a critical role in Alzheimer disease (AD). Expression and phosphorylation of tau are regulated developmentally, but its dynamic regulation and the responsible kinases or phosphatases remain elusive. Here, we studied the developmental regulation of tau in rats during development from embryonic day 15 through the age of 24 months. We found that tau expression increased sharply during the embryonic stage and then became relatively stable, whereas tau phosphorylation was much higher in developing brain than in mature brain. However, the extent of tau phosphorylation at seven of the 14 sites studied was much less in developing brain than in AD brain. Tau phosphorylation during development matched the period of active neurite outgrowth in general. Tau phosphorylation at various sites had different topographic distributions. Several tau kinases appeared to regulate tau phosphorylation collectively at overlapping sites, and the decrease of overall tau phosphorylation in adult brain might be due to the higher levels of tau phosphatases in mature brain. These studies provide new insight into the developmental regulation of site-specific tau phosphorylation and identify the likely sites required for the abnormal hyperphosphorylation of tau in AD. PMID:19183272

Yu, Yang; Run, Xiaoqin; Liang, Zhihou; Li, Yi; Liu, Fei; Liu, Ying; Iqbal, Khalid; Grundke-Iqbal, Inge; Gong, Cheng-Xin

2009-01-01

307

Literature mining of protein phosphorylation using dependency parse trees.  

PubMed

As one of the most common post-translational modifications (PTMs), protein phosphorylation plays an important role in various biological processes, such as signaling transduction, cellular metabolism, differentiation, growth, regulation and apoptosis. Protein phosphorylation is of great value not only in illustrating the underlying molecular mechanisms but also in treatment of diseases and design of new drugs. Recently, there is an increasing interest in automatically extracting phosphorylation information from biomedical literatures. However, it still remains a challenging task due to the tremendous volume of literature and circuitous modes of expression for protein phosphorylation. To address this issue, we propose a novel text-mining method for efficiently retrieving and extracting protein phosphorylation information from literature. By employing natural language processing (NLP) technologies, this method transforms each sentence into dependency parse trees that can precisely reflect the intrinsic relationship of phosphorylation-related key words, from which detailed information of substrates, kinases and phosphorylation sites is extracted based on syntactic patterns. Compared with other existing approaches, the proposed method demonstrates significantly improved performance, suggesting it is a powerful bioinformatics approach to retrieving phosphorylation information from a large amount of literature. A web server for the proposed method is freely available at http://bioinformatics.ustc.edu.cn/pptm/. PMID:24440484

Wang, Mang; Xia, Hong; Sun, Dongdong; Chen, Zhaoxiong; Wang, Minghui; Li, Ao

2014-06-01

308

Troponin I phosphorylation in heart homogenate from diabetic rat  

Microsoft Academic Search

Although cardiac myofibrillar ATPase activity has been shown to be depressed during the development of diabetic heart dysfunction, the mechanisms of this alteration are not fully understood. Since phosphorylation of troponin I (TnI) is known to decrease the myofibrillar ATPase activity, the present study was undertaken to examine the TnI phosphorylation capacity in the diabetic heart homogenate. For this purpose

Xueliang Liu; Nobuakira Takeda; Naranjan S. Dhalla

1996-01-01

309

RESEARCH ARTICLE Phosphorylation of Rat Aquaporin-4 at Ser111  

E-print Network

RESEARCH ARTICLE Phosphorylation of Rat Aquaporin-4 at Ser111 Is Not Required for Channel Gating gating of the channel itself. Protein kinase (PK)-dependent phosphorylation of Ser111 has been reported, questioned based on the crystal structure of the human AQP4. Our study aimed to resolve if Ser111 was indeed

de Groot, Bert

310

A Peek into the Complex Realm of Histone Phosphorylation?  

PubMed Central

Although discovered long ago, posttranslational phosphorylation of histones has been in the spotlight only recently. Information is accumulating almost daily on phosphorylation of histones and their roles in cellular physiology and human diseases. An extensive cross talk exists between phosphorylation and other posttranslational modifications, which together regulate various biological processes, including gene transcription, DNA repair, and cell cycle progression. Recent research on histone phosphorylation has demonstrated that nearly all histone types are phosphorylated at specific residues and that these modifications act as a critical intermediate step in chromosome condensation during cell division, transcriptional regulation, and DNA damage repair. As with all young fields, apparently conflicting and sometimes controversial observations about histone phosphorylations and their true functions in different species are found in the literature. Accumulating evidence suggests that instead of functioning strictly as part of a general code, histone phosphorylation probably functions by establishing cross talk with other histone modifications and serving as a platform for recruitment or release of effector proteins, leading to a downstream cascade of events. Here we extensively review published information on the complexities of histone phosphorylation, the roles of proteins recognizing these modifications and the resuting physiological outcome, and, importantly, future challenges and opportunities in this fast-moving field. PMID:22006017

Banerjee, Taraswi; Chakravarti, Debabrata

2011-01-01

311

Phosphorylation influences the translation state of FMRP-associated polyribosomes.  

PubMed

Fragile X mental retardation protein, FMRP, is absent in patients with fragile X syndrome, a common form of mental retardation. FMRP is a nucleocytoplasmic RNA binding protein that is primarily associated with polyribosomes. FMRP is believed to be a translational repressor and may regulate the translation of certain mRNAs at the base of dendritic spines in neurons. However, little is known about the regulation of FMRP. Using mass spectrometry and site-directed mutagenesis, we show that FMRP is phosphorylated between residues 483 and 521, N-terminal to the RGG box, both in murine brain and in cultured cells. Primary phosphorylation occurs on the highly conserved serine 499, which triggers hierarchical phosphorylation of nearby serines. FMRP is phosphorylated within 2-4 h of synthesis, however, phosphorylation has no effect on the half-life of the protein. In contrast to the Drosophila ortholog dFxr, the phosphorylation status of mammalian FMRP does not influence its association with specific mRNAs in vivo. However, we find unphosphorylated FMRP associated with actively translating polyribosomes while a fraction of phosphorylated FMRP is associated with apparently stalled polyribosomes. Our data suggest that the phosphorylation may regulate FMRP and that the release of FMRP-induced translational suppression may involve a dephosphorylation signal. PMID:14570712

Ceman, Stephanie; O'Donnell, William T; Reed, Matt; Patton, Stephana; Pohl, Jan; Warren, Stephen T

2003-12-15

312

Polyamine Stimulation of Protein Phosphorylation in Isolated Pea Nuclei 1  

PubMed Central

The phosphorylation of several proteins in isolated nuclei from Pisum sativum L. was stimulated by spermine. Although spermine increased the general protein phosphorylation by 10 to 20%, it increased the phosphorylation of a 47 kilodalton polypeptide by 150%. By comparison other polyamines, spermidine, putrescine, and cadavarine had far less effect on the phosphorylation of the 47 kilodalton or any other polypeptide. Sodium fluoride was able to inhibit the phosphorylation of the 47 kilodalton polypeptide in the control, implying the participation of protein phosphatase(s) in the phosphorylation of nuclear proteins. Spermine stimulated the phosphorylation of the 47 kilodalton polypeptide over the controls, even in the presence of NaF. This result indicates that spermine probably activates a nuclear kinase, a conclusion supported also by thiophosphorylation data. The inability of ethyleneglycol-bis (?-amino-ethyl ether)-N, N?-tetraacetic acid and Compound 48/80, a calmodulin antagonist, to inhibit this spermine stimulated phosphorylation renders improbable any role of calcium and calmodulin in mediating this response. Images Fig. 1 PMID:16665091

Datta, Neeraj; Hardison, Linda K.; Roux, Stanley J.

1986-01-01

313

Tyrosine phosphorylation of Dbl regulates GTPase signaling.  

PubMed

Rho GTPases are molecular "switches" that cycle between "on" (GTP-bound) and "off" (GDP-bound) states and regulate numerous cellular activities such as gene expression, protein synthesis, cytoskeletal rearrangements, and metabolic responses. Dysregulation of GTPases is a key feature of many diseases, especially cancers. Guanine nucleotide exchange factors (GEFs) of the Dbl family are activated by mitogenic cell surface receptors and activate the Rho family GTPases Cdc42, Rac1, and RhoA. The molecular mechanisms that regulate GEFs from the Dbl family are poorly understood. Our studies reveal that Dbl is phosphorylated on tyrosine residues upon stimulation by growth factors and that this event is critical for the regulated activation of the GEF. These findings uncover a novel layer of complexity in the physiological regulation of this protein. PMID:24778185

Gupta, Meghana; Qi, Xiaojun; Thakur, Varsha; Manor, Danny

2014-06-13

314

Lime pretreatment and enzymatic hydrolysis of corn stover  

E-print Network

(Williams et 2 al. 1982, Ingram et al. 1995, and Holtzapple et al. 1997). To increase the enzymatic digestibility of lignocellulosic biomass, it is treated mechanically (e.g., ball milling) or chemically (e.g., acid/alkali treatment). The treated... biomass then is enzymatically hydrolyzed to sugars by cellulase and hemicellulase. The resulting sugars are fermented to ethanol by yeast fermentation (Hahn et al. 1996). This process needs cellulase enzyme complexes to convert biomass to sugars...

Kim, Se Hoon

2005-08-29

315

Effects of Enzymatic Sterilization Detergents on the Corneal Endothelium  

Microsoft Academic Search

Objective: To evaluate the potential of enzymatic de- tergents to cause endothelial damage and anterior seg- ment inflammation. Methods: Paired rabbit corneas were mounted in an in vitro specular microscope. Endothelia were perfused ei- ther with the sterile irrigating solution BSS Plus (Alcon Laboratories Inc, Ft Worth, Tex) (control) or 0.1%, 0.4%, or 1.0% Medline Enzymatic Detergent (Medline Indus- tries

Chirag Parikh; Brian D. Sippy; Daniel F. Martin; Henry F. Edelhauser

316

The regulation of STIM1 by phosphorylation  

PubMed Central

Calcium ion (Ca2+) concentration plays a key role in cell signaling in eukaryotic cells. At the cellular level, Ca2+ directly participates in such diverse cellular events as adhesion and migration, differentiation, contraction, secretion, synaptic transmission, fertilization, and cell death. As a consequence of these diverse actions, the cytosolic concentration of free Ca2+ is tightly regulated by the coordinated activity of Ca2+ channels, Ca2+ pumps, and Ca2+-binding proteins. Although many of these regulators have been studied in depth, other proteins have been described recently, and naturally far less is known about their contribution to cell physiology. Within this last group of proteins, STIM1 has emerged as a major contributor to Ca2+ signaling by means of its activity as Ca2+ channel regulator. STIM1 is a protein resident mainly, but not exclusively, in the endoplasmic reticulum (ER), and activates a set of plasma membrane Ca2+ channels termed store-operated calcium channels (SOCs) when the concentration of free Ca2+ within the ER drops transiently as a result of Ca2+ release from this compartment. Knowledge regarding the molecular architecture of STIM1 has grown considerably during the last years, and several structural domains within STIM1 have been reported to be required for the specific molecular interactions with other important players in Ca2+ signaling, such as Ca2+ channels and microtubules. Within the modulators of STIM1, phosphorylation has been shown to both activate and inactivate STIM1-dependent Ca2+ entry depending on the cell type, cell cycle phase, and the specific residue that becomes modified. Here we shall review current knowledge regarding the modulation of STIM1 by phosphorylation. PMID:24505502

Pozo-Guisado, Eulalia; Martin-Romero, Francisco Javier

2013-01-01

317

Factors Affecting Hexose Phosphorylation in Acetobacter xylinum  

PubMed Central

Fructose was oxidized and converted to cellulose by cells of Acetobacter xylinum grown on fructose or succinate, but not by cells grown on glucose. In resting fructose-grown cells, glucose strongly suppressed fructose utilization. Extracts obtained from fructose- or succinate-grown cells catalyzed the adenosine triphosphate (ATP)-dependent formation of the 6-phosphate esters of glucose and fructose, whereas glucose-grown cell extracts phosphorylated glucose but not fructose. Fructokinase and glucokinase activities were separated and partially purified from cells grown on glucose, fructose, or succinate. Whereas fructokinase phosphorylated fructose only, glucokinase was active towards glucose and less active towards mannose and glucosamine. The optimal pH for the fructokinase was 7.4 and for the glucokinase was 8.5. The Km values for the fructokinase were: fructose, 6.2 mm; and ATP, 0.83 mm. The Km values for the glucokinase were: glucose, 0.22 mm; and ATP, 4.2 mm. Fructokinase was inhibited by glucose, glucosamine, mannose, and deoxyglucose in a manner competitive with respect to fructose, with Ki values of 0.1, 0.14, 0.5, and 7.5 mm, respectively. Adenosine diphosphate (ADP) and adenosine monophosphate (AMP) inhibited both kinases noncompetitively with respect to ATP. The Ki values were: 1.8 mm (ADP) and 2.1 mm (AMP) for fructokinase, and 2.2 mm (ADP) and 9.6 mm (AMP) for glucokinase. Fructose metabolism in A. xylinum appears to be regulated by the synthesis and activity of fructokinase. PMID:5053462

Benziman, Moshe; Rivetz, B.

1972-01-01

318

Phosphorylation of the antiviral protein interferon-inducible transmembrane protein 3 (IFITM3) dually regulates its endocytosis and ubiquitination.  

PubMed

Interferon-inducible transmembrane protein 3 (IFITM3) is essential for innate defense against influenza virus in mice and humans. IFITM3 localizes to endolysosomes where it prevents virus fusion, although mechanisms controlling its trafficking to this cellular compartment are not fully understood. We determined that both mouse and human IFITM3 are phosphorylated by the protein-tyrosine kinase FYN on tyrosine 20 (Tyr(20)) and that mouse IFITM3 is also phosphorylated on the non-conserved Tyr(27). Phosphorylation led to a cellular redistribution of IFITM3, including plasma membrane accumulation. Mutation of Tyr(20) caused a similar redistribution of IFITM3 and resulted in decreased antiviral activity against influenza virus, whereas Tyr(27) mutation of mouse IFITM3 showed minimal effects on localization or activity. Using FYN knockout cells, we also found that IFITM3 phosphorylation is not a requirement for its antiviral activity. Together, these results indicate that Tyr(20) is part of an endocytosis signal that can be blocked by phosphorylation or by mutation of this residue. Further mutagenesis narrowed this endocytosis-controlling region to four residues conforming to a YXX? (where X is any amino acid and ? is Val, Leu, or Ile) endocytic motif that, when transferred to CD4, resulted in its internalization from the cell surface. Additionally, we found that phosphorylation of IFITM3 by FYN and mutagenesis of Tyr(20) both resulted in decreased IFITM3 ubiquitination. Overall, these results suggest that modification of Tyr(20) may serve in a cellular checkpoint controlling IFITM3 trafficking and degradation and demonstrate the complexity of posttranslational regulation of IFITM3. PMID:24627473

Chesarino, Nicholas M; McMichael, Temet M; Hach, Jocelyn C; Yount, Jacob S

2014-04-25

319

Exploiting holistic approaches to model specificity in protein phosphorylation  

PubMed Central

Phosphate plays a chemically unique role in shaping cellular signaling of all current living systems, especially eukaryotes. Protein phosphorylation has been studied at several levels, from the near-site context, both in sequence and structure, to the crowded cellular environment, and ultimately to the systems-level perspective. Despite the tremendous advances in mass spectrometry and efforts dedicated to the development of ad hoc highly sophisticated methods, phosphorylation site inference and associated kinase identification are still unresolved problems in kinome biology. The sequence and structure of the substrate near-site context are not sufficient alone to model the in vivo phosphorylation rules, and they should be integrated with orthogonal information in all possible applications. Here we provide an overview of the different contexts that contribute to protein phosphorylation, discussing their potential impact in phosphorylation site annotation and in predicting kinase-substrate specificity. PMID:25324856

Palmeri, Antonio; Ferrč, Fabrizio; Helmer-Citterich, Manuela

2014-01-01

320

Abiotic regioselective phosphorylation of adenosine with borate in formamide.  

PubMed

Nearly 40 years ago, Schoffstall and his coworkers used formamide as a solvent to permit the phosphorylation of nucleosides by inorganic phosphate to give nucleoside phosphates, which (due to their thermodynamic instability with respect to hydrolysis) cannot be easily created in water by an analogous phosphorylation (the "water problem" in prebiotic chemistry). More recently, we showed that borate could stabilize certain carbohydrates against degradation (the "asphalt problem"). Here, we combine the two concepts to show that borate can work in formamide to guide the reactivity of nucleosides under conditions where they are phosphorylated. Specifically, reaction of adenosine in formamide with inorganic phosphate and pyrophosphate in the presence of borate gives adenosine-5'-phosphate as the only detectable phosphorylated product, with formylation (as opposed to hydrolysis) being the competing reaction. Key Words: Prebiotic chemistry-Nucleoside phosphates-Phosphorylation-Borate-Formamide. Astrobiology 15, 259-267. PMID:25826074

Furukawa, Yoshihiro; Kim, Hyo-Joong; Hutter, Daniel; Benner, Steven A

2015-04-01

321

Enzymatically induced motion at nano- and micro-scales  

NASA Astrophysics Data System (ADS)

In contrast to adenosine triphosphate (ATP)-dependent motor enzymes, other enzymes are little-known as ``motors'' or ``pumps'', that is, for their ability to induce motion. The enhanced diffusive movement of enzyme molecules, the self-propulsion of enzyme-based nanomotors, and liquid pumping with enzymatic micropumps were indeed only recently reported. Enzymatically induced motion can be achieved in mild conditions and without the use of external fields. It is thus better suited for use in living systems (from single-cell to whole-body) than most other ways to achieve motion at small scales. Enzymatically induced motion is thus not only new but also important. Therefore, the present work reviews the most significant discoveries in enzymatically induced motion. As we will learn, freely diffusing enzymes enhance their diffusive movement by nonreciprocal conformational changes which parallel their catalytic cycles. Meanwhile, enzyme-modified nano- and micro-objects turn chemical energy into kinetic energy through mechanisms such as bubble recoil propulsion, self-electrophoresis, and self-diffusiophoresis. Enzymatically induced motion of small objects ranges from enhanced diffusive movement to directed motion at speeds as high as 1 cm s-1. In spite of the progress made in understanding how the energy of enzyme reactions is turned into motion, most enzymatically powered devices remain inefficient and need improvements before we will witness their application in real world environments.

Gáspár, Szilveszter

2014-06-01

322

Role of substrate unbinding in Michaelis–Menten enzymatic reactions  

PubMed Central

The Michaelis–Menten equation provides a hundred-year-old prediction by which any increase in the rate of substrate unbinding will decrease the rate of enzymatic turnover. Surprisingly, this prediction was never tested experimentally nor was it scrutinized using modern theoretical tools. Here we show that unbinding may also speed up enzymatic turnover—turning a spotlight to the fact that its actual role in enzymatic catalysis remains to be determined experimentally. Analytically constructing the unbinding phase space, we identify four distinct categories of unbinding: inhibitory, excitatory, superexcitatory, and restorative. A transition in which the effect of unbinding changes from inhibitory to excitatory as substrate concentrations increase, and an overlooked tradeoff between the speed and efficiency of enzymatic reactions, are naturally unveiled as a result. The theory presented herein motivates, and allows the interpretation of, groundbreaking experiments in which existing single-molecule manipulation techniques will be adapted for the purpose of measuring enzymatic turnover under a controlled variation of unbinding rates. As we hereby show, these experiments will not only shed first light on the role of unbinding but will also allow one to determine the time distribution required for the completion of the catalytic step in isolation from the rest of the enzymatic turnover cycle. PMID:24616494

Reuveni, Shlomi; Urbakh, Michael; Klafter, Joseph

2014-01-01

323

Silicon nanowires as a rechargeable template for hydride transfer in redox biocatalysis  

NASA Astrophysics Data System (ADS)

We report a new possible application of hydrogen-terminated silicon nanowires (H-SiNWs) as a rechargeable template for hydride transfer in redox biocatalysis. H-SiNWs transfer hydride efficiently to regenerate NADH by oxidizing Si-Hx bonds. The oxidized H-SiNWs were readily recharged for the continuous regeneration of NADH and enzymatic reactions.

Lee, Hwa Young; Kim, Jae Hong; Son, Eun Jin; Park, Chan Beum

2012-11-01

324

Involvement of histamine receptors in SAPK/JNK phosphorylation.  

PubMed

Histamine is a mediator of inflammation in allergic disease and asthma. Stress activated protein kinases/c-jun N-terminal kinases (SAPK/JNK) are involved in asthma. This study examined the role of histamine receptors on the phosphorylation of SAPK/JNK in splenocytes. C57BL/6 mice splenocytes were treated with histamine (10?? M to 10?ąą M), and its selective receptor agonists, phorbol 12 myristate 13-acetate (PMA) was used as a positive control, and phosphorylation of SAPK/JNK was determined. Histamine (10?? M-10?? M) inhibited phosphorylation of SAPK/JNK. H1R agonist betahistine (10?? M) decreased SAPK/JNK phosphorylation and H2R agonist amthamine (10?? M) did not show any significant effect. However, H3R agonist methimepip (10?? M) and H4R agonist 4-methyl histamine (10?? M), increased SAPK/JNK phosphorylation. We used TNF? knockout mice to determine if histamine regulated SAPK/JNK phosphorylation via TNF?. While the effects of histamine and H1 agonists were similar to that of wild type mice in inhibiting the phosphorylation of SAPK/JNK, the effects of H3 and H4 agonists differed in TNF? knockout mice splenocytes. Activation of H3 receptors decreased SAPK/JNK phosphorylation in TNF? knockout mice, as opposed to an increase in wild type mice, whereas H4 agonist did not show any significant effect on the phosphorylation of SAPK/JNK. This data showed that histamine acting through H4 receptors caused the phosphorylation of SAPK/JNK via TNF?. The role of H4 receptors in pro-inflammatory response is intriguing. PMID:22487127

Dandekar, Radhika D; Khan, Manzoor M

2012-06-01

325

Akt Phosphorylates Both Tsc1 and Tsc2 in Drosophila, but Neither Phosphorylation Is Required for Normal Animal Growth  

PubMed Central

Akt, an essential component of the insulin pathway, is a potent inducer of tissue growth. One of Akt's phosphorylation targets is Tsc2, an inhibitor of the anabolic kinase TOR. This could account for part of Akt's growth promoting activity. Although phosphorylation of Tsc2 by Akt does occur in vivo, and under certain circumstances can lead to reduced Tsc2 activity, the functional significance of this event is unclear since flies lacking Akt phosphorylation sites on Tsc2 are viable and normal in size and growth rate. Since Drosophila Tsc1, the obligate partner of Tsc2, has an Akt phosphorylation motif that is not conserved in mammals, we investigate here whether Akt redundantly phosphorylates the Tsc complex on Tsc1 and Tsc2. We provide evidence that Akt phosphorylates Tsc1 at Ser533. We show that flies lacking Akt phosphorylation sites on Tsc1 alone, or on both Tsc1 and Tsc2 concurrently, are viable and normal in size. This shows that phosphorylation of the Tsc1/2 complex by Akt is not required for Akt to activate TORC1 and to promote tissue growth in Drosophila. PMID:19609361

Schleich, Sibylle; Teleman, Aurelio A.

2009-01-01

326

NEMO/NLK phosphorylates PERIOD to initiate a time-delay phosphorylation circuit that sets circadian clock speed  

PubMed Central

SUMMARY The speed of circadian clocks in animals is tightly linked to complex phosphorylation programs that drive daily cycles in the levels of PERIOD (PER) proteins. Using Drosophila we identify a time-delay circuit based on hierarchical phosphorylation that controls the daily downswing in PER abundance. Phosphorylation by the NEMO/NLK kinase at the per-short domain on PER stimulates phosphorylation by DOUBLETIME (DBT/CK1?/?) at several nearby sites. This multi-site phosphorylation operates in a spatially-oriented and graded manner to delay progressive phosphorylation by DBT at other more distal sites on PER, including those required for recognition by the F-box protein SLIMB/?-TrCP and proteasomal degradation. Highly phosphorylated PER has a more open structure, suggesting that progressive increases in global phosphorylation contribute to the timing mechanism by slowly increasing PER susceptibility to degradation. Our findings identify NEMO as a clock kinase and demonstrate that long-range interactions between functionally distinct phospho-clusters collaborate to set clock speed. PMID:21514639

Chiu, Joanna C.; Ko, Hyuk Wan; Edery, Isaac

2011-01-01

327

Enzymatic Basis for N-Glycan Sialylation  

PubMed Central

Glycan structures on glycoproteins and glycolipids play critical roles in biological recognition, targeting, and modulation of functions in animal systems. Many classes of glycan structures are capped with terminal sialic acid residues, which contribute to biological functions by either forming or masking glycan recognition sites on the cell surface or secreted glycoconjugates. Sialylated glycans are synthesized in mammals by a single conserved family of sialyltransferases that have diverse linkage and acceptor specificities. We examined the enzymatic basis for glycan sialylation in animal systems by determining the crystal structures of rat ST6GAL1, an enzyme that creates terminal ?2,6-sialic acid linkages on complex-type N-glycans, at 2.4 ? resolution. Crystals were obtained from enzyme preparations generated in mammalian cells. The resulting structure revealed an overall protein fold broadly resembling the previously determined structure of pig ST3GAL1, including a CMP-sialic acid-binding site assembled from conserved sialylmotif sequence elements. Significant differences in structure and disulfide bonding patterns were found outside the sialylmotif sequences, including differences in residues predicted to interact with the glycan acceptor. Computational substrate docking and molecular dynamics simulations were performed to predict and evaluate the CMP-sialic acid donor and glycan acceptor interactions, and the results were compared with kinetic analysis of active site mutants. Comparisons of the structure with pig ST3GAL1 and a bacterial sialyltransferase revealed a similar positioning of donor, acceptor, and catalytic residues that provide a common structural framework for catalysis by the mammalian and bacterial sialyltransferases. PMID:24155237

Meng, Lu; Forouhar, Farhad; Thieker, David; Gao, Zhongwei; Ramiah, Annapoorani; Moniz, Heather; Xiang, Yong; Seetharaman, Jayaraman; Milaninia, Sahand; Su, Min; Bridger, Robert; Veillon, Lucas; Azadi, Parastoo; Kornhaber, Gregory; Wells, Lance; Montelione, Gaetano T.; Woods, Robert J.; Tong, Liang; Moremen, Kelley W.

2013-01-01

328

Nanocrystal Bioassembly: Asymmetry, Proximity, and Enzymatic Manipulation  

SciTech Connect

Research at the interface between biomolecules and inorganic nanocrystals has resulted in a great number of new discoveries. In part this arises from the synergistic duality of the system: biomolecules may act as self-assembly agents for organizing inorganic nanocrystals into functional materials; alternatively, nanocrystals may act as microscopic or spectroscopic labels for elucidating the behavior of complex biomolecular systems. However, success in either of these functions relies heavily uponthe ability to control the conjugation and assembly processes.In the work presented here, we first design a branched DNA scaffold which allows hybridization of DNA-nanocrystal monoconjugates to form discrete assemblies. Importantly, the asymmetry of the branched scaffold allows the formation of asymmetric2assemblies of nanocrystals. In the context of a self-assembled device, this can be considered a step toward the ability to engineer functionally distinct inputs and outputs.Next we develop an anion-exchange high performance liquid chromatography purification method which allows large gold nanocrystals attached to single strands of very short DNA to be purified. When two such complementary conjugates are hybridized, the large nanocrystals are brought into close proximity, allowing their plasmon resonances to couple. Such plasmon-coupled constructs are of interest both as optical interconnects for nanoscale devices and as `plasmon ruler? biomolecular probes.We then present an enzymatic ligation strategy for creating multi-nanoparticle building blocks for self-assembly. In constructing a nanoscale device, such a strategy would allow pre-assembly and purification of components; these constructs can also act as multi-label probes of single-stranded DNA conformational dynamics. Finally we demonstrate a simple proof-of-concept of a nanoparticle analog of the polymerase chain reaction.

Claridge, Shelley A

2008-05-01

329

Enzymatic sequencing of partially acetylated chitosan oligomers.  

PubMed

Chitosan oligosaccharides have diverse biological activities with potentially valuable applications, for example, in the fields of medicine and agriculture. These functionalities are thought to depend on their degree of polymerization and acetylation, and possibly on specific patterns of acetylation. Chitosan oligomers with fully defined architecture are difficult to produce, and their complete analysis is demanding. Analysis is typically done using MS or NMR, requiring access to expensive infrastructure, and yielding unequivocal results only in the case of rather small oligomers. We here describe a simple and cost-efficient method for the sequencing of ?g amounts of chitosan oligosaccharides which is based on the sequential action of two recombinant glycosidases, namely an exo-?-N-acetylhexosaminidase (GlcNAcase) from Bacillus subtilis 168 and an exo-?-d-glucosaminidase (GlcNase) from Thermococcus kodakarensis KOD1. Starting from the non-reducing end, GlcNAcase and GlcNase specifically remove N-acetyl glucosamine (A) and glucosamine (D) units, respectively. By the sequential addition and removal of these enzymes in an alternating way followed by analysis of the products using high-performance thin-layer chromatography, the sequence of chitosan oligosaccharides can be revealed. Importantly, both enzymes work under identical conditions so that no buffer exchange is required between steps, and the enzyme can be removed conveniently using simple ultra-filtration devices. As proof-of-principle, the method was used to sequence the product of enzymatic deacetylation of chitin pentamer using a recombinant chitin deacetylase from Vibrio cholerae which specifically removes the acetyl group from the second unit next to the non-reducing end of the substrate, yielding mono-deacetylated pentamer with the sequence ADAAA. PMID:24824785

Hamer, Stefanie Nicole; Moerschbacher, Bruno Maria; Kolkenbrock, Stephan

2014-06-17

330

Versatile strategy for biochemical, electrochemical and immunoarray detection of protein phosphorylations.  

PubMed

Protein kinases catalyze the phosphorylation of cellular proteins involved in the regulation of many cellular processes and have emerged as promising targets for the treatment of several diseases. Conventional assays to monitor protein kinase activity are limited because they typically rely on transfer of radioactive phosphate or phospho-specific antibodies that recognize specific substrates or sequence motifs. To overcome the limitations of conventional assays, we have developed a versatile approach based on transfer of ferrocene-phosphate that can be readily monitored using electrochemical detection or detection with antiferrocene antibodies in an immunoarray format. This assay is readily adapted to multiplex arrays and can be employed for monitoring kinase activity in complex mixtures and for kinase inhibitor profiling. PMID:22764889

Marti?, Sanela; Gabriel, Michelle; Turowec, Jacob P; Litchfield, David W; Kraatz, Heinz-Bernhard

2012-10-17

331

Proteomics Analysis Identifies Phosphorylation-dependent ?-Synuclein Protein Interactions *S?  

PubMed Central

Mutations and copy number variation in the SNCA gene encoding the neuronal protein ?-synuclein have been linked to familial Parkinson disease (Thomas, B., and Beal, M. F. (2007) Parkinson's disease. Hum. Mol. Genet. 16, R183–R194). The carboxyl terminus of ?-synuclein can be phosphorylated at tyrosine 125 and serine 129, although only a small fraction of the protein is phosphorylated under normal conditions (Okochi, M., Walter, J., Koyama, A., Nakajo, S., Baba, M., Iwatsubo, T., Meijer, L., Kahle, P. J., and Haass, C. (2000) Constitutive phosphorylation of the Parkinson's disease associated ?-synuclein. J. Biol. Chem. 275, 390–397). Under pathological conditions, such as in Parkinson disease, ?-synuclein is a major component of Lewy bodies, a pathological hallmark of Parkinson disease, and is mostly phosphorylated at Ser-129 (Anderson, J. P., Walker, D. E., Goldstein, J. M., de Laat, R., Banducci, K., Caccavello, R. J., Barbour, R., Huang, J. P., Kling, K., Lee, M., Diep, L., Keim, P. S., Shen, X. F., Chataway, T., Schlossmacher, M. G., Seubert, P., Schenk, D., Sinha, S., Gai, W. P., and Chilcote, T. J. (2006) Phosphorylation of Ser-129 is the dominant pathological modification of ?-synuclein in familial and sporadic Lewy body disease. J. Biol. Chem. 281, 29739–29752). Controversy exists over the extent to which phosphorylation of ?-synuclein and/or the visible protein aggregation in Lewy bodies are steps in disease pathogenesis, are protective, or are neutral markers for the disease process. Here we used the combination of peptide pulldown assays and mass spectrometry to identify and compare protein-protein interactions of phosphorylated and non-phosphorylated ?-synuclein. We showed that non-phosphorylated ?-synuclein carboxyl terminus pulled down protein complexes that were highly enriched for mitochondrial electron transport proteins, whereas ?-synuclein carboxyl terminus phosphorylated on either Ser-129 or Tyr-125 did not. Instead the set of proteins pulled down by phosphorylated ?-synuclein was highly enriched in certain cytoskeletal proteins, in vesicular trafficking proteins, and in a small number of enzymes involved in protein serine phosphorylation. This targeted comparative proteomics approach for unbiased identification of protein-protein interactions suggests that there are functional consequences when ?-synuclein is phosphorylated. PMID:18614564

McFarland, Melinda A.; Ellis, Christopher E.; Markey, Sanford P.; Nussbaum, Robert L.

2008-01-01

332

Transfer Functions  

Microsoft Academic Search

In statistical time-series analysis, signal processing and control engineering, a transfer function is a mathematical relationship between a numerical input to a dynamic system and the resulting output. The theory of transfer functions describes how the input\\/output relationship is affected by the structure of the transfer function. The theory of the transfer functions of linear time-invariant (LTI) systems has been

David Stephen Pollock

2011-01-01

333

Ionizing radiation causes increased tau phosphorylation in primary neurons.  

PubMed

Radiotherapy is the major treatment modality for primary and metastatic brain tumors which involves the exposure of brain to ionizing radiation. Ionizing radiation can induce various detrimental pathophysiological effects in the adult brain, and Alzheimer's disease and related neurodegenerative disorders are considered to be late effects of radiation. In this study, we investigated whether ionizing radiation causes changes in tau phosphorylation in cultured primary neurons similar to that in Alzheimer's disease. We demonstrated that exposure to 0.5 or 2 Gy ? rays causes increased phosphorylation of tau protein at several phosphorylation sites in a time- and dose-dependent manner. Consistently, we also found ionizing radiation causes increased activation of GSK3?, c-Jun N-terminal kinase and extracellular signal-regulated kinase before radiation-induced increase in tau phosphorylation. Specific inhibitors of these kinases almost fully blocked radiation-induced tau phosphorylation. Our studies further revealed that oxidative stress plays an important role in ionizing radiation-induced tau phosphorylation, likely through the activation of c-Jun N-terminal kinase and extracellular signal-regulated kinase, but not GSK3?. Overall, our studies suggest that ionizing radiation may cause increased risk for development of Alzheimer's disease by promoting abnormal tau phosphorylation. PMID:24861936

Li, Li; Wang, Wenzhang; Welford, Scott; Zhang, Teng; Wang, Xinglong; Zhu, Xiongwei

2014-10-01

334

Phosphorylation of the pyruvate dehydrogenase complex isolated from Ascaris suum  

SciTech Connect

The pyruvate dehydrogenase complex (PDC) from body wall muscle of the porcine nematode, Ascaris suum, plays a pivotal role in anaerobic mitochondrial metabolism. As in mammalian mitochondria, PDC activity is inhibited by the phosphorylation of the ..cap alpha..PDH subunit, catalyzed by an associated PDH/sub a/ kinase. However, in contrast to PDC's isolated from all other eukaryotic sources, phosphorylation decreases the mobility of the ..cap alpha..PDH subunit on SDS-PAGE and permits the separation of the phosphorylated and nonphosphorylated ..cap alpha..PDH's. Phosphorylation and the inactivation of the Ascaris PDC correspond directly, and the additional phosphorylation that occurs after complete inactivation in mammalian PDC's is not observed. The purified ascarid PDC incorporates 10 nmoles /sup 32/P/mg P. Autoradiography of the radiolabeled PDC separated by SDS-PAGE yields a band which corresponds to the phosphorylated ..cap alpha..PDH and a second, faint band which is present only during the first three minutes of PDC inactivation, intermediate between the phosphorylated and nonphosphorylated ..cap alpha..PDH subunit. Tryptic digests of the /sup 32/P-PDC yields one major phosphopeptide, when separated by HPLC, and its amino acid sequence currently is being determined.

Thissen, J.; Komuniecki, R.

1987-05-01

335

Phosphorylation at serine 331 is required for Aurora B activation  

PubMed Central

Aurora B kinase activity is required for successful cell division. In this paper, we show that Aurora B is phosphorylated at serine 331 (Ser331) during mitosis and that phosphorylated Aurora B localizes to kinetochores in prometaphase cells. Chk1 kinase is essential for Ser331 phosphorylation during unperturbed prometaphase or during spindle disruption by taxol but not nocodazole. Phosphorylation at Ser331 is required for optimal phosphorylation of INCENP at TSS residues, for Survivin association with the chromosomal passenger complex, and for complete Aurora B activation, but it is dispensable for Aurora B localization to centromeres, for autophosphorylation at threonine 232, and for association with INCENP. Overexpression of Aurora BS331A, in which Ser331 is mutated to alanine, results in spontaneous chromosome missegregation, cell multinucleation, unstable binding of BubR1 to kinetochores, and impaired mitotic delay in the presence of taxol. We propose that Chk1 phosphorylates Aurora B at Ser331 to fully induce Aurora B kinase activity. These results indicate that phosphorylation at Ser331 is an essential mechanism for Aurora B activation. PMID:22024163

Petsalaki, Eleni; Akoumianaki, Tonia; Black, Elizabeth J.; Gillespie, David A.F.

2011-01-01

336

?-Aminobutyric acid type A (GABAA) receptor activation modulates tau phosphorylation.  

PubMed

Abnormal phosphorylation and aggregation of the microtubule-associated protein Tau are hallmarks of various neurodegenerative diseases, such as Alzheimer disease. Molecular mechanisms that regulate Tau phosphorylation are complex and currently incompletely understood. We have developed a novel live cell reporter system based on protein-fragment complementation assay to study dynamic changes in Tau phosphorylation status. In this assay, fusion proteins of Tau and Pin1 (peptidyl-prolyl cis-trans-isomerase 1) carrying complementary fragments of a luciferase protein serve as a sensor of altered protein-protein interaction between Tau and Pin1, a critical regulator of Tau dephosphorylation at several disease-associated proline-directed phosphorylation sites. Using this system, we identified several structurally distinct GABA(A) receptor modulators as novel regulators of Tau phosphorylation in a chemical library screen. GABA(A) receptor activation promoted specific phosphorylation of Tau at the AT8 epitope (Ser-199/Ser-202/Thr-205) in cultures of mature cortical neurons. Increased Tau phosphorylation by GABA(A) receptor activity was associated with reduced Tau binding to protein phosphatase 2A and was dependent on Cdk5 but not GSK3? kinase activity. PMID:22235112

Nykänen, Niko-Petteri; Kysenius, Kai; Sakha, Prasanna; Tammela, Päivi; Huttunen, Henri J

2012-02-24

337

CAPS Activity in Priming Vesicle Exocytosis Requires CK2 Phosphorylation*  

PubMed Central

CAPS (Ca2+-dependent activator protein for secretion) functions in priming Ca2+-dependent vesicle exocytosis, but the regulation of CAPS activity has not been characterized. Here we show that phosphorylation by protein kinase CK2 is required for CAPS activity. Dephosphorylation eliminated CAPS activity in reconstituting Ca2+-dependent vesicle exocytosis in permeable and intact PC12 cells. Ser-5, -6, and -7 and Ser-1281 were identified by mass spectrometry as the major phosphorylation sites in the 1289 residue protein. Ser-5, -6, and -7 but not Ser-1281 to Ala substitutions abolished CAPS activity. Protein kinase CK2 phosphorylated CAPS in vitro at these sites and restored the activity of dephosphorylated CAPS. CK2 is the likely in vivo CAPS protein kinase based on inhibition of phosphorylation by tetrabromo-2-benzotriazole in PC12 cells and by the identity of in vivo and in vitro phosphorylation sites. CAPS phosphorylation by CK2 was constitutive, but the elevation of Ca2+ in synaptosomes increased CAPS Ser-5 and -6 dephosphorylation, which terminates CAPS activity. These results identify a functionally important N-terminal phosphorylation site that regulates CAPS activity in priming vesicle exocytosis. PMID:19460754

Nojiri, Mari; Loyet, Kelly M.; Klenchin, Vadim A.; Kabachinski, Gregory; Martin, Thomas F. J.

2009-01-01

338

Comparison of CID, ETD and metastable atom-activated dissociation (MAD) of doubly and triply charged phosphorylated tau peptides.  

PubMed

The fragmentation behavior of the 2+ and 3+ charge states of eleven different phosphorylated tau peptides was studied using collision-induced dissociation (CID), electron transfer dissociation (ETD) and metastable atom-activated dissociation (MAD). The synthetic peptides studied contain up to two known phosphorylation sites on serine or threonine residues, at least two basic residues, and between four and eight potential sites of phosphorylation. CID produced mainly b-/y-type ions with abundant neutral losses of the phosphorylation modification. ETD produced c-/z-type ions in highest abundance but also showed numerous y-type ions at a frequency about 50% that of the z-type ions. The major peaks observed in the ETD spectra correspond to the charge-reduced product ions and small neutral losses from the charge-reduced peaks. ETD of the 2+ charge state of each peptide generally produced fewer backbone cleavages than the 3+ charge state, consistent with previous reports. Regardless of charge state, MAD achieved more extensive backbone cleavage than CID or ETD, while retaining the modification(s) in most cases. In all but one case, unambiguous modification site determination was achieved with MAD. MAD produced 15-20% better sequence coverage than CID and ETD for both the 2+ and 3+ charge states and very different fragmentation products indicating that the mechanism of fragmentation in MAD is unique and complementary to CID and ETD. PMID:22707171

Cook, Shannon L; Zimmermann, Carolyn M; Singer, David; Fedorova, Maria; Hoffmann, Ralf; Jackson, Glen P

2012-06-01

339

Acute exercise modifies titin phosphorylation and increases cardiac myofilament stiffness  

PubMed Central

Titin-based myofilament stiffness is largely modulated by phosphorylation of its elastic I-band regions N2-Bus (decreases passive stiffness, PT) and PEVK (increases PT). Here, we tested the hypothesis that acute exercise changes titin phosphorylation and modifies myofilament stiffness. Adult rats were exercised on a treadmill for 15 min, untrained animals served as controls. Titin phosphorylation was determined by Western blot analysis using phosphospecific antibodies to Ser4099 and Ser4010 in the N2-Bus region (PKG and PKA-dependent. respectively), and to Ser11878 and Ser 12022 in the PEVK region (PKC? and CaMKII?-dependent, respectively). Passive tension was determined by step-wise stretching of isolated skinned cardiomyocytes to sarcomere length (SL) ranging from 1.9 to 2.4 ?m and showed a significantly increased PT from exercised samples, compared to controls. In cardiac samples titin N2-Bus phosphorylation was significantly decreased by 40% at Ser4099, however, no significant changes were observed at Ser4010. PEVK phosphorylation at Ser11878 was significantly increased, which is probably mediated by the observed exercise-induced increase in PKC? activity. Interestingly, relative phosphorylation of Ser12022 was substantially decreased in the exercised samples. Surprisingly, in skeletal samples from acutely exercised animals we detected a significant decrease in PEVK phosphorylation at Ser11878 and an increase in Ser12022 phosphorylation; however, PKC? activity remained unchanged. In summary, our data show that a single exercise bout of 15 min affects titin domain phosphorylation and titin-based myocyte stiffness with obviously divergent effects in cardiac and skeletal muscle tissues. The observed changes in titin stiffness could play an important role in adapting the passive and active properties of the myocardium and the skeletal muscle to increased physical activity. PMID:25477822

Müller, Anna E.; Kreiner, Matthias; Kötter, Sebastian; Lassak, Philipp; Bloch, Wilhelm; Suhr, Frank; Krüger, Martina

2014-01-01

340

PKC isoforms interact with and phosphorylate DNMT1  

PubMed Central

Background DNA methyltransferase 1 (DNMT1) has been shown to be phosphorylated on multiple serine and threonine residues, based on cell type and physiological conditions. Although recent studies have suggested that protein kinase C (PKC) may be involved, the individual contribution of PKC isoforms in their ability to phosphorylate DNMT1 remains unknown. The PKC family consists of at least 12 isoforms that possess distinct differences in structure, substrate requirement, expression and localization. Results Here we show that PKC?, ?I, ?II, ?, ?, ?, ? and ? preferentially phosphorylate the N-terminal domain of human DNMT1. No such phosphorylation of DNMT1 was observed with PKC?. Using PKC? as a prototype model, we also found that PKC physically interacts with and phosphorylates DNMT1. In vitro phosphorylation assays conducted with recombinant fragments of DNMT1 showed that PKC? preferentially phosphorylated the N-terminal region of DNMT1. The interaction of PKC? with DNMT1 was confirmed by GST pull-down and co-immunoprecipitation experiments. Co-localization experiments by fluorescent microscopy further showed that endogenous PKC? and DNMT1 were present in the same molecular complex. Endogenous PKC? activity was also detected when DNMT1 was immunoprecipitated from HEK-293 cells. Overexpression of both PKC? and DNMT1 in HEK-293 cells, but not of either alone, reduced the methylation status of genes distributed across the genome. Moreover, in vitro phosphorylation of DNMT1 by PKC? reduced its methytransferase activity. Conclusions Our results indicate that phosphorylation of human DNMT1 by PKC is isoform-specific and provides the first evidence of cooperation between PKC? and DNMT1 in the control of the DNA methylation patterns of the genome. PMID:21619587

2011-01-01

341

Pathophysiological implications of mitochondrial oxidative stress mediated by mitochondriotropic agents and polyamines: the role of tyrosine phosphorylation.  

PubMed

Mitochondria, once merely considered as the "powerhouse" of cells, as they generate more than 90 % of cellular ATP, are now known to play a central role in many metabolic processes, including oxidative stress and apoptosis. More than 40 known human diseases are the result of excessive production of reactive oxygen species (ROS), bioenergetic collapse and dysregulated apoptosis. Mitochondria are the main source of ROS in cells, due to the activity of the respiratory chain. In normal physiological conditions, ROS generation is limited by the anti-oxidant enzymatic systems in mitochondria. However, disregulation of the activity of these enzymes or interaction of respiratory complexes with mitochondriotropic agents may lead to a rise in ROS concentrations, resulting in oxidative stress, mitochondrial permeability transition (MPT) induction and triggering of the apoptotic pathway. ROS concentration is also increased by the activity of amine oxidases located inside and outside mitochondria, with oxidation of biogenic amines and polyamines. However, it should also be recalled that, depending on its concentration, the polyamine spermine can also protect against stress caused by ROS scavenging. In higher organisms, cell signaling pathways are the main regulators in energy production, since they act at the level of mitochondrial oxidative phosphorylation and participate in the induction of the MPT. Thus, respiratory complexes, ATP synthase and transition pore components are the targets of tyrosine kinases and phosphatases. Increased ROS may also regulate the tyrosine phosphorylation of target proteins by activating Src kinases or phosphatases, preventing or inducing a number of pathological states. PMID:25792113

Grancara, Silvia; Zonta, Francesca; Ohkubo, Shinji; Brunati, Anna Maria; Agostinelli, Enzo; Toninello, Antonio

2015-05-01

342

Decipher the dynamic coordination between enzymatic activity and structural modulation at focal adhesions in living cells  

NASA Astrophysics Data System (ADS)

Focal adhesions (FAs) are dynamic subcellular structures crucial for cell adhesion, migration and differentiation. It remains an enigma how enzymatic activities in these local complexes regulate their structural remodeling in live cells. Utilizing biosensors based on fluorescence resonance energy transfer (FRET), we developed a correlative FRET imaging microscopy (CFIM) approach to quantitatively analyze the subcellular coordination between the enzymatic Src activation and the structural FA disassembly. CFIM reveals that the Src kinase activity only within the microdomain of lipid rafts at the plasma membrane is coupled with FA dynamics. FA disassembly at cell periphery was linearly dependent on this raft-localized Src activity, although cells displayed heterogeneous levels of response to stimulation. Within lipid rafts, the time delay between Src activation and FA disassembly was 1.2 min in cells seeded on low fibronectin concentration ([FN]) and 4.3 min in cells on high [FN]. CFIM further showed that the level of Src-FA coupling, as well as the time delay, was regulated by cell-matrix interactions, as a tight enzyme-structure coupling occurred in FA populations mediated by integrin ?v?3, but not in those by integrin ?5?1. Therefore, different FA subpopulations have distinctive regulation mechanisms between their local kinase activity and structural FA dynamics.

Lu, Shaoying; Seong, Jihye; Wang, Yi; Chang, Shiou-Chi; Eichorst, John Paul; Ouyang, Mingxing; Li, Julie Y.-S.; Chien, Shu; Wang, Yingxiao

2014-07-01

343

Highly ordered Ni-Ti-O nanotubes for non-enzymatic glucose detection.  

PubMed

Anodization is used to fabricate Ni-Ti-O nanotube (NT) electrodes for non-enzymatic glucose detection. The morphology, microstructure and composition of the materials are characterized by field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Our results show amorphous and highly ordered NTs with diameter of 50nm, length of 800nm, and Ni/Ti ratio (at %) of 0.35 can be fabricated in ethylene glycol electrolyte supplemented with 0.2 wt.% NH4F and 0.5 vol.% H2O at 30°C and 25V for 1h. Electrochemical experiments indicate that at an applied potential of 0.60V vs. Ag/AgCl, the electrode exhibits a linear response window for glucose concentrations from 0.002mM to 0.2mM with a response time of 10s, detection limit of 0.13?M (S/N=3), and sensitivity of 83?AmM(-1)cm(-2). The excellent performance of the electrode is attributed to its large specific area and fast electron transfer between the NT walls. The good electrochemical performance of the Ni-Ti-O NTs as well as their simple and low-cost preparation method make the strategy promising in non-enzymatic glucose detection. PMID:25842105

Hang, Ruiqiang; Liu, Yanlian; Gao, Ang; Bai, Long; Huang, Xiaobo; Zhang, Xiangyu; Lin, Naiming; Tang, Bin; Chu, Paul K

2015-06-01

344

Evaluation of binary solvent mixtures for efficient monoacylglycerol production by continuous enzymatic glycerolysis.  

PubMed

This study was aimed at evaluating different binary solvent mixtures for efficient industrial monoacylglycerol (MAG) production by enzymatic glycerolysis. Of all investigated cases, the binary mixture of tert-butanol:tert-pentanol (TB:TP) 80:20 vol % was the most suitable organic medium for continuous enzymatic glycerolysis, ensuring high MAG formation in a short time, reasonable solvent price, and easy handling during distillation/condensation processing. A minimum solvent dosage of 44-54 wt % of the reaction mixture was necessary to achieve high MAG yields of 47-56 wt %, within 20 min. The melting and boiling points of the TB:TP mixture were estimated to be 7 and 85 degrees C, respectively, using thermodynamic models. These predictions were in good agreement with experimentally determined values. In spite of the high reaction efficiency in the binary TB:TP system, the mixture of glycerol and sunflower oil (containing 97.1% triacylglycerol) yielded surprisingly a liquid/liquid phase split behavior even at high temperatures (>80 degrees C). This in contrast to thermodynamic model calculations suggested full miscibility in all proportions. These findings suggest that enhanced reaction efficiency in organic solvent also depends upon aspects other than the system homogeneity such as reduced viscosity, reduced mass transfer limitations, and the accessibility of the substrate to the active site of the enzyme. PMID:16968070

Damstrup, Marianne L; Abildskov, Jens; Kiil, Sřren; Jensen, Anker D; Sparsř, Flemming V; Xu, Xuebing

2006-09-20

345

Relationship between glucose phosphorylating activities and erythrocyte age.  

PubMed

Glucose phosphorylating activity of human erythrocytes quickly decreases during cell ageing; the electrophoretic pattern suggests that this fast decrease is due mainly to the isozyme II. We have shown that in the young cells only hexokinase I and II are responsible for the glucose phosphorylation, while in the old cells another glucose phosphorylating activity, more evident at high glucose concentration, is also present. The appearance of this activity during cell ageing could be interpreted as a post-translational modification of the native hexokinase. PMID:703400

Fornaini, G; Magnani, M; Dachŕ, M; Bossú, M; Stocchi, V

1978-10-01

346

Cyanogen induced phosphorylation of D-fructose. [prebiotic modeling  

NASA Technical Reports Server (NTRS)

It has been demonstrated that a phosphorylated sugar, identified as alpha-D-fructopyranose, can be formed as the result of cyanogen-induced phosphorylation of D-fructose at pH 8.8. The product was isolated from barium and cyclohexylammonium salts and identified on the basis of its chromatographic and electrophoretic properties, its lability to hydrolysis by alkaline phosphatase, the rate of its acid-catalyzed hydrolysis, and the results of periodate oxidation and optical rotatory measurements. These results support the suggestion that the cyanogen-induced phosphorylation of free sugars could be a possible process for formation of sugar phosphates under prebiotic conditions (Halman et al., 1969).

Degani, CH.; Kawatsuji, M.; Halmann, M.

1975-01-01

347

Technology transfer  

NASA Technical Reports Server (NTRS)

The requirements for a successful technology transfer program and what such a program would look like are discussed. In particular, the issues associated with technology transfer in general, and within the Jet Propulsion Laboratory (JPL) environment specifically are addressed. The section on background sets the stage, identifies the barriers to successful technology transfer, and suggests actions to address the barriers either generally or specifically. The section on technology transfer presents a process with its supporting management plan that is required to ensure a smooth transfer process. Viewgraphs are also included.

Handley, Thomas

1992-01-01

348

Redox polymer mediation for enzymatic biofuel cells  

NASA Astrophysics Data System (ADS)

Mediated biocatalytic cathodes prepared from the oxygen-reducing enzyme laccase and redox-conducting osmium hydrogels were characterized for use as cathodes in enzymatic biofuel cells. A series of osmium-based redox polymers was synthesized with redox potentials spanning the range from 0.11 V to 0.85 V (SHE), and the resulting biocatalytic electrodes were modeled to determine reaction kinetic constants using the current response, measured osmium concentration, and measured apparent electron diffusion. As in solution-phase systems, the bimolecular rate constant for mediation was found to vary greatly with mediator potential---from 250 s-1M-1 when mediator and enzyme were close in potential to 9.4 x 10 4 s-1M-1 when this overpotential was large. Optimum mediator potential for a cell operating with a non-limiting platinum anode and having no mass transport limitation from bulk solution was found to be 0.66 V (SHE). Redox polymers were synthesized under different concentrations, producing osmium variation. An increase from 6.6% to 7.2% osmium increased current response from 1.2 to 2.1 mA/cm2 for a planar film in 40°C oxygen-saturated pH 4 buffer, rotating at 900 rpm. These results translated to high surface area electrodes, nearly doubling current density to 13 mA/cm2, the highest to date for such an electrode. The typical fungal laccase from Trametes versicolor was replaced by a bacterially-expressed small laccase from Streptomyces coelicolor, resulting in biocatalytic films that reduced oxygen at increased pH, with full functionality at pH 7, producing 1.5 mA/cm 2 in planar configuration. Current response was biphasic with pH, matching the activity profile of the free enzyme in solution. The mediated enzyme electrode system was modeled with respect to apparent electron diffusion, mediator concentration, and transport of oxygen from bulk solution, all of which are to some extent controlled by design. Each factor was found to limit performance in certain circumstances. In systems relying on stagnant solution, oxygen transport was found to dominate. However, if mass transport was efficient, differences in mediator design greatly affected performance.

Gallaway, Joshua

349

Phosphorylation site on yeast pyruvate dehydrogenase complex  

SciTech Connect

The pyruvate dehydrogenase complex was purified to homogeneity from baker's yeast (Saccharomyces cerevisiae). Yeast cells were disrupted in a Manton-Gaulin laboratory homogenizer. The pyruvate dehydrogenase complex was purified by fractionation with polyethylene glycol, isoelectric precipitation, ultracentrifugation and chromatography on hydroxylapatite. Final purification of the yeast pyruvate dehydrogenase complex was achieved by cation-exchange high pressure liquid chromatography (HPLC). No endogenous pyruvate dehydrogenase kinase activity was detected during the purification. However, the yeast pyruvate dehydrogenase complex was phosphorylated and inactivated with purified pyruvate dehydrogenase kinase from bovine kidney. Tryptic digestion of the /sup 32/P-labeled complex yielded a single phosphopeptide which was purified to homogeniety. The tryptic digest was subjected to chromatography on a C-18 reverse phase HPLC column with a linear gradient of acetonitrile. Radioactive fractions were pooled, concentrated, and subjected to anion-exchange HPLC. The column was developed with a linear gradient of ammonium acetate. Final purification of the phosphopeptide was achieved by chromatography on a C-18 reverse phase HPLC column developed with a linear gradient of acetonitrile. The amino acid sequence of the homogeneous peptide was determined by manual modified Edman degradation.

Uhlinger, D.J.

1986-01-01

350

Mengovirus-Induced Rearrangement of the Nuclear Pore Complex: Hijacking Cellular Phosphorylation Machinery?  

PubMed Central

Representatives of several picornavirus genera have been shown previously to significantly enhance noncontrollable bidirectional exchange of proteins between nuclei and cytoplasm. In enteroviruses and rhinoviruses, enhanced permeabilization of the nuclear pores appears to be primarily due to proteolytic degradation of some nucleoporins (protein components of the pore), whereas this effect in cardiovirus-infected cells is triggered by the leader (L) protein, devoid of any enzymatic activities. Here, we present evidence that expression of L alone was sufficient to cause permeabilization of the nuclear envelope in HeLa cells. In contrast to poliovirus, mengovirus infection of these cells did not elicit loss of nucleoporins Nup62 and Nup153 from the nuclear pore complex. Instead, nuclear envelope permeabilization was accompanied by hyperphosphorylation of Nup62 in cells infected with wild-type mengovirus, whereas both of these alterations were suppressed in L-deficient virus mutants. Since phosphorylation of Nup62 (although less prominent) did accompany permeabilization of the nuclear envelope prior to its mitotic disassembly in uninfected cells, we hypothesize that cardiovirus L alters the nucleocytoplasmic traffic by hijacking some components of the normal cell division machinery. The variability and biological significance of picornaviral interactions with the nucleocytoplasmic transport in the infected cells are discussed. PMID:19144712

Bardina, Maryana V.; Lidsky, Peter V.; Sheval, Eugene V.; Fominykh, Ksenia V.; van Kuppeveld, Frank J. M.; Polyakov, Vladimir Y.; Agol, Vadim I.

2009-01-01

351

Effects of organic carbon sequestration strategies on soil enzymatic activities  

NASA Astrophysics Data System (ADS)

Greenhouse gases emissions can be counterbalanced with proper agronomical strategies aimed at sequestering carbon in soils. These strategies must be tested not only for their ability in reducing carbon dioxide emissions, but also for their impact on soil quality: enzymatic activities are related to main soil ecological quality, and can be used as early and sensitive indicators of alteration events. Three different strategies for soil carbon sequestration were studied: minimum tillage, protection of biodegradable organic fraction by compost amendment and oxidative polimerization of soil organic matter catalyzed by biometic porfirins. All strategies were compared with a traditional agricultural management based on tillage and mineral fertilization. Experiments were carried out in three Italian soils from different pedo-climatic regions located respectively in Piacenza, Turin and Naples and cultivated with maize or wheat. Soil samples were taken for three consecutive years after harvest and analyzed for their content in phosphates, ß-glucosidase, urease and invertase. An alteration index based on these enzymatic activities levels was applied as well. The biomimetic porfirin application didn't cause changes in enzymatic activities compared to the control at any treatment or location. Enzymatic activities were generally higher in the minimum tillage and compost treatment, while differences between location and date of samplings were limited. Application of the soil alteration index based on enzymatic activities showed that soils treated with compost or subjected to minimum tillage generally have a higher biological quality. The work confirms the environmental sustainability of the carbon sequestering agronomical practices studied.

Puglisi, E.; Suciu, N.; Botteri, L.; Ferrari, T.; Coppolecchia, D.; Trevisan, M.; Piccolo, A.

2009-04-01

352

Stereochemistry and Mechanism of Enzymatic and Non-Enzymatic Hydrolysis of Benzylic sec-Sulfate Esters  

PubMed Central

The substrate scope of inverting alkylsulfatase Pisa1 was extended towards benzylic sec-sulfate esters by suppression of competing non-enzymatic autohydrolysis by addition of dimethyl sulfoxide as co-solvent. Detailed investigation of the mechanism of autohydrolysis in 18O-labeled buffer by using an enantiopure sec-benzylic sulfate ester as substrate revealed that from the three possible pathways (i) inverting SN2-type nucleophilic attack of [OH–] at the benzylic carbon represents the major pathway, whereas (ii) SN1-type formation of a planar benzylic carbenium ion leading to racemization was a minor event, and (iii) Retaining SN2-type nucleophilic attack at sulfur took place at the limits of detection. The data obtained are interpreted by analysis of Hammett constants of meta substituents. PMID:25232289

Toesch, Michael; Schober, Markus; Breinbauer, Rolf; Faber, Kurt

2014-01-01

353

Three-dimensional graphene-carbon nanotube hybrid for high-performance enzymatic biofuel cells.  

PubMed

Enzymatic biofuel cells (EBFCs) are promising renewable and implantable power sources. However, their power output is often limited by inefficient electron transfer between the enzyme molecules and the electrodes, hindered mass transport, low conductivity, and small active surface area of the electrodes. To tackle these issues, we herein demonstrated a novel EBFC equipped with enzyme-functionalized 3D graphene-single walled carbon nanotubes (SWCNTs) hybrid electrodes using the naturally abundant glucose as the fuel and oxygen as the oxidizer. Such EBFCs, with high stability, can nearly attain the theoretical limit of open circuit voltage (?1.2 V) and a high power density ever reported (2.27 ± 0.11 mW cm(-2)). PMID:24533856

Prasad, Kenath Priyanka; Chen, Yun; Chen, Peng

2014-03-12

354

HALOACETIC ACIDS PERTURB PROTEIN PHOSPHORYLATION IN MOUSE EMBRYOS IN VITRO  

EPA Science Inventory

HALOACETIC ACIDS PERTURB PROTEIN PHOSPHORYLATION IN MOUSE EMBRYOS IN VITRO. MR Blanton and ES Hunter. Reproductive Toxicology Division, NHEERL, ORD, US EPA, RTP, NC, USA. Sponsor: JM Rogers. Haloacetic Acids (HAAs) formed during the disinfection process are present in drin...

355

Efficient Identification of Phosphorylation by Mass Spectrometric Phosphopeptide Fingerprinting  

E-print Network

for the identi- fication of phosphopeptides, which we term mass spec- trometric (MS) phosphopeptide are used to identify phosphopeptides, which can be confirmed and further studied by tandem mass specEfficient Identification of Phosphorylation by Mass Spectrometric Phosphopeptide Fingerprinting

Chait, Brian T.

356

Phosphorylation of Mad Controls Competition Between Wingless and BMP Signaling  

PubMed Central

Bone morphogenetic proteins (BMPs) and Wnts are growth factors that provide essential patterning signals for cell proliferation and differentiation. Here, we describe a molecular mechanism by which the phosphorylation state of the Drosophila transcription factor Mad determines its ability to transduce either BMP or Wingless (Wg) signals. Previously, Mad was thought to function in gene transcription only when phosphorylated by BMP receptors. We found that the unphosphorylated form of Mad was required for canonical Wg signaling by interacting with the Pangolin-Armadillo transcriptional complex. Phosphorylation of the carboxyl terminus of Mad by BMP receptor directed Mad toward BMP signaling, thereby preventing Mad from functioning in the Wg pathway. The results show that Mad has distinct signal transduction roles in the BMP and Wnt pathways depending on its phosphorylation state. PMID:21990430

Eivers, Edward; Demagny, Hadrien; Choi, Renee H.; De Robertis, Edward M.

2011-01-01

357

Phosphorylation of Mad controls competition between wingless and BMP signaling.  

PubMed

Bone morphogenetic proteins (BMPs) and Wnts are growth factors that provide essential patterning signals for cell proliferation and differentiation. Here, we describe a molecular mechanism by which the phosphorylation state of the Drosophila transcription factor Mad determines its ability to transduce either BMP or Wingless (Wg) signals. Previously, Mad was thought to function in gene transcription only when phosphorylated by BMP receptors. We found that the unphosphorylated form of Mad was required for canonical Wg signaling by interacting with the Pangolin-Armadillo transcriptional complex. Phosphorylation of the carboxyl terminus of Mad by BMP receptor directed Mad toward BMP signaling, thereby preventing Mad from functioning in the Wg pathway. The results show that Mad has distinct signal transduction roles in the BMP and Wnt pathways depending on its phosphorylation state. PMID:21990430

Eivers, Edward; Demagny, Hadrien; Choi, Renee H; De Robertis, Edward M

2011-01-01

358

Methods for generating phosphorylation site-specific immunological reagents  

DOEpatents

The present invention provides methods for generating phosphorylation site-specific immunological reagents. More specifically, a phosphopeptide mimetic is incorporated into a polypeptide in place of a phosphorylated amino acid. The polypeptide is used as antigen by standard methods to generate either monoclonal or polyclonal antibodies which cross-react with the naturally phosphorylated polypeptide. The phosphopeptide mimetic preferably contains a non-hydrolyzable linkage from the appropriate carbon atom of the amino acid residue to a phosphate group. A preferred linkage is a CF.sub.2 group. Such a linkage is used to generate the phosphoserine mimetic F.sub.2 Pab, which is incorporated into a polypeptide sequence derived from p53 to produce antibodies which recognize a specific phosphorylation state of p53. A CF.sub.2 group linkage is also used to produce the phosphothreonine mimetic F.sub.2 Pmb, and to produce the phosphotyrosine mimetic, F.sub.2 Pmp.

Anderson, Carl W. (Stony Brook, NY); Appella, Ettore (Montgomery, MD); Sakaguchi, Kazuyasu (Montgomery, MD)

2001-01-01

359

Aging effects on oxidative phosphorylation in rat adrenocortical mitochondria.  

PubMed

Does aging in itself lead to alteration in adrenocortical mitochondrial oxidative phosphorylation? Mitochondria from Fischer 344 (F344) rats (6 and 24 months old), Brown Norway rats (6 and 32 months old) and F344-Brown Norway hybrid rats (6 and 30 months old) were compared. Mitochondria were isolated from extirpated adrenal cortex. The yields of mitochondria were quantitatively similar in all rat strains irrespective of age. In order to assess the activity of each mitochondrial complex, several different substrates were tested and the rate of oxidative phosphorylation measured. Aging does not affect mitochondrial activity except in the F344 rat adrenal cortex where the maximal ADP-stimulated oxidative phosphorylation decreased with age. We hypothesize that impaired synthesis of steroid hormones by the adrenal cortex with age in F344 rats might be due to decreased adrenocortical mitochondrial oxidative phosphorylation. We conclude that aging results in adrenocortical mitochondria effects that are non-uniform across different rat strains. PMID:24486556

Solinas, Paola; Fujioka, Hisashi; Radivoyevitch, Tomas; Tandler, Bernard; Hoppel, Charles L

2014-06-01

360

Molybdenum in enzymatic and heterogeneous catalysis.  

PubMed

The chemistry common to molybdenum at the active centers of molybdoenzymes and at the surface of heterogeneous catalysts is described. Oxomolybdenum(VI) compounds catalyze selective oxidation of unsaturated hydrocarbons, e.g., propene to acrolein. Similarly, oxomolybdenum species take part in reactions catalyzed by molybdoenzymes, e.g., xanthine oxidase, sulfite oxidase, nitrate reductase. In these reactions H+, O2- or HO-, and electrons transfer between substrate molecules and molybdenum atoms and groups at the active centres. The chemistry involved is the acid-base and redox chemistry of molybdenum. Molybdenum disulfide catalyzes hydrogenation of unsaturated hydrocarbons, e.g., acetylene. The active site is a coordinately unsaturated molybdenum atom in a sulfur-ligand environment. The enzyme nitrogenase, which is a protein-bound iron-molybdenum sulfide, is also an excellent hydrogenation catalyst. Both catalysts exploit the chemistry of lower-valent molybdenum coordinated by sulfur. The extent to which understanding of the catalysis can be transferred between the two types of catalyst is assessed. PMID:3806088

Mitchell, P C

1986-01-01

361

Green liquor pretreatment for improving enzymatic hydrolysis of corn stover.  

PubMed

Green liquor consists of sodium carbonate and sodium sulfide and is readily available in any kraft mills. The green liquor pretreatment process for bioethanol production was developed for wood chips. This process uses only proven technology and equipment currently used in a kraft pulp mill and has several additional advantages such as high sugar recovery and concentration, no inhibitive substances produced, as compared to acid-based pretreatment methods. The liquor was used to pretreat corn stover for enhancing enzymatic hydrolysis in bioethanol production. Pulp yield of 70% with 45% lignin removal was achieved under optimized conditions (8% total titratable alkali, 40% sulfidity and 140°C). About 70% of the original polysaccharides were converted into fermentable sugars, using 20 FPU/g-pulp of enzyme in the subsequent enzymatic hydrolysis. The result indicates that green liquor is a feasible pretreatment to improve the enzymatic saccharification of corn stover for bioethanol production. PMID:22989657

Gu, Feng; Yang, Linfeng; Jin, Yongcan; Han, Qiang; Chang, Hou-min; Jameel, Hasan; Phillips, Richard

2012-11-01

362

Biocolloids with ordered urease multilayer shells as enzymatic reactors.  

PubMed

The preparation of biocolloids with organized enzyme-containing multilayer shells for exploitation as colloidal enzymatic nanoreactors is described. Urease multilayers were assembled onto submicrometer-sized polystyrene spheres by the sequential adsorption of urease and polyelectrolyte, in a predetermined order, utilizing electrostatic interactions for layer growth. The catalytic activity of the biocolloids increased proportionally with the number of urease layers deposited on the particles, demonstrating that biocolloid particles with tailored enzymatic activities can be produced. It was further found that precoating the latex spheres with nanoparticles (40-nm silica or 12-nm magnetite) enhanced both the stability (with respect to adsorption) and enzymatic activity of the urease multilayers. The presence of the magnetite nanoparticle coating also provided a magnetic function that allowed the biocolloids to be easily and rapidly separated with a permanent magnet. The fabrication of such colloids opens new avenues for the application of bioparticles and represents a promising route for the creation of complex catalytic particles. PMID:11569811

Lvov, Y; Caruso, F

2001-09-01

363

An oxidative enzyme boosting the enzymatic conversion of recalcitrant polysaccharides.  

PubMed

Efficient enzymatic conversion of crystalline polysaccharides is crucial for an economically and environmentally sustainable bioeconomy but remains unfavorably inefficient. We describe an enzyme that acts on the surface of crystalline chitin, where it introduces chain breaks and generates oxidized chain ends, thus promoting further degradation by chitinases. This enzymatic activity was discovered and further characterized by using mass spectrometry and chromatographic separation methods to detect oxidized products generated in the absence or presence of H(2)(18)O or (18)O(2). There are strong indications that similar enzymes exist that work on cellulose. Our findings not only demonstrate the existence of a hitherto unknown enzyme activity but also provide new avenues toward more efficient enzymatic conversion of biomass. PMID:20929773

Vaaje-Kolstad, Gustav; Westereng, Bjřrge; Horn, Svein J; Liu, Zhanliang; Zhai, Hong; Sřrlie, Morten; Eijsink, Vincent G H

2010-10-01

364

Micro-electro-mechanical systems (MEMS) for enzymatic detection  

NASA Astrophysics Data System (ADS)

Early enzymatic identification and confirmation is essential for diagnosis and prevention as in the case of Acute Myocardial Infarction (AMI). Biochemical markers continue to be an important clinical tool for the enzymatic detection. The advent of MEMS devices can enable the use of various microstructures for the detection of enzymes. In this study, the concept of MEMS is applied for the detection of enzyme reaction, in which microcantilevers undergo changes in mechanical behavior that can be optically detected when enzyme molecules adsorb on their surface. This paper presents the static behavior of microcantilevers under Horse Radish Peroxide (HRP) enzyme reaction. The reported experimental results provide valuable information that will be useful in the development of MEMS sensors for enzymatic detection. The surface stress produced due to enzyme reactions results in the bending of cantilevers as similar to the influencing of thermal stress in the cantilevers. This paper also reports the influence of thermal gradient on the microcantilevers.

Jeetender, Amritsar; Packirisamy, Muthukumaran; Stiharu, Ion G.; Balagopal, Ganesharam

2004-08-01

365

Plasmon-Enhanced Enzymatic Reactions: A Study of Nanoparticle-Enzyme Distance- and Nanoparticle Loading-Dependent Enzymatic Activity.  

PubMed

A detailed investigation of the dependence of the efficiency of plasmon-enhanced enzymatic reactions on the distance between silver island films (SIFs) and horse radish peroxidase (HRP) enzyme and on the loading of SIFs on glass surfaces is presented. Three different extent of loading of SIFs on glass slides were used: 1) low, 2) medium and 3) high, which was characterized by using optical absorption spectroscopy and scanning electron microscopy. Streptavidin-linked HRP enzyme was deposited onto SIFs and glass slides by using three different strategies: strategy 1: biotin-avidin protein assay (distance between SIFs and HRP = 4-8 nm), strategy 2: self assembled monolayers (SAMs) (1-5 nm), strategy 3: polymer layer (1-5 nm). The efficiency of enzymatic conversion of O-phenylenediamine dihydrochloride (OPD) to a colored product by HRP on SIFs and glass surfaces was assessed by optical absorption spectroscopy. The distance between SIFs and HRP and the extent of loading of SIFs on the glass surfaces were shown to have significant effect on the efficiency of plasmon-enhanced enzymatic reactions. In this regard, up to an %250 increase in enzymatic conversion of OPD was observed from SIFs with high loading using strategy 1. In addition, we have studied the potential of repeated use of SIFs in plasmon-enhanced enzymatic reactions. PMID:21949594

Abel, Biebele; Akinsule, Alice; Andrews, Canisha; Aslan, Kadir

2011-01-01

366

Cascade catalysis in membranes with enzyme immobilization for multi-enzymatic conversion of CO2 to methanol.  

PubMed

Facile co-immobilization of enzymes is highly desirable for bioconversion methods involving multi-enzymatic cascade reactions. Here we show for the first time that three enzymes can be immobilized in flat-sheet polymeric membranes simultaneously or separately by simple pressure-driven filtration (i.e. by directing membrane fouling formation), without any addition of organic solvent. Such co-immobilization and sequential immobilization systems were examined for the production of methanol from CO2 with formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH) and alcohol dehydrogenase (ADH). Enzyme activity was fully retained by this non-covalent immobilization strategy. The two immobilization systems had similar catalytic efficiencies because the second reaction (formic acid?formaldehyde) catalyzed by FaldDH was found to be the cascade bottleneck (a threshold substrate concentration was required). Moreover, the trade-off between the mitigation of product inhibition and low substrate concentration for the adjacent enzymes probably made the co-immobilization meaningless. Thus, sequential immobilization could be used for multi-enzymatic cascade reactions, as it allowed the operational conditions for each single step to be optimized, not only during the enzyme immobilization but also during the reaction process, and the pressure-driven mass transfer (flow-through mode) could overcome the diffusion resistance between enzymes. This study not only offers a green and facile immobilization method for multi-enzymatic cascade systems, but also reveals the reaction bottleneck and provides possible solutions for the bioconversion of CO2 to methanol. PMID:25698375

Luo, Jianquan; Meyer, Anne S; Mateiu, R V; Pinelo, Manuel

2015-05-25

367

AMP-activated protein kinase phosphorylation of endothelial NO synthase  

Microsoft Academic Search

The AMP-activated protein kinase (AMPK) in rat skeletal and cardiac muscle is activated by vigorous exercise and ischaemic stress. Under these conditions AMPK phosphorylates and inhibits acetyl-coenzyme A carboxylase causing increased oxidation of fatty acids. Here we show that AMPK co-immunoprecipitates with cardiac endothelial NO synthase (eNOS) and phosphorylates Ser-1177 in the presence of Ca2+-calmodulin (CaM) to activate eNOS both

Zhi-Ping Chen; Ken I Mitchelhill; Belinda J Michell; David Stapleton; Ignacio Rodriguez-Crespo; Lee A Witters; David A Power; Paul R Ortiz de Montellano; Bruce E Kemp

1999-01-01

368

Fission Yeast Rad52 Phosphorylation Restrains Error Prone Recombination Pathways  

PubMed Central

Rad52 is a key protein in homologous recombination (HR), a DNA repair pathway dedicated to double strand breaks and recovery of blocked or collapsed replication forks. Rad52 allows Rad51 loading on single strand DNA, an event required for strand invasion and D-loop formation. In addition, Rad52 functions also in Rad51 independent pathways because of its ability to promote single strand annealing (SSA) that leads to loss of genetic material and to promote D-loops formation that are cleaved by Mus81 endonuclease. We have previously reported that fission yeast Rad52 is phosphorylated in a Sty1 dependent manner upon oxidative stress and in cells where the early step of HR is impaired because of lack of Rad51. Here we show that Rad52 is also constitutively phosphorylated in mus81 null cells and that Sty1 partially impinges on such phosphorylation. As upon oxidative stress, the Rad52 phosphorylation in rad51 and mus81 null cells appears to be independent of Tel1, Rad3 and Cdc2. Most importantly, we show that mutating serine 365 to glycine (S365G) in Rad52 leads to loss of the constitutive Rad52 phosphorylation observed in cells lacking Rad51 and to partial loss of Rad52 phosphorylation in cells lacking Mus81. Contrariwise, phosphorylation of Rad52-S365G protein is not affected upon oxidative stress. These results indicate that different Rad52 residues are phosphorylated in a Sty1 dependent manner in response to these distinct situations. Analysis of spontaneous HR at direct repeats shows that mutating serine 365 leads to an increase in spontaneous deletion-type recombinants issued from mitotic recombination that are Mus81 dependent. In addition, the recombination rate in the rad52-S365G mutant is further increased by hydroxyurea, a drug to which mutant cells are sensitive. PMID:24748152

Bellini, Angela; Girard, Pierre-Marie; Tessier, Ludovic; Sage, Evelyne; Francesconi, Stefania

2014-01-01

369

Cloning and expression of the enzymatic region of Streptococcal hyaluronidase  

PubMed Central

Objective(s): Streptococcus pyogenes produces extracellular hyaluronidase enzyme. This enzyme is directly associated with the spread of the organism during infection. The objective of the present study was to clone and express the nucleotide sequence of the enzyme which is involved in hyaluronidase enzymatic activity. Materials and Methods: The enzymatic region of hyaluronidase gene was detected by bioinformatics method. The PCR method was used to amplify enzymatic region of hyaluronidase gene from chromosomal DNA of Streptococcus pyogenes. The eluted product was cloned into the prokaryotic expression vector pET32a which was digested by BamHI and HindIII restriction endonuclease enzymes. The target protein was expressed in the Escherichia coli. The bacteria including pET32a-hylA (hylA is abbreviation of Streptococcus pyogenes hyaluronidase gene and hylA is abbreviation of Streptococcus pyogenes hyaluronidase protein) plasmids were induced by IPTG and analyzed by SDS-PAGE. The enzymatic evaluation and antigenicity was finally studied. Results: Enzymes digestion analysis, sequencing results showed that the target gene (1296 base pair) was inserted correctly into the recombinant vector. The expressed protein (65 KDa) was purified successfully via affinity chromatography. Data also indicated that enzymatic region of hyaluronidase protein from Streptococcus pyogenes was recognized in all 5 patient's sera. Conclusion: In general, it is possible to produce the enzymatic regions of the Streptococcus pyogenes hyaluronidase in E. coli. The antigenic property of the produced protein is well retained. Considering the product's domestic demand and also low efficiency of production and pathogenicity of Streptococcus species, it is possible to produce it as recombinant product. PMID:25691943

Mirjamali, Nafiseh Al-Sadat; Soufian, Safieh; Molaee, Neda; Abbasian, Shabnam Sadoogh; Abtahi, Hamid

2014-01-01

370

Excited singlet molecular O2 (1?g) is generated enzymatically from excited carbonyls in the dark  

PubMed Central

In mammalian tissues, ultraweak chemiluminescence arising from biomolecule oxidation has been attributed to the radiative deactivation of singlet molecular oxygen [O2 (1?g)] and electronically excited triplet carbonyl products involving dioxetane intermediates. Herein, we describe evidence of the generation of O2 (1?g) in aqueous solution via energy transfer from excited triplet acetone. This involves thermolysis of 3,3,4,4-tetramethyl-1,2-dioxetane, a chemical source, and horseradish peroxidase-catalyzed oxidation of 2-methylpropanal, as an enzymatic source. Both sources of excited carbonyls showed characteristic light emission at 1,270?nm, directly indicative of the monomolecular decay of O2 (1?g). Indirect analysis of O2 (1?g) by electron paramagnetic resonance using the chemical trap 2,2,6,6-tetramethylpiperidine showed the formation of 2,2,6,6-tetramethylpiperidine-1-oxyl. Using [18O]-labeled triplet, ground state molecular oxygen [18O2 (3?g-)], chemical trapping of 18O2 (1?g) with disodium salt of anthracene-9,10-diyldiethane-2,1-diyl disulfate yielding the corresponding double-[18O]-labeled 9,10-endoperoxide, was detected through mass spectrometry. This corroborates formation of O2 (1?g). Altogether, photoemission and chemical trapping studies clearly demonstrate that chemically and enzymatically nascent excited carbonyl generates 18O2 (1?g) by triplet-triplet energy transfer to ground state oxygen O2 (3?g?), and supports the long formulated hypothesis of O2 (1?g) involvement in physiological and pathophysiological events that might take place in tissues in the absence of light. PMID:25087485

Mano, Camila M.; Prado, Fernanda M.; Massari, Júlio; Ronsein, Graziella E.; Martinez, Glaucia R.; Miyamoto, Sayuri; Cadet, Jean; Sies, Helmut; Medeiros, Marisa H. G.; Bechara, Etelvino J. H.; Di Mascio, Paolo

2014-01-01

371

Enzymatic oxidation-reduction processes under magnetic fields up to 8 T (abstract)  

NASA Astrophysics Data System (ADS)

The question of whether magnetic fields affect enzymatic activities or not is of considerable interest in biochemistry and in biomagnetics. Xanthine oxidase, contained in liver, lungs, intestine, and other organs, catalyzes the degradation of hypoxanthine to xanthine, and xanthine to uric acid, which is the terminal waste of purine nucleotides in mammals. During the oxidation of xanthine, the enzyme releases superoxide anion radicals as intermediates which reduce ferricytochrome c (Fe3+). Superoxide anion, as well as any type of free radical, is also paramagnetic. The study is focused on whether these magnetically related enzymatic activities can be affected by magnetic fields. There is a possibility that free radicals, as intermediates, can be modified by magnetic fields of specific intensities. In our previously reported study, we examined a possible effect of magnetic fields up to 1.0 T on biochemical reaction catalyzed by xanthine oxidase, and obtained negative results. In the present abstract, we examine the effect of magnetic fields up to 8 T on this oxidation-reduction process. Reduced cytochrome c (Fe2+) has an absorption maximum at 550 nm which can be detected by a spectrophotometer. Xanthine oxidase was assayed by superoxide dismutase—inhibitable reduction of cytochrome c. We measured optical absorbance of reduced cytochrome c by superoxide anion which was produced by the reaction catalyzed by xanthine oxidase. The absorbances of the mixture exposed to an 8 T magnetic field at 25 °C were higher than control samples in the re-oxidation proces of cytochrome c. The results show that the 8 T magnetic fields altered the rate of reduction of cytochrome c by superoxide anion which was produced by the reaction catalyzed by xanthine oxidase. It may conclude that the electron transfer from xanthine to molecular oxygen or the transfer from superoxide anion to cytochrome c, can be affected by the magnetic fields up to 8 T.

Iwasaka, M.; Ueno, S.

1994-05-01

372

Egf binding to its receptor triggers a rapid tyrosine phosphorylation of the erbB-2 protein in the mammary tumor cell line SK-BR-3.  

PubMed Central

The epidermal growth factor receptor (EGF-R) and the erbB-2 proto-oncogene product protein are closely related by their structural homology and their shared enzymatic activity as autophosphorylating tyrosine kinases. We show that in mammary tumor cells (SK-BR-3) EGF causes a rapid increase in tyrosine phosphorylation of the erbB-2 protein. Phosphorylation of erbB-2 does not occur in cells lacking the EGF-R (MDA-MB-453). Phosphorylation of erbB-2 in SK-BR-3 cells is blocked if EGF is prevented from interacting with its receptor by specific monoclonal antibodies. While EGF induces the down-regulation of its receptor in SK-BR-3 cells, EGF has no effect on the stability of the erbB-2 protein. This result suggests that the erbB-2 protein is a substrate of the EGF-R and indicates the possibility of communication between these two proteins early in the signal transduction process. Images PMID:2901952

King, C R; Borrello, I; Bellot, F; Comoglio, P; Schlessinger, J

1988-01-01

373

Functionalized Graphene Oxide as a Nanocarrier in a Multienzyme Labeling Amplification Strategy for Ultrasensitive Electrochemical Immunoassay of Phosphorylated p53 (S392)  

SciTech Connect

P53 phosphorylation plays an important role in many biological processes and might be used as a potential biomarker in clinical diagnoses. We report a new electrochemical immunosensor for ultrasensitive detection of phosphorylated p53 at Ser392 (phospho-p53-392) based on graphene oxide (GO) as a nanocarrier in multienzymes amplification strategy. Greatly enhanced sensitivity was achieved by using the bioconjugates featuring horseradish peroxidase (HRP) and p53392 signal antibody (p53Ab2) linked to functionalized GO (HRP-p53Ab2-GO) at high ratio of HRP/p53Ab2. After a sandwich immunoreaction, the HRP-p53Ab2-GO captured onto the electrode surface produced an amplified electrocatalytic response by the reduction of enzymatically oxidized thionine in the presence of hydrogen peroxide. The increase of response current was proportional to the phospho-p53 concentration in the range of 0.02 to 2 nM with the detection limit of 0.01 nM, which was 10-fold lower than that of traditional sandwich electrochemical measurement for p53. The amplified immunoassay developed in this work shows acceptable stability and reproducibility and the assay results for phospho-p53 spiked in human plasma also show good recovery (92%~103.8%). This simple and low-cost immunosensor shows great promise for detection of other phosphorylated proteins and clinical applications.

Du, Dan; Wang, Limin; Shao, Yuyan; Wang, Jun; Engelhard, Mark H.; Lin, Yuehe

2011-01-06

374

A Mitotic Phosphorylation Feedback Network Connects Cdk1, Plk1, 53BP1, and Chk2 to Inactivate the G2/M DNA Damage Checkpoint  

PubMed Central

DNA damage checkpoints arrest cell cycle progression to facilitate DNA repair. The ability to survive genotoxic insults depends not only on the initiation of cell cycle checkpoints but also on checkpoint maintenance. While activation of DNA damage checkpoints has been studied extensively, molecular mechanisms involved in sustaining and ultimately inactivating cell cycle checkpoints are largely unknown. Here, we explored feedback mechanisms that control the maintenance and termination of checkpoint function by computationally identifying an evolutionary conserved mitotic phosphorylation network within the DNA damage response. We demonstrate that the non-enzymatic checkpoint adaptor protein 53BP1 is an in vivo target of the cell cycle kinases Cyclin-dependent kinase-1 and Polo-like kinase-1 (Plk1). We show that Plk1 binds 53BP1 during mitosis and that this interaction is required for proper inactivation of the DNA damage checkpoint. 53BP1 mutants that are unable to bind Plk1 fail to restart the cell cycle after ionizing radiation-mediated cell cycle arrest. Importantly, we show that Plk1 also phosphorylates the 53BP1-binding checkpoint kinase Chk2 to inactivate its FHA domain and inhibit its kinase activity in mammalian cells. Thus, a mitotic kinase-mediated negative feedback loop regulates the ATM-Chk2 branch of the DNA damage signaling network by phosphorylating conserved sites in 53BP1 and Chk2 to inactivate checkpoint signaling and control checkpoint duration. PMID:20126263

van Vugt, Marcel A. T. M.; Reinhardt, H. Christian; Ong, Shao-En; Tan, Chris S.; Miao, Hua; Keezer, Susan M.; Li, Jeijin; Pawson, Tony; Lewis, Timothy A.; Carr, Steven A.; Smerdon, Stephen J.; Brummelkamp, Thijn R.; Yaffe, Michael B.

2010-01-01

375

A mitotic phosphorylation feedback network connects Cdk1, Plk1, 53BP1, and Chk2 to inactivate the G(2)/M DNA damage checkpoint.  

PubMed

DNA damage checkpoints arrest cell cycle progression to facilitate DNA repair. The ability to survive genotoxic insults depends not only on the initiation of cell cycle checkpoints but also on checkpoint maintenance. While activation of DNA damage checkpoints has been studied extensively, molecular mechanisms involved in sustaining and ultimately inactivating cell cycle checkpoints are largely unknown. Here, we explored feedback mechanisms that control the maintenance and termination of checkpoint function by computationally identifying an evolutionary conserved mitotic phosphorylation network within the DNA damage response. We demonstrate that the non-enzymatic checkpoint adaptor protein 53BP1 is an in vivo target of the cell cycle kinases Cyclin-dependent kinase-1 and Polo-like kinase-1 (Plk1). We show that Plk1 binds 53BP1 during mitosis and that this interaction is required for proper inactivation of the DNA damage checkpoint. 53BP1 mutants that are unable to bind Plk1 fail to restart the cell cycle after ionizing radiation-mediated cell cycle arrest. Importantly, we show that Plk1 also phosphorylates the 53BP1-binding checkpoint kinase Chk2 to inactivate its FHA domain and inhibit its kinase activity in mammalian cells. Thus, a mitotic kinase-mediated negative feedback loop regulates the ATM-Chk2 branch of the DNA damage signaling network by phosphorylating conserved sites in 53BP1 and Chk2 to inactivate checkpoint signaling and control checkpoint duration. PMID:20126263

van Vugt, Marcel A T M; Gardino, Alexandra K; Linding, Rune; Ostheimer, Gerard J; Reinhardt, H Christian; Ong, Shao-En; Tan, Chris S; Miao, Hua; Keezer, Susan M; Li, Jeijin; Pawson, Tony; Lewis, Timothy A; Carr, Steven A; Smerdon, Stephen J; Brummelkamp, Thijn R; Yaffe, Michael B

2010-01-01

376

Phosphorylation of bovine rod photoreceptor cyclic GMP phosphodiesterase.  

PubMed Central

The cyclic GMP phosphodiesterase (PDE) of retinal rods plays a key role in phototransduction and consists of two catalytic subunits (PDE alpha and PDE beta) and two identical inhibitory subunits (PDE gamma). Here we report that PDE alpha and PDE gamma are phosphorylated by protein kinase(s) C (PKC) from brain and rod outer segments (ROS). These same two types of PKC also phosphorylate PDE alpha in trypsin-activated PDE (without PDE gamma). In contrast, cyclic-AMP-dependent protein kinase catalytic subunit phosphorylates both PDE alpha and PDE beta, but not PDE gamma. This kinase does not phosphorylate trypsin-activated PDE. The synthetic peptides AKVISNLLGPREAAV (PDE alpha 30-44) and KQRQTRQFKSKPPKK (PDE gamma 31-45) inhibited phosphorylation of PDE by PKC from ROS. These data suggest that sites (at least one for each subunit) for phosphorylation of PDE by PKC are localized in these corresponding regions of PDE alpha and PDE gamma. Isoenzyme-specific PKC antibodies against peptides unique to the alpha, beta, gamma, delta, epsilon and zeta isoforms of protein kinase C were used to show that a major form of PKC in ROS is PKC alpha. However, other minor forms were also present. Images Figure 1 Figure 4 Figure 6 Figure 7 PMID:8216238

Udovichenko, I P; Cunnick, J; Gonzales, K; Takemoto, D J

1993-01-01

377

Depolarization and neurotransmitters increase neuronal protein tyrosine phosphorylation.  

PubMed

In rat hippocampal slices and in neurons in primary culture, K(+)-induced depolarization increased markedly and rapidly tyrosine phosphorylation of a 110-kDa protein (pp110) and, to a lesser degree, of a 120-kDa protein (pp120), in a calcium-dependent fashion. Glutamate, 1-aminocyclopentane-trans-1,3-dicarboxylic acid (an agonist of metabotropic glutamate receptors), and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (an agonist of ionotropic glutamate receptors) stimulated also tyrosine phosphorylation of pp110 and pp120. These effects were not observed in astrocytes in primary culture. In hippocampal slices tyrosine phosphorylation of pp110 and pp120 was stimulated by Ca(2+)-ionophores and by phorbol esters and antagonized by a chelator of intracellular Ca2+ and by drugs that inhibit protein kinase C. Stimulation of muscarinic and alpha 1-adrenergic receptors increased also tyrosine phosphorylation of pp110 and pp120. These results demonstrate that membrane depolarization and stimulation of neurotransmitter receptors activate a tyrosine phosphorylation pathway in neurons. This pathway involves an increase in intracellular Ca2+ concentrations and the activation of protein kinase C. It may provide a biochemical basis for some neurotrophic effects of electrical activity and neurotransmitters and may contribute to the role of tyrosine phosphorylation in long-term potentiation. PMID:7509378

Siciliano, J C; Gelman, M; Girault, J A

1994-03-01

378

Characterisation and properties of homo- and heterogenously phosphorylated nanocellulose.  

PubMed

Nano-sized cellulose ester derivatives having phosphoryl side groups were synthesised by phosphorylation of nanofibrilated cellulose (NFC) and nanocrystaline cellulose (NCC), using different heterogeneous (in water) and homogeneous (in molten urea) processes with phosphoric acid as phosphoryl donor. The phosphorylation mechanism, efficacy, stability, as well as its influence on the NC crystallinity and thermal properties, were evaluated using ATR-FTIR and (13)C NMR spectroscopies, potentiometric titration, capillary electrophoresis, X-ray diffraction, colorimetry, thermogravimmetry and SEM. Phosphorylation under both processes created dibasic phosphate and monobasic tautomeric phosphite groups at C6 and C3 positioned hydroxyls of cellulose, yielded 60-fold (?1173mmol/kg) and 2-fold (?1038mmol/kg) higher surface charge density for p-NFC and p-NCC, respectively, under homogenous conditions. None of the phosphorylations affected neither the NC crystallinity degree nor the structure, and noticeably preventing the derivatives from weight loss during the pyrolysis process. The p-NC showed high hydrolytic stability to water at all pH mediums. Reusing of the treatment bath was examined after the heterogeneous process. PMID:25857987

Kokol, Vanja; Boži?, Mojca; Vogrin?i?, Robert; Mathew, Aji P

2015-07-10

379

Protein phosphorylation differs significantly among ontogenetic phases in Malus seedlings  

PubMed Central

Background Although protein phosphorylation is an important post-translational modification affecting protein function and metabolism, dynamic changes in this process during ontogenesis remain unexplored in woody angiosperms. Methods Phosphorylated proteins from leaves of three apple seedlings at juvenile, adult vegetative and reproductive stages were extracted and subjected to alkaline phosphatase pre-treatment. After separating the proteins by two-dimensional gel electrophoresis and phosphoprotein-specific Pro-Q Diamond staining, differentially expressed phosphoproteins were identified by MALDI-TOF-TOF mass spectrometry. Results A total of 107 phosphorylated protein spots on nine gels (three ontogenetic phases?×?three seedlings) were identified by MALDI-TOF-TOF mass spectrometry. The 55 spots of ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) large-chain fragments varied significantly in protein abundance and degree of phosphorylation among ontogenetic phases. Abundances of the 27 spots corresponding to Rubisco activase declined between juvenile and reproductive phases. More extensively, phosphorylated ?-tubulin chain spots with lower isoelectric points were most abundant during juvenile and adult vegetative phases. Conclusions Protein phosphorylation varied significantly during vegetative phase change and floral transition in apple seedlings. Most of the observed changes were consistent among seedlings and between hybrid populations. PMID:24904238

2014-01-01

380

Huntingtin-interacting protein 1 phosphorylation by receptor tyrosine kinases.  

PubMed

Huntingtin-interacting protein 1 (HIP1) binds inositol lipids, clathrin, actin, and receptor tyrosine kinases (RTKs). HIP1 is elevated in many tumors, and its expression is prognostic in prostate cancer. HIP1 overexpression increases levels of the RTK epidermal growth factor receptor (EGFR) and transforms fibroblasts. Here we report that HIP1 is tyrosine phosphorylated in the presence of EGFR and platelet-derived growth factor ? receptor (PDGF?R) as well as the oncogenic derivatives EGFRvIII, HIP1/PDGF?R (H/P), and TEL/PDGF?R (T/P). We identified a four-tyrosine "HIP1 phosphorylation motif" (HPM) in the N-terminal region of HIP1 that is required for phosphorylation mediated by both EGFR and PDGF?R but not by the oncoproteins H/P and T/P. We also identified a tyrosine residue (Y152) within the HPM motif of HIP1 that inhibits HIP1 tyrosine phosphorylation. The HPM tyrosines are conserved in HIP1's only known mammalian relative, HIP1-related protein (HIP1r), and are also required for HIP1r phosphorylation. Tyrosine-to-phenylalanine point mutations in the HPM of HIP1 result in proapoptotic activity, indicating that an intact HPM may be necessary for HIP1's role in cellular survival. These data suggest that phosphorylation of HIP1 by RTKs in an N-terminal region contributes to the promotion of cellular survival. PMID:23836884

Ames, Heather M; Wang, Anmin A; Coughran, Alanna; Evaul, Kristen; Huang, Sha; Graves, Chiron W; Soyombo, Abigail A; Ross, Theodora S

2013-09-01

381

Whose Entropy: A Maximal Entropy Analysis of Phosphorylation Signaling  

NASA Astrophysics Data System (ADS)

High throughput experiments, characteristic of studies in systems biology, produce large output data sets often at different time points or under a variety of related conditions or for different patients. In several recent papers the data is modeled by using a distribution of maximal information-theoretic entropy. We pose the question: `whose entropy' meaning how do we select the variables whose distribution should be compared to that of maximal entropy. The point is that different choices can lead to different answers. Due to the technological advances that allow for the system-wide measurement of hundreds to thousands of events from biological samples, addressing this question is now part of the analysis of systems biology datasets. The analysis of the extent of phosphorylation in reference to the transformation potency of Bcr-Abl fusion oncogene mutants is used as a biological example. The approach taken seeks to use entropy not simply as a statistical measure of dispersion but as a physical, thermodynamic, state function. This highlights the dilemma of what are the variables that describe the state of the signaling network. Is what matters Boolean, spin-like, variables that specify whether a particular phosphorylation site is or is not actually phosphorylated. Or does the actual extent of phosphorylation matter. Last but not least is the possibility that in a signaling network some few specific phosphorylation sites are the key to the signal transduction even though these sites are not at any time abundantly phosphorylated in an absolute sense.

Remacle, F.; Graeber, T. G.; Levine, R. D.

2011-07-01

382

Enzymatic determination of the cellulose content of atmospheric aerosols  

NASA Astrophysics Data System (ADS)

A new analytical method for the quantitative determination of cellulose in aerosols was developed. For the first time cellulose can be successfully determined in atmospheric aerosols. This determination became possible by means of enzymes. It is not necessary to isolate the cellulose before determination. The test can be carried out without further purification steps. The analytical procedure is subdivided into three main steps: (1) an alkaline peroxide pretreatment to improve the enzymatic accessibility by removing parts of hcmicellulose and lignin; (2) enzymatic conversion of cellulose to D-glucose and (3) photometric detection of D-glucose. First measurements have shown that cellulose may be a main organic component in atmospheric aerosols.

Kunit, M.; Puxbaum, H.

383

Enzymatic Processing of Bioactive Glycosides from Natural Sources  

NASA Astrophysics Data System (ADS)

A number of biologically active natural products are glycosides. Often, the glycosidic residue is crucial for their activity. In other cases, glycosylation only improves their pharmacokinetic parameters. Enzymatic modification of these glycosides - both extension of the glycoside moiety and its selective trimming - is advantageous due to their selectivity and mildness of the reaction conditions in the presence of reactive and sensitive complex aglycones. Enzymatic reactions enable the resulting products to be used as "natural products", e.g., in nutraceuticals. This chapter concentrates on naturally occurring glycosides used in medicine but also in the food and flavor industry (e.g., sweeteners). Both "classical" and modern methods will be discussed.

Weignerová, Lenka; K?en, Vladimír

384

Study on beta-galactosidase enzymatic activity of herbal yogurt.  

PubMed

Different types of herbal yogurts were developed by mixing standardized milk with pretreated herbs, namely tulsi leaf (Ocimum sanctum), pudina leaf (Mentha arvensis) and coriander leaf (Coriandrum sativum), with leaves separately and a 1:1 (v/v) mixture of the strains of lactic starter cultures---Lactobacillus acidophilus (NCIM 2903) and Lactobacillus plantarum (NCIM 2083)-followed by incubation at 40 degrees C for 6 h. The beta-galactosidase enzymatic activity of the abovementioned herbal yogurts was determined and interestingly noted to exhibit higher enzymatic activity compared with the control yogurt (without any herbs). Among all herbal yogurts, tulsi yogurt had the maximum beta-galactosidase activity. PMID:17852503

Chowdhury, Banani Ray; Chakraborty, Runu; Raychaudhuri, Utpal

2008-03-01

385

Protein microchips : use for immunoassay and enzymatic reactions.  

SciTech Connect

Different proteins such as antibodies, antigens, and enzymes were immobilized within the 100 x 100 x 20-{mu}m gel pads of protein microchips. A modified polyacrylamide gel has been developed to accommodate proteins of a size up to 400,000 daltons. Electrophoresis in the microchip reaction chamber speeded up antigen-antibody interactions within the gel. Protein microchips were used in immunoassays for detection of antigens or antibodies, as well as to carry out enzymatic reactions and to measure their kinetics in the absence or presence of an inhibitor. A protein microchip can be used several times in different immunoassays and enzymatic kinetic measurements.

Arenkov, P.; Kukhtin, A.; Gemmell, A.; Voloschuk, S.; Chupeeva, V.; Mirzabekov, A.; Biochip Technology Center; Russian Academy of Sciences

2000-02-15

386

Synthesis of Red-Shifted 8-Hydroxyquinoline Derivatives Using Click Chemistry and Their Incorporation into Phosphorylation Chemosensors  

PubMed Central

Protein phosphorylation is a ubiquitous post-translational modification and protein kinases, the enzymes that catalyze the phosphoryl transfer, are involved in nearly every aspect of normal, as well as aberrant, cell function. Here we describe the synthesis of novel, red-shifted 8-hydroxyquinoline-based fluorophores and their incorporation into peptidyl kinase activity reporters. Replacement of the sulfonamide group of the sulfonamido-oxine (1, Sox) chromophore, which has been previously used in kinase sensing, by a 1,4-substituted-triazole moiety, via click chemistry, resulted in a significant bathochromic shift in the fluorescence excitation (15 nm) and emission (40 nm) maxima for the Mg2+ chelate. Furthermore, when a click derivative was incorporated into a chemosensor for MK2, the kinase accepted the new substrate as efficiently as the previously reported Sox-based sensor. Taken together, these results extend the utility range of kinase sensors that are based on chelation-enhanced fluorescence (CHEF). PMID:19725503

González-Vera, Juan A.; Lukovi?, Elvedin; Imperiali, Barbara

2009-01-01

387

Synthesis of red-shifted 8-hydroxyquinoline derivatives using click chemistry and their incorporation into phosphorylation chemosensors.  

PubMed

Protein phosphorylation is a ubiquitous post-translational modification, and protein kinases, the enzymes that catalyze the phosphoryl transfer, are involved in nearly every aspect of normal, as well as aberrant, cell function. Here we describe the synthesis of novel, red-shifted 8-hydroxyquinoline-based fluorophores and their incorporation into peptidyl kinase activity reporters. Replacement of the sulfonamide group of the sulfonamido-oxine (1, Sox) chromophore, which has been previously used in kinase sensing, by a 1,4-substituted triazole moiety prepared via click chemistry resulted in a significant bathochromic shift in the fluorescence excitation (15 nm) and emission (40 nm) maxima for the Mg(2+) chelate. Furthermore, when a click derivative was incorporated into a chemosensor for MK2, the kinase accepted the new substrate as efficiently as the previously reported Sox-based sensor. Taken together, these results extend the utility range of kinase sensors that are based on chelation-enhanced fluorescence (CHEF). PMID:19725503

González-Vera, Juan A; Lukovi?, Elvedin; Imperiali, Barbara

2009-10-01

388

FEBS Letters 372 (1995)238-242 FEBS 16062 Histidine and tyrosine phosphorylation in pea mitochondria  

E-print Network

mitochondria: evidence for protein phosphorylation in respiratory redox signalling Gunilla H~kansson*, John F Abstract A 37 kDa protein in pea mitochondria was found to contain phosphorylated residues. Phosphorylation in plant mitochondria. We also describe the first example of tyrosine phosphorylation in plant organelles

Allen, John F.

389

Heat Transfer  

NSDL National Science Digital Library

Students explore heat transfer and energy efficiency using the context of energy efficient houses. They gain a solid understanding of the three types of heat transfer: radiation, convection and conduction, which are explained in detail and related to the real world. They learn about the many ways solar energy is used as a renewable energy source to reduce the emission of greenhouse gasses and operating costs. Students also explore ways in which a device can capitalize on the methods of heat transfer to produce a beneficial result. They are given the tools to calculate the heat transferred between a system and its surroundings.

2014-09-18

390

Tyrosines 1021 and 1009 are phosphorylation sites in the carboxy terminus of the platelet-derived growth factor receptor beta subunit and are required for binding of phospholipase C gamma and a 64-kilodalton protein, respectively.  

PubMed

Binding of platelet-derived growth factor (PDGF) to the PDGF receptor (PDGFR) beta subunit triggers receptor tyrosine phosphorylation and the stable association of a number of signal transduction molecules, including phospholipase C gamma (PLC gamma), the GTPase activating protein of ras (GAP), and phosphatidylinositol-3 kinase (PI3K). Previous reports have identified three PDGFR tyrosine phosphorylation sites in the kinase insert domain that are important for stable association of GAP and PI3K. Two of them, tyrosine (Y) 740, and Y-751 are required for the stable association of PI3K, while Y-771 is required for binding of GAP. Here we present data for two additional tyrosine phosphorylation sites, Y-1009 and Y-1021, that are both in the carboxy-terminal region of the PDGFR. Characterization of PDGFR mutants in which these phosphorylation sites are substituted with phenylalanine (F) indicated that Y-1021 and Y-1009 were required for the stable association of PLC gamma and a 64-kDa protein, respectively. An F-1009/F-1021 double mutant selectively failed to bind both PLC gamma and the 64-kDa protein, whereas all of the carboxy-terminal mutants bound wild-type levels of GAP and PI3K. The carboxy terminus encodes the complete binding site for PLC gamma, since a phosphorylated carboxy-terminal fusion protein selectively bound PLC gamma. To determine the biological consequences of failure to associate with PLC gamma, we measured PDGF-dependent inositol phosphate production and initiation of DNA synthesis. The PDGFR mutants that failed to associate with PLC gamma were not able to mediate the PDGF-dependent production of inositol phosphates. Since tyrosine phosphorylation of PLC gamma enhances its enzymatic activity, we speculated that PDGFR mutants that failed to activate PLC gamma were unable to mediate its tyrosine phosphorylation. Surprisingly, the F-1021 receptor mediated readily detectable levels of PDGF-dependent PLC gamma tyrosine phosphorylation. Thus, the production of inositol phosphates requires not only PLC gamma tyrosine phosphorylation but also its association with the PDGFR. Comparison of the mutant PDGFRs' abilities to initiate PDGF-dependent DNA synthesis indicated that failure to associate with PLC gamma and produce inositol phosphates diminished the mitogenic response by 30%. In contrast, preventing the PDGFR from binding the 64-kDa protein did not compromise PDGF-triggered DNA synthesis at saturating concentrations of PDGF. Thus, it appears that phosphorylation of the PDGFR at Y-1021 is required for the stable association of PLC gamma to the receptor's carboxy terminus, the production of inositol phosphates, and initiation of the maximal mitogenic response. PMID:7678051

Valius, M; Bazenet, C; Kazlauskas, A

1993-01-01

391

Anaplastic lymphoma kinase protein expression, genetic abnormalities, and phosphorylation in soft tissue tumors: Phosphorylation is associated with recurrent metastasis.  

PubMed

Gene and protein abnormalities of anaplastic lymphoma kinase (ALK) play an important role in the pathogenesis of various cancers and serve as important therapeutic targets. We investigated ALK protein expression, phosphorylation, and genetic aberrations using fluorescence in situ hybridization (FISH) in 81 soft tissue tumor samples: inflammatory myofibroblastic tumor, n=1; alveolar soft part sarcoma, n=2; leiomyosarcoma, n=10; well-differentiated liposarcoma, n=7; pleomorphic liposarcoma, n=2; extraskeletal osteosarcoma, n=1; epithelioid sarcoma, n=1; synovial sarcoma, n=4; malignant peripheral nerve sheath tumor, n=4; undifferentiated pleomorphic sarcoma, n=19; rhabdomyosarcoma, n=6; myxofibrosarcoma, n=8; myxoid liposarcoma, n=11; fibrosarcoma, n=4; and desmoid-type fibromatosis, n=1. ALK protein expression, gene signal gain (without translocation), and phosphorylation were observed in 33/81 (40.7%), 55/81 (67.9%), and 30/81 (37.0%) tumor samples, respectively. ALK protein expression was statistically associated with phosphorylation, but not with gene signal gain. ALK phosphorylation-positive cases showed a statistically worse metastasis-free survival compared with phosphorylation-negative cases (P=0.0215). Particularly, metastasis of myxoid liposarcoma was associated with ALK phosphorylation (P=0.0019), but not with ALK protein expression or gene signal gain. However, the prognosis had no association with ALK protein expression, gene signal gain, or phosphorylation. ALK protein expression and phosphorylation play an important role in tumor biology and provide potential therapeutic targets for soft tissue tumors. Future research should focus on the oncogenic role and the efficacy of potential inhibitors of ALK. PMID:25683346

Ishibashi, Yukinao; Miyoshi, Hiroaki; Hiraoka, Koji; Arakawa, Fumiko; Haraguchi, Toshiaki; Nakashima, Shinji; Hashiguchi, Toshihiro; Shoda, Takanori; Hamada, Tetsuya; Okawa, Takahiro; Higuchi, Fujio; Shiba, Naoto; Nagata, Kensei; Ohshima, Koichi

2015-04-01

392

Thr(175)-phosphorylated tau induces pathologic fibril formation via GSK3?-mediated phosphorylation of Thr(231) in vitro.  

PubMed

We have previously shown that amyotrophic lateral sclerosis with cognitive impairment can be characterized by pathologic inclusions of microtubule-associated protein tau (tau) phosphorylated at Thr(175) (pThr(175)) in association with GSK3? activation. We have now examined whether pThr(175) induces GSK3? activation and whether this leads to pathologic fibril formation through Thr(231) phosphorylation. Seventy-two hours after transfection of Neuro2A cells with pseudophosphorylated green fluorescent protein-tagged 2N4R tau (Thr(175)Asp), phosphorylated kinase glycogen synthase kinase 3 beta (active GSK3?) levels were significantly increased as was pathologic fibril formation and cell death. Treatment with each of 4 GSK3? inhibitors or small hairpin RNA knockdown of GSK3? abolished fibril formation and prevented cell death. Inhibition of Thr(231) phosphorylation (Thr(231)Ala) prevented pathologic tau fibril formation, regardless of Thr(175) state, whereas Thr(231)Asp (pseudophosphorylated at Thr(231)) developed pathologic tau fibrils. Ser(235) mutations did not affect fibril formation, indicating an unprimed mechanism of Thr(231) phosphorylation. These findings suggest a mechanism of tau pathology by which pThr(175) induces GSK3? phosphorylation of Thr(231) leading to fibril formation, indicating a potential therapeutic avenue for amyotrophic lateral sclerosis with cognitive impairment. PMID:25573097

Moszczynski, Alexander J; Gohar, May; Volkening, Kathryn; Leystra-Lantz, Cheryl; Strong, Wendy; Strong, Michael J

2015-03-01

393

Structural Basis for Inactivation of the Human Pyruvate Dehydrogenase Complex by Phosphorylation: Role of Disordered Phosphorylation Loops  

SciTech Connect

We report the crystal structures of the phosporylated pyruvate dehydrogenase (E1p) component of the human pyruvate dehydrogenase complex (PDC). The complete phosphorylation at Ser264-{alpha} (site 1) of a variant E1p protein was achieved using robust pyruvate dehydrogenase kinase 4 free of the PDC core. We show that unlike its unmodified counterpart, the presence of a phosphoryl group at Ser264-{alpha} prevents the cofactor thiamine diphosphate-induced ordering of the two loops carrying the three phosphorylation sites. The disordering of these phosphorylation loops is caused by a previously unrecognized steric clash between the phosphoryl group at site 1 and a nearby Ser266-{alpha}, which nullifies a hydrogen-bonding network essential for maintaining the loop conformations. The disordered phosphorylation loops impede the binding of lipoyl domains of the PDC core to E1p, negating the reductive acetylation step. This results in the disruption of the substrate channeling in the PDC, leading to the inactivation of this catalytic machine.

Kato, Masato; Wynn, R. Max; Chuang, Jacinta L.; Tso, Shih-Chia; Machius, Mischa; Li, Jun; Chuang, David T. (UTSMC)

2009-09-11

394

Oxidative enzymatic response of white-rot fungi to single-walled carbon nanotubes  

E-print Network

: Saprotrophic fungi Enzymatics Carbon nanomaterials a b s t r a c t Although carbon nanomaterials such as single. This study investigates the peroxidase and laccase enzymatic response of the saprotrophic white-rot fungi

Blanchette, Robert A.

395

Monitoring the kinetics and thermodynamics of interfacial enzymatic catalysis by differential scanning calorimetryq  

E-print Network

Monitoring the kinetics and thermodynamics of interfacial enzymatic catalysis by differential calorimetry; Enzyme; Phospholipase A2; Interfacial enzymatic catalysis; DPPC; Lateral phase separation Phospholipase A2 (PLA2) catalyzed phosphatidylch- oline hydrolysis, a model system to study interfacial

Luhua, Lai

396

Linkage disequilibrium between enzymatic loci in natural populations of Drosophila simulans  

E-print Network

Linkage disequilibrium between enzymatic loci in natural populations of Drosophila simulans measured in three Mediterranean populations of Drosophila simulans. Gametic frequencies were estimated are not repeatable from sample to sample. Key words :Drosophila simulans, enzymatic polymorphism, linkage

Boyer, Edmond

397

Threonine 149 Phosphorylation Enhances ?FosB Transcriptional Activity to Control Psychomotor Responses to Cocaine  

PubMed Central

Stable changes in neuronal gene expression have been studied as mediators of addicted states. Of particular interest is the transcription factor ?FosB, a truncated and stable FosB gene product whose expression in nucleus accumbens (NAc), a key reward region, is induced by chronic exposure to virtually all drugs of abuse and regulates their psychomotor and rewarding effects. Phosphorylation at Ser27 contributes to ?FosB's stability and accumulation following repeated exposure to drugs, and our recent work demonstrates that the protein kinase CaMKII? phosphorylates ?FosB at Ser27 and regulates its stability in vivo. Here, we identify two additional sites on ?FosB that are phosphorylated in vitro by CaMKII?, Thr149 and Thr180, and demonstrate their regulation in vivo by chronic cocaine. We show that phosphomimetic mutation of Thr149 (T149D) dramatically increases AP-1 transcriptional activity while alanine mutation does not affect transcriptional activity when compared with wild-type (WT) ?FosB. Using in vivo viral-mediated gene transfer of ?FosB-T149D or ?FosB-T149A in mouse NAc, we determined that overexpression of ?FosB-T149D in NAc leads to greater locomotor activity in response to an initial low dose of cocaine than does WT ?FosB, while overexpression of ?FosB-T149A does not produce the psychomotor sensitization to chronic low-dose cocaine seen after overexpression of WT ?FosB and abrogates the sensitization seen in control animals at higher cocaine doses. We further demonstrate that mutation of Thr149 does not affect the stability of ?FosB overexpressed in mouse NAc, suggesting that the behavioral effects of these mutations are driven by their altered transcriptional properties. PMID:25143625

Cates, Hannah M.; Thibault, Mackenzie; Pfau, Madeline; Heller, Elizabeth; Eagle, Andrew; Gajewski, Paula; Bagot, Rosemary; Colangelo, Christopher; Abbott, Thomas; Rudenko, Gabby; Neve, Rachael; Nestler, Eric J.

2014-01-01

398

Squid neurofilaments. Phosphorylation and Ca2+-dependent proteolysis in situ.  

PubMed Central

Three major polypeptides co-purify with neurofilaments from squid (Loligo forbesi) axoplasm: P60 (apparent Mr 60,000), P200 (apparent Mr 200,000) and Band 1 (apparent Mr 400,000). Anti-IFA, a monoclonal antibody that recognizes an epitope common to all classes of intermediate filaments, binds to P200 and P60. When axoplasm is incubated with [32P]Pi, the major phosphorylated polypeptides are P200 and Band 1. We have investigated Ca2+-dependent proteolysis of [32P]phosphorylated axoplasm in order to localize the major sites of phosphorylation and to probe the arrangement of the polypeptides in the filament. The proteinase preferentially cleaves P200 and Band 1, liberating the phosphorylated domains. Analysis of proteolysed filaments by electron microscopy and gel electrophoresis shows that most of P200 and Band 1 can be cleaved while still maintaining intact filaments. We suggest that P200 is initially cleaved within a single highly sensitive region, generating two major fragments called P100p (apparent Mr 100,000) and P110s (apparent Mr 110,000). P100p contains the Anti-IFA epitope and co-sediments with filaments, whereas P110s is highly phosphorylated and does not sediment with filaments. Band 1 is cleaved to produce a soluble high-Mr fragment that is phosphorylated and that represents a major portion of the undigested component, whereas P60 is relatively resistant to limited proteolysis. Thus proteolysis appears to define two major filament domains: a conserved core that forms the backbone of the filament, and a highly phosphorylated peripheral region that is not essential for filament integrity. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. PMID:3800978

Brown, A; Eagles, P A

1986-01-01

399

Cytokines Alter Glucocorticoid Receptor Phosphorylation in Airway Cells  

PubMed Central

Corticosteroid insensitivity (CSI) represents a profound challenge in managing patients with asthma. We recently demonstrated that short exposure of airway smooth muscle cells (ASMCs) to proasthmatic cytokines drastically reduced their responsiveness to glucocorticoids (GCs), an effect that was partially mediated via interferon regulatory factor-1, suggesting the involvement of additional mechanisms (Am J Respir Cell Mol Biol 2008;38:463–472). Although GC receptor (GR) can be phosphorylated at multiple serines in the N-terminal region, the major phosphorylation sites critical for GR transcriptional activity are serines 211 (Ser211) and 226 (Ser226). We tested the novel hypothesis that cytokine-induced CSI in ASMCs is due to an impaired GR phosphorylation. Cells were treated with TNF-? (10 ng/ml) and IFN-? (500 UI/ml) for 6 hours and/or fluticasone (100 nm) added 2 hours before. GR was constitutively phosphorylated at Ser226 but not at Ser211 residues. Cytokines dramatically suppressed fluticasone-induced phosphorylation of GR on Ser211 but not on Ser226 residues while increasing the expression of Ser/Thr protein phosphatase (PP)5 but not that of PP1 or PP2A. Transfection studies using a reporter construct containing GC responsive elements showed that the specific small interfering RNA–induced mRNA knockdown of PP5, but not that of PP1 or PP2A, partially prevented the cytokine suppressive effects on GR-meditated transactivation activity. Similarly, cytokines failed to inhibit GC-induced GR-Ser211 phosphorylation when expression of PP5 was suppressed. We propose that the novel mechanism that proasthmatic cytokine-induced CSI in ASMCs is due, in part, to PP5-mediated impairment of GR-Ser211 phosphorylation. PMID:22592921

Bouazza, Belaid; Krytska, Kateryna; Debba-Pavard, Manel; Amrani, Yassine; Honkanen, Richard E.; Tran, Jennifer

2012-01-01

400

ETHANOL PRODUCTION FROM ALKALINE PEROXIDE PRETREATED ENZYMATICALLY SACCHARIFIED WHEAT STRAW  

Technology Transfer Automated Retrieval System (TEKTRAN)

Wheat straw used in this study contained 44.24 ± 0.28% cellulose and 25.23 ± 0.11% hemicellulose. Alkaline H2O2 pretreatment and enzymatic saccharification were evaluated for conversion of wheat straw cellulose and hemicellulose to fermentable sugars. The maximum yield of monomeric sugars from whe...

401

Structural modifications of lignocellulosics by pretreatments to enhance enzymatic hydrolysis  

Microsoft Academic Search

In this work an evaluation was made of a wide variety of single and multiple pretreatment methods for enhancing the rate of enzymatic hydrolysis of wheat straw. A multiple pretreatment consisted of a physical pretreatment followed by a chemical pretreatment. The structural features of wheat straw, including the specific surface area, crystallinity index, and lignin content, were measured to understand

M. M. Gharpuray; Yong-Hyun Lee; L. T. Fan

1983-01-01

402

Acid-Induced Gelation of Enzymatically Modified, Preheated Whey Proteins  

E-print Network

Acid-Induced Gelation of Enzymatically Modified, Preheated Whey Proteins AHMED S. EISSA AND SAAD A, North Carolina 27695-7905 Low-pH whey protein gels are formulated using a sequential protocol of heat in the gel microstructure and linear viscoelastic properties. INTRODUCTION Whey proteins have become

Khan, Saad A.

403

Antagonists' impact on enzymatic response in wilt infected cotton plants  

Technology Transfer Automated Retrieval System (TEKTRAN)

A number of PR-proteins possess enzymatic activity. As such, these proteins maybe indicators of defensive response of plants. Thus, we have conducted a comparative analysis of beta-1,3-glucanase, peroxidase and xylanase activity in cotton plants to determine how these enzymes are affected by the pat...

404

Enzymatic microreactors in chemical analysis and kinetic studies  

Microsoft Academic Search

The fields of application of microreactors are becoming wider every year. A considerable number of papers have been published recently reporting successful application of enzymatic microreactors in chemistry and biochemistry. Most are devices with enzymes immobilized on beads or walls of microfluidic channels, whilst some use dissolved enzymes to run a reaction in the microfluidic system. Apart from model systems,

Pawel L. Urban; David M. Goodall; Neil C. Bruce

2006-01-01

405

Enzymatic aminoacylation of tRNA with unnatural amino acids  

E-print Network

Enzymatic aminoacylation of tRNA with unnatural amino acids Matthew C. T. Hartman, KristopherRNAs with amino acids. We have developed an AARS assay based on mass spectrometry that can be used to rapidly functional properties. Remarkably, many -amino acids, N-methyl amino acids, and , -disubstituted amino acids

Heller, Eric

406

Enzymatic properties and cholesterol content of mitochondrial outer mem-  

E-print Network

Enzymatic properties and cholesterol content of mitochondrial outer mem- branes in liver of obese and microsomes. Simultaneously microsomes were shown to be richer in cholesterol than mitochondrial outer, it was determined that outer membranes are extremely poor in cholesterol, far richer in to- tal fatty acids than

Boyer, Edmond

407

Hot biological catalysis: isothermal titration calorimetry to characterize enzymatic reactions.  

PubMed

Isothermal titration calorimetry (ITC) is a well-described technique that measures the heat released or absorbed during a chemical reaction, using it as an intrinsic probe to characterize virtually every chemical process. Nowadays, this technique is extensively applied to determine thermodynamic parameters of biomolecular binding equilibria. In addition, ITC has been demonstrated to be able of directly measuring kinetics and thermodynamic parameters (kcat, KM, ?H) of enzymatic reactions, even though this application is still underexploited. As heat changes spontaneously occur during enzymatic catalysis, ITC does not require any modification or labeling of the system under analysis and can be performed in solution. Moreover, the method needs little amount of material. These properties make ITC an invaluable, powerful and unique tool to study enzyme kinetics in several applications, such as, for example, drug discovery. In this work an experimental ITC-based method to quantify kinetics and thermodynamics of enzymatic reactions is thoroughly described. This method is applied to determine kcat and KM of the enzymatic hydrolysis of urea by Canavalia ensiformis (jack bean) urease. Calculation of intrinsic molar enthalpy (?Hint) of the reaction is performed. The values thus obtained are consistent with previous data reported in literature, demonstrating the reliability of the methodology. PMID:24747990

Mazzei, Luca; Ciurli, Stefano; Zambelli, Barbara

2014-01-01

408

Effect of Pretreatment of Poplar Wood Upon Enzymatic Saccharification  

Microsoft Academic Search

The wood of young poplar grown in short rotation coppices was used as a substrate for enzymatic saccharification. Several pretreatments of the wood, both physical and chemical, including delignification were applied to enhance the polysaccharide conversion into fermentable sugars. Comparing the yields obtained on a delignified material and on alkali treated material pointed out that lignin is not the major

F. Al Katrib; G. Chambat; J. P. Joseleau

1992-01-01

409

Enzymatic Reactions in Microfluidic Devices: Michaelis-Menten Kinetics  

E-print Network

in biochemistry, medicine, food science, and biochemical engineering. Many enzymatic reactions are characterized with a series of experiments at different sub- strate concentrations in a well-mixed container. Here we, and product. In a well-mixed system, the initial rate of product formation (i.e., the reaction "velocity

Bou-Zeid, Elie

410

Enzymatic corn wet milling: engineering process and cost model  

Microsoft Academic Search

BACKGROUND: Enzymatic corn wet milling (E-milling) is a process derived from conventional wet milling for the recovery and purification of starch and co-products using proteases to eliminate the need for sulfites and decrease the steeping time. In 2006, the total starch production in USA by conventional wet milling equaled 23 billion kilograms, including modified starches and starches used for sweeteners

Edna C Ramírez; David B Johnston; Andrew J McAloon; Vijay Singh

2009-01-01

411

Enzymatic treatment of sunflower kernels before oil extraction  

Microsoft Academic Search

Sunflower kernels were enzymatically treated before pressing, with the aim of enhancing oil extractability. Following the response surface methodology, the combined effects of moisture, enzyme\\/kernel ratio and treatment time were examined. The effect of these variables on the pressing efficiency, the protein digestibility, the fiber content and the meal color was assessed. In a wide range of conditions, it was

H. Domínguez; J. Sineiro; M. J. Núńez; J. M. Lema

1995-01-01

412

Coupled chemo(enzymatic) reactions in continuous flow  

PubMed Central

Summary This review highlights the state of the art in the field of coupled chemo(enzymatic) reactions in continuous flow. Three different approaches to such reaction systems are presented herein and discussed in view of their advantages and disadvantages as well as trends for their future development. PMID:22238518

Yuryev, Ruslan; Strompen, Simon

2011-01-01

413

Electrochemical transistors with ionic liquids for enzymatic sensing  

E-print Network

Electrochemical transistors with ionic liquids for enzymatic sensing Kevin J. Frasera , Sang Yoon and lactate. Room temperature ionic liquids (RTILs) are organic salts, which are liquid at ambient temperature to ionic liquids (ILs), IL ­ enzyme mixtures and a combination of these novel materials being used on OECTs

Lee, Hyowon

414

The Preparation and Enzymatic Hydrolysis of a Library of Esters  

ERIC Educational Resources Information Center

An investigative case study involving the preparation of a library of esters using Fischer esterification and alcoholysis of acid chlorides and their subsequent enzymatic hydrolysis by pig liver esterase and orange peel esterase is described. Students work collaboratively to prepare and characterize the library of esters and complete and evaluate…

Sanford, Elizabeth M.; Smith, Traci L.

2008-01-01

415