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1

Soraphen A, an inhibitor of acetyl CoA carboxylase activity, interferes with fatty acid elongation  

PubMed Central

Acetyl CoA carboxylase (ACC1 & ACC2) generates malonyl CoA, a substrate for de novo lipogenesis (DNL) and an inhibitor of mitochondrial fatty acid ?-oxidation (FAO). Malonyl CoA is also a substrate for microsomal fatty acid elongation, an important pathway for saturated (SFA), mono- (MUFA) and polyunsaturated fatty acid (PUFA) synthesis. Despite the interest in ACC as a target for obesity and cancer therapy, little attention has been given to the role ACC plays in long chain fatty acid synthesis. This report examines the effect of pharmacological inhibition of ACC on DNL & palmitate (16:0) and linoleate (18:2,n-6) metabolism in HepG2 and LnCap cells. The ACC inhibitor, soraphen A, lowers cellular malonyl CoA, attenuates DNL and the formation of fatty acid elongation products derived from exogenous fatty acids, i.e., 16:0 & 18:2,n-6; IC50 ~ 5 nM. Elevated expression of fatty acid elongases (Elovl5, Elovl6) or desaturases (FADS1, FADS2) failed to override the soraphen A effect on SFA, MUFA or PUFA synthesis. Inhibition of fatty acid elongation leads to the accumulation of 16- and 18-carbon unsaturated fatty acids derived from 16:0 and 18:2,n-6, respectively. Pharmacological inhibition of ACC activity will not only attenuate DNL and induce FAO, but will also attenuate the synthesis of very long chain saturated, mono- and polyunsaturated fatty acids. PMID:21184748

Jump, Donald B.; Torres-Gonzalez, Moises; Olson, L. Karl

2010-01-01

2

Materials and methods for the alteration of enzyme and acetyl CoA levels in plants  

DOEpatents

The present invention provides nucleic acid and amino acid sequences of acetyl CoA synthetase (ACS), plastidic pyruvate dehydrogenase (pPDH), ATP citrate lyase (ACL), Arabidopsis pyruvate decarboxylase (PDC), and Arabidopsis aldehyde dehydrogenase (ALDH), specifically ALDH-2 and ALDH-4. The present invention also provides a recombinant vector comprising a nucleic acid sequence encoding one of the aforementioned enzymes, an antisense sequence thereto or a ribozyme therefor, a cell transformed with such a vector, antibodies to the enzymes, a plant cell, a plant tissue, a plant organ or a plant in which the level of an enzyme has been altered, and a method of producing such a plant cell, plant tissue, plant organ or plant. Desirably, alteration of the level of enzyme results in an alteration of the level of acetyl CoA in the plant cell, plant tissue, plant organ or plant. In addition, the present invention provides a recombinant vector comprising an antisense sequence of a nucleic acid sequence encoding pyruvate decarboxylase (PDC), the E1.alpha. subunit of pPDH, the E1.beta. subunit of pPDH, the E2 subunit of pPDH, mitochondrial pyruvate dehydrogenase (mtPDH) or aldehyde dehydrogenase (ALDH) or a ribozyme that can cleave an RNA molecule encoding PDC, E1.alpha. pPDH, E1.beta. pPDH, E2 pPDH, mtPDH or ALDH.

Nikolau, Basil J. (Ames, IA); Wurtele, Eve S. (Ames, IA); Oliver, David J. (Ames, IA); Schnable, Patrick S. (Ames, IA); Wen, Tsui-Jung (Ames, IA)

2009-04-28

3

Enhanced Activity of Acetyl CoA Synthetase Adsorbed on Smart Microgel: an Implication for Precursor Biosynthesis.  

PubMed

Acetyl coenzyme A (acetyl CoA) is an essential precursor molecule for synthesis of metabolites such as the polyketide-based drugs (tetracycline, mitharamycin, Zocor, etc.) fats, lipids, and cholesterol. Acetyl CoA synthetase (Acs) is one of the enzymes that catalyzes acetyl CoA synthesis, and this enzyme is essentially employed for continuous supply of the acetyl CoA for the production of these metabolites. To achieve reusable and a more robust entity of the enzyme, we carried out the immobilization of Acs on poly(N-isopropylacrylamide)-poly(ethylenimine) (PNIPAm-PEI) microgels via adsorption. Cationic PNIPAm-PEI microgel was synthesized by one-step graft copolymerization of NIPAm and N,N-methylene bis-acrylamide (MBA) from PEI. Adsorption studies of Acs on microgel indicated high binding of enzymes, with a maximum binding capacity of 286 ?g/mg of microgel for Acs was achieved. The immobilized enzymes showed improved biocatalytic efficiency over free enzymes, beside this, the reaction parameters and circular dichroism (CD) spectroscopy studies indicated no significant changes in the enzyme structure after immobilization. This thoroughly characterized enzyme bioconjugate was further immobilized on an ultrathin membrane to assess the same reaction in flow through condition. Bioconjugate was covalently immobilized on a thin layer of preformed microgel support upon polyethylene terephthalate (PET) track etched membrane. The prepared membrane was used in a dead end filtration device to monitor the bioconversion efficiency and operational stability of cross-linked bioconjugate. The membrane reactor showed consistent operational stability and maintained >70% of initial activity after 7 consecutive operation cycles. PMID:25561344

Dubey, Nidhi Chandrama; Tripathi, Bijay Prakash; Müller, Martin; Stamm, Manfred; Ionov, Leonid

2015-01-28

4

Dilute acid hydrolysis of paper birch: kinetics studies of xylan and acetyl-group hydrolysis.  

PubMed

Batch hydrolysis kinetics of paper birch (Betula papyrifera) xylan and its associated acetyl groups in dilute sulfuric acid have been measured for acid concentrations of between 0.04 and 0.18M and temperatures of between 100 and 170 degrees C. Only 5% of the cellulose was hydrolyzed for up to 85% xylan removal. Rate data were correlated well by a parallel reaction model based on the existence of reactive and resistant xylan portions. The resulting rate equation predicts the experimental xylan concentrations in the residue to within 10%. Hydrolysis of xylan-associated acetyl groups was found to occur at the same rate as that of xylan, except at 100 degrees C, where acetyl is released preferentially. No effect of acid concentration on the rate of acetyl removal relative to that of xylan was evident. PMID:18553680

Maloney, M T; Chapman, T W; Baker, A J

1985-03-01

5

Correlation of ATP Citrate Lyase and Acetyl CoA Levels with Trichothecene Production in Fusarium graminearum  

PubMed Central

Thecorrelation of ATP citrate lyase (ACL) and acetyl CoA levels with trichothecene production in Fusarium graminearum was investigated using an inhibitor (precocene II) and an enhancer (cobalt chloride) of trichothecene production by changing carbon sources in liquid medium. When precocene II (30 µM) was added to inhibit trichothecene production in a trichothecene high-production medium containing sucrose, ACL expression was reduced and ACL mRNA level as well as acetyl CoA amount in the fungal cells were reduced to the levels observed in a trichothecene trace-production medium containing glucose or fructose. The ACL mRNA level was greatly increased by addition of cobalt chloride in the trichothecene high-production medium, but not in the trichothecene trace-production medium. Levels were reduced to those level in the trichothecene trace-production medium by addition of precocene II (300 µM) together with cobalt chloride. These results suggest that ACL expression is activated in the presence of sucrose and that acetyl CoA produced by the increased ALC level may be used for trichothecene production in the fungus. These findings also suggest that sucrose is important for the action of cobalt chloride in activating trichothecene production and that precocene II may affect a step down-stream of the target of cobalt chloride. PMID:24284828

Sakamoto, Naoko; Tsuyuki, Rie; Yoshinari, Tomoya; Usuma, Jermnak; Furukawa, Tomohiro; Nagasawa, Hiromichi; Sakuda, Shohei

2013-01-01

6

Stevioside Counteracts Beta-Cell Lipotoxicity without Affecting Acetyl CoA Carboxylase  

PubMed Central

Chronic exposure to high levels of free fatty acids impairs beta-cell function (lipotoxicity). Then basal insulin secretion (BIS) is increased and glucose-stimulated insulin secretion (GSIS) is inhibited. Acetyl CoA carboxylase (ACC) acts as the sensor for insulin secretion in pancreatic beta-cells in response to glucose and other nutrients. Stevioside (SVS), a diterpene glycoside, has recently been shown to prevent glucotoxic effect by regulating ACC activity. The aim of this study was to investigate whether SVS can alleviate impaired beta-cell function by regulating ACC activity. We exposed isolated rat islets and the clonal beta-cell line, INS-1E, to palmitate concentrations of 1.0 or 0.6 mM, respectively, for a period of 24 h to 120 h. The results showed that lipotoxicity occurred in rat islets after 72 h exposure to 1.0 mM palmitate. The lipotoxicity was counteracted by 10-6 M SVS (n = 8, p < 0.001). Similar results were obtained in INS-1E cells. Neither SVS nor palmitate had any effect on the gene expression of ACC, insulin 2, and glucose transporter 2 in INS-1E cells. In contrast, palmitate significantly increased the gene expression of carnitine palmitoyl transporter 1 (n = 6, p = 0.003). However, the addition of SVS to palmitate did not counteract this effect (n = 6, p = 1.0). During lipotoxicity, SVS did not alter levels of ACC protein, phosphorylated-ACC, ACC activity or glucose uptake. Our results showed that SVS counteracts the impaired insulin secretion during lipotoxicity in rat islets as well as in INS-1E cells without affecting ACC activity. PMID:17487342

Chen, Jianguo; Jeppesen, Per Bendix; Nordentoft, Iver; Hermansen, Kjeld

2006-01-01

7

Stevioside Counteracts Beta-Cell Lipotoxicity without Affecting Acetyl CoA Carboxylase.  

PubMed

Chronic exposure to high levels of free fatty acids impairs beta-cell function (lipotoxicity). Then basal insulin secretion (BIS) is increased and glucose-stimulated insulin secretion (GSIS) is inhibited. Acetyl CoA carboxylase (ACC) acts as the sensor for insulin secretion in pancreatic beta-cells in response to glucose and other nutrients. Stevioside (SVS), a diterpene glycoside, has recently been shown to prevent glucotoxic effect by regulating ACC activity. The aim of this study was to investigate whether SVS can alleviate impaired beta-cell function by regulating ACC activity. We exposed isolated rat islets and the clonal beta-cell line, INS-1E, to palmitate concentrations of 1.0 or 0.6 mM, respectively, for a period of 24 h to 120 h. The results showed that lipotoxicity occurred in rat islets after 72 h exposure to 1.0 mM palmitate. The lipotoxicity was counteracted by 10(-6) M SVS (n = 8, p < 0.001). Similar results were obtained in INS-1E cells. Neither SVS nor palmitate had any effect on the gene expression of ACC, insulin 2, and glucose transporter 2 in INS-1E cells. In contrast, palmitate significantly increased the gene expression of carnitine palmitoyl transporter 1 (n = 6, p = 0.003). However, the addition of SVS to palmitate did not counteract this effect (n = 6, p = 1.0). During lipotoxicity, SVS did not alter levels of ACC protein, phosphorylated-ACC, ACC activity or glucose uptake. Our results showed that SVS counteracts the impaired insulin secretion during lipotoxicity in rat islets as well as in INS-1E cells without affecting ACC activity. PMID:17487342

Chen, Jianguo; Jeppesen, Per Bendix; Nordentoft, Iver; Hermansen, Kjeld

2006-01-01

8

Effect of acetyl groups on enzymatic hydrolysis of cellulosic substrates  

Microsoft Academic Search

Evidence showed that acetyl groups introduced during acetic acid delignification was a primary cause of the poor enzymatic digestibility of acetic acid pulp. The inhi- bition by acetyl groups could be removed by saponifi- cation. Acetyl groups might inhibit the enzymes by interfering with the productive binding (hydrogen bonds) between cellulose and the catalytic domain of cellulases, by affecting the

Xuejun Pan; Neil Gilkes; Jack N. Saddler

2006-01-01

9

Impact of Cell Wall Acetylation on Corn Stover Hydrolysis by Cellulolytic and Xylanolytic Enzymes  

SciTech Connect

Analysis of variously pretreated corn stover samples showed neutral to mildly acidic pretreatments were more effective at removing xylan from corn stover and more likely to maintain the acetyl to xylopyranosyl ratios present in untreated material than were alkaline treatments. Retention of acetyl groups in the residual solids resulted in greater resistance to hydrolysis by endoxylanase alone, although the synergistic combination of endoxylanase and acetyl xylan esterase enzymes permitted higher xylan conversions to be observed. Acetyl xylan esterase alone did little to improve hydrolysis by cellulolytic enzymes, although a direct relationship was observed between the enzymatic removal of acetyl groups and improvements in the enzymatic conversion of xylan present in substrates. In all cases, effective xylan conversions were found to significantly improve glucan conversions achievable by cellulolytic enzymes. Additionally, acetyl and xylan removal not only enhanced the respective initial rates of xylan and glucan conversion, but also the overall extents of conversion. This work emphasizes the necessity for xylanolytic enzymes during saccharification processes and specifically for the optimization of acetyl esterase and xylanase synergies when biomass processes include milder pretreatments, such as hot water or sulfite steam explosion.

Selig, M. J.; Adney, W. S.; Himmel, M. E.; Decker, S. R.

2009-01-01

10

Effect of food deprivation and hormones of glucose homeostasis on the acetyl CoA carboxylase activity in mouse brain: a potential role of acc in the regulation of energy balance  

Microsoft Academic Search

We studied the regulation of brain acetyl CoA carboxylase (ACC) activity during food deprivation and under the influence of hormones of glucose homeostasis: glucagon and insulin. Mice were deprived of food and water for time periods of 1, 3, 6, 9, 12 and 24 hours and were then allowed to re-feed for 5, 30 and 60 minutes. Mice that were

Kristophe J Karami; John Coppola; Karthik Krishnamurthy; Domingo J Llanos; Amrita Mukherjee; K V Venkatachalam

2006-01-01

11

Properties of retrograded and acetylated starch produced via starch extrusion or starch hydrolysis with pullulanase.  

PubMed

The aim of the present study was to determine the impact of serial modifications of starch, including firstly starch extrusion or hydrolysis with pullulanase, followed by retrogradation (through freezing and defrosting of pastes) and acetylation (under industrial conditions), on its susceptibility to amylolysis. The method of production had a significant effect on properties of the resultant preparations, whilst the direction and extent of changes depended on the type of modification applied. In the produced starch esters, the degree of substitution, expressed by the per cent of acetylation, ranged from 3.1 to 4.4 g/100 g. The acetylation had a significant impact on contents of elements determined with the atomic emission spectrometry, as it contributed to an increased Na content and decreased contents of Ca and K. The DSC thermal characteristics enabled concluding that the modifications caused an increase in temperatures and a decrease in heat of transition (or its lack). The acetylation of retrograded starch preparations increased their solubility in water and water absorbability. The modifications were found to exert various effects on the rheological properties of pastes determined based on the Brabender's pasting characteristics and flow curves determined with the use of an oscillatory-rotating viscosimeter. All starch acetates produced were characterized by ca. 40% resistance to amylolysis. PMID:23911484

Kapelko, M; Zi?ba, T; Gryszkin, A; Styczy?ska, M; Wilczak, A

2013-09-12

12

The acid and enzymic hydrolysis of O-acetylated sialic acid residues from rabbit Tamm–Horsfall glycoprotein  

PubMed Central

Rabbit Tamm–Horsfall glycoprotein and bovine submaxillary glycoprotein were both found to contain sialic acid residues which are released at a slow rate by the standard conditions of acid hydrolysis. These residues are also resistant to neuraminidases from Vibrio cholerae and Clostridium perfringens. This behaviour was attributed to the presence of O-acetylated sialic acid, since the removal of O-acetyl groups by mild alkaline treatment normalized the subsequent release of sialic acid from rabbit Tamm–Horsfall glycoprotein by acid and by enzymic hydrolysis. Determination of the O-acetyl residues in rabbit Tamm–Horsfall glycoprotein indicated that on average two hydroxyl groups of sialic acid are O-acetylated, and these were located on the polyhydroxy side-chain of sialic acid or on C-4 and C-8. These findings confirm the assumption that certain O-acetylated forms of sialic acid are not substrates for bacterial neuraminidases. Several explanations have been suggested to explain the effect of O-acetylation of the side-chain on the rate of acidcatalysed hydrolysis of sialic acid residues. PMID:4349114

Neuberger, A.; Ratcliffe, Wendy A.

1972-01-01

13

Hydrolysis of Wheat Arabinoxylan by Two Acetyl Xylan Esterases from Chaetomium thermophilum.  

PubMed

The thermophilic filamentous ascomycete Chaetomium thermophilum produces functionally diverse hemicellulases when grown on hemicellulose as carbon source. Acetyl xylan esterase (EC 3.1.1.72) is an important accessory enzyme in hemicellulose biodegradation. Although the genome of C. thermophilum has been sequenced, its carbohydrate esterases are not annotated yet. We applied peptide pattern recognition (PPR) tool for sequence analysis of the C. thermophilum genome, and 11 carbohydrate esterase genes were discovered. Furthermore, we cloned and heterologously expressed two putative acetyl xylan esterase genes, CtAxeA and CtAxeB, in Pichia pastoris. The recombinant proteins, rCtAxeA and rCtAxeB, released acetic acids from p-nitrophenyl acetate and water-insoluble wheat arabinoxylan. These results indicate that CtAxeA and CtAxeB are true acetyl xylan esterases. For both recombinant esterases, over 93 % of the initial activity was retained after 24 h of incubation at temperatures up to 60 °C, and over 90 % of the initial activity was retained after 24 h of incubation in different buffers from pH 4.0 to 9.0 at 4 and 50 °C. The overall xylose yield from wheat arabinoxylan hydrolysis was 8 % with xylanase treatment and increased to 34 % when xylanase was combined with rCtAxeA and rCtAxeB. In sum, the present study first report the biochemical characterization of two acetyl xylan esterases from C. thermophilum, which are efficient in hydrolyzing hemicellulose with potential application in biomass bioconversion to high value chemicals or biofuels. PMID:25369895

Tong, Xiaoxue; Lange, Lene; Grell, Morten Nedergaard; Busk, Peter Kamp

2015-01-01

14

From Arylamine N-Acetyltransferase to Folate-Dependent Acetyl CoA Hydrolase: Impact of Folic Acid on the Activity of (HUMAN)NAT1 and Its Homologue (MOUSE)NAT2  

PubMed Central

Acetyl Coenzyme A-dependent N-, O- and N,O-acetylation of aromatic amines and hydrazines by arylamine N-acetyltransferases is well characterised. Here, we describe experiments demonstrating that human arylamine N-acetyltransferase Type 1 and its murine homologue (Type 2) can also catalyse the direct hydrolysis of acetyl Coenzyme A in the presence of folate. This folate-dependent activity is exclusive to these two isoforms; no acetyl Coenzyme A hydrolysis was found when murine arylamine N-acetyltransferase Type 1 or recombinant bacterial arylamine N-acetyltransferases were incubated with folate. Proton nuclear magnetic resonance spectroscopy allowed chemical modifications occurring during the catalytic reaction to be analysed in real time, revealing that the disappearance of acetyl CH3 from acetyl Coenzyme A occurred concomitantly with the appearance of a CH3 peak corresponding to that of free acetate and suggesting that folate is not acetylated during the reaction. We propose that folate is a cofactor for this reaction and suggest it as an endogenous function of this widespread enzyme. Furthermore, in silico docking of folate within the active site of human arylamine N-acetyltransferase Type 1 suggests that folate may bind at the enzyme’s active site, and facilitate acetyl Coenzyme A hydrolysis. The evidence presented in this paper adds to our growing understanding of the endogenous roles of human arylamine N-acetyltransferase Type 1 and its mouse homologue and expands the catalytic repertoire of these enzymes, demonstrating that they are by no means just xenobiotic metabolising enzymes but probably also play an important role in cellular metabolism. These data, together with the characterisation of a naphthoquinone inhibitor of folate-dependent acetyl Coenzyme A hydrolysis by human arylamine N-acetyltransferase Type 1/murine arylamine N-acetyltransferase Type 2, open up a range of future avenues of exploration, both for elucidating the developmental role of these enzymes and for improving chemotherapeutic approaches to pathological conditions including estrogen receptor-positive breast cancer. PMID:24823794

Laurieri, Nicola; Dairou, Julien; Egleton, James E.; Stanley, Lesley A.; Russell, Angela J.; Dupret, Jean-Marie; Sim, Edith; Rodrigues-Lima, Fernando

2014-01-01

15

From arylamine N-acetyltransferase to folate-dependent acetyl CoA hydrolase: impact of folic acid on the activity of (HUMAN)NAT1 and its homologue (MOUSE)NAT2.  

PubMed

Acetyl Coenzyme A-dependent N-, O- and N,O-acetylation of aromatic amines and hydrazines by arylamine N-acetyltransferases is well characterised. Here, we describe experiments demonstrating that human arylamine N-acetyltransferase Type 1 and its murine homologue (Type 2) can also catalyse the direct hydrolysis of acetyl Coenzyme A in the presence of folate. This folate-dependent activity is exclusive to these two isoforms; no acetyl Coenzyme A hydrolysis was found when murine arylamine N-acetyltransferase Type 1 or recombinant bacterial arylamine N-acetyltransferases were incubated with folate. Proton nuclear magnetic resonance spectroscopy allowed chemical modifications occurring during the catalytic reaction to be analysed in real time, revealing that the disappearance of acetyl CH3 from acetyl Coenzyme A occurred concomitantly with the appearance of a CH3 peak corresponding to that of free acetate and suggesting that folate is not acetylated during the reaction. We propose that folate is a cofactor for this reaction and suggest it as an endogenous function of this widespread enzyme. Furthermore, in silico docking of folate within the active site of human arylamine N-acetyltransferase Type 1 suggests that folate may bind at the enzyme's active site, and facilitate acetyl Coenzyme A hydrolysis. The evidence presented in this paper adds to our growing understanding of the endogenous roles of human arylamine N-acetyltransferase Type 1 and its mouse homologue and expands the catalytic repertoire of these enzymes, demonstrating that they are by no means just xenobiotic metabolising enzymes but probably also play an important role in cellular metabolism. These data, together with the characterisation of a naphthoquinone inhibitor of folate-dependent acetyl Coenzyme A hydrolysis by human arylamine N-acetyltransferase Type 1/murine arylamine N-acetyltransferase Type 2, open up a range of future avenues of exploration, both for elucidating the developmental role of these enzymes and for improving chemotherapeutic approaches to pathological conditions including estrogen receptor-positive breast cancer. PMID:24823794

Laurieri, Nicola; Dairou, Julien; Egleton, James E; Stanley, Lesley A; Russell, Angela J; Dupret, Jean-Marie; Sim, Edith; Rodrigues-Lima, Fernando

2014-01-01

16

Simvastatin Induced Neurite Outgrowth Unveils Role of Cell Surface Cholesterol and Acetyl CoA Carboxylase in SH-SY5Y Cells  

PubMed Central

Statins are known to modulate cell surface cholesterol (CSC) and AMP-activated protein kinase (AMPK) in non-neural cells; however no study demonstrates whether CSC and AMPK may regulate simvastatin induced neuritogenesis (SIN). We found that simvastatin (SIM) maintains CSC as shown by Fillipin III staining, Flotillin-2 protein expression / localization and phosphorylation of various receptor tyrosine kinases (RTKs) in the plasma membrane. Modulation of CSC revealed that SIN is critically dependent on this CSC. Simultaneously, phospho array for mitogen activated protein kinases (MAPKs) revealed PI3K / Akt as intracellular pathway which modulates lipid pathway by inhibiting AMPK activation. Though, SIM led to a transient increase in AMPK phosphorylation followed by a sudden decline; the effect was independent of PI3K. Strikingly, AMPK phosphorylation was regulated by protein phosphatase 2A (PP2A) activity which was enhanced upon SIM treatment as evidenced by increase in threonine phosphorylation. Moreover, it was observed that addition of AMP analogue and PP2A inhibitor inhibited SIN. Bio-composition of neurites shows that lipids form a major part of neurites and AMPK is known to regulate lipid metabolism majorly through acetyl CoA carboxylase (ACC). AMPK activity is negative regulator of ACC activity and we found that phosphorylation of ACC started to decrease after 6 hrs which becomes more pronounced at 12 hrs. Addition of ACC inhibitor showed that SIN is dependent on ACC activity. Simultaneously, addition of Fatty acid synthase (FAS) inhibitor confirmed that endogenous lipid pathway is important for SIN. We further investigated SREBP-1 pathway activation which controls ACC and FAS at transcriptional level. However, SIM did not affect SREBP-1 processing and transcription of its target genes likes ACC1 and FAS. In conclusion, this study highlights a distinct role of CSC and ACC in SIN which might have implication in process of neuronal differentiation induced by other agents. PMID:24040277

Raina, Varshiesh; Gupta, Sarika; Yadav, Saurabh; Surolia, Avadhesha

2013-01-01

17

Measurement of the rates of acetyl-CoA hydrolysis and synthesis from acetate in rat hepatocytes and the role of these fluxes in substrate cycling.  

PubMed Central

1. Acetyl-CoA hydrolysis, acetyl-CoA synthesis from acetate and several related fluxes were measured in rat hepatocytes. 2. In contrast with acetyl-CoA hydrolysis, most of the acetyl-CoA synthesis from acetate occurred in the mitochondria. 3. Acetyl-CoA hydrolysis was not significantly affected by 24 h starvation or (-)-hydroxycitrate. 4. In the cytoplasm there was a net flux of acetyl-CoA to acetate, and substrate cycling between acetate and acetyl-CoA in this compartment was very low, accounting for less than 0.1% of the total heat production by the animal. 5. A larger cycle, involving mitochondrial and cytoplasmic acetate and acetyl-CoA, may operate in fed animals, but would account for only approx 1% of total heat production. 6. It is proposed that the opposing fluxes of mitochondrial acetate utilization and cytoplasmic net acetate production may provide sensitivity, feedback and buffering, even when these fluxes are not linked to form a conventional substrate cycle. PMID:2396982

Crabtree, B; Gordon, M J; Christie, S L

1990-01-01

18

Hydrolysis of wheat B-starch and characterisation of acetylated maltodextrin.  

PubMed

Wheat B-starch was hydrolysed by ?-amylase "Liquozyme supra" from Bacillus licheniformis at 90 °C and pH 7. After 2 h, the dextrose equivalent was 18; according to size exclusion chromatography, however, the hydrolysate contained not only dominant malto-oligosaccharides with the degree of polymerisation (DP)<10 but also more than 20% of components with DP higher than 40. The product was acetylated to a high degree as verified by FTIR and (1)H NMR (degree of substitution DS=3.1); nevertheless, detailed analysis of the MALDI-TOF mass spectra of the product showed that most of the malto-oligosaccharides molecules contained one or two residual hydroxyls. Size exclusion chromatography confirmed that the acetylated maltodextrin still contained a significant part with DP>40. This non-uniformity of acetylated maltodextrin, both with respect to DP and to DS, must be taken into account in the development of acetylated-maltodextrin applications such as use as plasticisers or compatibilisers in biodegradable composites. PMID:23987315

Smr?ková, Petra; Horský, Ji?í; Šárka, Evžen; Kolá?ek, Jaroslav; Netopilík, Miloš; Walterová, Zuzana; Kruliš, Zden?k; Synytsya, Andrey; Hrušková, Kate?ina

2013-10-15

19

Synthesis of ?-(1?6)-linked N-acetyl-D-glucosamine oligosaccharide substrates and their hydrolysis by Dispersin B.  

PubMed

Dispersin B (DspB) from Aggregatibacter actinomycetemcomitans is a ?-hexosaminidase exhibiting biofilm detachment activity. A series of ?-(1?6)-linked N-acetyl-D-glucosamine thiophenyl glycosides with degree of polymerisation (DP) of 2, 3, 4 and 5 were synthesized, and substrate specificity of DspB was studied on the obtained oligosaccharides. For oligomer synthesis a 1+2, 2+2, 1+4 coupling strategy was applied, using bromo-sugars as glycosyl donors. The formation of 1,2-trans interglycosidic bond has been ensured by 2-phtalimido protecting group; chloroacetyl group was installed to mask temporarily the 6-hydroxyl and acetate esters were applied as permanent protecting groups. Enzymatic studies revealed that DP of the GlcNAc oligomers strongly affected the hydrolysis rate, and the hydrolytic activity of DspB on the tetramer and pentamer have been found to be approximately 10-fold higher than that of the dimer. This fact indicates that four units are required for a strong binding at the active centre of DspB. The role of aromatic amino acids W237, Y187 and Y278 in substrate specificity and catalysis was also examined using mutant enzymes. PMID:21482420

Fekete, Anikó; Borbás, Anikó; Gyémánt, Gyöngyi; Kandra, Lili; Fazekas, Erika; Ramasubbu, Narayanan; Antus, Sándor

2011-09-01

20

Prebiotic Fiber Increases Hepatic Acetyl CoA Carboxylase Phosphorylation and Suppresses Glucose-Dependent Insulinotropic Polypeptide Secretion More Effectively When Used with Metformin in Obese Rats1,2  

PubMed Central

Independently, metformin (MET) and the prebiotic, oligofructose (OFS), have been shown to increase glucagon-like peptide (GLP-1) secretion. Our objective was to determine whether using OFS as an adjunct with MET augments GLP-1 secretion in obese rats. Male, diet-induced obese Sprague Dawley rats were randomized to: 1) high-fat/-sucrose diet [HFHS; control (C); 20% fat, 50% sucrose wt:wt]; 2) HFHS+10% OFS (OFS); 3) HFHS + MET [300 mg/kg/d (MET)]; 4) HFHS+10% OFS+MET (OFS +MET). Body composition, glycemia, satiety hormones, and mechanisms related to dipeptidyl peptidase 4 (DPP4) activity in plasma, hepatic AMP-activated protein kinase (AMPK; Western blots), and gut microbiota (qPCR) were examined. Direct effects of MET and SCFA were examined in human enteroendocrine cells. The interaction between OFS and MET affected fat mass, hepatic TG, secretion of glucose-dependent insulinotropic polypeptide (GIP) and leptin, and AMPK?2 mRNA and phosphorylated acetyl CoA carboxylase (pACC) levels (P < 0.05). Combined, OFS and MET reduced GIP secretion to a greater extent than either treatment alone (P < 0.05). The hepatic pACC level was increased by OFS+MET by at least 50% above all other treatments, which did not differ from each other (P < 0.05). OFS decreased plasma DPP4 activity (P < 0.001). Cecal Bifidobacteria (P < 0.001) were markedly increased and C. leptum decreased (P < 0.001) with OFS consumption. In human enteroendocrine cells, the interaction between MET and SCFA affected GLP-1 secretion (P < 0.04) but was not associated with higher GLP-1 than the highest individual doses. In conclusion, the combined actions of OFS and MET were associated with important interaction effects that have the potential to improve metabolic outcomes associated with obesity. PMID:22223580

Pyra, Kim A.; Saha, Dolan C.; Reimer, Raylene A.

2013-01-01

21

Synthesis and Kinetics of Hydrolysis of 3,5-Dimethyl-N-acetyl-p-benzoquinone Imine: An Undergraduate Laboratory  

NASA Astrophysics Data System (ADS)

The synthesis of the title compound by a three-step procedure is described. The hydrolysis kinetics, which involve two consecutive psuedo-first-order processes, are also described. The synthesis and kinetics experiments described here are proposed for incorporation into undergraduate laboratory courses under a variety of formats. The compound described here is related to a toxic metabolite of the common analgesics acetaminophen and phenacetin.

Buccigross, Jeanne M.; Metz, Christa; Elliot, Lori; Becker, Pamela; Earley, Angela S.; Hayes, Jerry W.; Novak, Michael; Underwood, Gayl A.

1996-04-01

22

Identification of a novel CoA synthase isoform, which is primarily expressed in Brain  

SciTech Connect

CoA and its derivatives Acetyl-CoA and Acyl-CoA are important players in cellular metabolism and signal transduction. CoA synthase is a bifunctional enzyme which mediates the final stages of CoA biosynthesis. In previous studies, we have reported molecular cloning, biochemical characterization, and subcellular localization of CoA synthase (CoASy). Here, we describe the existence of a novel CoA synthase isoform, which is the product of alternative splicing and possesses a 29aa extension at the N-terminus. We termed it CoASy {beta} and originally identified CoA synthase, CoASy {alpha}. The transcript specific for CoASy {beta} was identified by electronic screening and by RT-PCR analysis of various rat tissues. The existence of this novel isoform was further confirmed by immunoblot analysis with antibodies directed to the N-terminal peptide of CoASy {beta}. In contrast to CoASy {alpha}, which shows ubiquitous expression, CoASy {beta} is primarily expressed in Brain. Using confocal microscopy, we demonstrated that both isoforms are localized on mitochondria. The N-terminal extension does not affect the activity of CoA synthase, but possesses a proline-rich sequence which can bring the enzyme into complexes with signalling proteins containing SH3 or WW domains. The role of this novel isoform in CoA biosynthesis, especially in Brain, requires further elucidation.

Nemazanyy, Ivan [Department of Structure and Function of Nucleic Acids, Institute of Molecular Biology and Genetics, 150 Zabolotnogo St, Kyiv 03680 (Ukraine)]. E-mail: nemazanyy@imbg.org.ua; Panasyuk, Ganna [Department of Structure and Function of Nucleic Acids, Institute of Molecular Biology and Genetics, 150 Zabolotnogo St, Kyiv 03680 (Ukraine); Breus, Oksana [Department of Structure and Function of Nucleic Acids, Institute of Molecular Biology and Genetics, 150 Zabolotnogo St, Kyiv 03680 (Ukraine); Zhyvoloup, Alexander [Department of Structure and Function of Nucleic Acids, Institute of Molecular Biology and Genetics, 150 Zabolotnogo St, Kyiv 03680 (Ukraine); Filonenko, Valeriy [Department of Structure and Function of Nucleic Acids, Institute of Molecular Biology and Genetics, 150 Zabolotnogo St, Kyiv 03680 (Ukraine); Gout, Ivan T. [Department of Structure and Function of Nucleic Acids, Institute of Molecular Biology and Genetics, 150 Zabolotnogo St, Kyiv 03680 (Ukraine) and Department of Biochemistry and Molecular Biology, Royal Free and University College Medical School, Gower Street, London WC1E 6BT (United Kingdom)]. E-mail: i.gout@ucl.ac.uk

2006-03-24

23

Protein acetylation and acetyl coenzyme a metabolism in budding yeast.  

PubMed

Cells sense and appropriately respond to the physical conditions and availability of nutrients in their environment. This sensing of the environment and consequent cellular responses are orchestrated by a multitude of signaling pathways and typically involve changes in transcription and metabolism. Recent discoveries suggest that the signaling and transcription machineries are regulated by signals which are derived from metabolism and reflect the metabolic state of the cell. Acetyl coenzyme A (CoA) is a key metabolite that links metabolism with signaling, chromatin structure, and transcription. Acetyl-CoA is produced by glycolysis as well as other catabolic pathways and used as a substrate for the citric acid cycle and as a precursor in synthesis of fatty acids and steroids and in other anabolic pathways. This central position in metabolism endows acetyl-CoA with an important regulatory role. Acetyl-CoA serves as a substrate for lysine acetyltransferases (KATs), which catalyze the transfer of acetyl groups to the epsilon-amino groups of lysines in histones and many other proteins. Fluctuations in the concentration of acetyl-CoA, reflecting the metabolic state of the cell, are translated into dynamic protein acetylations that regulate a variety of cell functions, including transcription, replication, DNA repair, cell cycle progression, and aging. This review highlights the synthesis and homeostasis of acetyl-CoA and the regulation of transcriptional and signaling machineries in yeast by acetylation. PMID:25326522

Galdieri, Luciano; Zhang, Tiantian; Rogerson, Daniella; Lleshi, Rron; Vancura, Ales

2014-12-01

24

Acetate/acetyl-CoA metabolism associated with cancer fatty acid synthesis: overview and application.  

PubMed

Understanding cancer-specific metabolism is important for identifying novel targets for cancer diagnosis and therapy. Induced acetate/acetyl CoA metabolism is a notable feature that is related to fatty acid synthesis supporting tumor growth. In this review, we focused on the recent findings related to cancer acetate/acetyl CoA metabolism. We also introduce [1-ąąC]acetate positron emission tomography (PET), which is a useful tool to visualize up-regulation of acetate/acetyl CoA metabolism in cancer, and discuss the utility of [1-ąąC]acetate PET in cancer diagnosis and its application to personalized medicine. PMID:24569091

Yoshii, Yukie; Furukawa, Takako; Saga, Tsuneo; Fujibayashi, Yasuhisa

2015-01-28

25

A novel neutral xylanase with high SDS resistance from Volvariella volvacea: characterization and its synergistic hydrolysis of wheat bran with acetyl xylan esterase.  

PubMed

A neutral xylanase (XynII) from Volvariella volvacea was identified and characterized. Unlike other modular xylanases, it consists of only a single GH10 catalytic domain with a unique C-terminal sequence (W-R-W-F) and a phenylalanine and proline-rich motif (T-P-F-P-P-F) at N-terminus, indicating that it is a novel GH10 xylanase. XynII exhibited optimal activity at pH 7 and 60 °C and stability over a broad range of pH 4.0-10.0. XynII displayed extreme highly SDS resistance retaining 101.98, 92.99, and 69.84 % activity at the presence of 300 mM SDS on birchwood, soluble oat spelt, and beechwood xylan, respectively. It remained largely intact after 24 h of incubation with proteinase K at a protease to protein ratio of 1:50 at 37 °C. The kinetic constants K(m) value towards beechwood xylan was 0.548 mg ml?ą, and the k(cat)/K(m) ratio, reflecting the catalytic efficiency of the enzyme, was 126.42 ml mg?ą s?ą at 60 °C. XynII was a true endo-acting xylanase lacking cellulase activity. It has weak activity towards xylotriose but efficiently hydrolyzed xylans and xylooligosaccharides larger than xylotriose mainly to xylobiose. Synergistic action with acetyl xylan esterase (AXEI) from V. volvacea was observed for de-starched wheat bran. The highest degree of synergy (DS 1.42) was obtained in sequential reactions with AXEI digestion preceding XynII. The high SDS resistance and intrinsic stability suggested XynII may have potential applications in various industrial processes especially for the detergent and textile industries and animal feed industries. PMID:23903903

Zheng, Fei; Huang, Jingxuan; Yin, Yuhao; Ding, Shaojun

2013-10-01

26

SIRT4 coordinates the balance between lipid synthesis and catabolism by repressing malonyl CoA decarboxylase  

PubMed Central

Summary Lipid metabolism is tightly controlled by the nutritional state of the organism. Nutrient-rich conditions increase lipogenesis whereas nutrient deprivation promotes fat oxidation. In this study, we identify the mitochondrial sirtuin, SIRT4, as a novel regulator of lipid homeostasis. SIRT4 is active in nutrient-replete conditions to repress fatty acid oxidation while promoting lipid anabolism. SIRT4 deacetylates and inhibits malonyl CoA decarboxylase (MCD), an enzyme that produces acetyl CoA from malonyl CoA. Malonyl CoA provides the carbon skeleton for lipogenesis and also inhibits fat oxidation. Mice lacking SIRT4 display elevated MCD activity and decreased malonyl CoA in skeletal muscle and white adipose tissue. Consequently, SIRT4 KO mice display deregulated lipid metabolism leading to increased exercise tolerance and protection against diet-induced obesity. In sum, this work elucidates SIRT4 as an important regulator of lipid homeostasis, identifies MCD as a novel SIRT4 target, and deepens our understanding of the malonyl CoA regulatory axis. PMID:23746352

Laurent, Gaëlle; German, Natalie J.; Saha, Asish K.; de Boer, Vincent C. J.; Davies, Michael; Koves, Timothy R.; Dephoure, Noah; Fischer, Frank; Boanca, Gina; Vaitheesvaran, Bhavapriya; Lovitch, Scott B.; Sharpe, Arlene H.; Kurland, Irwin J.; Steegborn, Clemens; Gygi, Steven P.; Muoio, Deborah M.; Ruderman, Neil B.; Haigis, Marcia C.

2013-01-01

27

104 COAS Administration Building Corvallis, OR 97331  

E-print Network

104 COAS Administration Building Corvallis, OR 97331 Tel: 541-737-9682 May 27, 2008 Dear Friends. Furthermore, orcoos.org now provides NRT one, three and eight-day composite maps showing wind stress, derived

Goldfinger, Chris

28

Acetyl coenzyme a-glutamate acetyltransferase and N-acetylornithine-glutamate acetyltransferase of chlorella.  

PubMed

The enzymic formation of acetylglutamate has been studied in Chlorella vulgaris extracts. Acetyl CoA and N(2)-acetyl-l-ornithine served as substrates for glutamate acetylation whereas acetylphosphate, N(5)-acetyl-l-ornithine, and N(2)-acetyl-2,4-diamino butyrate were ineffective. Acetyl CoA-glutamate transacetylase and acetylornithine-glutamate transacetylase activities have been purified over 180-fold with no indication of any separation of activities. The acetyl CoA activity was more labile than acetylornithine activity so that preparations having acetylornithine-glutamate transacetylase activity but no acetyl CoA-glutamate transacetylase activity were obtained. The two acetylating activities appear to be properties of one enzyme with one portion more easily denatured.Both acetylating activities had pH optima between 8 and 8.5. The Km value for glutamate was 3 mm for both activities. The Km values were 0.2 mm for acetylornithine and 3.2 mm for acetyl CoA. Arginine inhibited acetyl CoA-glutamate transacetylase (Ki = 0.94 mm) and acetylglutamate phosphokinase (Ki = 0.5 mm) but had no effect on acetylornithine-glutamate transacetylase. The lack of an inhibitory effect of proline on any of the three enzymic activities indicates that acetylglutamate is not a normal intermediate in proline biosynthesis. Growth of Chlorella with arginine as a nitrogen source had no effect on enzyme levels, showing that end-product repression is not a control factor in arginine biosynthesis in Chlorella. In Chlorella, arginine controls its own biosynthesis by inhibiting acetylglutamate phosphokinase and controls the level of acetylated intermediates by inhibiting acetyl CoA-glutamate transacetylase. PMID:16659227

Morris, C J; Thompson, J F

1975-06-01

29

Robust COA planning with varying durations  

Microsoft Academic Search

COA (Course of Action) planning involves resource allocation and task scheduling. Traditionally, this problem is tackled with the assumption that task duration is constant and with the objective to minimize the makespan. In contrast to this, this paper assumes task duration can vary in a time interval and the objective is to maximize the RM (Robustness Measure) given the deadline,

Luohao Tang; Cheng Zhu; Weiming Zhang; Zhong Liu

2011-01-01

30

Doping Induced Itinerant Ferromagnetism in CoAs  

NASA Astrophysics Data System (ADS)

The magnetism in ?-CoAs is dominated by strong spin fluctuations. In this study, we explore the effects of Phosphorus doping in ?-CoAs. Phosphorus is isovalent with Arsenic, and the resulting doping introduces disorder and chemical pressure. In CoAs1-xPx, a cross-over from the spin fluctuation-dominated regime to an itinerant ferromagnetic (IFM) state take places around x = 0.04. The IFM state persists up to x <= 0.27. For compositions between x = 0.28 and 0.40, the magnetization data suggests a possible Stoner enhanced state. We acknowledge the support from DOD PECASE.

Chen, Chih-Wei; Morosan, Emilia

2013-03-01

31

CAPTAN HYDROLYSIS  

EPA Science Inventory

Captan (N-(trichloromethylthio)-4-cyclohexene-1,2-dicarboximide) undergoes hydrolysis readily in water with a maximum half-life of 710 min. Over the pH range 2-6, the reaction is pH independent and the pseudo-first-order rate constant is (1.8 + or - 0.1) x 10 to the -5th power/s....

32

Postmortem Degradation of N-Acetyl Aspartate and N-Acetyl Aspartylglutamate: An HPLC Analysis of Different Rat CNS Regions  

Microsoft Academic Search

N-acetyl aspartate (NAA), a putative marker of neuronal injury, can be measured non-invasively in patients by magnetic resonance spectroscopy (MRS). Interpretation of in vivo MRS data, however, requires neuropathological correlates to NAA alterations using autopsy or biopsy material. Since detailed hydrolysis data is lacking, NAA and the related dipeptide N-acetyl aspartylglutamate (NAAG) were quantified by high performance liquid chromatography (HPLC)

Jan Battistuta; Carl Bjartmar; Bruce D. Trapp

2001-01-01

33

AMP-forming acetylCoA synthetase from the extremely halophilic archaeon Haloarcula marismortui : purification, identification and expression of the encoding gene, and phylogenetic affiliation  

Microsoft Academic Search

Halophilic archaea activate acetate via an (acetate)-inducible AMP-forming acetyl-CoA synthetase (ACS), (Acetate + ATP + CoA ? Acetyl-CoA + AMP + PPi). The enzyme from Haloarcula marismortui was purified to homogeneity. It constitutes a 72-kDa monomer and exhibited a temperature optimum of 41°C and a pH optimum of 7.5. For optimal activity, concentrations between 1 M and 1.5 M KCl were required, whereas

Christopher Bräsen; Peter Schönheit

2005-01-01

34

Synthesis of polyrotaxanes from acetyl-?-cyclodextrin  

NASA Astrophysics Data System (ADS)

Polyrotaxanes are intermediary products in the synthesis of topological gels. They are created by inclusion complex formation of hydrophobic linear macromolecules with cyclodextrins or their derivatives. Then, pairs of cyclodextrin molecules with covalently linkage were practically forming the nodes of the semi-flexible polymer network. Such gels are called topological gels and they can absorb huge quantities of water due to the net flexibility allowing the poly(ethylene oxide) chains to slide through the cyclodextrin cavities, without being pulled out altogether. For polyrotaxane formation poly(ethylene oxide) was used like linear macromolecules. There are hydroxyl groups at poly(ethylene oxide) chains, whereby the linking of the voluminous molecules should be made. To avoid the reaction of cyclodextrin OH groups with stoppers, they should be protected by, e.g., acetylation. In this work, the acetylation of the OH groups of ?-cyclodextrin was performed by acetic acid anhydride with iodine as the catalyst. The acetylation reaction was assessed by the FTIR and HPLC method. By the HPLC analysis was found that the acetylation was completed in 20 minutes. Inserting of poly(ethylene oxide) with 4000 g/mol molecule mass into acetyl-?-cyclodextrin with 2:1 poly(ethylene oxide) monomer unit to acetyl-?-cyclodextrin ratio was also monitored by FTIR, and it was found that the process was completed in 12 h at the temperature of 10°C. If the process is performed at temperatures above 10°C, or for periods longer than 12 hours, the process of uncontrolled hydrolysis of acetate groups was initiated.

Risti?, I. S.; Nikoli?, L.; Nikoli?, V.; Ili?, D.; Budinski-Simendi?, J.

2011-12-01

35

Migration and hydrolysis of hydrophobic polylactide plasticizer.  

PubMed

Hydrophobic plasticizer protects polylactide (PLA) against hydrolytic degradation but still migrates to aging medium and there undergoes further hydrolysis contributing to the spectrum of degradation products. PLA plasticized with hydrophobic acetyl tributyl citrate (ATC) plasticizer showed a slower degradation rate compared with pure PLA because of the increased hydrophobicity of the material. The enhanced bulk hydrophobicity also overcame the degradation enhancing effect of hydrophilic surface grafting. In addition to plasticization with ATC, some of the samples were also surface grafted with acrylic acid. The materials were subjected to hydrolysis at 37 and 60 degrees C for up to 364 days to compare the effect of hydrophobic and hydrophilic bulk and surface modifications. Although considered insoluble in water, the plasticizer was detected in the water solutions immediately upon immersion of the materials, and the relative abundance of the ATC degradation products increased with hydrolysis time. PMID:19928814

Höglund, Anders; Hakkarainen, Minna; Albertsson, Ann-Christine

2010-01-11

36

Global Hawk Pacific (GloPac) COA and Mission Coordination  

NASA Technical Reports Server (NTRS)

This slide presentation reviews the science objectives of the Global Hawk unmanned aircraft system (UAS) in the Pacific region, shows examp le flight tracks, the satellite under-flight requirement, the flight planning, and the agencies coordination of the airspace required for the Certificate of Authorization (COA).

Dillon, Mark; Hall, Philip

2010-01-01

37

Enzymatic hydrolysis of cellulose  

SciTech Connect

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; Ethanol Economics.

Wilke, C.R.

1983-01-01

38

Acetylation and chromosomal functions  

Microsoft Academic Search

Since the initial discovery of histone acetyltransferases, numerous reports have established that histone acetyltransferases and histone deacetylases regulate transcription by acetylating and deacetylating histones, respectively. Recent studies have focused on the effects of histone acetylation on gene expression regulation during development and the roles of histone hypoacetylation in the maintenance of centromeric structure, X-inactivation and genomic imprinting. Recent findings have

Wang L Cheung; Scott D Briggs; C David Allis

2000-01-01

39

Role of Feedback Regulation of Pantothenate Kinase (CoaA) in Control of Coenzyme A Levels in Escherichia coli  

PubMed Central

Pantothenate kinase (CoaA) is a key regulator of coenzyme A (CoA) biosynthesis in Escherichia coli, and its activity is controlled by feedback inhibition by CoA and its thioesters. The importance of feedback inhibition in the control of the intracellular CoA levels was tested by constructing three site-directed mutants of CoaA that were predicted to be feedback resistant based on the crystal structure of the CoaA-CoA binary complex. CoaA[R106A], CoaA[H177Q], and CoaA[F247V] were purified and shown to retain significant catalytic activity and be refractory to inhibition by CoA. CoaA[R106A] retained 50% of the catalytic activity of CoaA, whereas the CoaA[H177Q] and CoaA[F247V] mutants were less active. The importance of feedback control of CoaA to the intracellular CoA levels was assessed by expressing either CoaA or CoaA[R106A] in strain ANS3 [coaA15(Ts) panD2]. Cells expressing CoaA[R106A] had significantly higher levels of phosphorylated pantothenate-derived metabolites and CoA in vivo and excreted significantly more 4?-phosphopantetheine into the medium compared to cells expressing the wild-type protein. These data illustrate the key role of feedback regulation of pantothenate kinase in the control of intracellular CoA levels. PMID:12754240

Rock, Charles O.; Park, Hee-Won; Jackowski, Suzanne

2003-01-01

40

Acetylation Goes Global: The Emergence of Acetylation Biology  

NSDL National Science Digital Library

For the first 30 years since its discovery, reversible protein acetylation has been studied and understood almost exclusively in the context of histone modification and gene transcription. With the discovery of non–histone acetylated proteins and acetylation-modifying enzymes in cellular compartments outside the nucleus, the regulatory potential of reversible acetylation has slowly been recognized in the last decade. However, the scope of protein acetylation involvement in complex biological processes remains uncertain. The recent development of new technology has enabled, for the first time, the identification and quantification of the acetylome, acetylation events at the whole-proteome level. These efforts have uncovered a stunning complexity of the acetylome that potentially rivals that of the phosphoproteome. The remarkably ubiquitous and conserved nature of protein acetylation revealed by these new studies suggests the regulatory power of this dynamic modification. The establishment of comprehensive acetylomes will change the landscape of protein acetylation, where an exciting research frontier awaits.

Kristi L. Norris (Duke University;Department of Pharmacology and Cancer Biology REV); Joo-Yong Lee (Duke University;Department of Pharmacology and Cancer Biology REV); Tso-Pang Yao (Duke University;Department of Pharmacology and Cancer Biology REV)

2009-11-17

41

Final report on the safety assessment of acetyl triethyl citrate, acetyl tributyl citrate, acetyl trihexyl citrate, and acetyl trioctyl citrate.  

PubMed

Acetyl Triethyl Citrate, Acetyl Tributyl Citrate, Acetyl Trihexyl Citrate, and Acetyl Trioctyl Citrate all function as plasticizers in cosmetics. Additionally, the Trihexyl and Trioctyl forms are described as skin-conditioning agents-emollients, although there are currently no reported uses of Acetyl Trihexyl Citrate or Acetyl Trioctyl Citrate. Acetyl Triethyl Citrate and Acetyl Tributyl Citrate are used in nail products at concentrations up to 7%. Recognizing that there are no reported uses of Acetyl Trihexyl or Trioctyl Citrate, if they were to be used in the future, their concentration of use is expected to be no higher than that reported for Acetyl Triethyl and Tributyl Citrate. These ingredients were sufficiently similar in structure that safety test data on one were considered applicable to all. Approximately 99% of orally administered Acetyl Tributyl Citrate is excreted-intermediate metabolites include acetyl citrate, monobutyl citrate, acetyl monobutyl citrate, dibutyl citrate, and acetyl dibutyl citrate. In acute, short-term, subchronic, and chronic feeding studies, these ingredients were relatively nontoxic. Differences from controls were either not statistically significant or not related to any organ toxicity. Ocular exposures produced moderate reactions that cleared by 48 hours after instillation. Dermal application was not toxic in rabbits. In a guinea pig maximization test, Acetyl Triethyl Citrate was a sensitizer whereas Acetyl Tributyl Citrate was not. Limited clinical testing of Acetyl Triethyl Citrate and Acetyl Tributyl Citrate was negative for both skin irritation and sensitization. These clinical data were considered more relevant than the guinea pig maximization data, suggesting to the Cosmetic Ingredient Review Expert Panel that none of these ingredients would be a sensitizer. Physiologic effects noted with intravenous delivery of Acetyl Triethyl Citrate or Acetyl Tributyl Citrate include dose-related decreases in blood pressure and intestinal muscular spasms. These ingredients were not genotoxic in bacterial or mammalian test systems. No significant differences in tumor induction (lymphomas) were noted in rats fed Acetyl Tributyl Citrate for 2 year. Acetyl Tributyl Citrate was not a developmental or reproductive toxicant in studies in mice and rats. Based on all the available data, these ingredients were considered safe as used in cosmetics. PMID:12396673

Johnson, Wilbur

2002-01-01

42

Hydrolysis in supercritical water  

SciTech Connect

Reaction of guaiacol (o-methoxyphenol) in supercritical water and with added salts showed its hydrolysis to catechol (o-hydroxyphenol) and methanol to be through a polar transition state. Correlation of the reaction kinetics following a modified Herbrandson analysis provided a quantitative summary of the greater polarity of the hydrolysis transition state relative to the hydrolysis reactants. Salt addition further shifted the transition-state equilibrium toward the transition-state species.

Huppert, G.L.; Wu, B.C.; Townsend, S.H.; Klein, M.T.; Paspek, S.C.

1989-02-01

43

The hydrolysis of polyimides  

NASA Technical Reports Server (NTRS)

Thermal polymerization of aspartic acid produces a polysuccinimide (I), a chain of aspartoyl residues. An investigation was made of the alkaline hydrolysis of the imide rings of (I) which converts the polyimide to a polypeptide. The alkaline hydrolysis of polyimides can be expected to be kinetically complex due to increasing negative charge generated by carboxylate groups. For this reason, a diimide, phthaloyl-DL-aspartoyl-beta-alanine (IIA) was synthesized for a progressive study of the hydrolysis of polyimides. In addition, this diimide (IIA) can be related to thalidomide and might be expected to exhibit similar reactivity during hydrolysis of the phthalimide ring.

Hoagland, P. D.; Fox, S. W.

1973-01-01

44

ATP-Citrate Lyase Is Required for Production of Cytosolic Acetyl Coenzyme A and Development in Aspergillus nidulans?  

PubMed Central

Acetyl coenzyme A (CoA) is a central metabolite in carbon and energy metabolism and in the biosynthesis of cellular molecules. A source of cytoplasmic acetyl-CoA is essential for the production of fatty acids and sterols and for protein acetylation, including histone acetylation in the nucleus. In Saccharomyces cerevisiae and Candida albicans acetyl-CoA is produced from acetate by cytoplasmic acetyl-CoA synthetase, while in plants and animals acetyl-CoA is derived from citrate via ATP-citrate lyase. In the filamentous ascomycete Aspergillus nidulans, tandem divergently transcribed genes (aclA and aclB) encode the subunits of ATP-citrate lyase, and we have deleted these genes. Growth is greatly diminished on carbon sources that do not result in cytoplasmic acetyl-CoA, such as glucose and proline, while growth is not affected on carbon sources that result in the production of cytoplasmic acetyl-CoA, such as acetate and ethanol. Addition of acetate restores growth on glucose or proline, and this is dependent on facA, which encodes cytoplasmic acetyl-CoA synthetase, but not on the regulatory gene facB. Transcription of aclA and aclB is repressed by growth on acetate or ethanol. Loss of ATP-citrate lyase results in severe developmental effects, with the production of asexual spores (conidia) being greatly reduced and a complete absence of sexual development. This is in contrast to Sordaria macrospora, in which fruiting body formation is initiated but maturation is defective in an ATP-citrate lyase mutant. Addition of acetate does not repair these defects, indicating a specific requirement for high levels of cytoplasmic acetyl-CoA during differentiation. Complementation in heterokaryons between aclA and aclB deletions for all phenotypes indicates that the tandem gene arrangement is not essential. PMID:20495057

Hynes, Michael J.; Murray, Sandra L.

2010-01-01

45

The Natural Mentors of Adolescent Children of Alcoholics (COAs): Implications for Preventive Practices.  

ERIC Educational Resources Information Center

Late adolescent children of alcoholics (COAs) were interviewed about their relationship with a natural mentor. Results showed that a typical mentor was a same-sex relative who had been responsible for initiating the mentor-like relationship. Differences in the reported adjustment of COAs with and without natural mentors are considered in light of…

Cavell, Timothy A.; Meehan, Barbara T.; Heffer, Robert W.; Holladay, Janice J.

2002-01-01

46

N-Acetyl-4-aminophenol (paracetamol), N-acetyl-2-aminophenol and acetanilide in urine samples from the general population, individuals exposed to aniline and paracetamol users.  

PubMed

Epidemiological studies suggest associations between the use of N-acetyl-4-aminophenol (paracetamol) during pregnancy and increased risks of reproductive disorders in the male offspring. Previously we have reported a ubiquitous urinary excretion of N-acetyl-4-aminophenol in the general population. Possible sources are (1) direct intake of paracetamol through medication, (2) paracetamol residues in the food chain and (3) environmental exposure to aniline or related substances that are metabolized into N-acetyl-4-aminophenol. In order to elucidate the origins of the excretion of N-acetyl-4-aminophenol in urine and to contribute to the understanding of paracetamol and aniline metabolism in humans we developed a rapid, turbulent-flow HPLC-MS/MS method with isotope dilution for the simultaneous quantification of N-acetyl-4-aminophenol and two other aniline related metabolites, N-acetyl-2-aminophenol and acetanilide. We applied this method to three sets of urine samples: (1) individuals with no known exposure to aniline and also no recent paracetamol medication; (2) individuals after occupational exposure to aniline but no paracetamol medication and (3) paracetamol users. We confirmed the omnipresent excretion of N-acetyl-4-aminophenol. Additionally we revealed an omnipresent excretion of N-acetyl-2-aminophenol. In contrast, acetanilide was only found after occupational exposure to aniline, not in the general population or after paracetamol use. The results lead to four preliminary conclusions: (1) other sources than aniline seem to be responsible for the major part of urinary N-acetyl-4-aminophenol in the general population; (2) acetanilide is a metabolite of aniline in man and a valuable biomarker for aniline in occupational settings; (3) aniline baseline levels in the general population measured after chemical hydrolysis do not seem to originate from acetanilide and hence not from a direct exposure to aniline itself and (4) N-acetyl-2-aminophenol does not seem to be related to aniline nor to N-acetyl-4-aminophenol in man. PMID:24370547

Dierkes, Georg; Weiss, Tobias; Modick, Hendrik; Käfferlein, Heiko Udo; Brüning, Thomas; Koch, Holger M

2014-01-01

47

Binding of activated isoniazid with acetyl-CoA carboxylase from Mycobacterium tuberculosis  

PubMed Central

AccD6 (acetyl coenzyme A (CoA) carboxylase), plays an important role in mycolic acid synthesis of Mycobacterium tuberculosis (Mtb). Induced gene expression by isoniazid (isonicotinylhydrazine - INH), anti-tuberculosis drug) shows the expression of accD6. It is our interest to study the binding of activated INH with the AccD6 model using molecular docking procedures. The study predicts a primary binding site for activated INH (isonicotinyl acyl radical) in AccD6 as a potential target. PMID:22125378

Unissa, Ameeruddin Nusrath; Sudha, Subramanian; Selvakumar, Nagamiah; Hassan, Sameer

2011-01-01

48

Simultaneous pretreatment and enzymatic hydrolysis of forage biomass  

SciTech Connect

Sweet sorghum is an attractive fermentation feedstock because as much as 40% of the dry weight consists of readily femented sugars such as sucrose, glucose and frutose. Cellulose and hemicellulose comprise another 50%. However, if this material is to be used a year-round feedstock for ethanol production, a stable method of storage must be developed to maintain the sugar content. A modified version of the traditional ensiling process is made effective by the addition of cellulolytic/hemicellulolytic enzymes and lactic acid bacteria to freshly chopped sweet sorghum prior to the production of silage. In situ hydrolysis of cellulose and hemicellulose occurs concurrently with the acidic ensiling fementation. By hydolyzing the acetyl groups using acetyl xylan esterase and 3-0-methyl glucuronyl side chains using pectinase from hemicellulose, cellulose becomes accessible to hydrolysis by cellulase, both during in situ ensiling with enzymes and in the simultaneous saccharification and fermentation (SSF) to ethanol.

Henk, L.; Linden, J.C. [Colorado State Univ., Fort Collins, CO (United States)

1993-12-31

49

N-Acetylaspartate reductions in brain injury: impact on post-injury neuroenergetics, lipid synthesis, and protein acetylation.  

PubMed

N-Acetylaspartate (NAA) is employed as a non-invasive marker for neuronal health using proton magnetic resonance spectroscopy (MRS). This utility is afforded by the fact that NAA is one of the most concentrated brain metabolites and that it produces the largest peak in MRS scans of the healthy human brain. NAA levels in the brain are reduced proportionately to the degree of tissue damage after traumatic brain injury (TBI) and the reductions parallel the reductions in ATP levels. Because NAA is the most concentrated acetylated metabolite in the brain, we have hypothesized that NAA acts in part as an extensive reservoir of acetate for acetyl coenzyme A synthesis. Therefore, the loss of NAA after TBI impairs acetyl coenzyme A dependent functions including energy derivation, lipid synthesis, and protein acetylation reactions in distinct ways in different cell populations. The enzymes involved in synthesizing and metabolizing NAA are predominantly expressed in neurons and oligodendrocytes, respectively, and therefore some proportion of NAA must be transferred between cell types before the acetate can be liberated, converted to acetyl coenzyme A and utilized. Studies have indicated that glucose metabolism in neurons is reduced, but that acetate metabolism in astrocytes is increased following TBI, possibly reflecting an increased role for non-glucose energy sources in response to injury. NAA can provide additional acetate for intercellular metabolite trafficking to maintain acetyl CoA levels after injury. Here we explore changes in NAA, acetate, and acetyl coenzyme A metabolism in response to brain injury. PMID:24421768

Moffett, John R; Arun, Peethambaran; Ariyannur, Prasanth S; Namboodiri, Aryan M A

2013-01-01

50

A Jojoba P-Ketoacyl-COA Synthase cDNA Complements the Canola Fatty Acid Elongation Mutation in Transgenic Plants  

Microsoft Academic Search

p-Ketoacyl-coenzyme A (COA) synthase (KCS) catalyzes the condensation of malonyl-COA with long-chain acyl-COA. This reaction is the initial step of the microsomal fatty acyl-COA elongation pathway responsible for formation of very long chain fatty acids (VLCFAs, or fatty acids with chain lengths >18 carbons). Manipulation of this pathway is significant for agriculture, because it is the basis of conversion of

Michael W. Lassner; Kathryn Lardizabal; James G. Metz

51

STAT5 acetylation  

PubMed Central

The cytokine-inducible transcription factors signal transducer and activator of transcription 5A and 5B (STAT5A and STAT5B) are important for the proper development of multicellular eukaryotes. Disturbed signaling cascades evoking uncontrolled expression of STAT5 target genes are associated with cancer and immunological failure. Here, we summarize how STAT5 acetylation is integrated into posttranslational modification networks within cells. Moreover, we focus on how inhibitors of deacetylases and tyrosine kinases can correct leukemogenic signaling nodes involving STAT5. Such small molecules can be exploited in the fight against neoplastic diseases and immunological disorders. PMID:24416653

Kosan, Christian; Ginter, Torsten; Heinzel, Thorsten; Krämer, Oliver H

2013-01-01

52

Characterization of chitin and its hydrolysis to GlcNAc and GlcN.  

PubMed

Proton NMR spectra of chitin dissolved in concentrated and deuterated hydrochloric acid (DCl) were found to be a simple and powerful method for identifying chitin from samples of biological origin. During the first hour after dissolving chitin in concentrated DCl (25 degrees C), insignificant de-N-acetylation occurred, meaning that the fraction of acetylated units (FA) of chitin could be determined. FA of demineralized shrimp shell samples treated with 1 M NaOH at 95 degrees C for 1-24 h were determined and were found to decrease linearly with time from 0.96 to 0.91 during the treatment with NaOH. Extrapolation to zero time suggested that chitin from shrimp shells has a FA of 0.96, that is, contains a small but significant fraction of de-N-acetylated units. Proton NMR spectra of chitin ( FA = 0.96) dissolved in concentrated DCl were obtained as a function of time until the samples were almost quantitatively hydrolyzed to the monomer glucosamine (GlcN). The initial phase of the reaction involves mainly depolymerization of the chitin chains, resulting in that almost 90% (molar fraction) of the chitin is converted to the monomer N-acetyl-glucosamine (GlcNAc).Thus, effective conversion of chitin to GlcNAc in concentrated acid is reported for the first time. GlcNAc is then further de-N-acetylated to GlcN. A new theoretical model was developed to simulate the experimental data of the kinetics of hydrolysis of chitin in concentrated acid. The model uses three different rate constants; two for the hydrolysis of the glycosidic linkages following an N-acetylated or a de-N-acetylated sugar unit and one for the de-N-acetylation reaction. The three rate constants were estimated by fitting model data to experimental results. The rate of hydrolysis of a glycosidic linkage following an N-acetylated unit was found to be 54 times higher as compared to the rate of de-N-acetylation and 115 times higher than the rate of hydrolysis of a glycosidic linkage following a de-N-acetylated unit. Two chitin samples with different F A values (0.96 and 0.70) were incubated in concentrated DCl until the samples were converted to the maximum yield of GlcNAc and the oligomer composition analyzed, showing that the maximum yield of GlcNAc was much higher when prepared from the chitin with the highest F A value. PMID:18540645

Einbu, Aslak; Vĺrum, Kjell M

2008-07-01

53

Aldehyde-alcohol dehydrogenase and/or thiolase overexpression coupled with CoA transferase downregulation lead to higher alcohol titers and selectivity in Clostridium acetobutylicum fermentations.  

PubMed

Metabolic engineering (ME) of Clostridium acetobutylicum has led to increased solvent (butanol, acetone, and ethanol) production and solvent tolerance, thus demonstrating that further efforts have the potential to create strains of industrial importance. With recently developed ME tools, it is now possible to combine genetic modifications and thus implement more advanced ME strategies. We have previously shown that antisense RNA (asRNA)-based downregulation of CoA transferase (CoAT, the first enzyme in the acetone-formation pathway) results in increased butanol to acetone selectivity, but overall reduced butanol yields and titers. In this study the alcohol/aldehyde dehydrogenase (aad) gene (encoding the bifunctional protein AAD responsible for butanol and ethanol production from butyryl-CoA and acetyl-CoA, respectively) was expressed from the phosphotransbutyrylase (ptb) promoter to enhance butanol formation and selectivity, while CoAT downregulation was used to minimize acetone production. This led to early production of high alcohol (butanol plus ethanol) titers, overall solvent titers of 30 g/L, and a higher alcohol/acetone ratio. Metabolic flux analysis revealed the likely depletion of butyryl-CoA. In order to increase then the flux towards butyryl-CoA, we examined the impact of thiolase (THL, thl) overexpression. THL converts acetyl-CoA to acetoacetyl-CoA, the first step of the pathway from acetyl-CoA to butyryl-CoA, and thus, combining thl overexpression with aad overexpression decreased, as expected, acetate and ethanol production while increasing acetone and butyrate formation. thl overexpression in strains with asRNA CoAT downregulation did not significantly alter product formation thus suggesting that a more complex metabolic engineering strategy is necessary to enhance the intracellular butyryl-CoA pool and reduce the acetyl-CoA pool in order to achieve improved butanol titers and selectivity. PMID:18726959

Sillers, Ryan; Al-Hinai, Mohab Ali; Papoutsakis, Eleftherios T

2009-01-01

54

University of Minnesota Center for Outdoor Adventure (COA) Health History Form  

E-print Network

1 University of Minnesota Center for Outdoor Adventure (COA) Health History Form Center for Outdoor_____________________________________________________Relationship_________________ Phone number___________________________________ #12;2 II. Past and Present Medical History Please mark

Amin, S. Massoud

55

Tools to tackle protein acetylation.  

PubMed

In the recent issue of Molecular Cell, Neumann et al. dissect the effect of H3K56 acetylation on chromatin structure using a novel method for generation of acetylated proteins. This is a valuable addition to the toolkit for those interested in unraveling how posttranslational modifications regulate protein function. PMID:19875076

Kamieniarz, Kinga; Schneider, Robert

2009-10-30

56

Distinct roles of carbohydrate esterase family CE16 acetyl esterases and polymer-acting acetyl xylan esterases in xylan deacetylation.  

PubMed

Mass spectrometric analysis was used to compare the roles of two acetyl esterases (AE, carbohydrate esterase family CE16) and three acetyl xylan esterases (AXE, families CE1 and CE5) in deacetylation of natural substrates, neutral (linear) and 4-O-methyl glucuronic acid (MeGlcA) substituted xylooligosaccharides (XOS). AEs were similarly restricted in their action and apparently removed in most cases only one acetyl group from the non-reducing end of XOS, acting as exo-deacetylases. In contrast, AXEs completely deacetylated longer neutral XOS but had difficulties with the shorter ones. Complete deacetylation of neutral XOS was obtained after the combined action of AEs and AXEs. MeGlcA substituents partially restricted the action of both types of esterases and the remaining acidic XOS were mainly substituted with one MeGlcA and one acetyl group, supposedly on the same xylopyranosyl residue. These resisting structures were degraded to great extent only after inclusion of ?-glucuronidase, which acted with the esterases in a synergistic manner. When used together with xylan backbone degrading endoxylanase and ?-xylosidase, both AE and AXE enhanced the hydrolysis of complex XOS equally. PMID:24140638

Koutaniemi, S; van Gool, M P; Juvonen, M; Jokela, J; Hinz, S W; Schols, H A; Tenkanen, M

2013-12-01

57

Mutations in COA6 cause Cytochrome c Oxidase Deficiency and Neonatal Hypertrophic Cardiomyopathy.  

PubMed

COA6/C1ORF31 is involved in cytochrome c oxidase (complex IV) biogenesis. We present a new pathogenic COA6 variant detected in a patient with neonatal hypertrophic cardiomyopathy and isolated complex IV deficiency. For the first time, clinical details about a COA6-deficient patient are given and patient fibroblasts are functionally characterized: COA6 protein is undetectable and steady-state levels of complex IV and several of its subunits are reduced. The monomeric COX1 assembly intermediate accumulates. Using pulse-chase experiments, we demonstrate an increased turnover of mitochondrial encoded complex IV subunits. Although monomeric complex IV is decreased in patient fibroblasts, the CI/CIII2 /CIVn -supercomplexes remain unaffected. Copper supplementation shows a partial rescue of complex IV deficiency in patient fibroblasts. We conclude that COA6 is required for complex IV subunit stability. Furthermore, the proposed role in the copper delivery pathway to complex IV subunits is substantiated and a therapeutic lead for COA6-deficient patients is provided. PMID:25339201

Baertling, Fabian; A M van den Brand, Mariel; Hertecant, Jozef L; Al-Shamsi, Aisha; P van den Heuvel, Lambert; Distelmaier, Felix; Mayatepek, Ertan; Smeitink, Jan A; Nijtmans, Leo G J; Rodenburg, Richard J T

2015-01-01

58

Mechanistic insight with HBCH2CoA as a probe to polyhydroxybutyrate (PHB) synthases.  

PubMed

Polyhydroxybutyrate (PHB) synthases catalyze the polymerization of 3-(R)-hydroxybutyrate coenzyme A (HBCoA) to produce polyoxoesters of 1-2 MDa. A substrate analogue HBCH2CoA, in which the S in HBCoA is replaced with a CH2 group, was synthesized in 13 steps using a chemoenzymatic approach in a 7.5% overall yield. Kinetic studies reveal it is a competitive inhibitor of a class I and a class III PHB synthases, with Kis of 40 and 14 ?M, respectively. To probe the elongation steps of the polymerization, HBCH2CoA was incubated with a synthase acylated with a [(3)H]-saturated trimer-CoA ([(3)H]-sTCoA). The products of the reaction were shown to be the methylene analogue of [(3)H]-sTCoA ([(3)H]-sT-CH2-CoA), saturated dimer-([(3)H]-sD-CO2H), and trimer-acid ([(3)H]-sT-CO2H), distinct from the expected methylene analogue of [(3)H]-saturated tetramer-CoA ([(3)H]-sTet-CH2-CoA). Detection of [(3)H]-sT-CH2-CoA and its slow rate of formation suggest that HBCH2CoA may be reporting on the termination and repriming process of the synthases, rather than elongation. PMID:24896226

Zhang, Wei; Shrestha, Ruben; Buckley, Rachael M; Jewell, Jamie; Bossmann, Stefan H; Stubbe, JoAnne; Li, Ping

2014-08-15

59

Progressing batch hydrolysis process  

DOEpatents

A progressive batch hydrolysis process for producing sugar from a lignocellulosic feedstock, comprising passing a stream of dilute acid serially through a plurality of percolation hydrolysis reactors charged with said feedstock, at a flow rate, temperature and pressure sufficient to substantially convert all the cellulose component of the feedstock to glucose; cooling said dilute acid stream containing glucose, after exiting the last percolation hydrolysis reactor, then feeding said dilute acid stream serially through a plurality of prehydrolysis percolation reactors, charged with said feedstock, at a flow rate, temperature and pressure sufficient to substantially convert all the hemicellulose component of said feedstock to glucose; and cooling the dilute acid stream containing glucose after it exits the last prehydrolysis reactor.

Wright, John D. (Denver, CO)

1986-01-01

60

Characterization of O-acetylation of N-acetylglucosamine: a novel structural variation of bacterial peptidoglycan.  

PubMed

Peptidoglycan (PG) N-acetyl muramic acid (MurNAc) O-acetylation is widely spread in gram-positive bacteria and is generally associated with resistance against lysozyme and endogenous autolysins. We report here the presence of O-acetylation on N-acetylglucosamine (GlcNAc) in Lactobacillus plantarum PG. This modification of glycan strands was never described in bacteria. Fine structural characterization of acetylated muropeptides released from L. plantarum PG demonstrated that both MurNAc and GlcNAc are O-acetylated in this species. These two PG post-modifications rely on two dedicated O-acetyltransferase encoding genes, named oatA and oatB, respectively. By analyzing the resistance to cell wall hydrolysis of mutant strains, we showed that GlcNAc O-acetylation inhibits N-acetylglucosaminidase Acm2, the major L. plantarum autolysin. In this bacterial species, inactivation of oatA, encoding MurNAc O-acetyltransferase, resulted in marked sensitivity to lysozyme. Moreover, MurNAc over-O-acetylation was shown to activate autolysis through the putative N-acetylmuramoyl-L-alanine amidase LytH enzyme. Our data indicate that in L. plantarum, two different O-acetyltransferases play original and antagonistic roles in the modulation of the activity of endogenous autolysins. PMID:21586574

Bernard, Elvis; Rolain, Thomas; Courtin, Pascal; Guillot, Alain; Langella, Philippe; Hols, Pascal; Chapot-Chartier, Marie-Pierre

2011-07-01

61

Exome sequence reveals mutations in CoA synthase as a cause of neurodegeneration with brain iron accumulation.  

PubMed

Neurodegeneration with brain iron accumulation (NBIA) comprises a clinically and genetically heterogeneous group of disorders with progressive extrapyramidal signs and neurological deterioration, characterized by iron accumulation in the basal ganglia. Exome sequencing revealed the presence of recessive missense mutations in COASY, encoding coenzyme A (CoA) synthase in one NBIA-affected subject. A second unrelated individual carrying mutations in COASY was identified by Sanger sequence analysis. CoA synthase is a bifunctional enzyme catalyzing the final steps of CoA biosynthesis by coupling phosphopantetheine with ATP to form dephospho-CoA and its subsequent phosphorylation to generate CoA. We demonstrate alterations in RNA and protein expression levels of CoA synthase, as well as CoA amount, in fibroblasts derived from the two clinical cases and in yeast. This is the second inborn error of coenzyme A biosynthesis to be implicated in NBIA. PMID:24360804

Dusi, Sabrina; Valletta, Lorella; Haack, Tobias B; Tsuchiya, Yugo; Venco, Paola; Pasqualato, Sebastiano; Goffrini, Paola; Tigano, Marco; Demchenko, Nikita; Wieland, Thomas; Schwarzmayr, Thomas; Strom, Tim M; Invernizzi, Federica; Garavaglia, Barbara; Gregory, Allison; Sanford, Lynn; Hamada, Jeffrey; Bettencourt, Conceiçăo; Houlden, Henry; Chiapparini, Luisa; Zorzi, Giovanna; Kurian, Manju A; Nardocci, Nardo; Prokisch, Holger; Hayflick, Susan; Gout, Ivan; Tiranti, Valeria

2014-01-01

62

Exome Sequence Reveals Mutations in CoA Synthase as a Cause of Neurodegeneration with Brain Iron Accumulation  

PubMed Central

Neurodegeneration with brain iron accumulation (NBIA) comprises a clinically and genetically heterogeneous group of disorders with progressive extrapyramidal signs and neurological deterioration, characterized by iron accumulation in the basal ganglia. Exome sequencing revealed the presence of recessive missense mutations in COASY, encoding coenzyme A (CoA) synthase in one NBIA-affected subject. A second unrelated individual carrying mutations in COASY was identified by Sanger sequence analysis. CoA synthase is a bifunctional enzyme catalyzing the final steps of CoA biosynthesis by coupling phosphopantetheine with ATP to form dephospho-CoA and its subsequent phosphorylation to generate CoA. We demonstrate alterations in RNA and protein expression levels of CoA synthase, as well as CoA amount, in fibroblasts derived from the two clinical cases and in yeast. This is the second inborn error of coenzyme A biosynthesis to be implicated in NBIA. PMID:24360804

Dusi, Sabrina; Valletta, Lorella; Haack, Tobias B.; Tsuchiya, Yugo; Venco, Paola; Pasqualato, Sebastiano; Goffrini, Paola; Tigano, Marco; Demchenko, Nikita; Wieland, Thomas; Schwarzmayr, Thomas; Strom, Tim M.; Invernizzi, Federica; Garavaglia, Barbara; Gregory, Allison; Sanford, Lynn; Hamada, Jeffrey; Bettencourt, Conceiçăo; Houlden, Henry; Chiapparini, Luisa; Zorzi, Giovanna; Kurian, Manju A.; Nardocci, Nardo; Prokisch, Holger; Hayflick, Susan; Gout, Ivan; Tiranti, Valeria

2014-01-01

63

Determination of the mechanism of reaction for bile acid: CoA ligase.  

PubMed Central

The reaction of cholic acid, CoA and ATP to yield cholyl-CoA was investigated by kinetic analysis of the reaction as catalysed by guinea pig liver microsomes. The enzyme has an absolute requirement for divalent cation for activity so all kinetic analyses were carried out in excess Mn2+. A trisubstrate kinetic analysis was conducted by varying, one at a time ATP cholate and CoA. Both ATP and cholate gave parallel double reciprocal plots versus CoA, which indicates a ping-pong mechanism with either pyrophosphate or AMP leaving prior to the binding of CoA. Addition of pyrophosphate to the assays changed the parallel plots to intersecting ones; addition of AMP did not. This indicates that pyrophosphate is the first product. The end-product, AMP, was a competitive inhibitor versus ATP, as was cholyl-CoA at saturating concentrations of cholate. Both AMP and cholyl-CoA were uncompetitive inhibitors versus CoA. Based on this information, it was concluded that the reaction follows a bi uni uni bi ping-pong mechanism with ATP binding first, and with the release of the final products, AMP and cholyl-CoA, being random. CoA showed substrate inhibition at high but non-saturating concentrations and this inhibition was competitive versus ATP, which is consistent with the predicted ping-pong mechanism. The ability of cholyl-CoA, but not cholate or CoA, to bind with high affinity to the free enzyme was suggestive of a high affinity of the enzyme for the thioester link. PMID:7818501

Kelley, M; Vessey, D A

1994-01-01

64

Acetylation of corn distillers dried grains  

Microsoft Academic Search

This paper shows that acidic conditions provide substantially higher % acetyl content, intrinsic viscosity and thermoplasticity even at low ratios of acetic anhydride and catalyst concentrations compared to using alkaline conditions for acetylation of oil-and-zein-free distillers dried grains with solubles (DDGS). Conventional methods of carbohydrate and protein acetylation are unsuitable for acetylating DDGS which is a mixture of carbohydrates and

Narendra Reddy; Chunyan Hu; Kelu Yan; Yiqi Yang

2011-01-01

65

De novo CoA biosynthesis is required to maintain DNA integrity during development of the Drosophila nervous system  

Microsoft Academic Search

In a forward genetic screen in Drosophila melanogaster, aimed to identify genes required for normal locomotor function, we isolated dPPCS (the second enzyme of the Coenzyme A biosynthesis pathway). The entire Drosophila CoA synthesis route was dissected, annotated and additional CoA mutants were obtained (dPANK\\/fumble) or generated (dPPAT-DPCK). Drosophila CoA mutants suffer from neurodegenera- tion, altered lipid homeostasis and the

Floris Bosveld; A. Rana; Petra E. van der Wouden; Willy Lemstra; Martha Ritsema; Harm H. Kampinga; Ody C. M. Sibon

2008-01-01

66

Acetyl-L-carnitine: from a biological curiosity to a drug for the peripheral nervous system and beyond.  

PubMed

Acetyl-L-carnitine (ALC) is a molecule derived from acetylation of carnitine in the mitochondria. Carnitine acetylation enables the function of CoA and facilitates elimination of oxidative products. Beyond this metabolic activity, ALC provides acetyl groups for acetylcholine synthesis, exerts a cholinergic effect and optimizes the balance of energy processes. Acetylcarnitine supplementation induces neuroprotective, neurotrophic and analgesic effects in the peripheral nervous system. In the recent studies, ALC, by acting as a donor of acetyl groups to NF-kb p65/RelA, enhanced the transcription of the GRM2 gene encoding the mGLU2 receptors, inducing long-term upregulation of the mGluR2, evidencing therefore that its long-term analgesic effects are dependent on epigenetic modifications. Several studies, including double-blind, placebo-controlled, parallel group studies and few open studies showed the effect of ALC in diseases characterized by neuropathies and neuropathic pain: the studies included diabetic neuropathy, HIV and antiretroviral therapy-induced neuropathies, neuropathies due to compression and chemotherapeutic agents. Double-blinded studies involved 1773 patients. Statistical evaluations evidenced reduction of pain, improvements of nerve function and trophism. In conclusion, ALC represents a consistent therapeutic option for peripheral neuropathies, and its complex effects, neurotrophic and analgesic, based on epigenetic mechanism, open new pathways in the study of peripheral nerve disease management. PMID:23965166

Onofrj, Marco; Ciccocioppo, Fausta; Varanese, Sara; di Muzio, Antonio; Calvani, Menotti; Chiechio, Santina; Osio, Maurizio; Thomas, Astrid

2013-08-01

67

Molecular Structure of Acetyl Peroxide  

NSDL National Science Digital Library

Acetyl peroxide is a colorless liquid with a pungent odor. It is generally stored as a 25% solution in dimethyl phthalate to prevent detonation. It may explode if heated, or in contact with combustible materials. As the pure material, acetyl peroxide is unstable and incompatible with organic materials. The compound is harmful by inhalation, ingestion and skin contact. It is used as an initiator and catalyst for resins, and it also promotes polymerization in the manufacture of certain plastics.

2002-10-09

68

Cohesin’s ATPase Activity Couples Cohesin Loading onto DNA with Smc3 Acetylation  

PubMed Central

Summary Background Cohesin mediates sister chromatid cohesion by topologically entrapping sister DNA molecules inside its ring structure. Cohesin is loaded onto DNA by the Scc2/NIPBL-Scc4/MAU2-loading complex in a manner that depends on the adenosine triphosphatase (ATPase) activity of cohesin’s Smc1 and Smc3 subunits. Subsequent cohesion establishment during DNA replication depends on Smc3 acetylation by Esco1 and Esco2 and on recruitment of sororin, which “locks” cohesin on DNA by inactivating the cohesin release factor Wapl. Results Human cohesin ATPase mutants associate transiently with DNA in a manner that depends on the loading complex but cannot be stabilized on chromatin by depletion of Wapl. These mutants cannot be acetylated, fail to interact with sororin, and do not mediate cohesion. The absence of Smc3 acetylation in the ATPase mutants is not a consequence of their transient association with DNA but is directly caused by their inability to hydrolyze ATP because acetylation of wild-type cohesin also depends on ATP hydrolysis. Conclusions Our data indicate that cohesion establishment involves the following steps. First, cohesin transiently associates with DNA in a manner that depends on the loading complex. Subsequently, ATP hydrolysis by cohesin leads to entrapment of DNA and converts Smc3 into a state that can be acetylated. Finally, Smc3 acetylation leads to recruitment of sororin, inhibition of Wapl, and stabilization of cohesin on DNA. Our finding that cohesin’s ATPase activity is required for both cohesin loading and Smc3 acetylation raises the possibility that cohesion establishment is directly coupled to the reaction in which cohesin entraps DNA. PMID:25220052

Ladurner, Rene; Bhaskara, Venugopal; Huis in ’t Veld, Pim J.; Davidson, Iain F.; Kreidl, Emanuel; Petzold, Georg; Peters, Jan-Michael

2014-01-01

69

Stabilization of Cox1p intermediates by the Cox14p-Coa3p complex  

PubMed Central

Cox14p and Coa3p have been shown to regulate translation of the mitochondrial COX1 mRNA and to be required for assembly of cytochrome oxidase. We present evidence that Cox14p and Coa3p stabilize previously identified Cox1p intermediates and that in the absence of either protein, Cox1p aggregates with itself and other mitochondrial gene products, including cytochrome b, Var1p and Cox2p. Our evidence suggests that Cox1p assembly intermediates are in close proximity to other mitochondrially translated proteins and that an important function of Cox14p and Coa3p is to prevent Cox1 from entering into unproductive aggregation pathways. PMID:23434581

McStay, Gavin P.; Su, Chen Hsien; Tzagoloff, Alexander

2013-01-01

70

First principles study of structural, electronic and magnetic properties of Mn2CoAs  

NASA Astrophysics Data System (ADS)

We have performed first-principle calculations of the structural, electronic and magnetic properties of Mn2CoAs Heusler alloy, using full-potential linearized augmented plane wave (FP-LAPW) scheme within the GGA. Features such as the lattice constant, the bulk modulus and its pressure derivative are reported. The electronic band structures and density of states of the Mn2CoAs compound show that the spin-up electrons are metallic, but the spin-down bands have a gap of 0.48 eV, resulting in stable half-metallic ferrimagnetic behavior with a magnetic moment of 4.00 ?B.

Berri, Saadi; Ibrir, M.; Maouche, D.; Bensalem, R.

2014-06-01

71

Acyl CoA Binding Protein (ACBP) Gene Ablation Induces Pre-Implantation Embryonic Lethality in Mice  

E-print Network

Unique among the intracellular lipid binding proteins, acyl CoA binding protein (ACBP) exclusively binds long chain fatty acyl CoAs (LCFA-CoAs). To test if ACBP is an essential protein in mammals, the ACBP gene was ablated by homologous...

Landrock, Danilo

2012-02-14

72

EXPRESSION OF TURKEY TRANSCRIPTION FACTORS AND ACYL COA OXIDASE IN DIFFERENT TISSUES AND GENETIC POPULATIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Several transcription factors are involved in regulating lipid metabolism in various animal tissues. Peroxisome proliferator activated receptor (PPAR) gamma and PPAR alpha regulate both lipogenesis and fatty acid oxidation. Gene fragments for PPAR gamma, PPAR alpha, and acyl CoA oxidase (ACO) have b...

73

COA's Barney Bright Sculpture In 1964, Louisville sculptor Jeptha Barnard "Barney" Bright was  

E-print Network

COA's Barney Bright Sculpture In 1964, Louisville sculptor Jeptha Barnard "Barney" Bright, whose studio was located at 2031 Frankfort Avenue in Louisville, was commissioned by architects McCulloch & Bickel (also of Louisville), who designed the Agricultural Sciences Building (AG North). It was one

Hayes, Jane E.

74

Variations in the Localization of Acetyl-Coenzyme A Synthetase in Aerobic Yeast Cells  

PubMed Central

In cells of Saccharomyces cerevisiae growing aerobically for 24 hr, acetyl-coenzyme A synthetase [acetate: CoA ligase (AMP), EC 6.2.1.1] was localized principally in the microsomal fraction. On density gradients, the enzyme in such cells behaved as a low-density particle, readily separable from the soluble proteins. After 48 hr of incubation, the cells showed a bimodal distribution of enzyme, with most of the activity now sedimenting with the mitochondrial fraction and only a smaller amount with the microsomal fraction. By using density gradients, two forms of synthetase were obtained from these cells: one band denser and the other band less dense than the intact mitochondria. In all preparations containing synthetase activity, appreciable levels of phospholipids were also detected. Images PMID:4102333

Klein, Harold P.; Jahnke, Linda

1971-01-01

75

Changing the Selectivity of p300 by Acetyl-CoA Modulation of Histone Acetylation.  

PubMed

Determining how histone acetylation is regulated is vital for treating the many diseases associated with its misregulation, including heart disease, neurological disorders, and cancer. We have previously reported that acetyl-CoA levels alter p300 histone acetylation in a site-specific manner in vitro. Here, we further investigate how changing acetyl-CoA concentrations alter the histone acetylation pattern by altering p300 specificity. Interestingly, these changes are not a simple global change in acetylation, but rather site specific changes, whereby acetylation at some sites increase while others decrease. We also demonstrate how the p300 inhibitor C646 can pharmacologically alter p300 histone acetylation patterns in vitro and in cells. This study provides insight into the mechanisms regulating p300 residue specificity, a potential means for altering p300 dependent histone acetylation, and an investigation into altering histone acetylation patterns in cells. PMID:25325435

Henry, Ryan A; Kuo, Yin-Ming; Bhattacharjee, Vikram; Yen, Timothy J; Andrews, Andrew J

2015-01-16

76

De novo CoA biosynthesis is required to maintain DNA integrity during development of the Drosophila nervous system.  

PubMed

In a forward genetic screen in Drosophila melanogaster, aimed to identify genes required for normal locomotor function, we isolated dPPCS (the second enzyme of the Coenzyme A biosynthesis pathway). The entire Drosophila CoA synthesis route was dissected, annotated and additional CoA mutants were obtained (dPANK/fumble) or generated (dPPAT-DPCK). Drosophila CoA mutants suffer from neurodegeneration, altered lipid homeostasis and the larval brains display increased apoptosis. Also, de novo CoA biosynthesis is required to maintain DNA integrity during the development of the central nervous system. In humans, mutations in the PANK2 gene, the first enzyme in the CoA synthesis route, are associated with pantothenate kinase-associated neurodegeneration. Currently, the pathogenesis of this neurodegenerative disease is poorly understood. We provide the first comprehensive analysis of the physiological implications of mutations in the entire CoA biosynthesis route in an animal model system. Surprisingly, our findings reveal a major role of this conserved pathway in maintaining DNA and cellular integrity, explaining how impaired CoA synthesis during CNS development can elicit a neurodegenerative phenotype. PMID:18407920

Bosveld, Floris; Rana, Anil; van der Wouden, Petra E; Lemstra, Willy; Ritsema, Martha; Kampinga, Harm H; Sibon, Ody C M

2008-07-01

77

Crystallographic trapping of the glutamyl-CoA thioester intermediate of family I CoA transferases  

SciTech Connect

Coenzyme A transferases are involved in a broad range of biochemical processes in both prokaryotes and eukaryotes, and exhibit a diverse range of substrate specificities. The YdiF protein from Escherichia coli O157:H7 is an acyl-CoA transferase of unknown physiological function, and belongs to a large sequence family of CoA transferases, present in bacteria to humans, which utilize oxoacids as acceptors. In vitro measurements showed that YdiF displays enzymatic activity with short-chain acyl-CoAs. The crystal structures of YdiF and its complex with CoA, the first co-crystal structure for any Family I CoA transferase, have been determined and refined at 1.9 and 2.0 Angstrom resolution, respectively. YdiF is organized into tetramers, with each monomer having an open {alpha}/{beta} structure characteristic of Family I CoA transferases. Co-crystallization of YdiF with a variety of CoA thioesters in the absence of acceptor carboxylic acid resulted in trapping a covalent {gamma}-glutamyl-CoA thioester intermediate. The CoA binds within a well defined pocket at the N- and C-terminal domain interface, but makes contact only with the C-terminal domain. The structure of the YdiF complex provides a basis for understanding the different catalytic steps in the reaction of Family I CoA transferases.

Rangarajan,E.; Li, Y.; Ajamian, E.; Iannuzzi, P.; Kernaghan, S.; Fraser, M.; Cygler, M.; Matte, A.

2005-01-01

78

ESTIMATION OF PHOSPHATE ESTER HYDROLYSIS RATE CONSTANTS - ALKALINE HYDROLYSIS  

EPA Science Inventory

SPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity models were extended to allow the calculation of alkaline hydrolysis rate constants of phosphate esters in water. The rate is calculated from the energy difference between the initial and transition state...

79

ESTIMATION OF PHOSPHATE ESTER HYDROLYSIS RATE CONSTANTS. I. ALKALINE HYDROLYSIS  

EPA Science Inventory

SPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity models were extended to allow the calculation of alkaline hydrolysis rate constants of phosphate esters in water. The rate is calculated from the energy difference between the initial and transition state...

80

Are long chain acyl CoAs responsible for suppression of mitochondrial metabolism in hibernating 13-lined ground squirrels?.  

E-print Network

??I found 44% suppression of succinate-fuelled liver mitochondrial respiration in torpid 13-lined ground squirrels compared to interbout euthermia (IBE). Palmitoyl CoA, predicted to suppress respiration… (more)

Cooper, Alex

2013-01-01

81

Upregulation of Endothelial Nitric Oxide Synthase by HMG CoA Reductase Inhibitors  

Microsoft Academic Search

Background—Oxidized low-density lipoprotein (ox-LDL) causes endothelial dysfunction in part by decreasing the availability of endothelial nitric oxide (NO). Although HMG CoA reductase inhibitors restore endothelial function by reducing serum cholesterol levels, it is not known whether they can also directly upregulate endothelial NO synthase (ecNOS) activity. Methods and Results—Human saphenous vein endothelial cells were treated with ox-LDL (50 mg\\/mL thiobarbituric

Ulrich Laufs; Vito La Fata; Jorge Plutzky; James K. Liao

82

Regulation of schistosome egg production by HMG CoA reductase  

SciTech Connect

Hydroxymethylglutaryl coenzyme A reductase (HMG CoA reductase) catalyzes the conversion of HMG CoA to mevalonate in the synthesis of steroids, isoprenoids and terpenes. Mevinolin, an inhibitor of this enzyme, decreased egg production in Schistosoma mansoni during in vitro incubations. This was associated with a reduction in the incorporation of /sup 14/C-acetate into polyisoprenoids and a reduction in the formation of a lipid-linked oligosaccharide. In vivo, mevinolin in daily doses of 50 mg/kg (p.o., from days 30-48 post-infection) caused no change in gross liver pathology in S. mansoni infected mice. However, when parasites exposed to mevinolin or its vehicle in vivo were cultured in vitro, worms from mevinolin-treated mice produced six times more eggs than control parasites. When infected mice were dosed with 250 mg/kg mevinolin daily (p.o., from days 35-45 post-infection), liver pathology was reduced in comparison to control mice. Thus, during in vivo exposure to a high dose of the drug egg production is decreased, while at a lower dose it appears unaffected until the parasites are cultured in a drug-free in vitro system wherein egg production is stimulated to extraordinarily high levels. It may be that at low doses mevinolin, by inhibiting the enzyme, is blocking the formation of a product (such as an isoprenoid) which normally acts to down-regulate enzyme synthesis, resulting in enzyme induction. Induction of HMG CoA reductase is then expressed as increased egg production when the worms are removed from the drug. These data suggest that HMG CoA reductase plays a role in schistosome egg production.

VandeWaa, E.A.; Bennett, J.L.

1986-03-05

83

The Yeast AMPK Homolog SNF1 Regulates Acetyl Coenzyme A Homeostasis and Histone Acetylation  

PubMed Central

Acetyl coenzyme A (acetyl-CoA) is a key metabolite at the crossroads of metabolism, signaling, chromatin structure, and transcription. Concentration of acetyl-CoA affects histone acetylation and links intermediary metabolism and transcriptional regulation. Here we show that SNF1, the budding yeast ortholog of the mammalian AMP-activated protein kinase (AMPK), plays a role in the regulation of acetyl-CoA homeostasis and global histone acetylation. SNF1 phosphorylates and inhibits acetyl-CoA carboxylase, which catalyzes the carboxylation of acetyl-CoA to malonyl-CoA, the first and rate-limiting reaction in the de novo synthesis of fatty acids. Inactivation of SNF1 results in a reduced pool of cellular acetyl-CoA, globally decreased histone acetylation, and reduced fitness and stress resistance. The histone acetylation and transcriptional defects can be partially suppressed and the overall fitness improved in snf1? mutant cells by increasing the cellular concentration of acetyl-CoA, indicating that the regulation of acetyl-CoA homeostasis represents another mechanism in the SNF1 regulatory repertoire. PMID:24081331

Zhang, Man; Galdieri, Luciano

2013-01-01

84

Coa3 and Cox14 are essential for negative feedback regulation of COX1 translation in mitochondria  

PubMed Central

Regulation of eukaryotic cytochrome oxidase assembly occurs at the level of Cox1 translation, its central mitochondria-encoded subunit. Translation of COX1 messenger RNA is coupled to complex assembly in a negative feedback loop: the translational activator Mss51 is thought to be sequestered to assembly intermediates, rendering it incompetent to promote translation. In this study, we identify Coa3 (cytochrome oxidase assembly factor 3; Yjl062w-A), a novel regulator of mitochondrial COX1 translation and cytochrome oxidase assembly. We show that Coa3 and Cox14 form assembly intermediates with newly synthesized Cox1 and are required for Mss51 association with these complexes. Mss51 exists in equilibrium between a latent, translational resting, and a committed, translation-effective, state that are represented as distinct complexes. Coa3 and Cox14 promote formation of the latent state and thus down-regulate COX1 expression. Consequently, lack of Coa3 or Cox14 function traps Mss51 in the committed state and promotes Cox1 synthesis. Our data indicate that Coa1 binding to sequestered Mss51 in complex with Cox14, Coa3, and Cox1 is essential for full inactivation. PMID:20876281

Mick, David U.; Vukotic, Milena; Piechura, Heike; Meyer, Helmut E.; Warscheid, Bettina; Deckers, Markus

2010-01-01

85

hCOA3 Stabilizes Cytochrome c Oxidase 1 (COX1) and Promotes Cytochrome c Oxidase Assembly in Human Mitochondria*  

PubMed Central

Cytochrome c oxidase (COX) or complex IV of the mitochondrial respiratory chain plays a fundamental role in energy production of aerobic cells. In humans, COX deficiency is the most frequent cause of mitochondrial encephalomyopathies. Human COX is composed of 13 subunits of dual genetic origin, whose assembly requires an increasing number of nuclear-encoded accessory proteins known as assembly factors. Here, we have identified and characterized human CCDC56, an 11.7-kDa mitochondrial transmembrane protein, as a new factor essential for COX biogenesis. CCDC56 shares sequence similarity with the yeast COX assembly factor Coa3 and was termed hCOA3. hCOA3-silenced cells display a severe COX functional alteration owing to a decreased stability of newly synthesized COX1 and an impairment in the holoenzyme assembly process. We show that hCOA3 physically interacts with both the mitochondrial translation machinery and COX structural subunits. We conclude that hCOA3 stabilizes COX1 co-translationally and promotes its assembly with COX partner subunits. Finally, our results identify hCOA3 as a new candidate when screening for genes responsible for mitochondrial diseases associated with COX deficiency. PMID:23362268

Clemente, Paula; Peralta, Susana; Cruz-Bermudez, Alberto; Echevarría, Lucía; Fontanesi, Flavia; Barrientos, Antoni; Fernandez-Moreno, Miguel A.; Garesse, Rafael

2013-01-01

86

Mitochondrial Acetylation and Diseases of Aging  

PubMed Central

In recent years, protein lysine acetylation has emerged as a prominent and conserved regulatory posttranslational modification that is abundant on numerous enzymes involved in the processes of intermediary metabolism. Well-characterized mitochondrial processes of carbon utilization are enriched in acetyl-lysine modifications. Although seminal discoveries have been made in the basic biology of mitochondrial acetylation, an understanding of how acetylation states influence enzyme function and metabolic reprogramming during pathological states remains largely unknown. This paper will examine our current understanding of eukaryotic acetate metabolism and present recent findings in the field of mitochondrial acetylation biology. The implications of mitochondrial acetylation for the aging process will be discussed, as well as its potential implications for the unique and localized metabolic states that occur during the aging-associated conditions of heart failure and cancer growth. PMID:21437190

Wagner, Gregory R.; Payne, R. Mark

2011-01-01

87

Hydrolysis reactor for hydrogen production  

DOEpatents

In accordance with certain embodiments of the present disclosure, a method for hydrolysis of a chemical hydride is provided. The method includes adding a chemical hydride to a reaction chamber and exposing the chemical hydride in the reaction chamber to a temperature of at least about 100.degree. C. in the presence of water and in the absence of an acid or a heterogeneous catalyst, wherein the chemical hydride undergoes hydrolysis to form hydrogen gas and a byproduct material.

Davis, Thomas A.; Matthews, Michael A.

2012-12-04

88

Enzymatic fat hydrolysis and synthesis  

Microsoft Academic Search

The hydrolysis of tallow, coconut oil and olive oil, by lipase fromCandida rugosa, was studied. The reaction approximates a firstorder kinetics model. Its rate is unaffected by temperature in the range of\\u000a 26–46 C. Olive oil is more rapidly hydrolyzed compared to tallow and coconut oil. Hydrolysis is adversely affected by hydrocarbon\\u000a solvents and a nonionic surfactant. Since amounts of

Warner M. Linfield; Robert A. Barauskas; Lorraine Sivieri; Samuel Serota; Robert W. Stevenson

1984-01-01

89

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

90

A Method to Determine Lysine Acetylation Stoichiometries  

PubMed Central

Lysine acetylation is a common protein posttranslational modification that regulates a variety of biological processes. A major bottleneck to fully understanding the functional aspects of lysine acetylation is the difficulty in measuring the proportion of lysine residues that are acetylated. Here we describe a mass spectrometry method using a combination of isotope labeling and detection of a diagnostic fragment ion to determine the stoichiometry of protein lysine acetylation. Using this technique, we determined the modification occupancy for ~750 acetylated peptides from mammalian cell lysates. Furthermore, the acetylation on N-terminal tail of histone H4 was cross-validated by treating cells with sodium butyrate, a potent deacetylase inhibitor, and comparing changes in stoichiometry levels measured by our method with immunoblotting measurements. Of note we observe that acetylation stoichiometry is high in nuclear proteins, but very low in mitochondrial and cytosolic proteins. In summary, our method opens new opportunities to study in detail the relationship of lysine acetylation levels of proteins with their biological functions. PMID:25143833

Nakayasu, Ernesto S.; Wu, Si; Sydor, Michael A.; Shukla, Anil K.; Weitz, Karl K.; Moore, Ronald J.; Hixson, Kim K.; Kim, Jong-Seo; Petyuk, Vladislav A.; Monroe, Matthew E.; Pasa-Tolic, Ljiljiana; Qian, Wei-Jun; Smith, Richard D.; Adkins, Joshua N.; Ansong, Charles

2014-01-01

91

Histone acetylation and deacetylation in yeast  

Microsoft Academic Search

Histone acetylation and deacetylation in the yeast Saccharomyces cerevisiae occur by targeting acetyltransferase and deacetylase enzymes to gene promoters and, in an untargeted and global manner, by affecting most nucleosomes. Recently, new roles for histone acetylation have been uncovered, not only in transcription but also in DNA replication, repair and heterochromatin formation. Interestingly, specific acetylatable lysines can function as binding

Siavash K. Kurdistani; Michael Grunstein

2003-01-01

92

Ultrastructural aspects of the acetylation of cellulose  

Microsoft Academic Search

An ultrastructural study of the acetylation of cellulose was achieved by subjecting well characterized cellulose samples fromValonia cell wall and tunicin tests to homogeneous and heterogeneous acetylation. The study involved transmission electron microscopy observations on negatively stained microcrystals as well as diffraction contrast images of the cross sections of wall fragments at various stages of the reaction. These observations showed

Jean-François Sassi; Henri Chanzy

1995-01-01

93

Histone Acetylation in Fungal Pathogens of Plants  

PubMed Central

Acetylation of histone lysine residues occurs in different organisms ranging from yeast to plants and mammals for the regulation of diverse cellular processes. With the identification of enzymes that create or reverse this modification, our understanding on histone acetylation has expanded at an amazing pace during the last two decades. In fungal pathogens of plants, however, the importance of such modification has only just begun to be appreciated in the recent years and there is a dearth of information on how histone acetylation is implicated in fungal pathogenesis. This review covers the current status of research related to histone acetylation in plant pathogenic fungi and considers relevant findings in the interaction between fungal pathogens and host plants. We first describe the families of histone acetyltransferases and deacetylases. Then we provide the cases where histone acetylation was investigated in the context of fungal pathogenesis. Finally, future directions and perspectives in epigenetics of fungal pathogenesis are discussed. PMID:25288980

Jeon, Junhyun; Kwon, Seomun; Lee, Yong-Hwan

2014-01-01

94

Are long chain acyl CoAs responsible for suppression of mitochondrial metabolism in hibernating 13-lined ground squirrels?  

PubMed

Hibernation in 13-lined ground squirrels (Ictidomys tridecemlineatus) is associated with a substantial suppression of whole-animal metabolism. We compared the metabolism of liver mitochondria isolated from torpid ground squirrels with those from interbout euthermic (IBE; recently aroused from torpor) and summer euthermic conspecifics. Succinate-fuelled state 3 respiration, calculated relative to mitochondrial protein, was suppressed in torpor by 48% and 44% compared with IBE and summer, respectively. This suppression remains when respiration is expressed relative to cytochrome c oxidase activity. We hypothesized that this suppression was caused by inhibition of succinate transport at the dicarboxylate transporter (DCT) by long-chain fatty acyl CoAs that may accumulate during torpor. We predicted, therefore, that exogenous palmitoyl CoA would inhibit respiration in IBE more than in torpor. Palmitoyl CoA inhibited respiration ~70%, in both torpor and IBE. The addition of carnitine, predicted to reverse palmitoyl CoA suppression by facilitating its transport into the mitochondrial matrix, did not rescue the respiration rates in IBE or torpor. Liver mitochondrial activities of carnitine palmitoyl transferase did not differ among IBE, torpor and summer animals. Although palmitoyl CoA inhibits succinate-fuelled respiration, this suppression is likely not related exclusively to inhibition of the DCT, and may involve additional mitochondrial transporters such as the adenine-nucleotide transporter. PMID:24561259

Cooper, Alex N; Brown, Jason C L; Staples, James F

2014-04-01

95

HYDROLYSIS OF CHLOROSTILBENE OXIDE: I. HYDROLYSIS IN HOMOGENEOUS SYSTEMS  

EPA Science Inventory

The hydrolysis kinetics of 4-chlorostilbene oxide (CSO) in buffered distilled water, in natural waters, and in sediment associated water are reported. he disappearance of CSO followed pseudo-first-order kinetics in buffered water over the experimental pH range of 3 to 11. elow pH...

96

Stability of acetyl-1-carnitine in 5% dextrose using a high-performance liquid chromatography-mass spectrometry times 2 method.  

PubMed

A stability-indicating high-performance liquid chromatography-mass spectrometry times 2 method was developed to establish the stability of acetyl-l-carnitine dissolved in 5% dextrose in water; quantitation of acetyl-l-carnitine and its hydrolysis product I-carnitine was performed using this method. Acetyl-l-carnitine dissolved in water was stress-degraded at a pH range of 3 to 12, and conversion to l-carnitine was quantified over 18 hours. The method was further validated by stressing the acetyl-l-carnitine solution at 68 degrees C, 82 degrees C, and 90 degrees C for up to 10 days, yielding a temperature-dependent hydrolysis rate constant. Acetyl-l-carnitine solutions were stored at 25 degrees C and 4 degrees C to 8 degrees C for 33 days to validate the kinetics prediction. The liquid chromatography-mass spectrometry times 2 method was sensitive and specific, allowing rapid separation and simultaneous quantitation of acetyl-l-carnitine and l-carnitine. Acetyl-l-carnitine dissolved in aqueous solutions is stable at neutral to acidic pH, but unstable at pH > 9. After 1 hour storage at room temperature, only 72.6% of acetyl-l-carnitine was left at pH 11 and 4.2% left at pH 12. The kinetics relationship between temperature and rate constant was In(k) = -8650.1 /T + 20.344 (r2 = 0.9851) at pH 5.2. The time required to degrade 15% of acetyl-I-carnitine was estimated to be 38 days at 25 degrees C or 234 days at 8 degrees C, and was confirmed with actual storage stability testing. Acetyl-l-carnitine dissolved in water (pH 5.2) at concentrations of 1 and 10 mg/mL was found stable at room temperature or refrigerated for at least 33 days using the established stability-indicating method. Acetyl-l-carnitine solutions are not stable at basic pH. When reconstituted in water, acetyl-l-carnitine is stable for over 30 days at room temperature or under refrigeration. PMID:23050330

Zhang, Yang; Jiang, Hongliang; Hutson, Paul

2012-01-01

97

Development and validation of an LC-MS/MS method for the toxicokinetic study of deoxynivalenol and its acetylated derivatives in chicken and pig plasma.  

PubMed

This study aims to develop an LC-MS/MS method allowing the determination of 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, deoxynivalenol and its main in vivo metabolite, deepoxy-deoxynivalenol, in broiler chickens and pigs. These species have a high exposure to these toxins, given their mainly cereal based diet. Several sample cleanup strategies were tested and further optimized by means of fractional factorial designs. A simple and straightforward sample preparation method was developed consisting out of a deproteinisation step with acetonitrile, followed by evaporation of the supernatant and reconstitution in water. The method was single laboratory validated according to European guidelines and found to be applicable for the intended purpose, with a linear response up to 200ngml(-1) and limits of quantification of 0.1-2ngml(-1). As a proof of concept, biological samples from a broiler chicken that received either deoxynivalenol, 3- or 15-acetyl-deoxynivalenol were analyzed. Preliminary results indicate nearly complete hydrolysis of 3-acetyl-deoxynivalenol to deoxynivalenol; and to a lesser extent of 15-acetyl-deoxynivalenol to deoxynivalenol. No deepoxy-deoxynivalenol was detected in any of the plasma samples. The method will be applied to study full toxicokinetic properties of deoxynivalenol, 3-acetyl-deoxynivalenol and 15-acetyl-deoxynivalenol in broiler chickens and pigs. PMID:25264912

Broekaert, N; Devreese, M; De Mil, T; Fraeyman, S; De Baere, S; De Saeger, S; De Backer, P; Croubels, S

2014-11-15

98

Acetylation of rice straw for thermoplastic applications.  

PubMed

An inexpensive and biodegradable thermoplastic was developed through acetylation of rice straw (RS) with acetic anhydride. Acetylation conditions were optimized. The structure and properties of acetylated RS were characterized by fourier transform infrared (FTIR), solid-state (13)C NMR spectroscopy, X-ray diffractometer (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results showed that acetylation of RS has successfully taken place, and comparing with raw RS, the degree of crystallinity decreased and the decomposition rate was slow. The acetylated RS has got thermoplasticity when weight ratio of RS and acetic anhydride was 1:3, using sulphuric acid (9% to RS) as catalyst in glacial acetic acid 35°C for 12h, and the dosage of solvent was 9 times RS, in which weight percent gain (WPG) of the modified RS powder was 35.5% and its percent acetyl content was 36.1%. The acetylated RS could be formed into transparent thin films with different amount of plasticizer diethyl phthalate (DEP) using tape casting technology. PMID:23688473

Zhang, Guangzhi; Huang, Kai; Jiang, Xue; Huang, Dan; Yang, Yiqi

2013-07-01

99

ABIOTIC HYDROLYSIS OF SORBED PESTICIDES  

EPA Science Inventory

The hydrolysis of pesticides that are sorbed to sterilized natural sediments has been investigated in aqueous systems at acid, neutral and alkaline pH's. The results show that the rate constants of pH independent ('neutral') hydrolyses are the same within experimental uncertainti...

100

Economics of enzymatic hydrolysis processes  

SciTech Connect

Enzymatic hydrolysis processes have the ability to produce high yields of sugars for fermentation to fuel ethanol from lignocellulosic biomass. However, these systems have been plagued with yields, product concentrations, and reactions rates far below those that are theoretically possible. Engineering and economic analyses are presented on several fungal enzyme hydrolysis processes to illustrate the effects of the important process parameters, to quantify the progress that has been made to date, and to estimate the cost reductions that can be made through research improvements. All enzymatic hydrolysis processes require pretreatment, hydrolysis, fermentation, and enzyme production. The key effect of pretreatment is to allow access of the enzymes to the substrate. Pretreatments have been devised that make the biomass completely digestible that increase the xylose yield and concentration, and that integrate pretreatment with lignin utilization. Major improvements in enzyme activity and use of simultaneous saccharification and fermentation (SSF) have greatly reduced the inhibition of the enzymes. It now appears that ethanol inhibition of the yeast is the limiting factor. Enzyme production costs have been dramatically reduced because use of SSF has reduced enzyme loading. However, further improvements may be possible by using soluble carbon sources for production. Over the past decade, the predicted cost of ethanol from such processes has dropped from more than $4.00/gallon to approximately $1.60. Research is currently under way in the United States and has the potential to reduce the projected cost to less than $1.00/gallon. 65 refs., 16 figs., 1 tab.

Wright, J.D.

1988-02-01

101

Insulin Signaling Regulates Fatty Acid Catabolism at the Level of CoA Activation  

PubMed Central

The insulin/IGF signaling pathway is a highly conserved regulator of metabolism in flies and mammals, regulating multiple physiological functions including lipid metabolism. Although insulin signaling is known to regulate the activity of a number of enzymes in metabolic pathways, a comprehensive understanding of how the insulin signaling pathway regulates metabolic pathways is still lacking. Accepted knowledge suggests the key regulated step in triglyceride (TAG) catabolism is the release of fatty acids from TAG via the action of lipases. We show here that an additional, important regulated step is the activation of fatty acids for beta-oxidation via Acyl Co-A synthetases (ACS). We identify pudgy as an ACS that is transcriptionally regulated by direct FOXO action in Drosophila. Increasing or reducing pudgy expression in vivo causes a decrease or increase in organismal TAG levels respectively, indicating that pudgy expression levels are important for proper lipid homeostasis. We show that multiple ACSs are also transcriptionally regulated by insulin signaling in mammalian cells. In sum, we identify fatty acid activation onto CoA as an important, regulated step in triglyceride catabolism, and we identify a mechanistic link through which insulin regulates lipid homeostasis. PMID:22275878

Xu, Xiaojun; Gopalacharyulu, Peddinti; Seppänen-Laakso, Tuulikki; Ruskeepää, Anna-Liisa; Aye, Cho Cho; Carson, Brian P.; Mora, Silvia; Oreši?, Matej; Teleman, Aurelio A.

2012-01-01

102

Efficient incorporation of CoA, NAD and FAD into RNA by in vitro transcription  

PubMed Central

Protein enzymes frequently recruit small molecule coenzymes to perform a variety of biochemical reactions. While the catalytic activities of RNA have been expanding rapidly, a similar strategy for RNA to utilize coenzymes and to increase its functional capabilities has yet to be demonstrated. A general in vitro transcription procedure has been developed to efficiently prepare RNA with coenzymes CoA, NAD and FAD covalently attached to the 5? end. These adenosine-containing coenzymes initiate transcription under the T7 class II promoter by T7 RNA polymerase. In addition to the three coenzymes, other adenosine-containing molecules may be incorporated into the first nucleotide position of RNA as well. This method provides easy access to CoA–, NAD– and FAD–RNA, which may find broad applications in generating coenzyme- utilizing ribozymes. In addition, both oxidized FAD and reduced NADH are highly fluorescent. NADH–RNA and FAD–RNA can therefore be used as probes for DNA/RNA detection and for structural investigation of RNA function by fluorescence spectroscopy. PMID:12560511

Huang, Faqing

2003-01-01

103

A Case of Dilated Cardiomyopathy Associated with 3-Hydroxy-3-Methylglutaryl-Coenzyme A (HMG CoA) Lyase Deficiency  

PubMed Central

3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) lyase deficiency is an inborn error of metabolism characterized by impairment of ketogenesis and leucine catabolism resulting in an organic acidopathy. In 1994, a case of dilated cardiomyopathy and fatal arrhythmia was reported in a 7-month-old infant. We report a case of dilated cardiomyopathy in association with HMG CoA lyase deficiency in a 23-year-old man with the acute presentation of heart failure. To our knowledge, this is the first case reported in an adult. PMID:19893767

Leung, Alexander A. C.; Chan, Alicia K.; Ezekowitz, Justin A.; Leung, Alexander K. C.

2009-01-01

104

Kinetics of the Hydrolysis of Atmospherically Relevant  

E-print Network

Kinetics of the Hydrolysis of Atmospherically Relevant Isoprene-Derived Hydroxy Epoxides N E I L C and that these epoxides are likely to undergo efficient acid- catalyzed hydrolysis on SOA to 2-methyl-1, the specifichydroxyepoxidesobservedintheisoprenephotooxidation experiment (as well as several other related species) were synthesized, and the hydrolysis

Elrod, Matthew J.

105

OUTCROP-BASED HIGH RESOLUTION GAMMA-RAY CHARACTERIZATION OF ARSENIC-BEARING LITHOFACIES IN THE PERMIAN GARBER SANDSTONE AND WELLINGTON FORMATION, CENTRAL OKLAHOMA AQUIFER (COA). CLEVELAND COUNTY, OKLAHOMA  

EPA Science Inventory

The COA supplies drinking water to a number of municipalities in central Oklahoma. Two major stratigraphic units in the COA, the Garber Sandstone and Wellington Formation, contain naturally occurring arsenic that exceeds government mandated drinking-water standards (EPA, 2001). ...

106

Structure of Mycobacterium tuberculosis phosphopantetheine adenylyltransferase in complex with the feedback inhibitor CoA reveals only one active-site conformation  

SciTech Connect

Phosphopantetheine adenylyltransferase (PPAT) catalyzes the penultimate step in the coenzyme A (CoA) biosynthetic pathway, reversibly transferring an adenylyl group from ATP to 4'-phosphopantetheine to form dephosphocoenzyme A (dPCoA). To complement recent biochemical and structural studies on Mycobacterium tuberculosis PPAT (MtPPAT) and to provide further insight into the feedback regulation of MtPPAT by CoA, the X-ray crystal structure of the MtPPAT enzyme in complex with CoA was determined to 2.11 {angstrom} resolution. Unlike previous X-ray crystal structures of PPAT-CoA complexes from other bacteria, which showed two distinct CoA conformations bound to the active site, only one conformation of CoA is observed in the MtPPAT-CoA complex.

Wubben, T.; Mesecar, A.D. (Purdue); (UIC)

2014-10-02

107

GENES ENCODING PLASTID ACETYL-COA CARBOXYLASE AND 3-PHOSPHOGLYCERATE KINASE OF THE TRITICUM/AEGILOPS COMPLEX AND THE EVOLUTIONARY HISTORY OF POLYPLOID WHEAT.  

Technology Transfer Automated Retrieval System (TEKTRAN)

The classic wheat evolutionary history is one of adaptive radiation of the diploid Triticum/Aegilops species (A, S, D) , genome convergence and divergence of the tetraploid (T. turgidum AABB, and T. timopheevii AAAGG) and hexaploid (T. aestivum, AABBDD) species. The objective of this study was to a...

108

4-Acetyl­piperazinium picrate  

PubMed Central

In the title salt, C6H13N2O+·C6H2N3O7 ? (systematic name: 4-acetyl­piperazin-1-ium 2,4,6-tri­nitro­phenolate), the piperazin-1-ium ring has a slightly distorted chair conformation. In the picrate anion, the mean planes of the two o-NO2 and p-NO2 groups are twisted with respect to the benzene ring by 15.0?(2), 68.9?(4) and 4.4?(3)°, respectively. In the crystal, N—H?O hydrogen bonds are observed, linking the ions into an infinite chain along [010]. In addition, weak cation–anion C—H?O inter­molecular inter­actions and a weak ?–? stacking inter­action between the benzene rings of the anions, with an inter-centroid distance of 3.771?(8)?Ĺ, help to stabilize the crystal packing, giving an overall sheet structure lying parallel to (100). Disorder was modelled for one of the O atoms in one of the o-NO2 groups over two sites with an occupancy ratio of 0.57?(6):0.43?(6). PMID:24940287

Kavitha, Channappa N.; Kaur, Manpreet; Jasinski, Jerry P.; Yathirajan, Hemmige S.

2014-01-01

109

Studies on the Mechanism of Ring Hydrolysis in Phenylacetate Degradation  

PubMed Central

The widespread, long sought-after bacterial aerobic phenylalanine/phenylacetate catabolic pathway has recently been elucidated. It proceeds via coenzyme A (CoA) thioesters and involves the epoxidation of the aromatic ring of phenylacetyl-CoA, subsequent isomerization to an uncommon seven-membered C-O-heterocycle (oxepin-CoA), and non-oxygenolytic ring cleavage. Here we characterize the hydrolytic oxepin-CoA ring cleavage catalyzed by the bifunctional fusion protein PaaZ. The enzyme consists of a C-terminal (R)-specific enoyl-CoA hydratase domain (formerly MaoC) that cleaves the ring and produces a highly reactive aldehyde and an N-terminal NADP+-dependent aldehyde dehydrogenase domain that oxidizes the aldehyde to 3-oxo-5,6-dehydrosuberyl-CoA. In many phenylacetate-utilizing bacteria, the genes for the pathway exist in a cluster that contains an NAD+-dependent aldehyde dehydrogenase in place of PaaZ, whereas the aldehyde-producing hydratase is encoded outside of the cluster. If not oxidized immediately, the reactive aldehyde condenses intramolecularly to a stable cyclic derivative that is largely prevented by PaaZ fusion in vivo. Interestingly, the derivative likely serves as the starting material for the synthesis of antibiotics (e.g. tropodithietic acid) and other tropone/tropolone related compounds as well as for ?-cycloheptyl fatty acids. Apparently, bacteria made a virtue out of the necessity of disposing the dead-end product with ring hydrolysis as a metabolic branching point. PMID:21296885

Teufel, Robin; Gantert, Carla; Voss, Michaela; Eisenreich, Wolfgang; Haehnel, Wolfgang; Fuchs, Georg

2011-01-01

110

Kinetics of hyaluronan hydrolysis in acidic solution at various pH values.  

PubMed

Hyaluronic acid (HA) was hydrolyzed using varying temperatures (40, 60, and 80 degrees C) and acid concentrations (0.0010, 0.010, 0.10, 0.50, 1.0, and 2.0 M HCl). The degradation process was monitored by determination of weight average molecular weight ( M w) by size-exclusion chromatography with online multiangle laser light scattering, refractive index, and intrinsic viscosity detectors (SEC-MALLS-RI-visc) on samples taken out continuously during the hydrolysis. SEC-MALLS-RI-visc showed that the degradation gave narrow molecular weight distributions with polydispersity indexes ( M w/ M n) of 1.3-1.7. Kinetic plots of 1/ M w versus time gave linear plots showing that acid hydrolysis of HA is a random process and that it follows a first order kinetics. For hydrolysis in HCl at 60 and 80 degrees C, it was shown that the kinetic rate constant ( k h) for the degradation depended linearly on the acid concentration. Further, the dependence of temperature on the hydrolysis in 0.1 M HCl was found to give a linear Arrhenius plot (ln k h vs 1/ T), with an activation energy ( E a) of 137 kJ/mol and Arrhenius constant ( A) of 7.86 x 10 (15) h (-1). (1)H NMR spectroscopy was used to characterize the product of extensive hydrolysis (48 h at 60 degrees C in 0.1 M HCl). No indication of de- N-acetylation of the N-acetyl glucosamine (GlcNAc) units or other byproducts were seen. Additionally, a low molecular weight HA was hydrolyzed in 0.1 M DCl for 4 h at 80 degrees C. It was shown that it was primarily the beta-(1-->4)-linkage between GlcNAc and glucuronic acid (GlcA) that was cleaved during hydrolysis at pH < p K a,GlcA. The dependence of the hydrolysis rate constant was further studied as a function of pH between -0.3 and 5. The degradation was found to be random (linear kinetic plots) over the entire pH range studied. Further, the kinetic rate constant was found to depend linearly on pH in the region -0.3 to 3. Above this pH (around the p K a of HA), the kinetic constant decreased more slowly, probably due to either a change in polymer conformation or due to an increased affinity for protons due to the polymer becoming charged as the GlcA units dissociated. PMID:18452332

Třmmeraas, Kristoffer; Melander, Claes

2008-06-01

111

DOWN-REGULATION OF CINNAMOYL-COA REDUCTASE (CCR) IN POPLAR INVESTIGATED WITH CHEMOMETRICS AND 2D-NMR  

Technology Transfer Automated Retrieval System (TEKTRAN)

An understanding of the lignification process is of vital importance, especially for the pulp and paper industry. Cinnamoyl-coa reductase (CCR) is an enzyme that plays a central role in the lignification process. Previous results have shown that down-regulation of CCR decreases the lignin content. B...

112

Lysozyme conjugate immune complex formation and the effects on substrate hydrolysis.  

PubMed

The defined estrone glucuronide-lysozyme conjugate E3, that is acylated solely at K33, was used as a probe for the steric requirements of the active site cleft of chicken type lysozymes. When the immune complex was formed with an anti-estrone glucuronide antiserum, the rate of lysis of the E3 conjugate with the large bacterial substrate Micrococcus lysodeikticus was inhibited by over 90%. However, when the small hexamer of N-acetyl glucosamine was used as the substrate, the rate of hydrolysis by the immune complex was accelerated by 350% compared with the control rate. Thus, inhibition by the anti-estrone glucuronide cannot be caused simply by steric occlusion of the active site. Other factor(s) in the immune complex activate the hydrolysis reaction, most likely by favouring the conformations that lead to the transition state. PMID:12727231

Smales, C Mark; Blackwell, Leonard F

2003-05-16

113

Stearoyl CoA Desaturase 1: Role in Cellular Inflammation and Stress12  

PubMed Central

Stearoyl CoA desaturase 1 (SCD1) catalyzes the rate-limiting step in the production of MUFA that are major components of tissue lipids. Alteration in SCD1 expression changes the fatty acid profile of these lipids and produces diverse effects on cellular function. High SCD1 expression is correlated with metabolic diseases such as obesity and insulin resistance, whereas low levels are protective against these metabolic disturbances. However, SCD1 is also involved in the regulation of inflammation and stress in distinct cell types, including ?-cells, adipocytes, macrophages, endothelial cells, and myocytes. Furthermore, complete loss of SCD1 expression has been implicated in liver dysfunction and several inflammatory diseases such as dermatitis, atherosclerosis, and intestinal colitis. Thus, normal cellular function requires the expression of SCD1 to be tightly controlled. This review summarizes the current understanding of the role of SCD1 in modulating inflammation and stress. PMID:22211186

Liu, Xueqing; Strable, Maggie S.; Ntambi, James M.

2011-01-01

114

Tandem mass spectrometry and nuclear magnetic resonance spectroscopy studies of Candida bombicola sophorolipids and product formed on hydrolysis by cutinase.  

PubMed

Natural mixtures of sophorolipids produced by the yeast Candida bombicola have been analyzed by fast atom bombardment (FAB)-MS and collision-induced dissociation (CID)-MS. Some pure components have been analysed by two-dimensional NMR spectroscopy. The presence of acidic, lactonic, and O-acetylated forms and the position of double bonds in the fatty acid part of these glycolipids can be easily inferred from positive and negative ion FAB-mass spectra. Details about position of O-acetylation can be obtained from CID mass spectra of [M+H]+ and [M-H]- ions and from the NMR spectra. Differences in CID fragmentation between protonated and sodiated molecular ions are discussed in detail. Enzymatic hydrolysis of 6',6"-di-O-acetyl sophorolipid lactone by cutinase from Fusarium solani results specifically in the removal of the 6'-O-acetyl group, whereas the 6"-O-acetyl and lactone group are resistant. This specificity is explained from a three-dimensional model of the sophorolipid generated on the basis of the short 1H,1H distances as inferred from the NMR (ROESY) spectra. PMID:8585609

de Koster, C G; Heerma, W; Pepermans, H A; Groenewegen, A; Peters, H; Haverkamp, J

1995-09-01

115

Structural, Kinetic and Proteomic Characterization of Acetyl Phosphate-Dependent Bacterial Protein Acetylation  

PubMed Central

The emerging view of N?-lysine acetylation in eukaryotes is of a relatively abundant post-translational modification (PTM) that has a major impact on the function, structure, stability and/or location of thousands of proteins involved in diverse cellular processes. This PTM is typically considered to arise by the donation of the acetyl group from acetyl-coenzyme A (acCoA) to the ?-amino group of a lysine residue that is reversibly catalyzed by lysine acetyltransferases and deacetylases. Here, we provide genetic, mass spectrometric, biochemical and structural evidence that N?-lysine acetylation is an equally abundant and important PTM in bacteria. Applying a recently developed, label-free and global mass spectrometric approach to an isogenic set of mutants, we detected acetylation of thousands of lysine residues on hundreds of Escherichia coli proteins that participate in diverse and often essential cellular processes, including translation, transcription and central metabolism. Many of these acetylations were regulated in an acetyl phosphate (acP)-dependent manner, providing compelling evidence for a recently reported mechanism of bacterial N?-lysine acetylation. These mass spectrometric data, coupled with observations made by crystallography, biochemistry, and additional mass spectrometry showed that this acP-dependent acetylation is both non-enzymatic and specific, with specificity determined by the accessibility, reactivity and three-dimensional microenvironment of the target lysine. Crystallographic evidence shows acP can bind to proteins in active sites and cofactor binding sites, but also potentially anywhere molecules with a phosphate moiety could bind. Finally, we provide evidence that acP-dependent acetylation can impact the function of critical enzymes, including glyceraldehyde-3-phosphate dehydrogenase, triosephosphate isomerase, and RNA polymerase. PMID:24756028

Sahu, Alexandria; Sorensen, Dylan; Minasov, George; Lima, Bruno P.; Scholle, Michael; Mrksich, Milan; Anderson, Wayne F.; Gibson, Bradford W.; Schilling, Birgit; Wolfe, Alan J.

2014-01-01

116

HYDROLYSIS  

EPA Science Inventory

Hydrolytic processes provide the baseline loss rate for any chemical in an aqueous envi- ronment. Although various hydrolytic pathways account for significant degradation of certain classes of organic chemicals, other organic structures are completely inert. Strictly speaking, hy...

117

Histone Acetylation Regulates Intracellular pH  

PubMed Central

SUMMARY Differences in global levels of histone acetylation occur in normal and cancer cells, although the reason why cells regulate these levels has been unclear. Here we demonstrate a role for histone acetylation in regulating intracellular pH (pHi). As pHi decreases, histones are globally deacetylated by histone deacetylases (HDACs), and the released acetate anions are coexported with protons out of the cell by monocarboxylate transporters (MCTs), preventing further reductions in pHi. Conversely, global histone acetylation increases as pHi rises, such as when resting cells are induced to proliferate. Inhibition of HDACs or MCTs decreases acetate export and lowers pHi, particularly compromising pHi maintenance in acidic environments. Global deacetylation at low pH is reflected at a genomic level by decreased abundance and extensive redistribution of acetylation throughout the genome. Thus, acetylation of chromatin functions as a rheostat to regulate pHi with important implications for mechanism of action and therapeutic use of HDAC inhibitors. PMID:23201122

McBrian, Matthew A.; Behbahan, Iman Saramipoor; Ferrari, Roberto; Su, Trent; Huang, Ta-Wei; Li, Kunwu; Hong, Candice S.; Christofk, Heather R.; Vogelauer, Maria; Seligson, David B.; Kurdistani, Siavash K.

2014-01-01

118

Acetyl-L-carnitine in hepatic encephalopathy.  

PubMed

Hepatic encephalopathy is a common complication of hepatic cirrhosis. The clinical diagnosis is based on two concurrent types of symptoms: impaired mental status and impaired neuromotor function. Impaired mental status is characterized by deterioration in mental status with psychomotor dysfunction, impaired memory, and increased reaction time, sensory abnormalities, poor concentration, disorientation and coma. Impaired neuromotor function include hyperreflexia, rigidity, myoclonus and asterixis. The pathogenesis of hepatic encephalopathy has not been clearly defined. The general consensus is that elevated levels of ammonia and an inflammatory response work in synergy to cause astrocyte to swell and fluid to accumulate in the brain which is thought to explain the symptoms of hepatic encephalopathy. Acetyl-L-carnitine, the short-chain ester of carnitine is endogenously produced within mitochondria and peroxisomes and is involved in the transport of acetyl-moieties across the membranes of these organelles. Acetyl-L-carnitine administration has shown the recovery of neuropsychological activities related to attention/concentration, visual scanning and tracking, psychomotor speed and mental flexibility, language short-term memory, attention, and computing ability. In fact, Acetyl-L-carnitine induces ureagenesis leading to decreased blood and brain ammonia levels. Acetyl-L-carnitine treatment decreases the severity of mental and physical fatigue, depression cognitive impairment and improves health-related quality of life. The aim of this review was to provide an explanation on the possible toxic effects of ammonia in HE and evaluate the potential clinical benefits of ALC. PMID:23389620

Malaguarnera, Michele

2013-06-01

119

Role of acetylation in colorectal cancer.  

PubMed

Acetylator phenotype is a common genetic trait in humans as well as other mammals. It results from the presence of several mutations in one of the genes encoding for arylamine N-acetyltransferase. The polymorphism has been associated with several disease states including colorectal cancer. Several epidemiological studies suggest that rapid acetylators are more susceptible to colorectal cancer than slow acetylators. Moreover, individuals that are both rapid acetylators and exhibit a high cytochrome P450 1A2 activity appear to have an even higher risk of colorectal cancer. These observations not only suggest an interesting genetic link to non-familial colon cancer but also suggest that carcinogens that are activated by N-acetyltransferase and cytochrome P450 1A2 may contribute to the etiology of this disease. Heterocyclic amines present in cooked food such as "well done" red meat are carcinogenic in experimental animals forming tumours in several target tissues including the small intestines. We have shown that human polymorphic N-acetyltransferase is present in human colon tissue and that it is capable of activating several heterocyclic amine carcinogens present in cooked food. These studies provide good circumstantial evidence that rapid acetylators may be predisposed to colorectal cancer. PMID:7694097

Minchin, R F; Kadlubar, F F; Ilett, K F

1993-11-01

120

Beating the acetyl coenzyme A-pathway to the origin of life  

PubMed Central

Attempts to draft plausible scenarios for the origin of life have in the past mainly built upon palaeogeochemical boundary conditions while, as detailed in a companion article in this issue, frequently neglecting to comply with fundamental thermodynamic laws. Even if demands from both palaeogeochemistry and thermodynamics are respected, then a plethora of strongly differing models are still conceivable. Although we have no guarantee that life at its origin necessarily resembled biology in extant organisms, we consider that the only empirical way to deduce how life may have emerged is by taking the stance of assuming continuity of biology from its inception to the present day. Building upon this conviction, we have assessed extant types of energy and carbon metabolism for their appropriateness to conditions probably pertaining in those settings of the Hadean planet that fulfil the thermodynamic requirements for life to come into being. Wood–Ljungdahl (WL) pathways leading to acetyl CoA formation are excellent candidates for such primordial metabolism. Based on a review of our present understanding of the biochemistry and biophysics of acetogenic, methanogenic and methanotrophic pathways and on a phylogenetic analysis of involved enzymes, we propose that a variant of modern methanotrophy is more likely than traditional WL systems to date back to the origin of life. The proposed model furthermore better fits basic thermodynamic demands and palaeogeochemical conditions suggested by recent results from extant alkaline hydrothermal seeps. PMID:23754811

Nitschke, Wolfgang; Russell, Michael J.

2013-01-01

121

Engineering Acetyl Coenzyme A Supply: Functional Expression of a Bacterial Pyruvate Dehydrogenase Complex in the Cytosol of Saccharomyces cerevisiae  

PubMed Central

ABSTRACT The energetic (ATP) cost of biochemical pathways critically determines the maximum yield of metabolites of vital or commercial relevance. Cytosolic acetyl coenzyme A (acetyl-CoA) is a key precursor for biosynthesis in eukaryotes and for many industrially relevant product pathways that have been introduced into Saccharomyces cerevisiae, such as isoprenoids or lipids. In this yeast, synthesis of cytosolic acetyl-CoA via acetyl-CoA synthetase (ACS) involves hydrolysis of ATP to AMP and pyrophosphate. Here, we demonstrate that expression and assembly in the yeast cytosol of an ATP-independent pyruvate dehydrogenase complex (PDH) from Enterococcus faecalis can fully replace the ACS-dependent pathway for cytosolic acetyl-CoA synthesis. In vivo activity of E. faecalis PDH required simultaneous expression of E. faecalis genes encoding its E1?, E1?, E2, and E3 subunits, as well as genes involved in lipoylation of E2, and addition of lipoate to growth media. A strain lacking ACS that expressed these E. faecalis genes grew at near-wild-type rates on glucose synthetic medium supplemented with lipoate, under aerobic and anaerobic conditions. A physiological comparison of the engineered strain and an isogenic Acs+ reference strain showed small differences in biomass yields and metabolic fluxes. Cellular fractionation and gel filtration studies revealed that the E. faecalis PDH subunits were assembled in the yeast cytosol, with a subunit ratio and enzyme activity similar to values reported for PDH purified from E. faecalis. This study indicates that cytosolic expression and assembly of PDH in eukaryotic industrial microorganisms is a promising option for minimizing the energy costs of precursor supply in acetyl-CoA-dependent product pathways. PMID:25336454

Kozak, Barbara U.; van Rossum, Harmen M.; Luttik, Marijke A. H.; Akeroyd, Michiel; Benjamin, Kirsten R.; Wu, Liang; de Vries, Simon; Daran, Jean-Marc; Pronk, Jack T.

2014-01-01

122

Enhancement of lysine acetylation accelerates wound repair.  

PubMed

In physiopathological conditions, such as diabetes, wound healing is significantly compromised and chronic complications, including ulcers, may occur. In a mouse model of skin repair, we recently reported that wound treatment with Sirtuin activators and class I HDAC inhibitors induced keratinocyte proliferation and enhanced healing via a nitric oxide (NO) dependent mechanism. We observed an increase in total protein acetylation in the wound area, as determined by acetylation of ?-tubulin and histone H3 Lysine 9. We reasoned that this process activated cell function as well as regulated gene expression to foster tissue repair. We report here that the direct activation of P300/CBP-associated factor (PCAF) by the histone acetylase activator pentadecylidenemalonate 1b (SPV-106) induced Lysine acetylation in the wound area. This intervention was sufficient to enhance repair process by a NO-independent mechanism. Hence, an impairment of PCAF and/or other GCN5 family acetylases may delay skin repair in physiopathological conditions. PMID:24265859

Spallotta, Francesco; Cencioni, Chiara; Straino, Stefania; Sbardella, Gianluca; Castellano, Sabrina; Capogrossi, Maurizio C; Martelli, Fabio; Gaetano, Carlo

2013-09-01

123

Ubiquitin acetylation inhibits polyubiquitin chain elongation.  

PubMed

Ubiquitylation is a versatile post-translational modification (PTM). The diversity of ubiquitylation topologies, which encompasses different chain lengths and linkages, underlies its widespread cellular roles. Here, we show that endogenous ubiquitin is acetylated at lysine (K)-6 (AcK6) or K48. Acetylated ubiquitin does not affect substrate monoubiquitylation, but inhibits K11-, K48-, and K63-linked polyubiquitin chain elongation by several E2 enzymes in vitro. In cells, AcK6-mimetic ubiquitin stabilizes the monoubiquitylation of histone H2B-which we identify as an endogenous substrate of acetylated ubiquitin-and of artificial ubiquitin fusion degradation substrates. These results characterize a mechanism whereby ubiquitin, itself a PTM, is subject to another PTM to modulate mono- and polyubiquitylation, thus adding a new regulatory layer to ubiquitin biology. PMID:25527407

Ohtake, Fumiaki; Saeki, Yasushi; Sakamoto, Kensaku; Ohtake, Kazumasa; Nishikawa, Hiroyuki; Tsuchiya, Hikaru; Ohta, Tomohiko; Tanaka, Keiji; Kanno, Jun

2015-02-01

124

Acid Hydrolysis of Trioxalatocobaltate (III) Ion  

ERIC Educational Resources Information Center

Describes an investigation involving acid hydrolysis and using both volumetric and kinetic techniques. Presents examples of the determination of the rate constant and its variation with temperature. (GS)

Wiggans, P. W.

1975-01-01

125

Acetylation of bleached Kraft pulp: effect of xylan content on properties of acetylated compounds.  

PubMed

Bleached Kraft pulp (BKP) from Eucalyptus globulus and cotton xylan blends (CXB) was acetylated. The effects of xylan content on cellulose acetylation and the properties of the acetylated material were studied. An increase in xylan content caused a slight decrease in the degree of substitution (2.98 to 2.68 for CXB; 2.93 to 2.84 for BKP). Thermal analysis showed that the melting temperature also decreases from 268.0 to 188.8 °C for CXB and from 221.4 to 212.8 °C for BKP. Moreover, the solubility decreased due to the partial dissolution of acetylated xylans. The presence of xylans during Kraft pulp acetylation does not have a significant negative effect on the physical properties of the acetylated material, but the decrease in melting temperature was beneficial for the application of acetylated polymer as a natural internal plasticizer. This is considered to be an important argument for BKP utilization in the cellulose acetate manufacturing process. PMID:25498729

Peredo, Karol; Reyes, Herna; Escobar, Danilo; Vega-Lara, Johana; Berg, Alex; Pereira, Miguel

2015-03-01

126

Enzymatic conversion of diacetylated sophoroselipid into acetylated glucoselipid: surface-active properties of novel bolaform biosurfactants.  

PubMed

Sophoroselipids (SL) are bolaform biosurafactants which are abundantly produced by microorganisms from renewable resources. In this study, four kinds of bolaform biosurfactants were produced, and these derivatives were chemoenzymatically synthesized from "acid form" diacetylated SL (SLdiAc), which are preferentially produced by Candida floricola TM 1502 which was newly found in our group. The effects of the structure of sugar moiety on their surface-active properties were investigated by surface tension measurement. After microbial production of SLdiAc from oleic acid/glucose, SLdiAc was converted into acetylated glucoselipid (GLAc). Among twelve species of glucosidases, pectinase and pectolyase including polygalacturonase were found to cleave the beta-1,2-glycosidic linked disaccharide, especially pectolyase produced GLAc effectively at 40 degrees C and pH 4.0. The structure of the major component of purified GLAc was assigned as 17- [(beta-D-glucopyranosyl)oxy]-cis-9-octadecenoate 6'-acetate by using NMR analyses, MALDI-TOF/MS and GC-MS. Glucoselipid (GL) without acetyl group was also enzymatically converted from SL obtained from alkaline hydrolysis of SLdiAc. Interestingly, the estimated CMC values of SLdiAc, SL, GLAc, GL indicated almost the same values despite their difference in hydrophilic structure. Although the difference in monosaccaride and disaccharide also did not affect gammaCMC, the presence of acetyl group on sugar moiety was found to lower the gammaCMC value slightly, suggesting that the acetyl group on produced bolaform biosurfactant is likely to play more important role to reduce the free energy of air/water interface. PMID:20720380

Imura, Tomohiro; Masuda, Yuma; Minamikawa, Hiroyuki; Fukuoka, Tokuma; Konishi, Masaaki; Morita, Tomotake; Sakai, Hideki; Abe, Masahiko; Kitamoto, Dai

2010-01-01

127

Retarded hydrolysis-condensing reactivity of tetrabutyl titanate by acetylacetone and the application in dye-sensitized solar cells  

SciTech Connect

Graphical abstract: - Highlights: • Effect of acetone acetyl on coarsening rate of TiO{sub 2} nanocrystallites was studied. • Hydrolysis reactivity of alkoxide was retarded with addition of acetone acetyl. • Coarsening rate of TiO{sub 2} nanocrystallites is retarded with addition of acetone acetyl. • The synthesized TiO{sub 2} sols were utilized in dye sensitized solar cells. • Small particles formed by Ti-complexes were beneficial for device performance. - Abstract: TiO{sub 2} nanocrystallites have been synthesized by hydrothermal reaction using tetrabutyl titanate as source material. Acetylacetone was utilized to modify hydrolysis-condensation behavior of the alkoxide and thus coarsening dynamics of TiO{sub 2} nanocrystallites in the reaction. With assistance of Fourier transformation infrared spectrum, transmission electron microscopy, selected area electron diffraction and X-ray diffraction, interaction between acetylacetone and tetrabutyltitanate was explored, crystallographic and morphological properties of TiO{sub 2} nanocrystallites were monitored. Less hydrolysable complex was formed by “method of chelating” as tetrabutyltitanate was mixed with acetylacetone, leading to retarded coarsening rate of nanocrystallites. The obtained TiO{sub 2} nanocrystallites were applied to fabricate nanoporous photoanode of dye sensitized solar cells. Improvement of 18% has been achieved for photo-to-electric energy conversion efficiency of the devices due to both upgraded open circuit voltage and photocurrent density.

Zhou, Conghua, E-mail: chzhou@csu.edu.cn; Ouyang, Jun; Yang, Bingchu

2013-10-15

128

SUBSURFACE WELL-LOG CORRELATION OF ARSENIC-BEARING LITHOFACIES IN THE PERMIAN GARBER SANDSTONE AND WELLINGTON FORMATION, CENTRAL OKLAHOMA AQUIFER (COA), CLEVELAND COUNTY, OKLAHOMA  

EPA Science Inventory

The fluvial Garber Sandstone and the underlying Wellington Formation are important sources of drinking water in central Oklahoma. These formations, which make up much of the COA, consist of amalgamated sandstones with some interbedded mudstones, siltstones, and local mudstone- a...

129

Mapping Global Histone Acetylation Patterns to Gene Expression  

Microsoft Academic Search

Histone acetyltransferases and deacetylases with specificities for different sites of acetylation affect common chromatin regions. This could generate unique patterns of acetylation that may specify downstream biological processes. To search for existence of these patterns and their relationship to gene activity, we analyzed the genome-wide acetylation profiles for eleven lysines in the four core histones of Saccharomyces cerevisiae. We find

Siavash K. Kurdistani; Saeed Tavazoie; Michael Grunstein

2004-01-01

130

The relationship between the acetylator and the sparteine hydroxylation polymorphisms.  

PubMed Central

Thirty-eight healthy white British Caucasian subjects were hydroxylator phenotyped with sparteine and acetylator phenotyped with sulphadimidine. The results showed that there was no significant difference in the mean sparteine metabolic ratio between eight rapid acetylator extensive hydroxylators and 27 slow acetylator extensive hydroxylators. PMID:3712391

Harmer, D; Evans, D A; Eze, L C; Jolly, M; Whibley, E J

1986-01-01

131

Microwave Pretreatment For Hydrolysis Of Cellulose  

NASA Technical Reports Server (NTRS)

Microwave pretreatment enhances enzymatic hydrolysis of cellulosic wastes into soluble saccharides used as feedstocks for foods, fuels, and other products. Low consumption of energy, high yield, and low risk of proposed hydrolysis process incorporating microwave pretreatment makes process viable alternative to composting.

Cullingford, Hatice S.; George, Clifford E.; Lightsey, George R.

1993-01-01

132

PHTHALATE ESTER HYDROLYSIS: LINEAR FREE ENERGY RELATIONSHIPS  

EPA Science Inventory

Alkaline hydrolysis rate constants were measured for dimethyl, diethyl, di-n-butyl, di-iso-butyl, and di-(2-ethylhexyl) phthalate esters in water. A linear free energy relationship (LFER) was established for estimating alkaline hydrolysis rate constants for other phthalate esters...

133

Rate of Hydrolysis of Tertiary Halogeno Alkanes  

ERIC Educational Resources Information Center

Describes an experiment to measure the relative rate of hydrolysis of the 2-x-2 methylpropanes, where x is bromo, chloro or iodo. The results are plotted on a graph from which the relative rate of hydrolysis can be deduced. (Author/GA)

Pritchard, D. R.

1978-01-01

134

Oligomerization of heme o synthase in cytochrome oxidase biogenesis is mediated by cytochrome oxidase assembly factor Coa2.  

PubMed

The synthesis of the heme a cofactor used in cytochrome c oxidase (CcO) is dependent on the sequential action of heme o synthase (Cox10) and heme a synthase (Cox15). The active state of Cox10 appears to be a homo-oligomeric complex, and formation of this complex is dependent on the newly synthesized CcO subunit Cox1 and the presence of an early Cox1 assembly intermediate. Cox10 multimerization is triggered by progression of Cox1 from the early assembly intermediate to downstream intermediates. The CcO assembly factor Coa2 appears important in coupling the presence of newly synthesized Cox1 to Cox10 oligomerization. Cells lacking Coa2 are impaired in Cox10 complex formation as well as the formation of a high mass Cox15 complex. Increasing Cox1 synthesis in coa2? cells restores respiratory function if Cox10 protein levels are elevated. The C-terminal segment of Cox1 is important in triggering Cox10 oligomerization. Expression of the C-terminal 54 residues of Cox1 appended to a heterologous matrix protein leads to efficient Cox10 complex formation in coa2? cells, but it fails to induce Cox15 complex formation. The state of Cox10 was evaluated in mutants, which predispose human patients to CcO deficiency and the neurological disorder Leigh syndrome. The presence of the D336V mutation in the yeast Cox10 backbone results in a catalytically inactive enzyme that is fully competent to oligomerize. Thus, Cox10 oligomerization and catalytic activation are separate processes and can be uncoupled. PMID:22669974

Khalimonchuk, Oleh; Kim, Hyung; Watts, Talina; Perez-Martinez, Xochitl; Winge, Dennis R

2012-08-01

135

Genetic Diversity of Staphylocoagulase Genes (coa): Insight into the Evolution of Variable Chromosomal Virulence Factors in Staphylococcus aureus  

PubMed Central

Background The production of staphylocoagulase (SC) causing the plasma coagulation is one of the important characteristics of Staphylococcus aureus. Although SCs have been classified into 10 serotypes based on the differences in the antigenicity, genetic bases for their diversities and relatedness to chromosome types are poorly understood. Methodology/Principal Findings We compared the nucleotide sequences of 105 SC genes (coa), 59 of which were determined in this study. D1 regions, which contain prothrombin-activating and -binding domains and are presumed to be the binding site of each type-specific antiserum, were classified into twelve clusters having more than 90% nucleotide identities, resulting to create two novel SC types, XI and XII, in addition to extant 10 types. Nine of the twelve SC types were further subdivided into subtypes based on the differences of the D2 or the central regions. The phylogenetical relations of the D1 regions did not correlate exactly with either one of agr types and multilocus sequence types (STs). In addition, genetic analysis showed that recombination events have occurred in and around coa. So far tested, STs of 126 S. aureus strains correspond to the combination of SC type and agr type except for the cases of CC1 and CC8, which contained two and three different SC types, respectively. Conclusion The data suggested that the evolution of coa was not monophyletic in the species. Chromosomal recombination had occurred at coa and agr loci, resulting in the carriage of the combinations of allotypically different important virulence determinants in staphylococcal chromosome. PMID:19492076

Watanabe, Shinya; Ito, Teruyo; Sasaki, Takashi; Li, Shanshuang; Uchiyama, Ikuo; Kishii, Kozue; Kikuchi, Ken; Skov, Robert Leo; Hiramatsu, Keiichi

2009-01-01

136

Acetate Metabolism in a pta Mutant of Escherichia coli W3110: Importance of Maintaining Acetyl Coenzyme A Flux for Growth and Survival  

PubMed Central

In order to study the physiological role of acetate metabolism in Escherichia coli, the growth characteristics of an E. coli W3100 pta mutant defective in phosphotransacetylase, the first enzyme of the acetate pathway, were investigated. The pta mutant grown on glucose minimal medium excreted unusual by-products such as pyruvate, d-lactate, and l-glutamate instead of acetate. In an analysis of the sequential consumption of amino acids by the pta mutant growing in tryptone broth (TB), a brief lag between the consumption of amino acids normally consumed was observed, but no such lag occurred for the wild-type strain. The pta mutant was found to grow slowly on glucose, TB, or pyruvate, but it grew normally on glycerol or succinate. The defective growth and starvation survival of the pta mutant were restored by the introduction of poly-?-hydroxybutyrate (PHB) synthesis genes (phbCAB) from Alcaligenes eutrophus, indicating that the growth defect of the pta mutant was due to a perturbation of acetyl coenzyme A (CoA) flux. By the stoichiometric analysis of the metabolic fluxes of the central metabolism, it was found that the amount of pyruvate generated from glucose transport by the phosphoenolpyruvate-dependent phosphotransferase system (PTS) exceeded the required amount of precursor metabolites downstream of pyruvate for biomass synthesis. These results suggest that E. coli excretes acetate due to the pyruvate flux from PTS and that any method which alleviates the oversupply of acetyl CoA would restore normal growth to the pta mutant. PMID:10542166

Chang, Dong-Eun; Shin, Sooan; Rhee, Joon-Shick; Pan, Jae-Gu

1999-01-01

137

Edinburgh Research Explorer Organotrifluoroborate Hydrolysis: Boronic Acid Release  

E-print Network

Edinburgh Research Explorer Organotrifluoroborate Hydrolysis: Boronic Acid Release Mechanism, 'Organotrifluoroborate Hydrolysis: Boronic Acid Release Mechanism and an Acid­Base Paradox in Cross-Coupling' Journal immediately and investigate your claim. Download date: 16. Sep. 2014 #12;Organotrifluoroborate Hydrolysis

Millar, Andrew J.

138

Contribution of CoA Ligases to Benzenoid Biosynthesis in Petunia Flowers[W  

PubMed Central

Biosynthesis of benzoic acid from Phe requires shortening of the side chain by two carbons, which can occur via the ?-oxidative or nonoxidative pathways. The first step in the ?-oxidative pathway is cinnamoyl-CoA formation, likely catalyzed by a member of the 4-coumarate:CoA ligase (4CL) family that converts a range of trans-cinnamic acid derivatives into the corresponding CoA thioesters. Using a functional genomics approach, we identified two potential CoA-ligases from petunia (Petunia hybrida) petal-specific cDNA libraries. The cognate proteins share only 25% amino acid identity and are highly expressed in petunia corollas. Biochemical characterization of the recombinant proteins revealed that one of these proteins (Ph-4CL1) has broad substrate specificity and represents a bona fide 4CL, whereas the other is a cinnamate:CoA ligase (Ph-CNL). RNA interference suppression of Ph-4CL1 did not affect the petunia benzenoid scent profile, whereas downregulation of Ph-CNL resulted in a decrease in emission of benzylbenzoate, phenylethylbenzoate, and methylbenzoate. Green fluorescent protein localization studies revealed that the Ph-4CL1 protein is localized in the cytosol, whereas Ph-CNL is in peroxisomes. Our results indicate that subcellular compartmentalization of enzymes affects their involvement in the benzenoid network and provide evidence that cinnamoyl-CoA formation by Ph-CNL in the peroxisomes is the committed step in the ?-oxidative pathway. PMID:22649270

Klempien, Antje; Kaminaga, Yasuhisa; Qualley, Anthony; Nagegowda, Dinesh A.; Widhalm, Joshua R.; Orlova, Irina; Shasany, Ajit Kumar; Taguchi, Goro; Kish, Christine M.; Cooper, Bruce R.; D’Auria, John C.; Rhodes, David; Pichersky, Eran; Dudareva, Natalia

2012-01-01

139

Conformational transitions of cinnamoyl CoA reductase 1 from Leucaena leucocephala.  

PubMed

Conformational transitions of cinnamoyl CoA reductase, a key regulatory enzyme in lignin biosynthesis, from Leucaena leucocephala (Ll-CCRH1) were studied using fluorescence and circular dichroism spectroscopy. The native protein possesses four trp residues exposed on the surface and 66% of helical structure, undergoes rapid structural transitions at and above 45 °C and starts forming aggregates at 55 °C. Ll-CCRH1 was transformed into acid induced (pH 2.0) molten globule like structure, exhibiting altered secondary structure, diminished tertiary structure and exposed hydrophobic residues. The molten globule like structure was examined for the thermal and chemical stability. The altered secondary structure of L1-CCRH1 at pH 2.0 was stable up to 90 °C. Also, in presence of 0.25 M guanidine hydrochloride (GdnHCl), it got transformed into different structure which was stable in the vicinity of 2M GdnHCl (as compared to drastic loss of native structure in 2M GdnHCl) as seen in far UV-CD spectra. The structural transition of Ll-CCRH1 at pH 2.0 followed another transition after readjusting the pH to 8.0, forming a structure with hardly any similarity to that of native protein. PMID:24309513

Sonawane, Prashant D; Khan, Bashir M; Gaikwad, Sushama M

2014-03-01

140

Acyl CoA Binding Proteins are Required for Cuticle Formation and Plant Responses to Microbes  

PubMed Central

Fatty acids (FA) and lipids are well known regulators of plant defense. Our previous studies have shown that components of prokaryotic (plastidal) FA biosynthesis pathway regulate various aspects of plant defense. Here, we investigated the defense related roles of the soluble acyl CoA binding proteins (ACBPs), which are thought to facilitate the intracellular transport of FA/lipids. We show that ACBP3 and 4 are required for maintaining normal lipid levels and that ACBP3 contributes to the lipid flux between the prokaryotic and eukaryotic pathways. We also show that loss of ACBP3, 4, or 6 impair normal development of the cuticle and affect both basal and resistance protein-mediated defense against bacterial and fungal pathogens. Loss of ACBP3, 4, or 6 also inhibits the induction of systemic acquired resistance (SAR) due to the plants inability to generate SAR inducing signal(s). Together, these data show that ACBP3, ACBP4, and ACBP6 are required for cuticle development as well as defense against microbial pathogens. PMID:23060893

Xia, Ye; Yu, Keshun; Gao, Qing-ming; Wilson, Ella V.; Navarre, Duroy; Kachroo, Pradeep; Kachroo, Aardra

2012-01-01

141

Assessing an Impulsive Model for Rotational Energy Partitioning to Acetyl Radicals from the Photodissociation of Acetyl Chloride at 235 nm  

E-print Network

Assessing an Impulsive Model for Rotational Energy Partitioning to Acetyl Radicals from the photodissociation of acetyl chloride to assess the utility of a recently proposed impulsive model when. The impulsive model explicitly includes an average over the vibrational quantum states of acetyl chloride when

Butler, Laurie J.

142

Crystal Structure of DmdD, a Crotonase Superfamily Enzyme That Catalyzes the Hydration and Hydrolysis of Methylthioacryloyl-CoA  

PubMed Central

Dimethyl-sulphoniopropionate (DMSP) is produced in abundance by marine phytoplankton, and the catabolism of this compound is an important source of carbon and reduced sulfur for marine bacteria and other organisms. The enzyme DmdD catalyzes the last step in the methanethiol (MeSH) pathway of DMSP catabolism. DmdD is a member of the crotonase superfamily of enzymes, and it catalyzes both the hydration and the hydrolysis of methylthioacryloyl-CoA (MTA-CoA), converting it to acetaldehyde, CO2, MeSH, and CoA. We report here the crystal structure of Ruegeria pomeroyi DmdD free enzyme at 1.5 Ĺ resolution and the structures of the E121A mutant in complex with MTA-CoA and 3-methylmercaptopropionate-CoA (MMPA-CoA) at 1.8 Ĺ resolution. DmdD is a hexamer, composed of a dimer of trimers where the three monomers of each trimer are related by a crystallographic 3-fold axis. The overall structure of this hexamer is similar to those of canonical crotonases. However, the C-terminal loops of DmdD in one of the trimers assume a different conformation and contribute to CoA binding in the active site of a neighboring monomer of the trimer, while these loops in the second trimer are disordered. MTA-CoA is bound deep in the active site in the first trimer, but shows a 1.5 Ĺ shift in its position in the second trimer. MMPA-CoA has a similar binding mode to MTA-CoA in the first trimer. MMPA-CoA cannot be hydrated and is only hydrolyzed slowly by DmdD. Replacement of the sulfur atom in MMPA-CoA with a methylene group abolishes hydrolysis, suggesting that the unique property of the substrate is a major determinant of the hydrolysis activity of DmdD. PMID:23704947

Tan, Dazhi; Crabb, Warren M.; Whitman, William B.; Tong, Liang

2013-01-01

143

Rapid kinetic studies of acetyl-CoA synthesis: evidence supporting the catalytic intermediacy of a paramagnetic NiFeC species in the autotrophic Wood-Ljungdahl pathway.  

PubMed

CO dehydrogenase/acetyl-CoA synthase (CODH/ACS), a key enzyme in the Wood-Ljungdahl pathway of anaerobic CO(2) fixation, is a bifunctional enzyme containing CODH, which catalyzes the reversible two-electron oxidation of CO to CO(2), and ACS, which catalyzes acetyl-CoA synthesis from CoA, CO, and a methylated corrinoid iron-sulfur protein (CFeSP). ACS contains an active site nickel iron-sulfur cluster that forms a paramagnetic adduct with CO, called the nickel iron carbon (NiFeC) species, which we have hypothesized to be a key intermediate in acetyl-CoA synthesis. This hypothesis has been controversial. Here we report the results of steady-state kinetic experiments; stopped-flow and rapid freeze-quench transient kinetic studies; and kinetic simulations that directly test this hypothesis. Our results show that formation of the NiFeC intermediate occurs at approximately the same rate as, and its decay occurs 6-fold faster than, the rate of acetyl-CoA synthesis. Kinetic simulations of the steady-state and transient kinetic results accommodate the NiFeC species in the mechanism and define the rate constants for the elementary steps in acetyl-CoA synthesis. The combined results strongly support the kinetic competence of the NiFeC species in the Wood-Ljungdahl pathway. The results also imply that the methylation of ACS occurs by attack of the Ni(1+) site in the NiFeC intermediate on the methyl group of the methylated CFeSP. Our results indicate that CO inhibits acetyl-CoA synthesis by inhibiting this methyl transfer reaction. Under noninhibitory CO concentrations (below 100 microM), formation of the NiFeC species is rate-limiting, while at higher inhibitory CO concentrations, methyl transfer to ACS becomes rate-limiting. PMID:11827525

Seravalli, Javier; Kumar, Manoj; Ragsdale, Stephen W

2002-02-12

144

Acetyl l -carnitine as a precursor of acetylcholine  

Microsoft Academic Search

Synthesis of [3H]acetylcholine from [3H]acetyl-l-carnitine was demonstrated in vitro by coupling the enzyme systems choline acetyltransferase and carnitine acetyltransferase. Likewise, both [3H] and [14C] labeled acetylcholine were produced when [3H]acetyl-l-carnitine andd-[U-14C] glucose were incubated with synaptosomal membrane preparations from rat brain. Transfer of the acetyl moiety from acetyl-l-carnitine to acetylcholine was dependent on concentration of acetyl-l-carnitine and required the presence

Helen L. White; Philip W. Scates

1990-01-01

145

Structural and functional characterization of HMG-COA reductase from Artemisia annua  

PubMed Central

Plants synthesize a great variety of isoprenoid products that are required not only for normal growth and development but also for their adaptive responses to environmental challenges. However, despite the remarkable diversity in the structure and function of plant isoprenoids, they all originate from a single metabolic precursor, mevalonic acid. The synthesis of mevalonic acid is catalysed by the enzyme, 3?hydroxy?3?methylglutaryl coenzyme A reductase (HMG? CoA reductase). The analysis of the amino acid sequence of HMG?CoA reductase from Artemisia annua L. plant showed that it belongs to class I HMG?CoA reductase family. The three dimensional structure of HMG?CoA reductase of Artemisia annua has been generated from amino acid sequence using homology modelling with backbone structure of human HMG?CoA reductase as template. The model was generated using the SWISS MODEL SERVER. The generated 3?D structure of HMG?CoA reductase was evaluated at various web interfaced servers to checks the stereo interfaced quality of the structure in terms of bonds, bond angles, dihedral angles and non-bonded atom-atom distances, structural as well as functional domains etc. The generated model was visualized using the RASMOL. Structural analysis of HMG-CoA reductase from Artemisia annua L. plant hypothesize that the N and C?terminals are positioned in cytosol by the two membrane spanning helices and the C-terminals domain shows similarity to the human HMG?CoA reductase enzyme indicating that they both had potential catalytic similarities. PMID:21364776

Kiran, Usha; Ram, Mauji; Khan, Mather Ali; Khan, Salim; Jha, Prabhakar; Alam, Afshar; Abdin, Malik Zainul

2010-01-01

146

Intracellular Long-Chain Acyl CoAs Activate TRPV1 Channels  

PubMed Central

TRPV1 channels are an important class of membrane proteins that play an integral role in the regulation of intracellular cations such as calcium in many different tissue types. The anionic phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2) is a known positive modulator of TRPV1 channels and the negatively charged phosphate groups interact with several basic amino acid residues in the proximal C-terminal TRP domain of the TRPV1 channel. We and other groups have shown that physiological sub-micromolar levels of long-chain acyl CoAs (LC-CoAs), another ubiquitous anionic lipid, can also act as positive modulators of ion channels and exchangers. Therefore, we investigated whether TRPV1 channel activity is similarly regulated by LC-CoAs. Our results show that LC-CoAs are potent activators of the TRPV1 channel and interact with the same PIP2-binding residues in TRPV1. In contrast to PIP2, LC-CoA modulation of TRPV1 is independent of Ca2+i, acting in an acyl side-chain saturation and chain-length dependent manner. Elevation of LC-CoAs in intact Jurkat T-cells leads to significant increases in agonist-induced Ca2+i levels. Our novel findings indicate that LC-CoAs represent a new fundamental mechanism for regulation of TRPV1 channel activity that may play a role in diverse cell types under physiological and pathophysiological conditions that alter fatty acid transport and metabolism such as obesity and diabetes. PMID:24798548

Youssef, Nermeen; Dyck, Jason R. B.; Light, Peter E.

2014-01-01

147

Biosynthesis and turnover of O-acetyl and N-acetyl groups in the gangliosides of human melanoma cells  

SciTech Connect

We and others previously described the melanoma-associated oncofetal glycosphingolipid antigen 9-O-acetyl-GD3, a disialoganglioside O-acetylated at the 9-position of the outer sialic acid residue. We have now developed methods to examine the biosynthesis and turnover of disialogangliosides in cultured melanoma cells and in Golgi-enriched vesicles from these cells. O-Acetylation was selectively expressed on di- and trisialogangliosides, but not on monosialogangliosides, nor on glycoprotein-bound sialic acids. Double-labeling of cells with (3H)acetate and (14C)glucosamine introduced easily detectable labels into each of the components of the ganglioside molecules. Pulse-chase studies of such doubly labeled molecules indicated that the O-acetyl groups turn over faster than the parent molecule. When Golgi-enriched vesicles from these cells were incubated with (acetyl-3H)acetyl-coenzyme A, the major labeled products were disialogangliosides. (Acetyl-3H)O-acetyl groups were found at both the 7- and the 9-positions, indicating that both 7-O-acetyl GD3 and 9-O-acetyl GD3 were synthesized by the action of O-acetyltransferase(s) on endogenous GD3. Analysis of the metabolically labeled molecules confirmed the existence of both 7- and 9-O-acetylated GD3 in the intact cells. Surprisingly, the major 3H-labeled product of the in vitro labeling reaction was not O-acetyl-GD3, but GD3, with the label exclusively in the sialic acid residues. Fragmentation of the labeled sialic acids by enzymatic and chemical methods showed that the 3H-label was exclusively in (3H)N-acetyl groups. Analyses of the double-labeled sialic acids from intact cells also showed that the 3H-label from (3H)acetate was exclusively in the form of (3H)N-acetyl groups, whereas the 14C-label was at the 4-position.

Manzi, A.E.; Sjoberg, E.R.; Diaz, S.; Varki, A.

1990-08-05

148

Fragrance material review on acetyl carene.  

PubMed

A toxicologic and dermatologic review of acetyl carene when used as a fragrance ingredient is presented. Acetyl carene is a member of the fragrance structural group Alkyl Cyclic Ketones. These fragrances can be described as being composed of an alkyl, R1, and various substituted and bicyclic saturated or unsaturated cyclic hydrocarbons, R2, in which one of the rings may include up to 12 carbons. Alternatively, R2 may be a carbon bridge of C2-C4 carbon chain length between the ketone and cyclic hydrocarbon. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for acetyl carene were evaluated then summarized and includes physical properties, acute toxicity, skin irritation, and skin sensitization data. A safety assessment of the entire Alkyl Cyclic Ketones will be published simultaneously with this document; please refer to Belsito et al. (Belsito, D., Bickers, D., Bruze, M., Calow, P., Dagli, M., Fryer, A.D., Greim, H., Miyachi, Y., Saurat, J.H., Sipes, I.G., 2013A Toxicologic and dermatologic assessment of alkyl cyclic ketones when used as fragrance ingredients. (submitted for publication).) for an overall assessment of the safe use of this material and all Alkyl Cyclic Ketones in fragrances. PMID:23911801

Scognamiglio, J; Letizia, C S; Api, A M

2013-12-01

149

Fragrance material review on acetyl cedrene.  

PubMed

A toxicologic and dermatologic review of acetyl cedrene when used as a fragrance ingredient is presented. Acetyl cedrene is a member of the fragrance structural group Alkyl Cyclic Ketones. The generic formula for this group can be represented as (R1)(R2)CO. These fragrances can be described as being composed of an alkyl, R1, and various substituted and bicyclic saturated or unsaturated cyclic hydrocarbons, R2, in which one of the rings may include up to 12 carbons. Alternatively, R2 may be a carbon bridge of C2-C4 carbon chain length between the ketone and cyclic hydrocarbon. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for acetyl cedrene were evaluated then summarized and includes physical properties, acute toxicity, skin irritation, mucous membrane (eye) irritation, skin sensitization, elicitation, phototoxicity, photoallergy, toxicokinetics, repeated dose, reproductive toxicity, and genotoxicity data. A safety assessment of the entire Alkyl Cyclic Ketones will be published simultaneously with this document; please refer to Belsito et al. (2013) (Belsito, D., Bickers, D., Bruze, M., Calow, P., Dagli, M., Fryer, A.D., Greim, H., Miyachi, Y., Saurat, J.H., Sipes, I.G., 2013. A Toxicologic and Dermatologic Assessment of Alkyl Cyclic Ketones When Used as Fragrance Ingredients. Submitted with this manuscript.) for an overall assessment of the safe use of this material and all Alkyl Cyclic Ketones in fragrances. PMID:23907023

Scognamiglio, J; Letizia, C S; Politano, V T; Api, A M

2013-12-01

150

Enzymatic hydrolysis of cellulose: theory and applications  

SciTech Connect

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 has been underway in the authors' laboratories at the University of California at Berkeley over the past ten years. This report is based in part upon this background of experience, and experimental data from relatively recent studies are presented in certain sections to make the information as timely and useful as possible. Because of current interest in production of ethanol a section is included which summarizes various methods for high productivity fermentation systems. Chapter titles are: Theory of enzymatic hydrolysis; production of cellulase and xylanase; hydrolysis of agricultural residues, enzymatic hydrolysis processes, high productivity ethanol fermentation; and ethanol economics. (DMC)

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

1980-06-01

151

Effect of surfactants on cellulose hydrolysis  

SciTech Connect

The effect of surfactants on the heterogeneous enzymatic hydrolysis of Sigmacell 100 cellulose and of steam-exploded wood was studied. Certain biosurfactants (sophorolipid, rhamnolipid, bacitracin) and Tween 80 increased the rate of hydrolysis of Sigmacell 100, as measured by the amount of reducing sugar produced, by as much as seven times. The hydrolysis of steam-exploded wood was increased by 67% in the presence of sophorolipid. At the same time, sophorolipid was found to decrease the amount of enzyme absorbed onto the cellulose at equilibrium. Sophorolipid had the greatest effect on cellulose hydrolysis when it was present from the beginning of the experiment and when the enzyme/cellulose ratio was low.

Helle, S.S.; Duff, S.J.B. (Univ. of British Columbia, Vancouver, British Columbia (Canada). Pulp and Paper Centre and Dept. of Chemical Engineering); Cooper, D.G. (McGill Univ., Montreal, Quebec (Canada). Chemical Engineering Dept.)

1993-08-20

152

Partially acetylated chitooligosaccharides bind to YKL-40 and stimulate growth of human osteoarthritic chondrocytes.  

PubMed

Recent evidences indicating that cellular kinase signaling cascades are triggered by oligomers of N-acetylglucosamine (ChOS) and that condrocytes of human osteoarthritic cartilage secrete the inflammation associated chitolectin YKL-40, prompted us to study the binding affinity of partially acetylated ChOS to YKL-40 and their effect on primary chondrocytes in culture. Extensive chitinase digestion and filtration of partially deacetylated chitin yielded a mixture of ChOS (Oligomin™) and further ultrafiltration produced T-ChOS™, with substantially smaller fraction of the smallest sugars. YKL-40 binding affinity was determined for the different sized homologues, revealing micromolar affinities of the larger homologues to YKL-40. The response of osteoarthritic chondrocytes to Oligomin™ and T-ChOS™ was determined, revealing 2- to 3-fold increases in cell number. About 500 ?g/ml was needed for Oligomin™ and around five times lower concentration for T-ChOS™, higher concentrations abolished this effect for both products. Addition of chitotriose inhibited cellular responses mediated by larger oligosaccharides. These results, and the fact that the partially acetylated T-ChOS™ homologues should resist hydrolysis, point towards a new therapeutic concept for treating inflammatory joint diseases. PMID:23541584

Einarsson, Jon M; Bahrke, Sven; Sigurdsson, Bjarni Thor; Ng, Chuen-How; Petersen, Petur Henry; Sigurjonsson, Olafur E; Jonsson, Halldor; Gislason, Johannes; Thormodsson, Finnbogi R; Peter, Martin G

2013-05-01

153

Random Hydrolysis Controls the Dynamic Instability of Microtubules Ranjith Padinhateeri,  

E-print Network

Random Hydrolysis Controls the Dynamic Instability of Microtubules Ranjith Padinhateeri, * Anatoly hydrolysis. Despite decades of experimental work in this field, the precise mechanism of hydrolysis to the vectorial model, hydrolysis occurs only at the unique interface between units bound to GTP/ATP and units

Lacoste, David

154

Epidemiological characterization of methicillin-resistant Staphylococcus aureus isolated in the North West of England by protein A (spa) and coagulase (coa) gene polymorphisms.  

PubMed

In a comparative study, isolates of methicillin-resistant Staphylococcus aureus (MRSA) with known pulsed-field gel electrophoresis (PFGE) and bacteriophage type were analysed by polymerase chain reaction (PCR) and restriction fragment length polymorphisms (RFLP) for additional discriminatory subtyping information. PFGE was previously performed using standardized, commercially available kits and pre-programmed software. Isolates were examined for coagulase (coa) and protein A (spa) gene polymorphisms following PCR amplification of the coa hypervariable and spa repeat regions. Coa gene RFLPs produced a total of 38 distinct combined patterns after digestion with HaeIII and AluI and identified the predominant epidemic (EMRSA) types 15 and 16. A unique HaeIII restriction site was identified by RFLP and sequence analysis in the coa gene for EMRSA 15 but not EMRSA 16. The spa gene PCR yielded a total of 14 different profiles ranging from 3-18 repeats with the 2 predominant EMRSA types falling into 2 distinct groups. PCR detection of coa and spa polymorphisms offer a rapid preliminary strain identification and discriminatory subtyping information for surveillance of MRSA. PMID:10030698

Walker, J; Borrow, R; Edwards-Jones, V; Oppenheim, B A; Fox, A J

1998-12-01

155

A yeast acetyl coenzyme A carboxylase mutant links very-long-chain fatty acid synthesis to the structure and function of the nuclear membrane-pore complex.  

PubMed Central

The conditional mRNA transport mutant of Saccharomyces cerevisiae, acc1-7-1 (mtr7-1), displays a unique alteration of the nuclear envelope. Unlike nucleoporin mutants and other RNA transport mutants, the intermembrane space expands, protuberances extend from the inner membrane into the intermembrane space, and vesicles accumulate in the intermembrane space. MTR7 is the same gene as ACC1, encoding acetyl coenzyme A (CoA) carboxylase (Acc1p), the rate-limiting enzyme of de novo fatty acid synthesis. Genetic and biochemical analyses of fatty acid synthesis mutants and acc1-7-1 indicate that the continued synthesis of malonyl-CoA, the enzymatic product of acetyl-CoA carboxylase, is required for an essential pathway which is independent from de novo synthesis of fatty acids. We provide evidence that synthesis of very-long-chain fatty acids (C26 atoms) is inhibited in acc1-7-1, suggesting that very-long-chain fatty acid synthesis is required to maintain a functional nuclear envelope. PMID:8943372

Schneiter, R; Hitomi, M; Ivessa, A S; Fasch, E V; Kohlwein, S D; Tartakoff, A M

1996-01-01

156

Biochemical and Crystallographic Analysis of Substrate Binding and Conformational Changes in Acetyl-CoA Synthetase  

SciTech Connect

The adenylate-forming enzymes, including acyl-CoA synthetases, the adenylation domains of non-ribosomal peptide synthetases (NRPS), and firefly luciferase, perform two half-reactions in a ping-pong mechanism. We have proposed a domain alternation mechanism for these enzymes whereby, upon completion of the initial adenylation reaction, the C-terminal domain of these enzymes undergoes a 140{sup o} rotation to perform the second thioester-forming half-reaction. Structural and kinetic data of mutant enzymes support this hypothesis. We present here mutations to Salmonella enterica acetyl-CoA synthetase (Acs) and test the ability of the enzymes to catalyze the complete reaction and the adenylation half-reaction. Substitution of Lys609 with alanine results in an enzyme that is unable to catalyze the adenylate reaction, while the Gly524 to leucine substitution is unable to catalyze the complete reaction yet catalyzes the adenylation half-reaction with activity comparable to the wild-type enzyme. The positions of these two residues, which are located on the mobile C-terminal domain, strongly support the domain alternation hypothesis. We also present steady-state kinetic data of putative substrate-binding residues and demonstrate that no single residue plays a dominant role in dictating CoA binding. We have also created two mutations in the active site to alter the acyl substrate specificity. Finally, the crystallographic structures of wild-type Acs and mutants R194A, R584A, R584E, K609A, and V386A are presented to support the biochemical analysis.

Reger,A.; Carney, J.; Gulick, A.

2007-01-01

157

Synthesis, biodistribution, and imaging of PEGylated-acetylated polyamidoamine dendrimers.  

PubMed

Polyamidoamine (PAMAM) dendrimers have been widely used as drug carriers, non-viral gene vectors and imaging agents. However, the use of dendrimers in biological system is constrained because of inherent toxicity and organ accumulation. In this study, the strategy of acetylation and PEGylation-acetylation was used to minimize PAMAM dendrimers toxicities and to improve their biodistribution and pharmacokinetics for medical application. PEGylated-acetylated PAMAM (G4-Ac-PEG) dendrimers were synthesized by PEGylation of acetylated PAMAM dendrimer of generation 4 (G4) with acetic anhydride and polyethylene glycol (PEG) 3.4 k. To investigate the cytotoxicity and in vivo biodistribution of the conjugates, in vitro cell viability analysis, Iodine-125 (125I) imaging, tissue distribution and hematoxylin-eosin (HE) staining were performed. We find that acetylation and PEGylation-acetylation essentially eliminates the inherent dendrimer cytotoxicity in vitro. Planar gamma (gamma) camera imaging revealed that all the conjugates were slowly eliminated from the body, and higher abdominal accumulation of acetylation PAMAM dendrimer was observed. Tissue distribution analysis showed that PEGylated-acetylated dendrimers have longer blood retention and lower accumulation in organs such as the kidney and liver than the non-PEGylated-acetylated dendrimers, but acetylation only can significantly increase the accumulation of G4 in the kidney and decrease the concentration in blood. Histology results reveal that no obvious damage was observed in all groups after high dose administration. This study indicates that PEGylation-acetylation could improve the blood retention, decrease organ accumulation, and improve pharmacokinetic profile, which suggests that PEGylation-acetylation provides an alternative method for PAMAM dendrimers modification. PMID:24734545

Liu, Jianfeng; Liu, Jinjian; Chu, Liping; Tong, Lingling; Gao, Hongjun; Yang, Cuihong; Wang, Dezhi; Shi, Linqi; Kong, Deling; Li, Zongjin

2014-05-01

158

Selective Acetylation of per-O-TMS-Protected Monosaccharides  

PubMed Central

Selective acetylation of various per-O-TMS-protected carbohydrates has been accomplished. Using a protecting group exchange strategy and microwave assistance, monosaccharides (glucose, galactose and mannose) can be selectively acetylated producing either the 6-O-monoacetate or 1,6-O-diacetylated species. This new class of molecules can be deprotected without migration of the acetyl groups providing useful synthetic intermediates. To demonstrate the scope of the reaction, the methodology was successfully extended to TMS-protected ceramide. PMID:20799705

Witschi, Mark A.

2010-01-01

159

Growth rate regulation of Escherichia coli acetyl coenzyme A carboxylase, which catalyzes the first committed step of lipid biosynthesis.  

PubMed Central

Acetyl coenzyme A (CoA) carboxylase catalyzes the synthesis of malonyl-CoA, the first intermediate of fatty acid synthesis. The Escherichia coli enzyme is encoded by four subunits located at three different positions on the E. coli chromosome. The accBC genes lie in a small operon at min 72, whereas accA and accD are located at min 4.3 and 50, respectively. We examined the expression of the genes that encode the E. coli acetyl-CoA carboxylase subunits (accA, accBC, and accD) under a variety of growth conditions by quantitative Northern (RNA) blot analysis. We found a direct correlation between the levels of transcription of the acc genes and the rate of cellular growth. Consistent results were also obtained upon nutritional upshift and downshift experiments and upon dilution of stationary-phase cultures into fresh media. We also determined the 5' end of the accA and accD mRNAs by primer extension and did transcriptional fusion analysis of the previously reported accBC promoter. Several interesting features were found in the promoter regions of these genes, including a bent DNA sequence and an open reading frame within the unusually long leader mRNA of the accBC operon, potential stem-loop structures in the accA and accD mRNA leader regions, and a stretch of GC-rich sequences followed by AT-rich sequences common to all three promoters. In addition, both accA and accD are located in complex gene clusters. For example, the accA promoter was localized within the upstream polC gene (which encodes the DNA polymerase III catalytic subunit), suggesting that additional regulatory mechanisms exist. Images PMID:7678242

Li, S J; Cronan, J E

1993-01-01

160

Intramuscular triacylglycerol, glycogen and acetyl group metabolism during 4 h of moderate exercise in man.  

PubMed

This study investigated intramuscular triacylglycerol (IMTG) and glycogen utilisation, pyruvate dehydrogenase activation (PDHa) and acetyl group accumulation during prolonged moderate intensity exercise. Seven endurance-trained men cycled for 240 min at 57 % maximal oxygen consumption (V(O2,max)) and duplicate muscle samples were obtained at rest and at 10, 120 and 240 min of exercise. We hypothesised that IMTG utilisation would be augmented during 2-4 h of exercise, while PDHa would be decreased secondary to reduced glycogen metabolism. IMTG was measured on both muscle samples at each time point and the coefficient of variation was 12.3 +/- 9.4 %. Whole body respiratory exchange ratio (RER) decreased from 0.89 +/- 0.01 at 30 min to 0.83 +/- 0.01 at 150 min and remained low throughout exercise. Plasma glycerol and free fatty acids (FFAs) had increased compared with rest at 90 min and progressively increased until exercise cessation. Although plasma glucose tended to decrease with exercise, this was not significant. IMTG was reduced at 120 min compared with rest (0 min, 15.6 +/- 0.8 mmol kg(-1) d.m.; 120 min, 12.8 +/- 0.7 mmol kg(-1) d.m.) but no further reduction in IMTG was observed at 240 min. Muscle glycogen was 468 +/- 49 mmol kg(-1) d.m. at rest and decreased at 120 min and again at 240 min (217 +/- 48 and 144 + 47 mmol kg(-1) d.m.). PDHa increased above rest at 10 and 120 min, but decreased at 240 min, which coincided with reduced whole body carbohydrate oxidation. Muscle pyruvate and ATP were unchanged with exercise. Acetyl CoA increased at 10 min and remained elevated throughout exercise. Acetylcarnitine increased at exercise onset but returned to resting values by 240 min. Contrary to our first hypothesis, significant utilisation of IMTG occurred during the first 2 h of moderate exercise but not during hours 2-4. The reduced utilisation of intramuscular fuels during the last 120 min was offset by greater FFA delivery and oxidation. Consistent with the second hypothesis, PDHa decreased late in moderate exercise and closely matched the estimates of lower carbohydrate flux. Although the factor underlying the PDHa decrease was not apparent, reduced pyruvate provision secondary to diminished glycolytic flux is the most likely mechanism. PMID:12068055

Watt, Matthew J; Heigenhauser, George J F; Dyck, David J; Spriet, Lawrence L

2002-06-15

161

Structure, morphology and functionality of acetylated and oxidised barley starches.  

PubMed

Acetylation and oxidation are chemical modifications which alter the properties of starch. The degree of modification of acetylated and oxidized starches is dependent on the catalyst and active chlorine concentrations, respectively. The objective of this study was to evaluate the effect of acetylation and oxidation on the structural, morphological, physical-chemical, thermal and pasting properties of barley starch. Barley starches were acetylated at different catalyst levels (11%, 17%, and 23% of NaOH solution) and oxidized at different sodium hypochlorite concentrations (1.0%, 1.5%, and 2.0% of active chlorine). Fourier-transformed infrared spectroscopy (FTIR), X-ray diffractograms, thermal, morphological, and pasting properties, swelling power and solubility of starches were evaluated. The degree of substitution (DS) of the acetylated starches increased with the rise in catalyst concentration. The percentage of carbonyl (CO) and carboxyl (COOH) groups in oxidized starches also increased with the rise of active chlorine level. The presence of hydrophobic acetyl groups, carbonyl and carboxyl groups caused a partial disorganization and depolymerization of starch granules. The structural, morphological and functional changes in acetylated and oxidized starches varied according to reaction conditions. Acetylation makes barley starch more hydrophobic by the insertion of acetyl groups. Also the oxidation promotes low retrogradation and viscosity. All these characteristics are important for biodegradable film production. PMID:25172707

El Halal, Shanise Lisie Mello; Colussi, Rosana; Pinto, Vânia Zanella; Bartz, Josiane; Radunz, Marjana; Carreńo, Neftali Lenin Villarreal; Dias, Alvaro Renato Guerra; Zavareze, Elessandra da Rosa

2015-02-01

162

Measurement of acetylation turnover at distinct lysines in human histones identifies long-lived acetylation sites  

PubMed Central

Histone acetylation has long been determined as a highly dynamic modification associated with open chromatin and transcriptional activation. Here we develop a metabolic labeling scheme using stable isotopes to study the kinetics of acetylation turnover at 19 distinct lysines on histones H3, H4, and H2A. Using human HeLa S3 cells, the analysis reveals 12 sites of histone acetylation with fast turnover and 7 sites stable over a 30 hour experiment. The sites showing fast turnover (anticipated from classical radioactive measurements of whole histones) have half-lives between ~1–2 hours. To support this finding, we use a broad-spectrum deacetylase inhibitor to verify that only fast turnover sites display 2–10 fold increases in acetylation whereas long-lived sites clearly do not. Most of these stable sites lack extensive functional studies or localization within global chromatin, and their role in non-genetic mechanisms of inheritance is as yet unknown. PMID:23892279

Zheng, Yupeng; Thomas, Paul M.; Kelleher, Neil L.

2013-01-01

163

Lipase-catalyzed synthesis of acetylated EGCG and antioxidant properties of the acetylated derivatives  

Technology Transfer Automated Retrieval System (TEKTRAN)

(-)-Epigallocatechin-3-O-gallate (EGCG) acetylated derivatives were prepared by lipase catalyzed acylation of EGCG with vinyl acetate to improve its lipophilicity and expand its application in lipophilic media. The immobilized lipase, Lipozyme RM IM, was found to be the optimum catalyst. The optimiz...

164

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

165

Acetylphosphate: a novel link between lysine acetylation and intermediary metabolism in bacteria.  

PubMed

In this issue of Molecular Cell, Weinert et al. (2013) demonstrate that the intermediary metabolite acetyl-phosphate is an important acetyl donor that contributes to global protein acetylation in growth-arrested E. coli. PMID:23870140

Verdin, Eric; Ott, Melanie

2013-07-25

166

Study on Dendrobium officinale O-acetyl-glucomannan (Dendronan®): part II. Fine structures of O-acetylated residues.  

PubMed

Main objective of this study was to investigate the detailed structural information about O-acetylated sugar residues in Dendronan(®). A water solution (2%, w/w) of Dendronan(®) was treated with endo-?-mannanase to produce oligosaccharides rich in O-acetylated sugar residues. The oligosaccharides were partly recovered by ethanol precipitation (70%, w/w). The recovered sample (designated Hydrolyzed Dendrobium officinale Polysaccharide, HDOP) had a yield of 24.7% based on the dry weight of Dendronan(®) and was highly O-acetylated. A D2O solution of HDOP (6%, w/w) generated strong signals in (1)H, (13)C, 2D (1)H-(1)H COSY, 2D (1)H-(1)H TOCSY, 2D (1)H-(1)H NOESY, 2D (1)H-(13)C HMQC, and 2D (1)H-(13)C HMBC NMR spectra. Results of NMR analyses showed that the majority of O-acetylated mannoses were mono-substituted with acetyl groups at O-2 or O-3 position. There were small amounts of mannose residues with di-O-acetyl substitution at both O-2 and O-3 positions. Minor levels of mannoses with 6-O-acetyl, 2,6-di-O-acetyl, and 3,6-di-O-acetyl substitutions were also identified. Much information about sugar residue sequence was extracted from 2D (1)H-(13)C HMBC and 2D (1)H-(1)H NOESY spectra. (1)J(C-H) coupling constants of major sugar residues were obtained. Evidences for the existence of branches or O-acetylated glucoses in HDOP were not found. The major structure of Dendronan(®) is shown as follows: [Formula: see text] M: ?-D-mannopyranose; G: ?-D-glucopyranose; a: O-acetyl group. PMID:25498655

Xing, Xiaohui; Cui, Steve W; Nie, Shaoping; Phillips, Glyn O; Goff, H Douglas; Wang, Qi

2015-03-01

167

Strawboard from vapor phase acetylation of wheat straw  

Microsoft Academic Search

Commercial ground wheat straw was used in a central composite response surface experimental design to examine four acetylating process variables: reaction temperature, reaction time, initial moisture content of straw, and the vapor flow rate of chemical reagent. The response variable was acetyl content determined as a function of straw weight gain. Diphenylmethyane diisocyante was used as a binder to prepare

Greggory S Karr; Xiuzhi S Sun

2000-01-01

168

Metobromuron: acetylation of the aniline moiety as a detoxification mechanism.  

PubMed

p-Bromoaniline is rapidly acetylated by four soil microorganisms. Two fungal species convert metobromuron to p-bromoacetanilide, but a bacterial and an algal species do not metabolize metobromuron. Acetylation may serve as a detoxification mechanism by competing with azobenzene formation in utilizing the aniline formed by metabolism of substituted urea herbicides. PMID:5436083

Tweedy, B G; Loeppky, C; Ross, J A

1970-04-24

169

Metobromuron: Acetylation of the Aniline Moiety as a Detoxification Mechanism  

Microsoft Academic Search

p-Bromoaniline is rapidly acetylated by four soil microorganisms. Two fungal species convert metobromuron to p-bromoacetanilide, but a bacterial and an algal species do not metabolize metobromuron. Acetylation may serve as a detoxification mechanism by competing with azobenzene formation in utilizing the aniline formed by metabolism of substituted urea herbicides.

B. G. Tweedy; Carol Loeppky; James A. Ross

1970-01-01

170

The biology of lysine acetylation integrates transcriptional programming and metabolism  

Microsoft Academic Search

The biochemical landscape of lysine acetylation has expanded from a small number of proteins in the nucleus to a multitude of proteins in the cytoplasm. Since the first report confirming acetylation of the tumor suppressor protein p53 by a lysine acetyltransferase (KAT), there has been a surge in the identification of new, non-histone targets of KATs. Added to the known

Jigneshkumar Patel; Ravi R Pathak; Shiraz Mujtaba

2011-01-01

171

Site-specific reactivity of nonenzymatic lysine acetylation.  

PubMed

Protein acetylation of lysine ?-amino groups is abundant in cells, particularly within mitochondria. The contribution of enzyme-catalyzed and nonenzymatic acetylation in mitochondria remains unresolved. Here, we utilize a newly developed approach to measure site-specific, nonenzymatic acetylation rates for 90 sites in eight native purified proteins. Lysine reactivity (as second-order rate constants) with acetyl-phosphate and acetyl-CoA ranged over 3 orders of magnitude, and higher chemical reactivity tracked with likelihood of dynamic modification in vivo, providing evidence that enzyme-catalyzed acylation might not be necessary to explain the prevalence of acetylation in mitochondria. Structural analysis revealed that many highly reactive sites exist within clusters of basic residues, whereas lysines that show low reactivity are engaged in strong attractive electrostatic interactions with acidic residues. Lysine clusters are predicted to be high-affinity substrates of mitochondrial deacetylase SIRT3 both in vitro and in vivo. Our analysis describing rate determination of lysine acetylation is directly applicable to investigate targeted and proteome-wide acetylation, whether or not the reaction is enzyme catalyzed. PMID:25555129

Baeza, Josue; Smallegan, Michael J; Denu, John M

2015-01-16

172

Semi-synthetic preparation of 1-O-(1'-/sup 14/C)hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor) using plant cell cultures  

SciTech Connect

Incubation of photomixotrophic cell suspension cultures of rape (Brassica napus) and heterotrophic cell suspension cultures of soya (Glycine max) with 1-O-(1'-/sup 14/C)hexadecyl-sn-glycerol or rac-1-O-(1'-/sup 14/C)hexadecylglycerol leads in high yield (up to 78%) to labeled 1-O-hexadecyl-2-acyl-sn-glycero-3-phosphocholines. Alkaline hydrolysis of the choline glycerophospholipids yields pure 1-O-(1'-/sup 14/C)hexadecyl-sn-glycero-3-phosphocholine. 1-O-(1'-14C)Hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor) is obtained by acetylating the lyso compound. The semi-synthetic preparation described leads to labeled platelet activating factor in an overall yield of 50-60% without loss of specific activity.

Weber, N.; Mangold, H.K.

1985-04-01

173

Different modes of carbon monoxide binding to acetyl-CoA synthase and the role of a conserved phenylalanine in the coordination environment of nickel.  

PubMed

Acetyl-CoA synthase (ACS) catalyzes the reversible condensation of CO and CH3 units at a unique Ni-Fe cluster, the A cluster, to form an acetyl-Ni intermediate that subsequently reacts with CoA to produce acetyl-CoA. ACS is a component of the multienzyme complex acetyl-CoA decarbonylase/synthase (ACDS) in Archaea and CO dehydrogenase/ACS (CODH/ACS) in bacteria; in both systems, intraprotein CO channeling takes place between the CODH and ACS active sites. Previous studies indicated that protein conformational changes control the chemical reactivity of the A cluster and suggested the involvement of a conserved Phe residue that moves concomitantly into and out of the coordination environment of Ni. Herein, steady-state rate measurements in which both CO and CH3-corrinoid are varied, and rapid methylation reactions of the ACDS ? subunit, measured by stopped-flow methods, provide a kinetic model for acetyl-CoA synthesis that includes a description of the inhibitory effects of CO explained by competition of CO and CH3 for the same form of the enzyme. Electron paramagnetic resonance titrations revealed that the formation of a paramagnetic Ni(+)-CO species does not match the kinetics of CO interaction as a substrate but instead correlates well with an inhibited state of the enzyme, which requires revision of previous models that postulate that this species is an intermediate. Characterization of the ? subunit F195A variant showed markedly increased substrate reactivity with CO, which provides biochemical functional evidence of steric shielding of the CO substrate interaction site by the phenyl group side chain. The phenyl group also likely enhances the nucleophilicity of the Ni center to facilitate CH3 group transfer. A model was developed for how the catalytic properties of the A cluster are optimized by linking conformational changes to a repositionable aromatic shield able to modulate the nucleophilicity of Ni, sterically select the most productive order of substrate addition, and overcome intrinsic inhibition by CO. PMID:23394607

Gencic, Simonida; Kelly, Kayla; Ghebreamlak, Selamawit; Duin, Evert C; Grahame, David A

2013-03-12

174

Mass Spectrometric Identification of Novel Lysine Acetylation Sites in Huntingtin*  

PubMed Central

Huntingtin (Htt) is a protein with a polyglutamine stretch in the N-terminus and expansion of the polyglutamine stretch causes Huntington's disease (HD). Htt is a multiple domain protein whose function has not been well characterized. Previous reports have shown, however, that post-translational modifications of Htt such as phosphorylation and acetylation modulate mutant Htt toxicity, localization, and vesicular trafficking. Lysine acetylation of Htt is of particular importance in HD as this modification regulates disease progression and toxicity. Treatment of mouse models with histone deacetylase inhibitors ameliorates HD-like symptoms and alterations in acetylation of Htt promotes clearance of the protein. Given the importance of acetylation in HD and other diseases, we focused on the systematic identification of lysine acetylation sites in Htt23Q (1–612) in a cell culture model using mass spectrometry. Myc-tagged Htt23Q (1–612) overexpressed in the HEK 293T cell line was immunoprecipitated, separated by SDS-PAGE, digested and subjected to high performance liquid chromatography tandem MS analysis. Five lysine acetylation sites were identified, including three novel sites Lys-178, Lys-236, Lys-345 and two previously described sites Lys-9 and Lys-444. Antibodies specific to three of the Htt acetylation sites were produced and confirmed the acetylation sites in Htt. A multiple reaction monitoring MS assay was developed to compare quantitatively the Lys-178 acetylation level between wild-type Htt23Q and mutant Htt148Q (1–612). This report represents the first comprehensive mapping of lysine acetylation sites in N-terminal region of Htt. PMID:21685499

Cong, Xin; Held, Jason M.; DeGiacomo, Francesco; Bonner, Akilah; Chen, Jan Marie; Schilling, Birgit; Czerwieniec, Gregg A.; Gibson, Bradford W.; Ellerby, Lisa M.

2011-01-01

175

A Bacterial Indole3-acetyl-L-aspartic Acid Hydrolase Inhibits Mung Bean ( Vigna radiata L.) Seed Germination Through Arginine-rich Intracellular Delivery  

Microsoft Academic Search

Indole-3-acetyl-L-aspartic acid (IAA-Asp) is a natural product in many plant species and plays many important roles in auxin\\u000a metabolism and plant physiology. IAA-Asp hydrolysis activity is, therefore, believed to affect plant physiology through changes\\u000a in IAA metabolism in plants. We applied a newly discovered technique, arginine-rich intracellular delivery (AID), to deliver\\u000a a bacterial IAA-Asp hydrolase into cells of mung bean

Kevin Liu; Han-Jung Lee; Sio San Leong; Chen-Lun Liu; Jyh-Ching Chou

2007-01-01

176

Cellulose hydrolysis in subcritical and supercritical water  

Microsoft Academic Search

In this paper we propose a new method to hydrolyze cellulose rapidly in supercritical water (SCW) to recover glucose, fructose and oligomers (cellobiose, cellotriose, cellotetraose, etc.). Cellulose decomposition experiments were conducted with a flow type reactor in the range of temperature from 290 to 400°C at 25MPa. A high pressure slurry feeder was developed to feed the cellulose–water slurries. Hydrolysis

Mitsuru Sasaki; Bernard Kabyemela; Roberto Malaluan; Satoshi Hirose; Naoko Takeda; Tadafumi Adschiri; Kunio Arai

1998-01-01

177

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

178

Acetylated histone H3 increases nucleosome dissociation  

NASA Astrophysics Data System (ADS)

Chromatin's basic unit structure is the nucleosome, i.e. genomic DNA wrapped around a particular class of proteins -- histones -- which due to their physical hindrance, block vital biological processes, such as DNA repair, DNA replication, and RNA transcription. Histone post-translational modifications, which are known to exist in vivo, are hypothesized to regulate these biological processes by directly altering DNA-histone interactions and thus nucleosome structure and stability. Using magnetic tweezers technique we studied the acetylation of histone H3 in the dyad region, i.e. at K115 and K122, on reconstituted arrays of nucleosomes under constant external force. Based on the measured increase in the probability of dissociation of modified nucleosomes, we infer that this double modification could facilitate histone chaperone mediated nucleosome disassembly in vivo.

Simon, Marek; Manohar, Mridula; Ottesen, Jennifer; Poirier, Michael

2009-03-01

179

HYDROLYSIS RATE CONSTANTS FOR ENHANCING PROPERTY-REACTIVITY RELATIONSHIPS  

EPA Science Inventory

Rate constants for hydrolysis in water of ten classes of organic compounds are examined with the objective of establishing new, or expanding existing, property reactivity correlations. These relationships then can be used to predict the environmental hydrolysis of chemicals that ...

180

Catalytic peptide hydrolysis by mineral surface: Implications for prebiotic chemistry  

E-print Network

Catalytic peptide hydrolysis by mineral surface: Implications for prebiotic chemistry Karina concentration to mineral surface area. The rate of pyrite catalysis of GGG hydrolysis was found to be saturable

Sverjensky, Dimitri A.

181

Oceanography June 2004 9 COA STA L O C E A N O P T I C S A N D DY N A M I C S  

E-print Network

Oceanography June 2004 9 COA STA L O C E A N O P T I C S A N D DY N A M I C S Studies of Coastal Increasing emphasis is being placed upon scientific research, monitoring, and manage- ment of the coastal including naviga- tion, shipping, and tactical naval operations. Bio-optical oceanography, also termed bio

Fabrikant, Sara Irina

182

Identification of Coa2 as an assembly factor for cytochrome c oxidase biogenesis1 Fabien Pierrel, Oleh Khalimonchuk, Paul A. Cobine and Dennis R. Winge*3  

E-print Network

).7 The biogenesis of CcO, occurring within the IM, commences with the mitochondrial8 synthesis of the Cox1 subunit1 Identification of Coa2 as an assembly factor for cytochrome c oxidase biogenesis1 2 Fabien with three mitochondrial encoded subunits (Cox1-Cox3) forming the core enzyme embedded4 within

Paris-Sud XI, Université de

183

EDC4 interacts with and regulates the dephospho-CoA kinase activity of CoA synthase.  

PubMed

Coenzyme A synthase (CoAsy) is a bifunctional enzyme which facilitates the last two steps of Coenzyme A biogenesis in higher eukaryotes. Here we describe that CoAsy forms a complex with enhancer of mRNA-decapping protein 4 (EDC4), a central scaffold component of processing bodies. CoAsy/EDC4 complex formation is regulated by growth factors and is affected by cellular stresses. EDC4 strongly inhibits the dephospho-CoA kinase activity of CoAsy in vitro. Transient overexpression of EDC4 decreases cell proliferation, and further co-expression of CoAsy diminishes this effect. Here we report that EDC4 might contribute to regulation of CoA biosynthesis in addition to its scaffold function in processing bodies. PMID:22982864

Gudkova, Daria; Panasyuk, Ganna; Nemazanyy, Ivan; Zhyvoloup, Alexander; Monteil, Pascale; Filonenko, Valeriy; Gout, Ivan

2012-10-19

184

QSAR and Molecular Docking Studies of Oxadiazole-Ligated Pyrrole Derivatives as Enoyl-ACP (CoA) Reductase Inhibitors  

PubMed Central

A quantitative structure-activity relationship model was developed on a series of compounds containing oxadiazole-ligated pyrrole pharmacophore to identify key structural fragments required for anti-tubercular activity. Two-dimensional (2D) and three-dimensional (3D) QSAR studies were performed using multiple linear regression (MLR) analysis and k-nearest neighbour molecular field analysis (kNN-MFA), respectively. The developed QSAR models were found to be statistically significant with respect to training, cross-validation, and external validation. New chemical entities (NCEs) were designed based on the results of the 2D- and 3D-QSAR. NCEs were subjected to Lipinski’s screen to ensure the drug-like pharmacokinetic profile of the designed compounds in order to improve their bioavailability. Also, the binding ability of the NCEs with enoyl-ACP (CoA) reductase was assessed by docking. PMID:24634843

Asgaonkar, Kalyani D.; Mote, Ganesh D.; Chitre, Trupti S.

2014-01-01

185

Acetylation of tau inhibits its degradation and contributes to tauopathy.  

PubMed

Neurodegenerative tauopathies characterized by hyperphosphorylated tau include frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17) and Alzheimer's disease (AD). Reducing tau levels improves cognitive function in mouse models of AD and FTDP-17, but the mechanisms regulating the turnover of pathogenic tau are unknown. We found that tau is acetylated and that tau acetylation prevents degradation of phosphorylated tau (p-tau). We generated two antibodies specific for acetylated tau and showed that tau acetylation is elevated in patients at early and moderate Braak stages of tauopathy. Histone acetyltransferase p300 was involved in tau acetylation and the class III protein deacetylase SIRT1 in deacetylation. Deleting SIRT1 enhanced levels of acetylated-tau and pathogenic forms of p-tau, probably by blocking proteasome-mediated degradation. Inhibiting p300 with a small molecule promoted tau deacetylation and eliminated p-tau associated with tauopathy. Modulating tau acetylation could be a new therapeutic strategy to reduce tau-mediated neurodegeneration. PMID:20869593

Min, Sang-Won; Cho, Seo-Hyun; Zhou, Yungui; Schroeder, Sebastian; Haroutunian, Vahram; Seeley, William W; Huang, Eric J; Shen, Yong; Masliah, Eliezer; Mukherjee, Chandrani; Meyers, David; Cole, Philip A; Ott, Melanie; Gan, Li

2010-09-23

186

Chitosan Molecular Structure as a Function of N-Acetylation  

SciTech Connect

Molecular dynamics simulations have been carried out to characterize the structure and solubility of chitosan nanoparticle-like structures as a function of the deacetylation level (0, 40, 60, and 100%) and the spatial distribution of the N-acetyl groups in the particles. The polysaccharide chains of highly N-deacetylated particles where the N-acetyl groups are uniformly distributed present a high flexibility and preference for the relaxed two-fold helix and five-fold helix motifs. When these groups are confined to a given region of the particle, the chains adopt preferentially a two-fold helix with f and w values close to crystalline chitin. Nanoparticles with up to 40% acetylation are moderately soluble, forming stable aggregates when the N-acetyl groups are unevenly distributed. Systems with 60% or higher N-acetylation levels are insoluble and present similar degrees of swelling regardless the distribution of their N-acetyl groups. Overall particle solvation is highly affected by electrostatic forces resulting from the degree of acetylation. The water mobility and orientation around the polysaccharide chains affects the stability of the intramolecular O3- HO3(n) ... O5(n+ 1) hydrogen bond, which in turn controls particle aggregation.

Franca, Eduardo F.; Freitas, Luiz C.; Lins, Roberto D.

2011-07-01

187

Coupling of actin hydrolysis and polymerization: Reduced description with two  

E-print Network

OFFPRINT Coupling of actin hydrolysis and polymerization: Reduced description with two nucleotide of actin hydrolysis and polymerization: Reduced description with two nucleotide states X. Li1,2 , R to the hydrolysis of adenosine triphosphate (ATP), which involves both the cleavage of ATP and the release

Kierfeld, Jan

188

Actin Polymerization Overshoots and Hydrolysis as Assayed by Pyrene Fluorescence  

E-print Network

Actin Polymerization Overshoots and Hydrolysis as Assayed by Pyrene Fluorescence F. J. Brooks and A in different ATP hydrolysis states are not consistent with experimental data. This strong sensitivity of intensity to hydrolysis state implies that a measured pyrene intensity curve does not im- mediately reveal

Carlsson, Anders

189

Effects of microtubule mechanics on hydrolysis and catastrophes  

E-print Network

Effects of microtubule mechanics on hydrolysis and catastrophes N Müller and J Kierfeld Department modeling steric constraints to investigate the influence of mechanical forces on hydrolysis bending angle, which changes from °0 to °22 by hydrolysis of a dimer. This also affects the lateral

Kierfeld, Jan

190

ATP Hydrolysis Stimulates Large Length Fluctuations in Single Actin Filaments  

E-print Network

ATP Hydrolysis Stimulates Large Length Fluctuations in Single Actin Filaments Evgeny B. Stukalin is investigated theoretically using a stochastic model that takes into account the hydrolysis of ATP filaments. It is found that the ATP hydrolysis has a strong effect on dynamic properties of single actin

191

Energy Optimization of Bioethanol Production via Hydrolysis of Switchgrass  

E-print Network

1 Energy Optimization of Bioethanol Production via Hydrolysis of Switchgrass Mariano MartĂ­n, via hydrolysis. A superstructure embedding a number of alternatives is proposed. Two technologies of the grass is broken down. Next, enzymatic hydrolysis follows any of the pretreaments to obtain fermentable

Grossmann, Ignacio E.

192

Synergistic Catalysis of Dimetilan Hydrolysis by Metal Ions and  

E-print Network

Synergistic Catalysis of Dimetilan Hydrolysis by Metal Ions and Organic Ligands C H I N G - H U A H, The Johns Hopkins University, Baltimore, Maryland 21218 Hydrolysis of the insecticide dimetilan, which ion-organic ligandsynergisticeffectsonthedegradationofagrochemicals. Dimetilan hydrolysis is strongly

Huang, Ching-Hua

193

Unconventional Relationshipsfor Hemicellulose Hydrolysis and Subsequent Cellulose Digestion  

E-print Network

Chapter 6 Unconventional Relationshipsfor Hemicellulose Hydrolysis and Subsequent Cellulose and subsequently by enzymatic hydrolysis of the residual cellulose, and these sugars can be used to produce fuels for such biological routes, and we seek to better understand hydrolysis kinetics to support emerging applications

California at Riverside, University of

194

FRONTIERS ARTICLE On the hydration and hydrolysis of carbon dioxide  

E-print Network

FRONTIERS ARTICLE On the hydration and hydrolysis of carbon dioxide Alice H. England a,b , Andrew M August 2011 a b s t r a c t The dissolution of carbon dioxide in water and the ensuing hydrolysis, and hydration strength. Ă? 2011 Elsevier B.V. All rights reserved. 1. Introduction The hydrolysis of carbon

Cohen, Ronald C.

195

Enantioselective monoterpene alcohol acetylation in Origanum, Mentha and Salvia species.  

PubMed

Selected plants within the Origanum, Mentha and Salvia genera, that contain significant amounts of chiral volatile alcohols and their related acetates, exhibit remarkable enantioselectivity of alcohol acetyl transferase (AAT) activity and particularly can discriminate between linalool enantiomers. Origanum dayi AAT produced almost enantiomerically pure (R)-linalyl acetate by enzymatic acetylation of racemic linalool, whereas the closely related O. majorana AAT produced a mixture of (R)- and (S)-linalyl acetate with a ratio of 6:4. V(max) of O. dayi acetylation activity was 30-fold higher for (R)-linalool, whereas in O. majorana no such differences were found. PMID:18834605

Larkov, Olga; Zaks, Alon; Bar, Einat; Lewinsohn, Efraim; Dudai, Nativ; Mayer, Alfred M; Ravid, Uzi

2008-10-01

196

Transesterification/acetylation of long chain alcohols with alkyl acetate.  

PubMed

Gas chromatographic characterizations of fatty alcohols are generally carried out as the free alcohols, trimethyl silyl or acetyl derivatives. In this study, transesterification/acetylation of long chain fatty alcohols is simply carried out by dissolving the alcohol in ethyl/methyl acetate and passing through a micro-column packed with solid NaOH. Reaction times are slightly different for alcohols of different chain length. Rice bran alcohols of 24-34 carbon atom are successfully acetylated. Also, castor oil methyl ester can be interesterified but with longer reaction time. PMID:20599854

Kaewkool, Phattaraporn; Krisnangkura, Kanit

2010-09-01

197

Ultrafast photodissociation studies of acetyl cyanide and acetic acid and unimolecular decomposition rates of the acetyl radical products  

NASA Astrophysics Data System (ADS)

Unimolecular decomposition rates for acetyl radical following the photodissociation of acetyl cyanide and acetic acid near 193 nm have been studied using ultrafast mass-resolved photoionization spectroscopy. In both cases, the parent decays with an instrumentally limited lifetime, while the acetyl radical behaves in a manner consistent with an RRKM mechanism, in contrast to our previous results on acetone. It is necessary to convolute the population distribution with the microcanonical RRKM rates in order to achieve this agreement. We have also undertaken an ab initio study of the excited states of acetyl cyanide to clarify the assignments of these states. The state excited at 193 nm arises from a ???* transition with a calculated transition velocity dipole moment oriented at an angle of 57° with respect to the C-C?N bond, resulting in an anisotropy parameter of -0.22. This is in reasonable agreement with the previous data of North et al. [J. Phys. Chem. A 101, 9224 (1997)]. The apparent RRKM behavior of the acetyl radical formed by the photodissociation of acetic acid and acetyl cyanide indicates that acetyl radical produced by the photodissociation of acetone at 193 nm may exhibit "extrinsic non-RRKM" effects, i.e., dynamic bottlenecks or mode specific effects.

Owrutsky, J. C.; Baronavski, A. P.

1999-10-01

198

Neuroprotection in rabbit retina with N-acetyl-aspartylglutamate and 2-phosphonyl-methyl pentanedioic acid  

NASA Astrophysics Data System (ADS)

Retinal tissue is subject to ischemia from diabetic retinopathy and other conditions that affect the retinal vasculature such as lupus erythematosus and temporal arteritis. There is evidence in animal models of reversible ischemia that a therapeutic window exists during early recovery when agents that reduce glutamate activity at its receptor sites can rescue neurons from injury. To model ischemia, we used sodium cyanide (NaCN), to inhibit oxidative metabolism, and 2-deoxyglucose (2-DG) to inhibit glycolysis. Dissociated rabbit retina cells were studied to evaluate the potential neuroprotective effects of N-acetyl-aspartyl-glutamate (MAAG), which competes with glutamate as a low-potency agonist at the NMDA receptor complex. N-acetylated ?-linked acidic dipeptidase (NAALADase; the NAAG-hydrolyzing enzyme) is responsible for the hydrolysis of NAAG into glutamate, a neurotransmitter and potent excitotoxin, and N-acetylaspartate. 2-Phosphonyl-methyl pentanedioic acid (PMPA) and ?-linked NAAG (?-NAAG), inhibitors of NAALADase, were also tested, since inhibition of NAALADase could reduce synaptic glutamate and increase the concentration of NAAG. We found that metabolic inhibition with NaCN/2-DG for 1 hour caused 50% toxicity as assessed with the MTT assay. Co-treatment with NAAG resulted in dose-dependent protection of up to 55% (p<0.005). When the non-hydrolyzable, NAALADase inhibitor ?-NAAG was employed dose-dependent protection of up to 37% was observed (p<0.001). PMPA also showed 48% protection (p<.05-.001) against these insults. These data suggest that NAAG may antagonize the effect of glutamate at the NMDA receptor complex in retina. Inhibition of NAALADase by PMPA and ?-NAAG may increase the activity of endogenous NAAG.

Hacker, Henry D.; Yourick, Debra L.; Koenig, Michael K.; Slusher, Barbara S.; Meyerhoff, James L.

1999-06-01

199

Identification of Acetylated, Tetrahalogenated Benzimidazole d-Ribonucleosides with Enhanced Activity against Human Cytomegalovirus?  

PubMed Central

DNA packaging is the key step in viral maturation and involves binding and cleavage of viral DNA containing specific DNA-packaging motifs. This process is mediated by a group of specific enzymes called terminases. We previously demonstrated that the human cytomegalovirus (HCMV) terminase is composed of the large subunit pUL56 and the small subunit pUL89. While the large subunit mediates sequence-specific DNA binding and ATP hydrolysis, pUL89 is required only for duplex nicking. An excellent inhibitor targeting HCMV terminase is 2-bromo-5,6-dichloro-1-(?-d-ribofuranosyl)benzimidazole (BDCRB), but it was not developed as an antiviral drug due to its metabolic cleavage in experimental animals. We now have tested several new benzimidazole d-ribonucleosides in order to determine whether these compounds represent new, potent inhibitors. Analysis by bioluminometric ATPase activity assays identified two of the new compounds with a high inhibitory effect, 2-bromo-4,5,6-trichloro-1-(2,3,5-tri-O-acetyl-?-d-ribofuranosyl) benzimidazole (BTCRB) and 2,4,5,6-tetrachloro-1-(2,3,5-tri-O-acetyl-?-d-ribofuranosyl benzimidazole (Cl4RB). By using viral plaque formation, viral yield, and viral growth kinetics, we demonstrated that the two compounds BTCRB and Cl4RB had antiviral activities similar to that of BDCRB. Interestingly, BTCRB retained its inhibitory activity after preincubation with HFF cells. By use of electron microscopy, we observed an increase of B capsids and a lack of cytoplasmic capsids in the presence of the compounds that correlated with the virus yield. Furthermore, cleavage of concatenated DNA was inhibited by both compounds, and inhibition by BTCRB was shown to be dose dependent. These results demonstrate that the new compounds are highly active against HCMV and act by mechanisms similar but not identical to those of BDCRB. PMID:17728228

Hwang, Jae-Seon; Kregler, Oliver; Schilf, Rita; Bannert, Norbert; Drach, John C.; Townsend, Leroy B.; Bogner, Elke

2007-01-01

200

Codominant Expression of N-Acetylation and O-Acetylation Activities Catalyzed by N-Acetyltransferase 2 in Human Hepatocytes  

PubMed Central

Human populations exhibit genetic polymorphism in N-acetylation capacity, catalyzed by N-acetyltransferase 2 (NAT2). We investigated the relationship between NAT2 acetylator genotype and phenotype in cryopreserved human hepatocytes. NAT2 genotypes determined in 256 human samples were assigned as rapid (two rapid alleles), intermediate (one rapid and one slow allele), or slow (two slow alleles) acetylator phenotypes based on functional characterization of the NAT2 alleles reported previously in recombinant expression systems. A robust and significant relationship was observed between deduced NAT2 phenotype (rapid, intermediate, or slow) and N-acetyltransferase activity toward sulfamethazine (p < 0.0001) and 4-aminobiphenyl (p < 0.0001) and for O-acetyltransferase-catalyzed metabolic activation of N-hydroxy-4-aminobiphenyl (p < 0.0001), N-hydroxy-2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (p < 0.01), and N-hydroxy-2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (p < 0.0001). NAT2-specific protein levels also significantly associated with the rapid, intermediate, and slow NAT2 acetylator phenotypes (p < 0.0001). As a negative control, p-aminobenzoic acid (an N-acetyltransferase 1-selective substrate) N-acetyltransferase activities from the same samples did not correlate with the three NAT2 acetylator phenotypes (p > 0.05). These results clearly document codominant expression of human NAT2 alleles resulting in rapid, intermediate, and slow acetylator phenotypes. The three phenotypes reflect levels of NAT2 protein catalyzing both N- and O-acetylation. Our results suggest a significant role of NAT2 acetylation polymorphism in arylamine-induced cancers and are consistent with differential cancer risk and/or drug efficacy/toxicity in intermediate compared with rapid or slow NAT2 acetylator phenotypes. PMID:20430842

Doll, Mark A.; Zang, Yu; Moeller, Timothy

2010-01-01

201

Acetylation and hydroxylation of sulphatroxazole in the snail Cepaea hortensis and the slug Arion rufus  

Microsoft Academic Search

The snail Cepaea hortensis can acetylate and hydroxylate sulphatroxazole via a pathway similar to that in man. The principal metabolic pathways, in order of decreasing rate, are hydroxylation, glucuronidation and acetylation. The slug Anion rufus also can acetylate and hydroxylate sulphatroxazole, although, in contrast to the snail, is rate of acetylation is higher than that of hydroxylation.

T. B. Vree; M. L. Vree; J. F. M. Nouws

1987-01-01

202

Acetylation and hydroxylation of sulphatroxazole in the snail Cepaea hortensis and the slug Arion rufus.  

PubMed

The snail Cepaea hortensis can acetylate and hydroxylate sulphatroxazole via a pathway similar to that in man. The principal metabolic pathways, in order of decreasing rate, are hydroxylation, glucuronidation and acetylation. The slug Arion rufus also can acetylate and hydroxylate sulphatroxazole, although, in contrast to the snail, is rate of acetylation is higher than that of hydroxylation. PMID:3564322

Vree, T B; Vree, M L; Nouws, J F

1987-01-01

203

In situ proton NMR study of acetyl and formyl group migration in mono-O-acyl D-glucose.  

PubMed

Acetyl and formyl group migration, mutarotation, and hydrolysis of mono-O-acylated glucose are studied by in situ 1D and 2D (1)H NMR spectroscopy. Alpha-D-glucosyl-1-acetate and alpha-D-glucosyl-1-formate serve as sole starting materials. They are generated in situ by configuration retaining glucosyltransfer from alpha-D-glucosyl-1-phosphate to formate and acetate, which is catalyzed by the Glu-237 --> Gln mutant of Leuconostoc mesenteroides sucrose phosphorylase. Temporary accumulated regio-isomeric mono-O-acyl D-glucoses are identified, characterized, and quantified directly from the reaction mixture. Time courses of the transformations give insight into pH dependence of acyl group migration and mutarotation as well as into the stability of various regioisomers. PMID:19172587

Brecker, Lothar; Mahut, Marek; Schwarz, Alexandra; Nidetzky, Bernd

2009-04-01

204

Effects of microtubule mechanics on hydrolysis and catastrophes  

E-print Network

We introduce a model for microtubule mechanics containing lateral bonds between dimers in neighboring protofilaments, bending rigidity of dimers, and repulsive interactions between protofilaments modeling steric constraints to investigate the influence of mechanical forces on hydrolysis and catastrophes. We use the allosteric dimer model, where tubulin dimers are characterized by an equilibrium bending angle, which changes from $0^\\circ$ to $22^\\circ$ by hydrolysis of a dimer. This also affects the lateral interaction and bending energies and, thus, the mechanical equilibrium state of the microtubule. As hydrolysis gives rise to conformational changes in dimers, mechanical forces also influence the hydrolysis rates by mechanical energy changes modulating the hydrolysis rate. The interaction via the microtubule mechanics then gives rise to correlation effects in the hydrolysis dynamics, which have not been taken into account before. Assuming a dominant influence of mechanical energies on hydrolysis rates, we i...

Müller, Nina

2014-01-01

205

?-cyclodextrin assistant flavonoid glycosides enzymatic hydrolysis  

PubMed Central

Background: The content of icaritin and genistein in herba is very low, preparation with relatively large quantities is an important issue for extensive pharmacological studies. Objective: This study focuses on preparing and enzymic hydrolysis of flavonoid glycosides /?-cyclodextrin inclusion complex to increase the hydrolysis rate. Materials and Methods: The physical property of newly prepared inclusion complex was tested by differential scanning calorimetry (DSC). The conditions of enzymatic hydrolysis were optimized for the bioconversion of flavonoid glycosides /?-cyclodextrin inclusion complex by mono-factor experimental design. The experiments are using the icariin and genistein as the model drugs. Results: The solubility of icariin and genistein were increased almost 17 times from 29.2 ?g/ml to 513.5 ?g/ml at 60°C and 28 times from 7.78 ?g/ml to 221.46 ?g/ml at 50°C, respectively, demonstrating that the inclusion complex could significantly increase the solubility of flavonoid glycosides. Under the optimal conditions, the reaction time of icariin and genistin decreased by 68% and 145%, when compared with that without ?-CD inclusion. By using this enzymatic condition, 473 mg icaritin (with the purity of 99.34%) and 567 mg genistein(with the purity of 99.46%), which was finally determined by melt point, ESI-MS, UV, IR, 1H NMR and 13C NMR, was obtained eventually by transforming the inclusion complex(contains 1.0 g substrates). Conclusion: This study can clearly indicate a new attempt to improve the speed of enzyme-hydrolysis of poorly water-soluble flavonoid glycosides and find a more superior condition which is used to prepare icaritin and genistein. PMID:24143039

Jin, Xin; Zhang, Zhen-hai; Sun, E.; Jia, Xiao-Bin

2013-01-01

206

Acetylation Targets Mutant Huntingtin to Autophagosomes for Degradation  

PubMed Central

SUMMARY Huntington’s disease (HD) is an incurable neurodegenerative disease caused by neuronal accumulation of the mutant protein huntingtin. Improving clearance of the mutant protein is expected to prevent cellular dysfunction and neurodegeneration in HD. We report here that such clearance can be achieved by posttranslational modification of the mutant Huntingtin (Htt) by acetylation at lysine residue 444 (K444). Increased acetylation at K444 facilitates trafficking of mutant Htt into autophagosomes, significantly improves clearance of the mutant protein by macroautophagy, and reverses the toxic effects of mutant huntingtin in primary striatal and cortical neurons and in a transgenic C. elegans model of HD. In contrast, mutant Htt that is rendered resistant to acetylation dramatically accumulates and leads to neurodegeneration in cultured neurons and in mouse brain. These studies identify acetylation as a mechanism for removing accumulated protein in HD, and more broadly for actively targeting proteins for degradation by autophagy. PMID:19345187

Jeong, Hyunkyung; Then, Florian; Melia, Thomas J.; Mazzulli, Joseph R.; Cui, Libin; Savas, Jeffrey N.; Voisine, Cindy; Paganetti, Paolo; Tanese, Naoko; Hart, Anne C.; Yamamoto, Ai; Krainc, Dimitri

2010-01-01

207

Acetylation negatively regulates glycogen phosphorylase by recruiting protein phosphatase 1  

PubMed Central

Glycogen phosphorylase (GP) catalyzes the rate-limiting step in glycogen catabolism and plays a key role in maintaining cellular and organismal glucose homeostasis. GP is the first protein whose function was discovered to be regulated by reversible protein phosphorylation, which is controlled by phosphorylase kinase (PhK) and protein phosphatase 1 (PP1). Here, we report that lysine acetylation negatively regulates GP activity by both inhibiting enzyme activity directly and promoting dephosphorylation. Acetylation of GP Lys470 enhances its interaction with the PP1 substrate targeting subunit, GL, and PP1, thereby promoting GP dephosphorylation and inactivation. We show that GP acetylation is stimulated by glucose and insulin and inhibited by glucagon. Our results provide molecular insights into the intricate regulation of the classical GP and a functional cross-talk between protein acetylation and phosphorylation. PMID:22225877

Zhang, Tengfei; Wang, Shiwen; Lin, Yan; Xu, Wei; Ye, Dan; Xiong, Yue; Zhao, Shimin; Guan, Kun-Liang

2012-01-01

208

Functional characterization of two new members of the caffeoyl CoA O -methyltransferase-like gene family from Vanilla planifolia reveals a new class of plastid-localized O -methyltransferases  

Microsoft Academic Search

Caffeoyl CoA O-methyltransferases (OMTs) have been characterized from numerous plant species and have been demonstrated to be involved in\\u000a lignin biosynthesis. Higher plant species are known to have additional caffeoyl CoA OMT-like genes, which have not been well\\u000a characterized. Here, we identified two new caffeoyl CoA OMT-like genes by screening a cDNA library from specialized hair cells\\u000a of pods of

Thomas Widiez; Thomas G. Hartman; Nativ Dudai; Qing Yan; Michael Lawton; Daphna Havkin-Frenkel; Faith C. Belanger

209

Fungal secretomes enhance sugar beet pulp hydrolysis  

PubMed Central

The recalcitrance of lignocellulose makes enzymatic hydrolysis of plant biomass for the production of second generation biofuels a major challenge. This work investigates an efficient and economic approach for the enzymatic hydrolysis of sugar beet pulp (SBP), which is a difficult to degrade, hemicellulose-rich by-product of the table sugar industry. Three fungal strains were grown on different substrates and the production of various extracellular hydrolytic and oxidative enzymes involved in pectin, hemicellulose, and cellulose breakdown were monitored. In a second step, the ability of the culture supernatants to hydrolyze thermally pretreated SBP was tested in batch experiments. The supernatant of Sclerotium rolfsii, a soil-borne facultative plant pathogen, was found to have the highest hydrolytic activity on SBP and was selected for further hydrolyzation experiments. A low enzyme load of 0.2 mg g–1 protein from the culture supernatant was sufficient to hydrolyze a large fraction of the pectin and hemicelluloses present in SBP. The addition of Trichoderma reesei cellulase (1–17.5 mg g–1 SBP) resulted in almost complete hydrolyzation of cellulose. It was found that the combination of pectinolytic, hemicellulolytic, and cellulolytic activities works synergistically on the complex SBP composite, and a combination of these hydrolytic enzymes is required to achieve a high degree of enzymatic SBP hydrolysis with a low enzyme load. PMID:24677771

Kracher, Daniel; Oros, Damir; Yao, Wanying; Preims, Marita; Rezic, Iva; Haltrich, Dietmar; Rezic, Tonci; Ludwig, Roland

2014-01-01

210

Mechanistic insights into the regulation of metabolic enzymes by acetylation  

PubMed Central

The activity of metabolic enzymes is controlled by three principle levels: the amount of enzyme, the catalytic activity, and the accessibility of substrates. Reversible lysine acetylation is emerging as a major regulatory mechanism in metabolism that is involved in all three levels of controlling metabolic enzymes and is altered frequently in human diseases. Acetylation rivals other common posttranslational modifications in cell regulation not only in the number of substrates it modifies, but also the variety of regulatory mechanisms it facilitates. PMID:22826120

2012-01-01

211

A phosphorylation-acetylation switch regulates STAT1 signaling  

PubMed Central

Cytokines such as interferons (IFNs) activate signal transducers and activators of transcription (STATs) via phosphorylation. Histone deacetylases (HDACs) and the histone acetyltransferase (HAT) CBP dynamically regulate STAT1 acetylation. Here we show that acetylation of STAT1 counteracts IFN-induced STAT1 phosphorylation, nuclear translocation, DNA binding, and target gene expression. Biochemical and genetic experiments altering the HAT/HDAC activity ratio and STAT1 mutants reveal that a phospho-acetyl switch regulates STAT1 signaling via CBP, HDAC3, and the T-cell protein tyrosine phosphatase (TCP45). Strikingly, inhibition of STAT1 signaling via CBP-mediated acetylation is distinct from the functions of this HAT in transcriptional activation. STAT1 acetylation induces binding of TCP45, which catalyzes dephosphorylation and latency of STAT1. Our results provide a deeper understanding of the modulation of STAT1 activity. These findings reveal a new layer of physiologically relevant STAT1 regulation and suggest that a previously unidentified balance between phosphorylation and acetylation affects cytokine signaling. PMID:19171783

Krämer, Oliver H.; Knauer, Shirley K.; Greiner, Georg; Jandt, Enrico; Reichardt, Sigrid; Gührs, Karl-Heinz; Stauber, Roland H.; Böhmer, Frank D.; Heinzel, Thorsten

2009-01-01

212

An acetylation switch controls TDP-43 function and aggregation propensity.  

PubMed

TDP-43 pathology is a disease hallmark that characterizes amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP). Although a critical role for TDP-43 as an RNA-binding protein has emerged, the regulation of TDP-43 function is poorly understood. Here, we identify lysine acetylation as a novel post-translational modification controlling TDP-43 function and aggregation. We provide evidence that TDP-43 acetylation impairs RNA binding and promotes accumulation of insoluble, hyper-phosphorylated TDP-43 species that largely resemble pathological inclusions in ALS and FTLD-TDP. Moreover, biochemical and cell-based assays identify oxidative stress as a signalling cue that promotes acetylated TDP-43 aggregates that are readily engaged by the cellular defense machinery. Importantly, acetylated TDP-43 lesions are found in ALS patient spinal cord, indicating that aberrant TDP-43 acetylation and loss of RNA binding are linked to TDP-43 proteinopathy. Thus, modulating TDP-43 acetylation represents a plausible strategy to fine-tune TDP-43 activity, which could provide new therapeutic avenues for TDP-43 proteinopathies. PMID:25556531

Cohen, Todd J; Hwang, Andrew W; Restrepo, Clark R; Yuan, Chao-Xing; Trojanowski, John Q; Lee, Virginia M Y

2015-01-01

213

Acetyl Radical Generation in Cigarette Smoke: Quantification and Simulations.  

PubMed

Free radicals are present in cigarette smoke and can have a negative effect on human health. However, little is known about their formation mechanisms. Acetyl radicals were quantified in tobacco smoke and mechanisms for their generation were investigated by computer simulations. Acetyl radicals were trapped from the gas phase using 3-amino-2, 2, 5, 5-tetramethyl-proxyl (3AP) on solid support to form stable 3AP adducts for later analysis by high performance liquid chromatography (HPLC), mass spectrometry/tandem mass spectrometry (MS-MS/MS) and liquid chromatography-mass spectrometry (LC-MS). Simulations were performed using the Master Chemical Mechanism (MCM). A range of 10-150 nmol/cigarette of acetyl radical was measured from gas phase tobacco smoke of both commerial and research cigarettes under several different smoking conditions. More radicals were detected from the puff smoking method compared to continuous flow sampling. Approximately twice as many acetyl radicals were trapped when a glass filber particle filter (GF/F specifications) was placed before the trapping zone. Simulations showed that NO/NO2 reacts with isoprene, initiating chain reactions to produce hydroxyl radical, which abstracts hydrogen from acealdehyde to generate acetyl radical. These mechanisms can account for the full amount of acetyl radical detected experimentally from cigarette smoke. Similar mechanisms may generate radicals in second hand smoke. PMID:25253993

Hu, Na; Green, Sarah A

2014-10-01

214

EPR of Gamma irradiated N?-acetyl L-glutamic acid and N?-acetyl L-glutamine  

NASA Astrophysics Data System (ADS)

Single crystals of N?-acetyl L-glutamic acid and N?-acetyl L-glutamine were ?-irradiated and the paramagnetic species formed were investigated at room temperature by electron spin resonance technique. The observed species in N?-acetyl L-glutamic acid single crystal were attributed to the, HOOCCH 2CH 2C(NHCOCH 3)COOH radical; and those in N?-acetyl L-glutamine single crystal to the NH2COCH2CH2 C( NHCOCH3) COOH and NH2COCH2CH2CH( NHCOCH3) C overlineOOH radicals. The g values and the hyperfine coupling constants of the unpaired electron with the environmental methylene, methine protons and 14N nucleus were determined.

Köksal, F.; Osmano?lu, ?.; Kartal, Í.; Ucun, F.

1997-05-01

215

Proteome-wide lysine acetylation profiling of the human pathogen Mycobacterium tuberculosis.  

PubMed

N(?)-Acetylation of lysine residues represents a pivotal post-translational modification used by both eukaryotes and prokaryotes to modulate diverse biological processes. Mycobacterium tuberculosis is the causative agent of tuberculosis, one of the most formidable public health threats. Many aspects of the biology of M. tuberculosis remain elusive, in particular the extent and function of N(?)-lysine acetylation. With a combination of anti-acetyllysine antibody-based immunoaffinity enrichment with high-resolution mass spectrometry, we identified 1128 acetylation sites on 658 acetylated M. tuberculosis proteins. GO analysis of the acetylome showed that acetylated proteins are involved in the regulation of diverse cellular processes including metabolism and protein synthesis. Six types of acetylated peptide sequence motif were revealed from the acetylome. Twenty lysine-acetylated proteins showed homology with acetylated proteins previously identified from Escherichia coli, Salmonella enterica, Bacillus subtilis and Streptomyces roseosporus, with several acetylation sites highly conserved among four or five bacteria, suggesting that acetylated proteins are more conserved. Notably, several proteins including isocitrate lyase involved in the persistence, virulence and antibiotic resistance are acetylated, and site-directed mutagenesis of isocitrate lyase acetylation site to glutamine led to a decrease of the enzyme activity, indicating major roles of KAc in these proteins engaged cellular processes. Our data firstly provides a global survey of M. tuberculosis acetylation, and implicates extensive regulatory role of acetylation in this pathogen. This may serve as an important basis to address the roles of lysine acetylation in M. tuberculosis metabolism, persistence and virulence. PMID:25456444

Xie, Longxiang; Wang, Xiaobo; Zeng, Jie; Zhou, Mingliang; Duan, Xiangke; Li, Qiming; Zhang, Zhen; Luo, Hongping; Pang, Lei; Li, Wu; Liao, Guojian; Yu, Xia; Li, Yunxu; Huang, Hairong; Xie, Jianping

2015-02-01

216

Inactivation kinetics of beta-N-acetyl-D-glucosaminidase from green crab (Scylla serrata) in dioxane solution.  

PubMed

Beta-N-acetyl-D-glucosaminidase (NAGase, EC.3.2.1.52), which catalyzes the cleavage of N-acetylglucosamine polymers, is a composition of chitinase and cooperates with endo-chitinase and exo-chitinase to disintegrate chitin into N-acetylglucosamine (NAG). In this investigation, A NAGase from green crab (Scylla serrata) was purified and the effects of dioxane on the enzyme activity for the hydrolysis of p-Nitrophenyl-N-acetyl-beta-D-glucosaminide (pNP-NAG) were studied. The results show that appropriate concentrations of dioxane can lead to reversible inactivation of the enzyme and the inactivation is classified as mixed type. The value of IC50, the dioxane (inactivator) concentration leading to 50% activity lost, is estimated to be 0.68%. The kinetics of inactivation of NAGase in the appropriate concentrations of dioxane solution has been studied using the kinetic method of the substrate reaction. The rate constants of inactivation have been determined. The results showed that k+0 is much larger than k'+0, indicating the free enzyme molecule is more fragile than the enzyme-substrate complex in the dioxane solution. It is suggested that the presence of the substrate offers marked protection of this enzyme against inactivation by dioxane. PMID:19108590

Xie, Jin-Jin; Chen, Chao-Qi; Yan, Ya-Wen; Zhang, Ji-Ping; Lin, Jian-Cheng; Wang, Qin; Zhou, Han-Tao; Chen, Qing-Xi

2009-02-01

217

Purification and characterization of an extracellular muramidase of Clostridium acetobutylicum ATCC 824 that acts on non-N-acetylated peptidoglycan.  

PubMed

An extracellular enzyme showing lytic activity on non-N-acetylated peptidoglycan has been isolated from Clostridium acetobutylicum ATCC 824. The lytic enzyme was purified to homogeneity by anion-exchange chromatography and gel filtration, with a recovery of 24%. The enzyme was monomeric and had an estimated molecular weight of 41,000 and an isoelectric point of 3.8. It has been characterized as a muramidase whose 23-amino-acid N terminus displayed 39% homology with the N,O-diacetyl muramidase of the fungus Chalaropsis sp. The muramidase hydrolyzed purified cell walls at an optimum pH of 3, with a maximum velocity of 9.1 mumol of reducing sugars released min-1 mg of muramidase-1 and a concentration of cell walls giving a half-maximum rate of 0.01 mg ml-1. Its activity was inhibited by glucosamine, N-acetylglucosamine, Hg2+, Fe3+, and Ag+ but not by choline. The muramidase-peptidoglycan complex rapidly dissociated before total hydrolysis of the chain and randomly reassociated on another peptidoglycan chain. The affinity of the muramidase was affected by the protein content and the acetylation of the cell wall. PMID:1599233

Croux, C; Canard, B; Goma, G; Soucaille, P

1992-04-01

218

Purification and characterization of an extracellular muramidase of Clostridium acetobutylicum ATCC 824 that acts on non-N-acetylated peptidoglycan.  

PubMed Central

An extracellular enzyme showing lytic activity on non-N-acetylated peptidoglycan has been isolated from Clostridium acetobutylicum ATCC 824. The lytic enzyme was purified to homogeneity by anion-exchange chromatography and gel filtration, with a recovery of 24%. The enzyme was monomeric and had an estimated molecular weight of 41,000 and an isoelectric point of 3.8. It has been characterized as a muramidase whose 23-amino-acid N terminus displayed 39% homology with the N,O-diacetyl muramidase of the fungus Chalaropsis sp. The muramidase hydrolyzed purified cell walls at an optimum pH of 3, with a maximum velocity of 9.1 mumol of reducing sugars released min-1 mg of muramidase-1 and a concentration of cell walls giving a half-maximum rate of 0.01 mg ml-1. Its activity was inhibited by glucosamine, N-acetylglucosamine, Hg2+, Fe3+, and Ag+ but not by choline. The muramidase-peptidoglycan complex rapidly dissociated before total hydrolysis of the chain and randomly reassociated on another peptidoglycan chain. The affinity of the muramidase was affected by the protein content and the acetylation of the cell wall. Images PMID:1599233

Croux, C; Canard, B; Goma, G; Soucaille, P

1992-01-01

219

Effect of hydrolysis time on the physicochemical and functional properties of corn glutelin by Protamex hydrolysis.  

PubMed

The physicochemical and functional properties, such as surface hydrophobicity, disulphide bond content, thermal properties, molecular weight distribution, antioxidant properties, of corn glutelin hydrolysates catalysed by Protamex at different hydrolysis times were evaluated. The hydrolysis influenced the properties of corn glutelin significantly, and not only decreased its molecular weight and disulphide bond content, but also eventually transformed its insoluble native aggregates to soluble aggregates during the hydrolysis process. Corn glutelin hydrolysates were found to have a higher solubility, which was associated with their relatively higher foaming and emulsifying properties compared to the original glutelin. Corn glutelin and its hydrolysates maintained a high thermal stability. In addition, the hydrolysates exhibited excellent antioxidant properties measured through in vitro assays, namely DPPH and OH radical scavenging activity, Fe(2+)-chelating capacity and reducing power; the values were 58.86%, 82.64%, 29.92% and 0.236% at 2.0mg/mL, respectively. PMID:25442571

Zheng, Xi-qun; Wang, Jun-tong; Liu, Xiao-lan; Sun, Ying; Zheng, Yong-jie; Wang, Xiao-jie; Liu, Yue

2015-04-01

220

Organosolv pretreatment for enzymatic hydrolysis of poplars: I. enzyme hydrolysis of cellulosic residues  

SciTech Connect

Aspen (Populus tremuloides) and black cottonwood (Populus trichocarpa) organosolv pulps produced in a wide range of solvent composition (between 30 and 70% by volume of methanol) and catalysts (H/sub 2/SO/sub 4/ and H/sub 3/PO/sub 4/) such that the cooking liquor pH less than or equal to 3 are easily digested by enzymes. The total yields of hydrolysis residues (pulps) are in the 40-60% range; the acid-catalyzed delignification followed by enzyme hydrolysis can generate 70-88% of the original six-carbon sugars contained in the wood. Glucomannan and arabinogalactan are dissolved in to the pulping liquor in the pH range of 2-4.5. Lower pH (less than or equal to 3) leads to additional solubilization of six-carbon sugars. These sugars may be fermented directly. From the insoluble hydrolysis residues, 36-41% conversions of wood into fermentable sugars were obtained after enzyme hydrolysis; the starting feedstocks contain 50.8 and 46.6% hexosans, respectively, for aspen and black cottonwood. The kinetics of enzymatic hydrolysis of cellulose can be formally treated as two simultaneous pseudo-first-order reactions in which fast and slow hydrolysis of cellulose occur. Correlations between the glucan digestibility and the effect of the pretreatment have been made. The higher residual xylan content reduces the amount of the rapidly hydrolyzable glucan fraction and lowers the glucan digestibility. The proposed simple kinetic treatment is very helpful in assessing the effect of the pretreatment on pulp enzyme hydrolyzability.

Chum, H.L.; Johnson, D.K.; Black, S.; Baker, J.; Grohmann, K.; Sarkanen, K.V.; Wallace, K.; Schroeder, H.A.

1988-01-01

221

Purification and properties of an O-acetyl-transferase from Escherichia coli that can O-acetylate polysialic acid sequences  

SciTech Connect

Certain strains of bacteria synthesize an outer polysialic acid (K1) capsule. Some strains of K1/sup +/ E.coli are also capable of adding O-acetyl-esters to the exocyclic hydroxyl groups of the sialic acid residues. Both the capsule and the O-acetyl modification have been correlated with differences in antigenicity and pathogenicity. The authors have developed an assay for an O-acetyl-transferase in E.coli that transfers O-(/sup 3/H)acetyl groups from (/sup 3/H)acetyl-Coenzyme A to colominic acid (fragments of the polysialic acid capsule). Using this assay, the enzyme was solubilized, and purified approx. 600-fold using a single affinity chromatography step with Procion Red-A Agarose. The enzyme also binds to Coenzyme A Sepharose, and can be eluted with high salt or Coenzyme A. The partially purified enzyme has a pH optimum of 7.0 - 7.5, is unaffected by divalent cations, is inhibited by high salt concentrations, is inhibited by Coenzyme A (50% inhibition at 100 ..mu..M), and shows an apparent Km for colominic acid of 3.7 mM (sialic acid concentration). This enzyme could be involved in the O-acetyl +/- form variation seen in some strains of K1/sup +/ E.coli.

Higa, H.; Varki, A.

1986-05-01

222

Effects of microtubule mechanics on hydrolysis and catastrophes  

E-print Network

We introduce a model for microtubule mechanics containing lateral bonds between dimers in neighboring protofilaments, bending rigidity of dimers, and repulsive interactions between protofilaments modeling steric constraints to investigate the influence of mechanical forces on hydrolysis and catastrophes. We use the allosteric dimer model, where tubulin dimers are characterized by an equilibrium bending angle, which changes from $0^\\circ$ to $22^\\circ$ by hydrolysis of a dimer. This also affects the lateral interaction and bending energies and, thus, the mechanical equilibrium state of the microtubule. As hydrolysis gives rise to conformational changes in dimers, mechanical forces also influence the hydrolysis rates by mechanical energy changes modulating the hydrolysis rate. The interaction via the microtubule mechanics then gives rise to correlation effects in the hydrolysis dynamics, which have not been taken into account before. Assuming a dominant influence of mechanical energies on hydrolysis rates, we investigate the most probable hydrolysis pathways both for vectorial and random hydrolysis. Investigating the stability with respect to lateral bond rupture, we identify initiation configurations for catastrophes along the hydrolysis pathways and values for a lateral bond rupture force. If we allow for rupturing of lateral bonds between dimers in neighboring protofilaments above this threshold force, our model exhibits avalanche-like catastrophe events.

Nina Müller; Jan Kierfeld

2014-06-05

223

1,3,4-Tri-O-acetyl-2-N-(tri­fluoro­acetyl)-?-l-fucose  

PubMed Central

The title compound, C14H18F3NO8, was produced through conjugation of 1,3,4-tri-O-acetyl-2-azidode­oxy-?,?-l-fucose with tri­fluoro­acetyl chloride in the presence of bis­(di­phenyl­phosphino)ethane in tetra­hydro­furan at room temperature. The X-ray crystal structure reveals that the ?-anomer of the product mixture crystallizes from ethyl acetate/hexa­nes. The compound exists in a typical chair conformation with the maximum possible number of substituents, four out of five, located in the sterically preferred equatorial positions. The major directional force facilitating packing of the mol­ecules are N—H?O hydrogen bonds involving the amide moieties of neighboring mol­ecules, which connect mol­ecules stacked along the a-axis direction into infinite strands with a C 1 1(4) graph-set motif. Formation of the strands is assisted by a number of weaker C—H?O inter­actions involving the methine and methyl H atoms. These strands are connected through further C—H?O and C—H?F inter­actions into a three dimensional network PMID:24764861

McCutcheon, David C.; Norris, Peter; Zeller, Matthias

2014-01-01

224

Human chitotriosidase-catalyzed hydrolysis of chitosan.  

PubMed

Chitotriosidase (HCHT) is one of two family 18 chitinases produced by humans, the other being acidic mammalian chitinase (AMCase). The enzyme is thought to be part of the human defense mechanism against fungal parasites, but its precise role and the details of its enzymatic properties have not yet been fully unraveled. We have studied the properties of HCHT by analyzing how the enzyme acts on high-molecular weight chitosans, soluble copolymers of ?-1,4-linked N-acetylglucosamine (GlcNAc, A), and glucosamine (GlcN, D). Using methods for in-depth studies of the chitinolytic machinery of bacterial family 18 enzymes, we show that HCHT degrades chitosan primarily via an endoprocessive mechanism, as would be expected on the basis of the structural features of its substrate-binding cleft. The preferences of HCHT subsites for acetylated versus nonacetylated sugars were assessed by sequence analysis of obtained oligomeric products showing a very strong, absolute, and a relative weak preference for an acetylated unit in the -2, -1, and +1 subsites, respectively. The latter information is important for the design of inhibitors that are specific for the human chitinases and also provides insight into what kind of products may be formed in vivo upon administration of chitosan-containing medicines or food products. PMID:22192075

Eide, Kristine Bistrup; Norberg, Anne Line; Heggset, Ellinor Bćvre; Lindbom, Anne Rita; Vĺrum, Kjell Morten; Eijsink, Vincent G H; Sřrlie, Morten

2012-01-10

225

[The different notions about beta-oxidation of fatty acids in peroxisomes, peroxisomes and ketonic bodies. The diabetic, acidotic coma as an acute deficiency of acetyl-CoA and ATP].  

PubMed

The mechanisms of beta-oxidation of fatty acids developed more than a century before have no compliance with actual physical chemical data. The oxidation of long-chain C 16:0 palmitic saturated fatty acid occurs not by sequential formation of eight molecules of acetyl-KoA but by force of formation of double bond and its hydrolysis on two short-chain C 8:0 fatty acids. Only short-chain fatty acids can become shorter under "chipping" of C 2-acetate with formation of C 4-butyric acid (butyrate) and its metabolites (beta-hidroxibutirate, acetoacetate, acetone). The critical moment of oxidation is a hydrolysis of acetoacetyl-KoA on two molecules of acetyl-KoA. The molecule of ATP is to be expended on hydrolysis. The foundation of nonspecific biological reaction of stress--ketoacidosis,--is a decrease in mitochondrions of acetyl-KoA pool formed both from glycogen and glucose and fatty acids. The oxalate acetate inputs into Krebs cycle inadequate amount of acetyl-KoA which limits synthesis of ATP. The insulin has no direct involvement into development of ketoacidosis but prepares conditions to facilitate nonspecific etiological factor to initiate diabetic ketoacidosis. These are the pooling of small amount of glycogen in cytozol and the predominance in cytozol of cells and adipocytes of palmitic triglycerides which are slowly hydrolyzed by hormone-dependent lipase to release non-esterified fatty acids into intercellular medium. The increase of their concentration in blood plasma precedes ketoacidosis which is developing in patients without diabetes mellitus too. When cells begin to oxidize unsaturated linoleic and linolenic acids with large number of double binds instead of medium-chain fatty acids, oleinic and palmitic fatty acids to support beta-oxidation in mitochondrions and synthesis of ATP the amount of butyric acid, beta-hidroxibutiryl-KoA and acetoacetyl-KoA increases and of acetyl-KoA decreases. The cause of fatal outcome is the development of metabolic acidosis, hyperhydration of cerebral cells with development of edema and a physiologic respiratory compensation of metabolic acidosis. The decarboxylation of acetoacetate and formation of acetone--initial stage of gluconeogenesis--formation of glucose from fatty acids--is manifested poorly both in primates and humans. From theoretical positions, to arrest ketoacidosis and to restore synthesis of AFT, it is reasonable to apply the infusion of optimal amount of acetyl-KoA which as nonpolar tioester can get over hematoencephalic barrier, plasma membrane and inner membrane of mitochondrions. It is supposed that diabetes mellitus is to be considered primarily as pathology of metabolism of fatty acids and only secondly as pathology of glucose. PMID:25080783

Kotkina, T I; Titov, V N; Parkhimovich, R M

2014-03-01

226

Determination of glucosamine and N-acetyl glucosamine in fungal cell walls.  

PubMed

A new method was developed to determine glucosamine (GlcN) and N-acetyl glucosamine (GlcNAc) in materials containing chitin and chitosan, such as fungal cell walls. It is based on two steps of hydrolysis with (i) concentrated sulfuric acid at low temperature and (ii) dilute sulfuric acid at high temperature, followed by one-step degradation with nitrous acid. In this process, chitin and chitosan are converted into anhydromannose and acetic acid. Anhydromannose represents the sum of GlcN and GlcNAc, whereas acetic acid is a marker for GlcNAc only. The method showed recovery of 90.1% of chitin and 85.7-92.4% of chitosan from commercial preparations. Furthermore, alkali insoluble material (AIM) from biomass of three strains of zygomycetes, Rhizopus oryzae, Mucor indicus, and Rhizomucor pusillus, was analyzed by this method. The glucosamine contents of AIM from R. oryzae and M. indicus were almost constant (41.7 +/- 2.2% and 42.0 +/- 1.7%, respectively), while in R. pusillus, it decreased from 40.0 to 30.0% during cultivation from 1 to 6 days. The GlcNAc content of AIM from R. oryzae and R. pusillus increased from 24.9 to 31.0% and from 36.3 to 50.8%, respectively, in 6 days, while it remained almost constant during the cultivation of M. indicus (23.5 +/- 0.8%). PMID:18729456

Zamani, Akram; Jeihanipour, Azam; Edebo, Lars; Niklasson, Claes; Taherzadeh, Mohammad J

2008-09-24

227

VimA-Dependent Modulation of Acetyl Coenzyme A Levels and Lipid A Biosynthesis Can Alter Virulence in Porphyromonas gingivalis  

PubMed Central

The Porphyromonas gingivalis VimA protein has multifunctional properties that can modulate several of its major virulence factors. To further characterize VimA, P. gingivalis FLL406 carrying an additional vimA gene and a vimA-defective mutant in a different P. gingivalis genetic background were evaluated. The vimA-defective mutant (FLL451) in the P. gingivalis ATCC 33277 genetic background showed a phenotype similar to that of the vimA-defective mutant (FLL92) in the P. gingivalis W83 genetic background. In contrast to the wild type, gingipain activity was increased in P. gingivalis FLL406, a vimA chimeric strain. P. gingivalis FLL451 had a five times higher biofilm-forming capacity than the parent strain. HeLa cells incubated with P. gingivalis FLL92 showed a decrease in invasion, in contrast to P. gingivalis FLL451 and FLL406, which showed increases of 30 and 40%, respectively. VimA mediated coenzyme A (CoA) transfer to isoleucine and reduced branched-chain amino acid metabolism. The lipid A content and associated proteins were altered in the vimA-defective mutants. The VimA chimera interacted with several proteins which were found to have an LXXTG motif, similar to the sorting motif of Gram-positive organisms. All the proteins had an N-terminal signal sequence with a putative sorting signal of L(P/T/S)X(T/N/D)G and two unique signatures of EXGXTX and HISXXGXG, in addition to a polar tail. Taken together, these observations further confirm the multifunctional role of VimA in modulating virulence possibly through its involvement in acetyl-CoA transfer and lipid A synthesis and possibly by protein sorting. PMID:22144476

Aruni, A. Wilson; Lee, J.; Osbourne, D.; Dou, Y.; Roy, F.; Muthiah, A.; Boskovic, D. S.

2012-01-01

228

Feedback regulation of plastidic acetyl-CoA carboxylase by 18:1-acyl carrier protein in Brassica napus  

PubMed Central

Plant seed oil represents a major renewable source of reduced carbon, but little is known about the biochemical regulation of its synthesis. The goal of this research was to identify potential feedback regulation of fatty acid biosynthesis in Brassica napus embryo-derived cell cultures and to characterize both the feedback signals and enzymatic targets of the inhibition. Fatty acids delivered via Tween esters rapidly reduced the rate of fatty acid synthesis in a dose-dependent and reversible manner, demonstrating the existence of feedback inhibition in an oil-accumulating tissue. Tween feeding did not affect fatty acid elongation in the cytosol or the incorporation of radiolabeled malonate into nascent fatty acids, which together pinpoint plastidic acetyl-CoA carboxylase (ACCase) as the enzymatic target of feedback inhibition. To identify the signal responsible for feedback, a variety of Tween esters were tested for their effects on the rate of fatty acid synthesis. Maximum inhibition was achieved upon feeding oleic acid (18:1) Tween esters that resulted in the intracellular accumulation of 18:1 free fatty acid, 18:1-CoA, and 18:1-acyl-carrier protein (ACP). Direct, saturable inhibition of ACCase enzyme activity was observed in culture extracts and in extracts of developing canola seeds supplemented with 18:1-ACP at physiological concentrations. A mechanism for feedback inhibition is proposed in which reduced demand for de novo fatty acids results in the accumulation of 18:1-ACP, which directly inhibits plastidic ACCase, leading to reduced fatty acid synthesis. Defining this mechanism presents an opportunity for mitigating feedback inhibition of fatty acid synthesis in crop plants to increase oil yield. PMID:22665812

Andre, Carl; Haslam, Richard P.; Shanklin, John

2012-01-01

229

Studies of Human 2,4-Dienoyl CoA Reductase Shed New Light on Peroxisomal ?-Oxidation of Unsaturated Fatty Acids  

SciTech Connect

Peroxisomes play an essential role in maintaining fatty acid homeostasis. Although mitochondria are also known to participate in the catabolism of fatty acids via ?-oxidation, differences exist between the peroxisomal and mitochondrial ?-oxidation. Only peroxisomes, but not mitochondrion, can shorten very long chain fatty acids. Here, we describe the crystal structure of a ternary complex of peroxisomal 2,4-dienoyl CoA reductases (pDCR) with hexadienoyl CoA and NADP, as a prototype for comparison with the mitochondrial 2,4-dienoyl CoA reductase (mDCR) to shed light on the differences between the enzymes from the two organelles at the molecular level. Unexpectedly, the structure of pDCR refined to 1.84 Ĺ resolution reveals the absence of the tyrosine-serine pair seen in the active site of mDCR, which together with a lysine and an asparagine have been deemed a hallmark of the SDR family of enzymes. Instead, aspartate hydrogen-bonded to the C? hydroxyl via a water molecule seems to perturb the water molecule for protonation of the substrate. Our studies provide the first structural evidence for participation of water in the DCR-catalyzed reactions. Biochemical studies and structural analysis suggest that pDCRs can catalyze the shortening of six-carbon-long substrates in vitro. However, the Km values of pDCR for short chain acyl CoAs are at least 6-fold higher than those for substrates with 10 or more aliphatic carbons. Unlike mDCR, hinge movements permit pDCR to process very long chain polyunsaturated fatty acids.

Hua, Tian; Wu, Dong; Ding, Wei; Wang, Jiangyun; Shaw, Neil; Liu, Zhi-Jie (Nankai) [Nankai; (Chinese Aca. Sci.)

2012-10-15

230

The hydrolysis of carbonyl sulfide at low temperature: a review.  

PubMed

Catalytic hydrolysis technology of carbonyl sulfide (COS) at low temperature was reviewed, including the development of catalysts, reaction kinetics, and reaction mechanism of COS hydrolysis. It was indicated that the catalysts are mainly involved metal oxide and activated carbon. The active ingredients which can load on COS hydrolysis catalyst include alkali metal, alkaline earth metal, transition metal oxides, rare earth metal oxides, mixed metal oxides, and nanometal oxides. The catalytic hydrolysis of COS is a first-order reaction with respect to carbonyl sulfide, while the reaction order of water changes as the reaction conditions change. The controlling steps are also different because the reaction conditions such as concentration of carbonyl sulfide, reaction temperature, water-air ratio, and reaction atmosphere are different. The hydrolysis of carbonyl sulfide is base-catalyzed reaction, and the force of the base site has an important effect on the hydrolysis of carbonyl sulfide. PMID:23956697

Zhao, Shunzheng; Yi, Honghong; Tang, Xiaolong; Jiang, Shanxue; Gao, Fengyu; Zhang, Bowen; Zuo, Yanran; Wang, Zhixiang

2013-01-01

231

Catalysts for the hydrolysis of thiophosphate triesters  

E-print Network

of similar basicity and are often referred to as supernucleophiles. Because of their relatively low pKa, these species exist in their deprotonated nucleophilic form even at low pH?s. 7 I O O OH I O O I O O O - I O O HO O - O O 5 67 (IBA)8 (IBX... hydrolysis is also largely enhanced by the addition of oximate anions such as benzaldoximes (14, figure 8) and pyridinealdoxime (15, figure 8) in presence of the cationic surfactants (CTACL). 23 These oximes posses a rather high pKa (9-12) which leads...

Picot, Alexandre

2005-02-17

232

Improved method for detection of starch hydrolysis  

SciTech Connect

A new starch hydrolysis detection method which does not rely on iodine staining or the use of color-complexed starch is described. A linear relationship was obtained with agar-starch plates when net clearing zones around colonies of yeasts were plotted against enzyme levels (semilogarithm scale) produced by the same yeast strains in liquid medium. A similar relationship between starch clearing zones and alpha-amylase levels from three different sources was observed. These observations suggest that the method is useful in mutant isolations, strain improvement programs, and the prediction of alpha-amylase activities in culture filtrates or column effluents. (Refs. 18).

Ohawale, M.R.; Wilson, J.J.; Khachatourians, G.G.; Ingledew, W.M.

1982-09-01

233

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.

234

Probing the active site of cinnamoyl CoA reductase 1 (Ll-CCRH1) from Leucaena leucocephala.  

PubMed

Lack of three dimensional crystal structure of cinnamoyl CoA reductase (CCR) limits its detailed active site characterization studies. Putative active site residues involved in the substrate/NADPH binding and catalysis for Leucaena leucocephala CCR (Ll-CCRH1; GenBank: DQ986907) were identified by amino acid sequence alignment and homology modeling. Putative active site residues and proximal H215 were subjected for site directed mutagenesis, and mutated enzymes were expressed, purified and assayed to confirm their functional roles. Mutagenesis of S136, Y170 and K174 showed complete loss of activity, indicating their pivotal roles in catalysis. Mutant S212G exhibited the catalytic efficiencies less than 10% of wild type, showing its indirect involvement in substrate binding or catalysis. R51G, D77G, F30V and I31N double mutants showed significant changes in Km values, specifying their roles in substrate binding. Finally, chemical modification and substrate protection studies corroborated the presence Ser, Tyr, Lys, Arg and carboxylate group at the active site of Ll-CCRH1. PMID:23688416

Sonawane, Prashant; Patel, Krunal; Vishwakarma, Rishi Kishore; Srivastava, Sameer; Singh, Somesh; Gaikwad, Sushama; Khan, Bashir M

2013-09-01

235

ESTIMATION OF PHOSPHATE ESTER HYDROLYSIS RATE CONSTANTS. II. ACID AND GENERAL BASE CATALYZED HYDROLYSIS  

EPA Science Inventory

SPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity models were extended to calculate acid and neutral hydrolysis rate constants of phosphate esters in water. The rate is calculated from the energy difference between the initial and transition states of a ...

236

NH2-terminal acetylation of ribosomal proteins of Saccharomyces cerevisiae.  

PubMed

Using a mutant of Saccharomyces cerevisiae defective in the NAT1 gene, that encodes one of the NH2-terminal acetyltransferases, we have identified 14 ribosomal proteins whose electrophoretic mobility at pH 5.0 suggests they carry an additional charge, presumably due to the lack of NH2-terminal acetylation. At least 30 other ribosomal proteins from the mutant are electrophoretically normal. Attempted NH2-terminal analysis of most of the presumed acetylated proteins from wild type cells indicated that all were blocked. NH2-terminal analysis of the same proteins from the nat1 mutant strain yielded unique sequences. Each one carries an NH2-terminal serine. We conclude that these are normally acetylated due to the presence of the NAT1 gene product. It seems surprising that cells whose ribosomes have been altered to this degree grow rather well and synthesize the same spectrum of proteins as do wild type cells (Mullen, J. R., Kayne, P. S., Moerschell, R. P., Tsunasawa, S. Gribskov, M., Sherman, F., and Sternglanz, R. (1989) EMBO J. 8, 2067-2075). Finally, this analysis has provided the first sequence information available for several of the acetylated ribosomal proteins and for one non-acetylated ribosomal protein, which is clearly the product of the MFT1 gene (Garrett, J. M., Singh, K. K., Vonder Haar, R. A., and Emr. S. D. (1991) Mol. Gen. Gen. 225, 483-491). PMID:1544921

Takakura, H; Tsunasawa, S; Miyagi, M; Warner, J R

1992-03-15

237

Histones of Chlamydomonas reinhardtii. Synthesis, acetylation, and methylation.  

PubMed Central

Histones of the green alga Chlamydomonas reinhardtii were prepared by a new method and fractionated by reversed-phase high-performance liquid chromatography. Acid-urea-Triton gel analysis and tritiated acetate labeling demonstrated high levels of steady-state acetylation for the single histone H3 protein, in contrast to low levels on histones H4 and H2B. Twenty percent of histone H3 is subject to dynamic acetylation with, on average, three acetylated lysine residues per protein molecule. Histone synthesis in light-dark-synchronized cultures was biphasic with pattern differences between two histone H1 variants, between two H2A variants, and between H2B and ubiquitinated H2B. Automated protein sequence analysis of histone H3 demonstrated a site-specific pattern of steady-state acetylation between 7 and 17% at five of the six amino-terminal lysines and of monomethylation between 5 and 81% at five of the eight amino-terminal lysines in a pattern that may limit dynamic acetylation. An algal histone H3 sequence was confirmed by protein sequencing with a single threonine as residue 28 instead of the serine28-alanine29 sequence, present in all other known plant and animal H3 histones. PMID:7480339

Waterborg, J H; Robertson, A J; Tatar, D L; Borza, C M; Davie, J R

1995-01-01

238

[Conformation aspects of peptide interaction with proteolytic enzymes. Alpha-chymotrypsin catalyzed hydrolysis of the cyclopeptides containing leucyltyrosyl fragments].  

PubMed

The studies were made on the interaction of alpha-chymotrypsin with a series of cyclopeptides cyclo(-L-leucyl-L-tyrosyl-glycyln-), n=4, 6 and 8 (I, II and III respectively), and cyclo(-L-leucyl-L-tryosyl-beta-aminovalero-yl2-) (IV). Compounds I and IV are resistant to enzyme action whereas cyclopeptides II and III proved to be the substrates, their kinetic constants being Km=15.4 and 13.2 mM and kcat=0.54 and 9.53 sec-1 respectively. The binding capacity of cyclopeptides I-IV is evaluated by their competitive inhibition of alpha-chymotrypsin catalyzed hydrolysis of N-acetyl-L-tyrosine methyl ester. PMID:1203366

Tsetlin, M M; Ivanov, V T; Ovchinnikov, Y A; Klyosov, A A

1975-01-01

239

Effect of gelatinization and hydrolysis conditions on the selectivity of starch hydrolysis with alpha-amylase from Bacillus licheniformis.  

PubMed

Enzymatic hydrolysis of starch can be used to obtain various valuable hydrolyzates with different compositions. The effects of starch pretreatment, enzyme addition point, and hydrolysis conditions on the hydrolyzate composition and reaction rate during wheat starch hydrolysis with alpha-amylase from Bacillus licheniformis were compared. Suspensions of native starch or starch gelatinized at different conditions either with or without enzyme were hydrolyzed. During hydrolysis, the oligosaccharide concentration, the dextrose equivalent, and the enzyme activity were determined. We found that the hydrolyzate composition was affected by the type of starch pretreatment and the enzyme addition point but that it was just minimally affected by the pressure applied during hydrolysis, as long as gelatinization was complete. The differences between hydrolysis of thermally gelatinized, high-pressure gelatinized, and native starch were explained by considering the granule structure and the specific surface area of the granules. These results show that the hydrolyzate composition can be influenced by choosing different process sequences and conditions. PMID:18095648

Baks, Tim; Bruins, Marieke E; Matser, Ariette M; Janssen, Anja E M; Boom, Remko M

2008-01-23

240

Coordinate Regulation of the Nuclear and Plastidic Genes Coding for the Subunits of the Heteromeric Acetyl-Coenzyme A Carboxylase1  

PubMed Central

Plastidic acetyl-coenzyme A (CoA) carboxylase (ACCase) catalyzes the first committed reaction of de novo fatty acid biosynthesis. This heteromeric enzyme is composed of one plastid-coded subunit (?-carboxyltransferase) and three nuclear-coded subunits (biotin carboxy-carrier, biotin carboxylase, and ?-carboxyltransferase). We report the primary structure of the Arabidopsis ?-carboxyltransferase and ?-carboxyltransferase subunits deduced from nucleotide sequences of the respective genes and/or cDNA. Co-immunoprecipitation experiments confirm that the ?-carboxyltransferase and ?-carboxyltransferase subunits are physically associated. The plant ?-carboxyltransferases have gained a C-terminal domain relative to eubacteria, possibly via the evolutionary acquisition of a single exon. This C-terminal domain is divergent among plants and may have a structural function rather than being essential for catalysis. The four ACCase subunit mRNAs accumulate to the highest levels in tissues and cells that are actively synthesizing fatty acids, which are used either for membrane biogenesis in rapidly growing tissues or for oil accumulation in developing embryos. Development coordinately affects changes in the accumulation of the ACCase subunit mRNAs so that these four mRNAs maintain a constant molar stoichiometric ratio. These data indicate that the long-term, developmentally regulated expression of the heteromeric ACCase is in part controlled by a mechanism(s) that coordinately affects the steady-state concentrations of each subunit mRNA. PMID:10759501

Ke, Jinshan; Wen, Tuan-Nan; Nikolau, Basil J.; Wurtele, Eve Syrkin

2000-01-01

241

Hydrolysis of lignocelluloses by penicillium funiculosum cellulase  

SciTech Connect

Enzymatic hydrolysis of cellulose is a promising method for the conversion of waste cellulose to glucose. During the past few years, the development of this technology has proceeded rapidly, with significant advances made in enzyme production, pretreatment, and hydrolysis. A variety of fungi are reported to produce cellulases but among these Trichoderma reesei and its mutants are powerful producers of cellulases. However, the search for new and possibly better sources of cellulase is continued due to the low levels of beta-glucosidase of T. reesei. Penicillium funiculosum produces a complete cellulase having endo-beta-1,4-glucanase (15-20 U/mL), exo-beta-1,4-glucanase (1.5-2.0 U/mL), and high beta-glucosidase (8-10 U/mL). The saccharification of alkali-treated cotton and bagasse by P. funiculosum enzyme was 70 and 63%, respectively. It was possible to obtain glucose concentration as high as 30% using 50% bagasse. It is of interest that the percent saccharification of cellulosic substrates with the Penicillium enzyme is comparable to that of T. reesei cellulase when the same amount of filter paper activity is used, although the endo-glucanase activity of the latter is two to three times higher. This communication reports the studies on saccharification of lignocelluloses by P. funiculosum cellulase and certain studies on the kinetic aspects. (Refs. 15).

Mishra, C.; Rao, M.; Seeta, R.; Srinivasan, M.C.; Deshpande, V.

1984-04-01

242

Small Molecule Inhibitors of Bromodomain-Acetyl-lysine Interactions.  

PubMed

Bromodomains are protein modules that bind to acetylated lysine residues. Their interaction with histone proteins suggests that they function as "readers" of histone lysine acetylation, a component of the proposed "histone code". Bromodomain-containing proteins are often found as components of larger protein complexes with roles in fundamental cellular process including transcription. The publication of two potent ligands for the BET bromodomains in 2010 demonstrated that small molecules can inhibit the bromodomain-acetyl-lysine protein-protein interaction. These molecules display strong phenotypic effects in a number of cell lines and affect a range of cancers in vivo. This work stimulated intense interest in developing further ligands for the BET bromodomains and the design of ligands for non-BET bromodomains. Here we review the recent progress in the field with particular attention paid to ligand design, the assays employed in early ligand discovery, and the use of computational approaches to inform ligand design. PMID:25549280

Brand, Michael; Measures, Angelina M; Wilson, Brian G; Cortopassi, Wilian A; Alexander, Rikki; Höss, Matthias; Hewings, David S; Rooney, Timothy P C; Paton, Robert S; Conway, Stuart J

2015-01-16

243

Synthetic Biology for Engineering Acetyl Coenzyme A Metabolism in Yeast  

PubMed Central

ABSTRACT The yeast Saccharomyces cerevisiae is a widely used cell factory for the production of fuels, chemicals, and pharmaceuticals. The use of this cell factory for cost-efficient production of novel fuels and chemicals requires high yields and low by-product production. Many industrially interesting chemicals are biosynthesized from acetyl coenzyme A (acetyl-CoA), which serves as a central precursor metabolite in yeast. To ensure high yields in production of these chemicals, it is necessary to engineer the central carbon metabolism so that ethanol production is minimized (or eliminated) and acetyl-CoA can be formed from glucose in high yield. Here the perspective of generating yeast platform strains that have such properties is discussed in the context of a major breakthrough with expression of a functional pyruvate dehydrogenase complex in the cytosol. PMID:25370498

2014-01-01

244

A BBSome subunit links ciliogenesis, microtubule stability, and acetylation.  

PubMed

Primary cilium dysfunction affects the development and homeostasis of many organs in Bardet-Biedl syndrome (BBS). We recently showed that seven highly conserved BBS proteins form a stable complex, the BBSome, that functions in membrane trafficking to and inside the primary cilium. We have now discovered a BBSome subunit that we named BBIP10. Similar to other BBSome subunits, BBIP10 localizes to the primary cilium, BBIP10 is present exclusively in ciliated organisms, and depletion of BBIP10 yields characteristic BBS phenotypes in zebrafish. Unexpectedly, BBIP10 is required for cytoplasmic microtubule polymerization and acetylation, two functions not shared with any other BBSome subunits. Strikingly, inhibition of the tubulin deacetylase HDAC6 restores microtubule acetylation in BBIP10-depleted cells, and BBIP10 physically interacts with HDAC6. BBSome-bound BBIP10 may therefore function to couple acetylation of axonemal microtubules and ciliary membrane growth. PMID:19081074

Loktev, Alexander V; Zhang, Qihong; Beck, John S; Searby, Charles C; Scheetz, Todd E; Bazan, J Fernando; Slusarski, Diane C; Sheffield, Val C; Jackson, Peter K; Nachury, Maxence V

2008-12-01

245

40 CFR 721.10152 - Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4+) salt and silica...  

Code of Federal Regulations, 2012 CFR

...Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4...Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4...oxirane, substituted silylmethyl-, hydrolysis products with alkanol...

2012-07-01

246

40 CFR 721.10152 - Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4+) salt and silica...  

Code of Federal Regulations, 2013 CFR

...Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4...Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4...oxirane, substituted silylmethyl-, hydrolysis products with alkanol...

2013-07-01

247

40 CFR 721.10152 - Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4+) salt and silica...  

Code of Federal Regulations, 2010 CFR

...Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4...Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4...oxirane, substituted silylmethyl-, hydrolysis products with alkanol...

2010-07-01

248

Reaction Dynamics of ATP Hydrolysis Catalyzed by P-Glycoprotein  

PubMed Central

P-glycoprotein (P-gp) is a member of the ABC transporter family that confers drug resistance to many tumors by catalyzing their efflux, and it is a major component of drug–drug interactions. P-gp couples drug efflux with ATP hydrolysis by coordinating conformational changes in the drug binding sites with the hydrolysis of ATP and release of ADP. To understand the relative rates of the chemical step for hydrolysis and the conformational changes that follow it, we exploited isotope exchange methods to determine the extent to which the ATP hydrolysis step is reversible. With ?18O4-labeled ATP, no positional isotope exchange is detectable at the bridging ?-phosphorus–O??-phosphorus bond. Furthermore, the phosphate derived from hydrolysis includes a constant ratio of three 18O/two 18O/one 18O that reflects the isotopic composition of the starting ATP in multiple experiments. Thus, H2O-exchange with HPO42– (Pi) was negligible, suggesting that a [P-gp·ADP·Pi] is not long-lived. This further demonstrates that the hydrolysis is essentially irreversible in the active site. These mechanistic details of ATP hydrolysis are consistent with a very fast conformational change immediately following, or concomitant with, hydrolysis of the ?-phosphate linkage that ensures a high commitment to catalysis in both drug-free and drug-bound states. PMID:24506763

2015-01-01

249

Ultrasound Enhancement of Enzymatic Hydrolysis of Cellulose Plant Matter  

Technology Transfer Automated Retrieval System (TEKTRAN)

The work reported here is based on acceleration of enzymatic hydrolysis of plant biomass substrate by introduction of low intensity, uniform ultrasound field into a reaction chamber (bio-reactor). This method may serve as improvement of rates in the hydrolysis of cellulosic materials to sugars, whi...

250

Mechanism of surfactant effect in enzymatic hydrolysis of lignocellulose  

Microsoft Academic Search

Lignocellulose is a potential substrate for ethanol production. However, high cellulose conversion requires high enzyme loading, which makes the process less economically feasible. Addition of surfactants to enzymatic hydrolysis of lignocellulose increases the conversion of cellulose into soluble sugars. The mechanism is not known for the increase of lignocellulose hydrolysis by surfactant addition, therefore, experiments were designed to explore mechanisms

Torny Eriksson; Johan Börjesson; Folke Tjerneld

2002-01-01

251

Class Projects in Physical Organic Chemistry: The Hydrolysis of Aspirin  

ERIC Educational Resources Information Center

An exercise that provides a hands-on demonstration of the hydrolysis of aspirin is presented. The key to understanding the hydrolysis is recognizing that all six process may occur simultaneously and that the observed rate constant is the sum of the rate constants that one rate constant dominates the overall process.

Marrs, Peter S.

2004-01-01

252

Pre-Steady-State Analysis of ATP Hydrolysis by Saccharomyces cereVisiae DNA Topoisomerase II. 2. Kinetic Mechanism for the Sequential Hydrolysis of Two  

E-print Network

Pre-Steady-State Analysis of ATP Hydrolysis by Saccharomyces cereVisiae DNA Topoisomerase II. 2. Kinetic Mechanism for the Sequential Hydrolysis of Two ATP Timothy T. Harkins,,| Timothy J. Lewis) sequential ATP hydrolysis or (2) simultaneous hydrolysis of both ATP. Here, we present results

Lewis, Timothy

253

Metabolic Regulation of Protein N-Alpha-Acetylation by Bcl-xL Promotes Cell Survival  

E-print Network

Previous experiments suggest a connection between the N-alpha-acetylation of proteins and sensitivity of cells to apoptotic signals. Here, we describe a biochemical assay to detect the acetylation status of proteins and ...

Yi, Caroline H.

254

Overexpressing TNF-alpha in pancreatic ductal adenocarcinoma cells and fibroblasts modifies cell survival and reduces fatty acid synthesis via downregulation of sterol regulatory element binding protein-1 and activation of acetyl CoA carboxylase.  

PubMed

The effect of tumor necrosis factor-alpha (TNF-?) gene delivery has been suggested as a potentially useful therapeutic approach to improve the chemotherapeutic treatment of patients with pancreatic ductal adenocarcinoma (PDA), but the exact mechanism of its action is not clearly understood. In this study, we analyzed the expression profile of TNF-? in PDA tissue and explored its potential role in fatty acid synthase (FAS) regulation in PDA cells and in fibroblasts. Quantitative real-time polymerase chain reaction was used to examine the expression of TNF-? in PDA, matching adjacent tissues, and benign lesions. Logistic regression models with robust variance were used to analyze the gene expression levels, and Kaplan-Meier survival curves were generated. In vitro, we overexpressed the TNF-? gene in PDA cells and fibroblasts and analyzed its effect on cell survival, migration, and on members of the FAS signaling pathway. We also evaluated TNF-? effects on a panel of inflammation-, angiogenesis-, and metastasis-related markers. In the tumor tissue of PDA patients, compared with their matched adjacent tissue, expression levels of TNF-? were not statistically different and did not correlate with survival or any other examined clinicopathological features. Overexpression of TNF-? significantly (p?

Al-Zoubi, Mazhar; Chipitsyna, Galina; Saxena, Shivam; Sarosiek, Konrad; Gandhi, Ankit; Kang, Christopher Y; Relles, Daniel; Andrelsendecki, Jocelyn; Hyslop, Terry; Yeo, Charles J; Arafat, Hwyda A

2014-02-01

255

Catalytic Zinc Complexes for Phosphate Diester Hydrolysis*  

PubMed Central

Creating efficient artificial catalysts that can compete with biocatalysis has been an enduring challenge which has yet to be met. Reported herein is the synthesis and characterization of a series of zinc complexes designed to catalyze the hydrolysis of phosphate diesters. By introducing a hydrated aldehyde into the ligand we achieve turnover for DNA-like substrates which, combined with ligand methylation, increases reactivity by two orders of magnitude. In contrast to current orthodoxy and mechanistic explanations, we propose a mechanism where the nucleophile is not coordinated to the metal ion, but involves a tautomer with a more effective Lewis acid and more reactive nucleophile. This data suggests a new strategy for creating more efficient metal ion based catalysts, and highlights a possible mode of action for metalloenzymes. PMID:24919567

Tirel, Emmanuel Y; Bellamy, Zoë; Adams, Harry; Lebrun, Vincent; Duarte, Fernanda; Williams, Nicholas H

2014-01-01

256

Fermentable sugars by chemical hydrolysis of biomass.  

PubMed

Abundant plant biomass has the potential to become a sustainable source of fuels and chemicals. Realizing this potential requires the economical conversion of recalcitrant lignocellulose into useful intermediates, such as sugars. We report a high-yielding chemical process for the hydrolysis of biomass into monosaccharides. Adding water gradually to a chloride ionic liquid-containing catalytic acid leads to a nearly 90% yield of glucose from cellulose and 70-80% yield of sugars from untreated corn stover. Ion-exclusion chromatography allows recovery of the ionic liquid and delivers sugar feedstocks that support the vigorous growth of ethanologenic microbes. This simple chemical process, which requires neither an edible plant nor a cellulase, could enable crude biomass to be the sole source of carbon for a scalable biorefinery. PMID:20194793

Binder, Joseph B; Raines, Ronald T

2010-03-01

257

Modeling of autocatalytic hydrolysis of adefovir dipivoxil in solid formulations.  

PubMed

The stability and hydrolysis kinetics of a phosphate prodrug, adefovir dipivoxil, in solid formulations were studied. The stability relationship between five solid formulations was explored. An autocatalytic mechanism for hydrolysis could be proposed according to the kinetic behavior which fits the Prout-Tompkins model well. For the classical kinetic models could hardly describe and predict the hydrolysis kinetics of adefovir dipivoxil in solid formulations accurately when the temperature is high, a feedforward multilayer perceptron (MLP) neural network was constructed to model the hydrolysis kinetics. The build-in approaches in Weka, such as lazy classifiers and rule-based learners (IBk, KStar, DecisionTable and M5Rules), were used to verify the performance of MLP. The predictability of the models was evaluated by 10-fold cross-validation and an external test set. It reveals that MLP should be of general applicability proposing an alternative efficient way to model and predict autocatalytic hydrolysis kinetics for phosphate prodrugs. PMID:21467805

Dong, Ying; Zhang, Yan; Xiang, Bingren; Deng, Haishan; Wu, Jingfang

2011-04-01

258

DNA-Catalyzed Hydrolysis of Esters and Aromatic Amides  

PubMed Central

We previously reported that DNA catalysts (deoxyribozymes) can hydrolyze DNA phosphodiester linkages, but DNA-catalyzed amide bond hydrolysis has been elusive. Here we used in vitro selection to identify DNA catalysts that hydrolyze ester linkages as well as DNA catalysts that hydrolyze aromatic amides, for which the leaving group is an aniline moiety. The aromatic amide-hydrolyzing deoxyribozymes were examined using linear free energy relationship analysis. The hydrolysis reaction is unaffected by substituents on the aromatic ring (? ? 0), suggesting general acid-catalyzed elimination as the likely rate-determining step of the addition-elimination hydrolysis mechanism. These findings establish that DNA has the catalytic ability to achieve hydrolysis of esters and aromatic amides as carbonyl-based substrates, and they suggest a mechanism-based approach to achieve DNA-catalyzed aliphatic amide hydrolysis. PMID:24127695

Brandsen, Benjamin M.; Hesser, Anthony R.; Castner, Marissa A.; Chandra, Madhavaiah

2013-01-01

259

[Enzymatic hydrolysis of cellulose in reverse micelles].  

PubMed

Several types of surfactants were adopted to construct reverse micelles, in order to investigate the characteristics of cellulose hydrolysis, we used the carboxymethyl cellulose as substrate. The electrical conductivity was measured to determine the maximum water solubilization W0( W0 = [H2O]/[SA] ) of CTAB, SDS, Tween-80 and rhamnolipid reverse micellar systems were 15.2, 20.1, 2.3 and 40.3. In this condition we studied the effects of surfactants concentrations and cellulose dosage on the enzymatic hydrolysis of reverse micelle,and compared with aqueous systems. It was shown by the results that when the cellulose dosage was 0.15 FPU/g substrate, the maximum yield of reducing sugar in reverse micelles was obtained at 1 cmc of CTAB, SDS, Tween-80 and rhamnolipid, in which the rhamnolipid yield was the highest of 198.03 mg substrate. When the concentrations of CTAB, SDS, Tween-80 and rhamnolipid were 1 cmc, the productions of reverse micelles systems were higher than that of aqueous systems of 34.36%, 21.24%, 11.44% and 34.62%. In the optimum conditions of the surfactant concentration, taking the saving cost and sugar yield into consideration, the cellulose dosage of 5 FPU substrate was the most suitable. The reducing sugar's yield of biosurfactant rhamnolipid reverse micellar system was higher than those of three chemical surfactant systems, it was shown that the adoption of biosurfactant has technologically promising prospect in constructing reverse micelles and enhancing the stability of reverse micelles. PMID:21072947

Wang, Wei-Wei; Yuan, Xing-Zhong; Zeng, Guang-Ming; Liang, Yun-Shan; Chao, Yang

2010-09-01

260

Simultaneous determination of hydrolysis and mutarotation rates during the enzymatic hydrolysis of lactose.  

PubMed

An experiment is described in which a custom-made glucose electrode is used to directly monitor the enzymatic hydrolysis of lactose to glucose. The transient profile of beta- d-glucose can be used to simultaneously determine the rate constants for mutarotation and for enzymatic hydrolysis by applying a dynamic nonlinear regression routine. Due to differences in the mutarotation rate constants between lactose and glucose, the beta- d-glucose concentration "overshoots" equilibrium under certain conditions, which can be modeled mathematically. This overshoot can be observed reliably and used to quantify the differences in mutarotational equilibria between glucose and lactose. These observations may be important for the analysis of dairy products and commercial lactase preparations and illustrate an unusual kinetic phenomenon caused by intramolecular forces. This approach may also be important for the accurate determination of a variety of oligosaccharides such as glycogen, which tend to be composed primarily of one stereoisomer. PMID:18712880

Jenkins, Daniel M; Teruel, Michael A; Reyes-de-Corcuera, José I; Young, Owen

2008-09-24

261

Cyclohexanecarboxyl-Coenzyme A (CoA) and Cyclohex-1-ene-1-Carboxyl-CoA Dehydrogenases, Two Enzymes Involved in the Fermentation of Benzoate and Crotonate in Syntrophus aciditrophicus  

PubMed Central

The strictly anaerobic Syntrophus aciditrophicus is a fermenting deltaproteobacterium that is able to degrade benzoate or crotonate in the presence and in the absence of a hydrogen-consuming partner. During growth in pure culture, both substrates are dismutated to acetate and cyclohexane carboxylate. In this work, the unknown enzymes involved in the late steps of cyclohexane carboxylate formation were studied. Using enzyme assays monitoring the oxidative direction, a cyclohex-1-ene-1-carboxyl-CoA (Ch1CoA)-forming cyclohexanecarboxyl-CoA (ChCoA) dehydrogenase was purified and characterized from S. aciditrophicus and after heterologous expression of its gene in Escherichia coli. In addition, a cyclohexa-1,5-diene-1-carboxyl-CoA (Ch1,5CoA)-forming Ch1CoA dehydrogenase was characterized after purification of the heterologously expressed gene. Both enzymes had a native molecular mass of 150 kDa and were composed of a single, 40- to 45-kDa subunit; both contained flavin adenine dinucleotide (FAD) as a cofactor. While the ChCoA dehydrogenase was competitively inhibited by Ch1CoA in the oxidative direction, Ch1CoA dehydrogenase further converted the product Ch1,5CoA to benzoyl-CoA. The results obtained suggest that Ch1,5CoA is a common intermediate in benzoate and crotonate fermentation that serves as an electron-accepting substrate for the two consecutively operating acyl-CoA dehydrogenases characterized in this work. In the case of benzoate fermentation, Ch1,5CoA is formed by a class II benzoyl-CoA reductase; in the case of crotonate fermentation, Ch1,5CoA is formed by reversing the reactions of the benzoyl-CoA degradation pathway that are also employed during the oxidative (degradative) branch of benzoate fermentation. PMID:23667239

Kung, Johannes W.; Seifert, Jana; von Bergen, Martin

2013-01-01

262

40 CFR 721.10499 - Substituted silane, hydrolysis products with silica (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Substituted silane, hydrolysis products with silica (generic...721.10499 Substituted silane, hydrolysis products with silica (generic...identified generically as substituted silane, hydrolysis products with silica (PMNs...

2013-07-01

263

Application of High Throughput Pretreatment and Co-Hydrolysis System to Thermochemical  

E-print Network

Application of High Throughput Pretreatment and Co-Hydrolysis System to Thermochemical Pretreatment, Tennessee ABSTRACT: High throughput pretreatment (HTPH) and enzymatic hydrolysis systems are now vital and enzymatic hydrolysis conditions. Although hydrothermal pretreatment is currently being employed in most high

California at Riverside, University of

264

Probing the Origins of Catalytic Discrimination between Phosphate and Sulfate Monoester Hydrolysis: Comparative Analysis of Alkaline  

E-print Network

Probing the Origins of Catalytic Discrimination between Phosphate and Sulfate Monoester Hydrolysis phosphatase (AP) catalyzes both phos- phate and sulfate monoester hydrolysis reactions with a 1010 - fold preference for phosphate monoester hydrolysis, despite the similarity between these reactions

Herschlag, Dan

265

40 CFR 721.10498 - Substituted alkyl ester, hydrolysis products with silica (generic).  

Code of Federal Regulations, 2013 CFR

... false Substituted alkyl ester, hydrolysis products with silica (generic...10498 Substituted alkyl ester, hydrolysis products with silica (generic...generically as substituted alkyl ester, hydrolysis products with silica (PMNs...

2013-07-01

266

40 CFR 721.10497 - Substituted alkyl ester, hydrolysis products with silica and substituted silane (generic).  

... false Substituted alkyl ester, hydrolysis products with silica and substituted...10497 Substituted alkyl ester, hydrolysis products with silica and substituted...generically as substituted alkyl ester, hydrolysis products with silica and...

2014-07-01

267

40 CFR 721.10498 - Substituted alkyl ester, hydrolysis products with silica (generic).  

... false Substituted alkyl ester, hydrolysis products with silica (generic...10498 Substituted alkyl ester, hydrolysis products with silica (generic...generically as substituted alkyl ester, hydrolysis products with silica (PMNs...

2014-07-01

268

Hydrolysis of organonitrate functional groups in aerosol particles , John E. Shilling2  

E-print Network

Hydrolysis of organonitrate functional groups in aerosol particles Shang Liu1 , John E Drive, La Jolla CA, 92093-0221 Running title: Hydrolysis of organonitrates Keywords: organonitrate, organic nitrate, hydrolysis, secondary organic aerosol #12; Abstract Organonitrate (ON) groups

Russell, Lynn

269

40 CFR 721.10499 - Substituted silane, hydrolysis products with silica (generic).  

...2014-07-01 false Substituted silane, hydrolysis products with silica (generic...721.10499 Substituted silane, hydrolysis products with silica (generic...identified generically as substituted silane, hydrolysis products with silica (PMNs...

2014-07-01

270

40 CFR 721.10497 - Substituted alkyl ester, hydrolysis products with silica and substituted silane (generic).  

Code of Federal Regulations, 2013 CFR

... false Substituted alkyl ester, hydrolysis products with silica and substituted...10497 Substituted alkyl ester, hydrolysis products with silica and substituted...generically as substituted alkyl ester, hydrolysis products with silica and...

2013-07-01

271

A colorimetric assay for the determination of acetyl xylan esterase or cephalosporin C acetyl esterase activities using 7-amino cephalosporanic acid, cephalosporin C, or acetylated xylan as substrate.  

PubMed

A bromothymol blue-based colorimetric assay has been devised to screen for acetyl xylan esterase or cephalosporin C (CPC) deacetylase activities using 7-amino cephalosporanic acid (7-ACA), CPC, or acetylated xylan as substrate. These enzymes are not screened with their natural substrates because of the tedious procedures available previously. Acetyl xylan esterase from Bacillus pumilus CECT 5072 was cloned, expressed in Escherichia coli Rosetta (DE3), and characterized using this assay. Similar K(M) values for 7-ACA and CPC were obtained when compared with those described using HPLC methods. The assay is easy to perform and can be carried out in robotic high-throughput colorimetric devices normally used in directed evolution experiments. The assay allowed us to detect improvements in activity at a minimum of twofold with a very low coefficient of variance in 96-well plates. This method is significantly faster and more convenient to use than are known HPLC and pH-stat procedures. PMID:17651681

Martínez-Martínez, Irene; Montoro-García, Silvia; Lozada-Ramírez, José Daniel; Sánchez-Ferrer, Alvaro; García-Carmona, Francisco

2007-10-15

272

Acetylation and cleavage of purine nucleosides. Synthesis of 6-azauridine, 5-fluorouridine, and 5-methyluridine.  

PubMed Central

Inosine (I) when acetylated with acetic anhydride in the presence of acetyl chloride in acetic acid solution (the so called "acid acetylation"), affords an acetylated nucleoside III (75%) along with cleavage products of the nucleoside (hypoxanthine, 19%). The reaction of I with acetyl chloride (7 days) results in the formation of hypoxanthine (95%) and triacetylribofuranosyl chloride (IV) isolated in the form of tetraacetylribofuranose (47%). The acetylated purine nucleoside affords a similar result by reaction with acetyl chloride or acetyl bromide. 2'-Deoxyuridine gives a diacetyl derivative (80%) by reaction with acetyl bromide. On treatment with acetyl bromide, the nucleoside bond of purine nucleosides is quantitatively cleavaged (4 h, 20 degrees C) with the formation of tri-O-acetyl-D-ribofuranosyl bromide (X). The halogenose X affords pure beta-anomers, namely, 1,2,3,5-tetra-O-acetyl-beta-D-ribofuranose (75%), the triacetyl derivatives of 5-methyluridine (XVIIa; 75%, referred to guanosine), 6-azauridine (XVIII; 71%), and 5-fluorouridine (XIXa; 75%). PMID:940772

Beránek, J; Hrebabecký, H

1976-01-01

273

MICROBIOLOGY: Bacteria Seize Control by Acetylating Host Proteins  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. The plague-causing bacterium Yersinia pestis injects toxic proteins into its hosts' cells. One of these interferes with the host's secretion of a protective factor by adding acetyl groups to a signaling kinase, blocking its activation.

Carolyn A. Worby (University of California; Departments of Pharmacology, Cellular and Molecular Medicine, and Chemistry and Biochemistry)

2006-05-24

274

Fully acetylated carbamate and hypotensive thiocarbamate glycosides from Moringa oleifera  

Microsoft Academic Search

Six new and three synthetically known glycosides have been isolated from the leaves of Moringa oleifera, employing a bioassay-directed isolation method on the ethanolic extract. Most of these compounds, bearing thiocarbamate, carbamate or nitrile groups, are fully acetylated glycosides, which are very rare in nature. Elucidation of the structures was made using chemical and spectroscopic methods, including 2D NMR techniques.

Shaheen Faizi; Bina Shaheen Siddiqui; Rubeena Saleem; Salimuzzaman Siddiqui; Khalid Aftab; Anwar-Ul-Hassan Gilani

1995-01-01

275

Sirtuins deacetylate and activate mammalian acetyl-CoA synthetases  

E-print Network

and nutrient homeostasis. Also, PGC-1 controls gene expression that stimulates mitochondrial biogenesis- lated AceCS1. In mammals, two AceCSs have been identified: cytoplasmic AceCS1 and mitochondrial AceCS2 by acetylation, and specifically deacety- lated by mitochondrial SIRT3. AceCS2 was completely inactivated upon

Denu, John

276

Genetic Control of Differential Acetylation in Diabetic Rats  

PubMed Central

Post-translational protein modifications such as acetylation have significant regulatory roles in metabolic processes, but their relationship to both variation in gene expression and DNA sequence is unclear. We address this question in the Goto-Kakizaki (GK) rat inbred strain, a model of polygenic type 2 diabetes. Expression of the NAD-dependent deacetylase Sirtuin-3 is down-regulated in GK rats compared to normoglycemic Brown Norway (BN) rats. We show first that a promoter SNP causes down-regulation of Sirtuin-3 expression in GK rats. We then use mass-spectrometry to identify proteome-wide differential lysine acetylation of putative Sirtuin-3 protein targets in livers of GK and BN rats. These include many proteins in pathways connected to diabetes and metabolic syndrome. We finally sequence GK and BN liver transcriptomes and find that mRNA expression of these targets does not differ significantly between GK and BN rats, in contrast to other components of the same pathways. We conclude that physiological differences between GK and BN rats are mediated by a combination of differential protein acetylation and gene transcription and that genetic variation can modulate acetylation independently of expression. PMID:24743600

Kaisaki, Pamela J.; Otto, Georg W.; McGouran, Joanna F.; Toubal, Amine; Argoud, Karčne; Waller-Evans, Helen; Finlay, Clare; Caldérari, Sophie; Bihoreau, Marie-Thérčse; Kessler, Benedikt M.; Gauguier, Dominique; Mott, Richard

2014-01-01

277

N-Acetyl cysteine for prevention of contrast induced nephropathy  

Microsoft Academic Search

The antioxidant N-acetyl Cysteine prevents contrast induced nephropathy in patients with impaired renal function who undergo coronary angiogeaphy. However its role in Bangladeshi population is not clear. This study was done determine whether oral acetylcysteine prevents contrast induced nephropathy in high risk patients.100 patients with mild to moderate renal insufficiency who are undergoing elective coronary angiography with or without intervention.50

Anisul Awal; Syed Ali Hasan; Abu Siddique; Bikash Subedi; Jahanara Arzu; Quazi Arif Ahmed; KMHS Sirajul Haque; Ashraf Uddin Sultan; Neena Islam

2009-01-01

278

Molecular Cell SAGA and ATAC Histone Acetyl Transferase  

E-print Network

the same catalytic HAT subunit (GCN5 or PCAF). Here, we show that these human HAT com- plexes are targeted- scription initiation and elongation. The metazoan ATAC (Ada-Two-A-Containing) and SAGA (Spt- Ada-Gcn5-Acetyl acetyltransferase (HAT) enzyme GCN5 (also named KAT2A) or its closely related paralog PCAF (KAT2B). The subunit

279

Ultrafast Photochemistry of Acetone and Dynamics of the Acetyl Radical  

NASA Astrophysics Data System (ADS)

Ultrafast, tunable, mass-resolved 1+1 photoionization spectroscopy has been use d to study the photochemistry of acetone. Results are obtained for excitation in the repulsive S1 state as well as the 3s Rydberg electronic state. Time-resolved photoio nization spectra are obtained using a quadrupole mass spectrometer in a flowing gas samp le. The two laser beams are harmonics of a Ti:Sapphire laser system and they are de pendently tunable in the near UV (?_NUV=257-272 nm) and deep UV (?_DUV= 193-205 nm). For ?_DUV shorter than 196 nm, the signal is primarily due to 3s Rydberg state excitation. Detection of either acetyl ion or acetone ion results in a long-lived signal (4.5 ps) for positive delay of the near UV relative to the deep UV. This is the lifetime of the 3s Rydberg state of acetone. The acetyl ion signal under these circumstances is due primarily to dissociative ionization. For ?_NUV longer than 265 nm, excitation of the S1 state by the near UV pulse dominates the signal. In this case th e acetyl fragment dynamics differ from those for acetone. Acetone dissociates rapidly (being nearly instrument-limited). The acetyl fragment partially dissociates. Dissociation rates will be compared to those obtained from an RRKM calculation.

Baronavski, Andrew P.; Owrutsky, Jeffrey C.

1997-04-01

280

Prebiotically plausible oligoribonucleotide ligation facilitated by chemoselective acetylation  

NASA Astrophysics Data System (ADS)

The recent synthesis of pyrimidine ribonucleoside-2?,3?-cyclic phosphates under prebiotically plausible conditions has strengthened the case for the involvement of ribonucleic acid (RNA) at an early stage in the origin of life. However, a prebiotic conversion of these weakly activated monomers, and their purine counterparts, to the 3?,5?-linked RNA polymers of extant biochemistry has been lacking (previous attempts led only to short oligomers with mixed linkages). Here we show that the 2?-hydroxyl group of oligoribonucleotide-3?-phosphates can be chemoselectively acetylated in water under prebiotically credible conditions, which allows rapid and efficient template-directed ligation. The 2?-O-acetyl group at the ligation junction of the product RNA strand can be removed under conditions that leave the internucleotide bonds intact. Remarkably, acetylation of mixed oligomers that possess either 2?- or 3?-terminal phosphates is selective for the 2?-hydroxyl group of the latter. This newly discovered chemistry thus suggests a prebiotic route from ribonucleoside-2?,3?-cyclic phosphates to predominantly 3?,5?-linked RNA via partially 2?-O-acetylated RNA.

Bowler, Frank R.; Chan, Christopher K. W.; Duffy, Colm D.; Gerland, Béatrice; Islam, Saidul; Powner, Matthew W.; Sutherland, John D.; Xu, Jianfeng

2013-05-01

281

Histone acetylation and heterochromatin content of cultured Peromyscus cells  

SciTech Connect

In order to explore the relationship between unacetylated arginine-rich histones and condensed chromatin structure, the extent of histone acetylation was examined in cultured cell lines derived from three species of deer mice. These species differ considerably in their genomic content of heterochromatin but contain essentially the same euchromatin content. Cells of Peromyscus eremicus, containing 34-36% more constitutive heterochromatin than Peromyscus boylii or Peromyscus crinitus cells were found to contain 28-35% more unacetylated histone H4, 22-29% more unacetylated histone H3, and 18-22% more unacetylated histone H2B. This relationship between unacetylated histone and heterochromatin content was further explored by inducing hyperacetylation of P. eremicus and P. boylli histones through treatment of cells with 15 mM sodium butyrate for 24 h. It was found that the percentages of unacetylated histones H3 and H4 remaining after butyrate treatment were proportional to the amount of constitutive heterochromatin in the genome. These data support the concept that a small core of histones in constitutive heterochromatin is inaccessible to acetylation. It was also found that the acetylated state of isolated histones was senstitive to the method of histone extraction. Thus concern must be given to preparative procedures when studying histone acetylation in order to minimize these acetate losses.

Halleck, M.S.; Carley, L.R.

1981-01-01

282

Stereoselectivity of the Chinese hamster ovary cell sialidase: sialoside hydrolysis with overall retention of configuration.  

PubMed

The stereochemical course of enzymatic hydrolysis by the soluble sialidase from Chinese hamster ovary cells, expressed as a recombinant protein in insect Sf9 cells, was determined using proton nuclear magnetic resonance spectroscopy. 4-Methyl umbelliferyl-N-acetyl neuraminic acid was employed as substrate, and the stereoselectivity of the enzyme catalysis was ascertained by monitoring the H3 axial and equatorial protons of the sialic acid product over the reaction course. At both high (3 U) and low concentrations (1 U) of the enzyme, the alpha anomer of the sialic acid was clearly observed as the initial reaction product. The corresponding beta anomer of sialic acid appeared much later in the reaction, arising from mutarotation of the alpha anomer. Similar studies were also carried out using the Salmonella typhimurium LT 2 sialidase, a protein of similar size and substrate specificity. Both enzymes apparently cleave the alpha linked sialoside substrate with retention of configuration. Based on the observations of a wide variety of other glycohydrolytic enzymes that have shown a strong correlation of the stereoselectivity of catalysis with active site topology (Gebler et al., J. Biol. Chem. 267, 12559-12561, 1992), the results obtained here suggest that the microbial and mammalian sialidases have a homologous active site architecture even though the molecules do not share significant primary sequence similarities. PMID:9184837

Kao, Y H; Lerner, L; Warner, T G

1997-06-01

283

Cladosporium fulvum Avr4 protects fungal cell walls against hydrolysis by plant chitinases accumulating during infection.  

PubMed

Resistance against the leaf mold fungus Cladosporium fulvum is mediated by the tomato Cf proteins which belong to the class of receptor-like proteins and indirectly recognize extracellular avirulence proteins (Avrs) of the fungus. Apart from triggering disease resistance, Avrs are believed to play a role in pathogenicity or virulence of C. fulvum. Here, we report on the avirulence protein Avr4, which is a chitin-binding lectin containing an invertebrate chitin-binding domain (CBM14). This domain is found in many eukaryotes, but has not yet been described in fungal or plant genomes. We found that interaction of Avr4 with chitin is specific, because it does not interact with other cell wall polysaccharides. Avr4 binds to chitin oligomers with a minimal length of three N-acetyl glucosamine residues. In vitro, Avr4 protects chitin against hydrolysis by plant chitinases. Avr4 also binds to chitin in cell walls of the fungi Trichoderma viride and Fusarium solani f. sp. phaseoli and protects these fungi against normally deleterious concentrations of plant chitinases. In situ fluorescence studies showed that Avr4 also binds to cell walls of C. fulvum during infection of tomato, where it most likely protects the fungus against tomato chitinases, suggesting that Avr4 is a counter-defensive virulence factor. PMID:17153926

van den Burg, Harrold A; Harrison, Stuart J; Joosten, Matthieu H A J; Vervoort, Jacques; de Wit, Pierre J G M

2006-12-01

284

Role of Carnitine Acetyltransferases in Acetyl Coenzyme A Metabolism in Aspergillus nidulans ?  

PubMed Central

The flow of carbon metabolites between cellular compartments is an essential feature of fungal metabolism. During growth on ethanol, acetate, or fatty acids, acetyl units must enter the mitochondrion for metabolism via the tricarboxylic acid cycle, and acetyl coenzyme A (acetyl-CoA) in the cytoplasm is essential for the biosynthetic reactions and for protein acetylation. Acetyl-CoA is produced in the cytoplasm by acetyl-CoA synthetase during growth on acetate and ethanol while ?-oxidation of fatty acids generates acetyl-CoA in peroxisomes. The acetyl-carnitine shuttle in which acetyl-CoA is reversibly converted to acetyl-carnitine by carnitine acetyltransferase (CAT) enzymes is important for intracellular transport of acetyl units. In the filamentous ascomycete Aspergillus nidulans, a cytoplasmic CAT, encoded by facC, is essential for growth on sources of cytoplasmic acetyl-CoA while a second CAT, encoded by the acuJ gene, is essential for growth on fatty acids as well as acetate. We have shown that AcuJ contains an N-terminal mitochondrial targeting sequence and a C-terminal peroxisomal targeting sequence (PTS) and is localized to both peroxisomes and mitochondria, independent of the carbon source. Mislocalization of AcuJ to the cytoplasm does not result in loss of growth on acetate but prevents growth on fatty acids. Therefore, while mitochondrial AcuJ is essential for the transfer of acetyl units to mitochondria, peroxisomal localization is required only for transfer from peroxisomes to mitochondria. Peroxisomal AcuJ was not required for the import of acetyl-CoA into peroxisomes for conversion to malate by malate synthase (MLS), and export of acetyl-CoA from peroxisomes to the cytoplasm was found to be independent of FacC when MLS was mislocalized to the cytoplasm. PMID:21296915

Hynes, Michael J.; Murray, Sandra L.; Andrianopoulos, Alex; Davis, Meryl A.

2011-01-01

285

Relativistic Density Functional Theory Calculations of the Electron Paramagnetic Resonance Parameters for Vanadyl Acetyl Acetonate and Copper Acetyl Acetonate  

NASA Astrophysics Data System (ADS)

Relativistic density functional theory calculations of electron paramagnetic resonance (EPR) parameters using a variety of basis sets have been computed for the model systems Vanadyl acetyl acetonate and Copper acetyl acetonate using the ORCA program. The basis set dependence of g and A tensor calculations for Vanadyl acetyl acetonate and Copper acetyl acetonate were studied using Pople Style and Ahlrichs basis sets in Local and gradient corrected functionals (BP86 and PWP) and Hybrid functionals (B3LYP and PW1PW). The PW1PW hybrid functional gives the best values for VO(acac)2 using the TZV basis set and for Cu(acac)2 using the 6-311G(d) basis set. The calculated A values with PW1PW hybrid functional for VO(acac)2 and Local and gradient corrected functional (BP86) for Cu(acac)2 with same basis set (DZ) give better results than previously reported values using the Amsterdam Density Functional Theory (ADF) Software. Our calculated g and A tensor values are in good agreement with the values determined from experiment.

Mainali, Laxman; Sahu, Indra; Earle, Keith

2008-03-01

286

Acetyl coenzyme A synthetase is acetylated on multiple lysine residues by a protein acetyltransferase with a single Gcn5-type N-acetyltransferase (GNAT) domain in Saccharopolyspora erythraea.  

PubMed

Reversible lysine acetylation (RLA) is used by cells of all domains of life to modulate protein function. To date, bacterial acetylation/deacetylation systems have been studied in a few bacteria (e.g., Salmonella enterica, Bacillus subtilis, Escherichia coli, Erwinia amylovora, Mycobacterium tuberculosis, and Geobacillus kaustophilus), but little is known about RLA in antibiotic-producing actinomycetes. Here, we identify the Gcn5-like protein acetyltransferase AcuA of Saccharopolyspora erythraea (SacAcuA, SACE_5148) as the enzyme responsible for the acetylation of the AMP-forming acetyl coenzyme A synthetase (SacAcsA, SACE_2375). Acetylated SacAcsA was deacetylated by a sirtuin-type NAD(+)-dependent consuming deacetylase (SacSrtN, SACE_3798). In vitro acetylation/deacetylation of SacAcsA enzyme was studied by Western blotting, and acetylation of lysine residues Lys(237), Lys(380), Lys(611), and Lys(628) was confirmed by mass spectrometry. In a strain devoid of SacAcuA, none of the above-mentioned Lys residues of SacAcsA was acetylated. To our knowledge, the ability of SacAcuA to acetylate multiple Lys residues is unique among AcuA-type acetyltransferases. Results from site-specific mutagenesis experiments showed that the activity of SacAcsA was controlled by lysine acetylation. Lastly, immunoprecipitation data showed that in vivo acetylation of SacAcsA was influenced by glucose and acetate availability. These results suggested that reversible acetylation may also be a conserved regulatory posttranslational modification strategy in antibiotic-producing actinomycetes. PMID:24957627

You, Di; Yao, Li-Li; Huang, Dan; Escalante-Semerena, Jorge C; Ye, Bang-Ce

2014-09-01

287

Ultrafast hydrolysis of a lewis photoacid.  

PubMed

This study explores the concept that electronic excitation can dramatically enhance Lewis acidity. Specifically, it is shown that photoexcitation transforms an electron-deficient organic compound of negligible Lewis acidity in its electronic ground state into a potent excited-state Lewis acid that releases a proton from a nearby water molecule in 3.1 ps. It was shown previously (Peon et al. J. Phys. Chem. A 2001, 105, 5768) that the excited state of methyl viologen (MV(2+)) is quenched rapidly in aqueous solution with the formation of an unidentified photoproduct. In this study, the quenching mechanism and the identity of the photoproduct were investigated by the femtosecond transient absorption and fluorescence upconversion techniques. Transient absorption signals at UV probe wavelengths reveal a long-lived species with a pH-dependent lifetime due to reaction with hydronium ions at a bimolecular rate of 3.1 × 10(9) M(-1) s(-1). This species is revealed to be a charge-transfer complex consisting of a ground-state MV(2+) ion and a hydroxide ion formed when a water molecule transfers a proton to the bulk solvent. Formation of a contact ion pair between MV(2+) and hydroxide shifts the absorption spectrum of the former ion by a few nm to longer wavelengths, yielding a transient absorption spectrum with a distinctive triangle wave appearance. The slight shift of this spectrum, which is in excellent agreement with steady-state difference spectra recorded for MV(2+) at high pH, is consistent with an ion pair but not with a covalent adduct (pseudobase). The long lifetime of the ion pair at neutral pH indicates that dissociation occurs many orders of magnitude more slowly than predicted by the Smoluchowski-Debye equation. Remarkably, there is no evidence of geminate recombination, suggesting that the proton that is transferred to the solvent is conducted at least several water shells away. Although the hydrolysis mechanism has yet to be fully established, evidence suggests that the strongly oxidizing excited state of MV(2+) triggers the proton-coupled oxidation of a water molecule. The observed kinetic isotope effect of 1.7 seen in D2O vs H2O is of the magnitude expected for an ultrafast concerted proton-electron transfer reaction. The ultrafast hydrolysis seen here may be a general excited-state quenching mechanism for electronically excited Lewis acids and other powerful photooxidants in aqueous solution. PMID:25510461

Henrich, Joseph D; Suchyta, Scott; Kohler, Bern

2015-02-12

288

Complex O-acetylation in non-typeable Haemophilus influenzae lipopolysaccharide: evidence for a novel site of O-acetylation.  

PubMed

The structure of the lipopolysaccharide (LPS) of non-typeable Haemophilus influenzae strain 723 has been elucidated using NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS) on O-deacylated LPS and core oligosaccharide material (OS), as well as ESI-MSn on permethylated dephosphorylated OS. It was found that the LPS contains the common structural element of H. influenzae, l-alpha-D-Hepp-(1-->2)-[PEtn-->6]-l-alpha-D-Hepp-(1-->3)-[beta-D-Glcp-(1-->4)]-l-alpha-D-Hepp-(1-->5)-[PPEtn-->4]-alpha-Kdo-(2-->6)-Lipid A, in which the beta-D-Glcp residue (GlcI) is substituted by phosphocholine at O-6 and the distal heptose residue (HepIII) by PEtn at O-3, respectively. In a subpopulation of glycoforms O-2 of HepIII was substituted by beta-D-Galp-(1-->4)-beta-D-Glcp-(1--> or beta-D-Glcp-(1-->. Considerable heterogeneity of the LPS was due to the extent of substitution by O-acetyl groups (Ac) and ester-linked glycine of the core oligosaccharide. The location for glycine was found to be at Kdo. Prominent acetylation sites were found to be at GlcI, HepIII, and the proximal heptose (HepI) residue of the triheptosyl moiety. Moreover, GlcI was acetylated at O-3 and/or O-4 and HepI was acetylated at O-2 as evidenced by capillary electrophoresis ESI-MSn in combination with NMR analyses. This is the first study to show that an acetyl group can substitute HepI of the inner-core region of H. influenzae LPS. PMID:16199021

Yildirim, Hĺkan H; Li, Jianjun; Richards, James C; Hood, Derek W; Moxon, E Richard; Schweda, Elke K H

2005-12-12

289

Stereoselective hydrolysis catalyzed by a Bacillus endoglucanase in family D.  

PubMed

An endoglucanase in family D, purified from a strain of Bacillus, was found to catalyze the hydrolysis of p-nitrophenyl beta-D-cellotrioside to generate alpha-cellobiose, as determined by 1H-NMR spectroscopy. The hydrolysis of the beta-1,4 glucosidic bond by the enzyme proceeds, therefore, by an inversion mechanism. Furthermore, the interconversion of the alpha- and beta-anomeric protons in the products of hydrolysis, after equilibrium had been reached by mutarotation, was directly characterized by magnetization transfer NMR experiment that exploited the truncated driven nuclear Overhauser effect. PMID:7626068

Kawaminami, S; Ozaki, K; Ito, S

1995-07-17

290

Vibrational spectroscopic studies in the hydrolysis and condensation of chlorotrimethylsilane.  

PubMed

Raman and infrared spectroscopy were used to study the hydrolysis and condensation of chlorotrimethylsilane (CTMC) in aqueous organic solvents. From the recorded spectra and their intensity variation with time, we were able to identify trimethylsilanol as the reaction intermediate or the hydrolysis product as well as hexamethyldisiloxane (HMDS) as the final condensation product. The measured Raman intensity of CTMS at different time revealed that hydrolysis of CTMS is first order in terms of the CTMS concentration. From the Raman spectra collected under different conditions, it was noted that condensation reaction rates is faster in neutral condition than in acidic condition. PMID:15036105

Li, Ying-Sing; Le, Kim

2004-03-01

291

Vibrational spectroscopic studies in the hydrolysis and condensation of chlorotrimethylsilane  

NASA Astrophysics Data System (ADS)

Raman and infrared spectroscopy were used to study the hydrolysis and condensation of chlorotrimethylsilane (CTMC) in aqueous organic solvents. From the recorded spectra and their intensity variation with time, we were able to identify trimethylsilanol as the reaction intermediate or the hydrolysis product as well as hexamethyldisiloxane (HMDS) as the final condensation product. The measured Raman intensity of CTMS at different time revealed that hydrolysis of CTMS is first order in terms of the CTMS concentration. From the Raman spectra collected under different conditions, it was noted that condensation reaction rates is faster in neutral condition than in acidic condition.

Li, Ying-Sing; Le, Kim

2004-03-01

292

Polarized light-stimulated enzymatic hydrolysis of chitin and chitosan.  

PubMed

Illumination with white linearly polarized light (WLPL) stimulated chitinase and chitosanase in their degradation of chitin and chitosan, respectively. Enzymes were illuminated at room temperature in separate vessels, then admixed in reactors containing polysaccharides. Hydrolysis of chitosan to glucosamine followed first order kinetics whereas hydrolysis of chitin to N-acetylglucosamine deviated from the first order kinetics. In both cases, an increase in the rate of hydrolysis depended on the illumination time. Efficient degradation required up to 60 min exposure of the enzyme to WLPL. PMID:18823881

Konieczna-Molenda, Anna; Fiedorowicz, Maciej; Zhong, Wei; Tomasik, Piotr

2008-12-01

293

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.

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

2010-07-01

294

Hydrolysis and Partial Recycling of a Chloroaluminate Ionic Liquid  

PubMed Central

Hydrolysis of the ionic liquid Et3NHCl-2AlCl3 and a process for recycling the triethylamine were studied. When the hydrolysis was carried out at a relatively high temperature, the released HCl could be absorbed more easily. With addition of sodium hydroxide to the aqueous hydrolysis solution, a feasible process for recycling triethylamine was developed, involving first distillation of triethylamine, followed by filtration of the aluminium hydroxide. The yield of recovered triethylamine was about 95%. The triethylhydrogenammonium chloride prepared from the recycled triethylamine was of good purity and could be reused to synthesize new chloroaluminate ionic liquids.

Fang, Ming-Hong; Wang, Li-Sheng

2007-01-01

295

Generation of Mature N?-Terminal Acetylated Thymosin ?1 by Cleavage of Recombinant Prothymosin ?  

PubMed Central

N?-terminal acetylation of peptides plays an important biological role but is rarely observed in prokaryotes. N?-terminal acetylated thymosin ?1 (T?1), a 28-amino-acid peptide, is an immune modifier that has been used in the clinic to treat hepatitis B and C virus (HBV/HCV) infections. We previously documented N?-terminal acetylation of recombinant prothymosin ? (ProT?) in E. coli. Here we present a method for production of N?-acetylated T?1 from recombinant ProT?. The recombinant ProT? was cleaved by human legumain expressed in Pichia pastoris to release T?1 in vitro. The N?-acetylated T?1 peptide was subsequently purified by reverse phase and cation exchange chromatography. Mass spectrometry indicated that the molecular mass of recombinant N?-acetylated T?1 was 3108.79 in, which is identical to the mass of N?-acetylated T?1 produced by total chemical synthesis. This mass corresponded to the nonacetylated T?1 mass with a 42?Da increment. The retention time of recombinant N?-acetylated T?1 and chemosynthetic N?-acetylated T?1 were both 15.4?min in RP-high performance liquid chromatography (HPLC). These data support the use of an E. coli expression system for the production of recombinant human N?-acetylated T?1 and also will provide the basis for the preparation of recombinant acetylated peptides in E. coli. PMID:24288480

Gong, Xin; Chang, Shaohong; Sun, Peng

2013-01-01

296

Generation of mature N?-terminal acetylated thymosin ? 1 by cleavage of recombinant prothymosin ?.  

PubMed

N(?)-terminal acetylation of peptides plays an important biological role but is rarely observed in prokaryotes. N(?)-terminal acetylated thymosin ?1 (T?1), a 28-amino-acid peptide, is an immune modifier that has been used in the clinic to treat hepatitis B and C virus (HBV/HCV) infections. We previously documented N(?)-terminal acetylation of recombinant prothymosin ? (ProT?) in E. coli. Here we present a method for production of N(?)-acetylated T?1 from recombinant ProT?. The recombinant ProT? was cleaved by human legumain expressed in Pichia pastoris to release T?1 in vitro. The N(?)-acetylated T?1 peptide was subsequently purified by reverse phase and cation exchange chromatography. Mass spectrometry indicated that the molecular mass of recombinant N(?)-acetylated T?1 was 3108.79 in, which is identical to the mass of N(?)-acetylated T?1 produced by total chemical synthesis. This mass corresponded to the nonacetylated T?1 mass with a 42 Da increment. The retention time of recombinant N(?)-acetylated T?1 and chemosynthetic N(?)-acetylated T?1 were both 15.4 min in RP-high performance liquid chromatography (HPLC). These data support the use of an E. coli expression system for the production of recombinant human N(?)-acetylated T?1 and also will provide the basis for the preparation of recombinant acetylated peptides in E. coli. PMID:24288480

Liu, Bo; Gong, Xin; Chang, Shaohong; Sun, Peng; Wu, Jun

2013-01-01

297

Stoichiometry of site-specific lysine acetylation in an entire proteome.  

PubMed

Acetylation of lysine ?-amino groups influences many cellular processes and has been mapped to thousands of sites across many organisms. Stoichiometric information of acetylation is essential to accurately interpret biological significance. Here, we developed and employed a novel method for directly quantifying stoichiometry of site-specific acetylation in the entire proteome of Escherichia coli. By coupling isotopic labeling and a novel pairing algorithm, our approach performs an in silico enrichment of acetyl peptides, circumventing the need for immunoenrichment. We investigated the function of the sole NAD(+)-dependent protein deacetylase, CobB, on both site-specific and global acetylation. We quantified 2206 peptides from 899 proteins and observed a wide distribution of acetyl stoichiometry, ranging from less than 1% up to 98%. Bioinformatic analysis revealed that metabolic enzymes, which either utilize or generate acetyl-CoA, and proteins involved in transcriptional and translational processes displayed the highest degree of acetylation. Loss of CobB led to increased global acetylation at low stoichiometry sites and induced site-specific changes at high stoichiometry sites, and biochemical analysis revealed altered acetyl-CoA metabolism. Thus, this study demonstrates that sirtuin deacetylase deficiency leads to both site-specific and global changes in protein acetylation stoichiometry, affecting central metabolism. PMID:24917678

Baeza, Josue; Dowell, James A; Smallegan, Michael J; Fan, Jing; Amador-Noguez, Daniel; Khan, Zia; Denu, John M

2014-08-01

298

Metabolic Regulation of Protein N-alpha-acetylation by Bcl-xL Promotes Cell Survival  

PubMed Central

Summary Previous experiments suggest a connection between the N-alpha-acetylation of proteins and the sensitivity of cells to apoptotic signals. Here, we describe a novel biochemical assay to detect the acetylation status of proteins and demonstrate that protein N-alpha-acetylation is regulated by the availability of acetyl-CoA. Because the anti-apoptotic protein Bcl-xL is known to influence mitochondrial metabolism, we reasoned that Bcl-xL may provide a link between protein N-alpha-acetylation and apoptosis. Indeed, Bcl-xL overexpression leads to a reduction in levels of acetyl-CoA and N-alpha-acetylated proteins in the cell. This effect is independent of Bax and Bak, the known binding partners of Bcl-xL. Increasing cellular levels of acetyl-CoA by addition of acetate or citrate restores protein N-alpha-acetylation in Bcl-xL-expressing cells and confers sensitivity to apoptotic stimuli. We conclude that acetyl-CoA serves as a signaling molecule that couples apoptotic sensitivity to metabolism by regulating protein N-alpha-acetylation. PMID:21854985

Yi, Caroline H.; Pan, Heling; Seebacher, Jan; Jang, Il-Ho; Hyberts, Sven G.; Heffron, Gregory J.; Vander Heiden, Matthew G.; Yang, Renliang; Li, Fupeng; Locasale, Jason W.; Sharfi, Hadar; Zhai, Bo; Rodriguez-Mias, Ricard; Luithardt, Harry; Cantley, Lewis C.; Daley, George Q.; Asara, John M.; Gygi, Steven P.; Wagner, Gerhard; Liu, Chuan-Fa; Yuan, Junying

2011-01-01

299

[Effect of acetylation and oxidation on some properties of breadfruit (Artocarpus altilis) seed starch].  

PubMed

Starch extracted from seeds of Artocarpus altilis (Breadfruit) was chemically modified by acetylation and oxidation, and its functional properties were evaluated and compared with these of native starch. Analysis of the chemical composition showed that moisture content was higher for modified starches. Ash, protein, crude fiber and amylose contents were reduced by the modifications, but did not alter the native starch granules' irregularity, oval shape and smooth surface. Acetylation produced changes in water absorption, swelling power and soluble solids, these values were higher for acetylated starch, while values for native and oxidized starches were similar. Both modifications reduced pasting temperature; oxidation reduced maximum peak viscosity but it was increased by acetylation. Hot paste viscosity was reduced by both modifications, whereas cold paste viscosity was lower in the oxidized starch and higher in the acetylated starch. Breakdown was increased by acetylation and reduced with oxidation. Setback value was reduced after acetylation, indicating it could minimize retrogradation of the starch. PMID:18271408

Rincón, Alicia Mariela; Bou Rached, Lizet; Aragoza, Luis E; Padilla, Fanny

2007-09-01

300

Dilute acid hydrolysis of wheat straw oligosaccharides.  

PubMed

The dilute acid posthydrolysis of wheat straw hemicellulosic oligosaccharides obtained by autohydrolysis was evaluated. An empirical model was used to describe the effect of catalyst concentration (sulfuric acid, 0.1-4% w/w) and reaction time (0-60 min) based on data from a Doehlert experimental design. Catalyst concentration is the main variable influencing posthydrolysis performance, as both its linear and quadratic coefficients are statistically significant for the majority of the studied variables, namely, the ones related to sugar and byproducts production. Reaction time influences xylose and furan derivatives concentrations but not phenolics or acetic acid content. Catalyst concentration and reaction time interact synergistically, minimizing sugar recovery and promoting furan derivatives production. Based on the proposed models, it was possible to delimit an operational range that enables to obtain high monosaccharides recovery together with a slight decrease in inhibitors content as compared to the standard acid hydrolysis treatment. Furthermore, this is achieved with up to 70% less acid spending or considerable savings on reaction time. PMID:19043676

Duarte, Luís C; Silva-Fernandes, Talita; Carvalheiro, Florbela; Gírio, Francisco M

2009-05-01

301

General lysosomal hydrolysis can process prorenin accurately.  

PubMed

Renin, an aspartyl protease that catalyzes the rate-limiting step of the renin-angiotensin system, is first synthesized as an inactive precursor, prorenin. Prorenin is activated by the proteolytic removal of an amino terminal prosegment in the dense granules of the juxtaglomerular (JG) cells of the kidney by one or more proteases whose identity is uncertain but commonly referred to as the prorenin-processing enzyme (PPE). Because several extrarenal tissues secrete only prorenin, we tested the hypothesis that the unique ability of JG cells to produce active renin might be explained by the existence of a PPE whose expression is restricted to JG cells. We found that inducing renin production by the mouse kidney by up to 20-fold was not associated with the concomitant induction of candidate PPEs. Because the renin-containing granules of JG cells also contain several lysosomal hydrolases, we engineered mouse Ren1 prorenin to be targeted to the classical vesicular lysosomes of cultured HEK-293 cells, where it was accurately processed and stored. Furthermore, we found that HEK cell lysosomes hydrolyzed any artificial extensions placed on the protein and that active renin was extraordinarily resistant to proteolytic degradation. Altogether, our results demonstrate that accurate processing of prorenin is not restricted to JG cells but can occur in classical vesicular lysosomes of heterologous cells. The implication is that renin production may not require a specific PPE but rather can be achieved by general hydrolysis in the lysosome-like granules of JG cells. PMID:24965790

Xa, Lucie K; Lacombe, Marie-Josée; Mercure, Chantal; Lazure, Claude; Reudelhuber, Timothy L

2014-09-01

302

The influence of GABA on the synthesis of N-acetylserotonin, melatonin, O-acetyl-5-hydroxytryptophol and  

E-print Network

The influence of GABA on the synthesis of N-acetylserotonin, melatonin, O-acetyl-5-acetylserotonin, melatonin, O-acetyl-5- hydroxytryptophol and 0-acetyl-5-methoxytryptophol has been investigated using to the incubation medium together, a significant increase in synthesis of the N-acetylated products occurred during

Paris-Sud XI, Université de

303

Structure of the O-polysaccharide of Cronobacter sakazakii O1 containing 3-(N-acetyl-l-alanyl)amino-3,6-dideoxy-d-glucose.  

PubMed

The O-polysaccharide (O-antigen) was released by mild acid hydrolysis of the lipopolysaccharide of Cronobacter sakazakii ATCC 29544(T) (serotype O1) and studied by composition analysis and Smith degradation, in addition to 1D and 2D (1)H and (13)C NMR spectroscopy. The following structure of the pentasaccharide repeating unit of the O-polysaccharide was established: [Formula: see text] where d-Qui3NAcyl stands for 3-(N-acetyl-l-alanyl)amino-3,6-dideoxy-d-glucose. The same composition but a different structure has been reported earlier for the O-polysaccharide of C. sakazakii 3290 [MacLean, L. L.; Pagotto, F.; Farber, J. M.; Perry, M. B. Biochem. Cell Biol.2009, 87, 459-465]. PMID:20719304

Arbatsky, Nikolay P; Wang, Min; Shashkov, Alexander S; Feng, Lu; Knirel, Yuriy A; Wang, Lei

2010-09-23

304

Coupled Ferredoxin and Crotonyl Coenzyme A (CoA) Reduction with NADH Catalyzed by the Butyryl-CoA Dehydrogenase/Etf Complex from Clostridium kluyveri? †  

PubMed Central

Cell extracts of butyrate-forming clostridia have been shown to catalyze acetyl-coenzyme A (acetyl-CoA)- and ferredoxin-dependent formation of H2 from NADH. It has been proposed that these bacteria contain an NADH:ferredoxin oxidoreductase which is allosterically regulated by acetyl-CoA. We report here that ferredoxin reduction with NADH in cell extracts from Clostridium kluyveri is catalyzed by the butyryl-CoA dehydrogenase/Etf complex and that the acetyl-CoA dependence previously observed is due to the fact that the cell extracts catalyze the reduction of acetyl-CoA with NADH via crotonyl-CoA to butyryl-CoA. The cytoplasmic butyryl-CoA dehydrogenase complex was purified and is shown to couple the endergonic reduction of ferredoxin (E0? = ?410 mV) with NADH (E0? = ?320 mV) to the exergonic reduction of crotonyl-CoA to butyryl-CoA (E0? = ?10 mV) with NADH. The stoichiometry of the fully coupled reaction is extrapolated to be as follows: 2 NADH + 1 oxidized ferredoxin + 1 crotonyl-CoA = 2 NAD+ + 1 ferredoxin reduced by two electrons + 1 butyryl-CoA. The implications of this finding for the energy metabolism of butyrate-forming anaerobes are discussed in the accompanying paper. PMID:17993531

Li, Fuli; Hinderberger, Julia; Seedorf, Henning; Zhang, Jin; Buckel, Wolfgang; Thauer, Rudolf K.

2008-01-01

305

Hydrolysis of fMet-tRNA by Peptidyl Transferase  

PubMed Central

Escherichia coli and rabbit reticulocyte (f[3H]Met-tRNA·AUG·ribosome) intermediates undergo hydrolysis, with release of f[3H]methionine, upon addition of tRNA or CpCpA in the presence of acetone. This ribosomal catalyzed reaction has similar requirements, pH optimum, and antibiotic sensitivity to those of peptidyl transferase. Two antibiotics, lincomycin with E. coli ribosomes and anisomycin with reticulocyte ribosomes, inhibit peptide-bond formation and transesterification activities of peptidyl transferase, but stimulate hydrolysis of f[3H]Met-tRNA. Earlier studies have suggested peptidyl transferase activity is essential for R factor-dependent hydrolysis of f(3H)Met-tRNA. These studies indicate that peptidyl transferase has the capacity for f(3H)Met-tRNA hydrolysis and, therefore, may be responsible for peptidyl-tRNA cleavage during peptide chain termination. PMID:4943558

Caskey, C. T.; Beaudet, A. L.; Scolnick, E. M.; Rosman, M.

1971-01-01

306

Responsive behavior of regenerated cellulose in hydrolysis under microwave radiation.  

PubMed

This work studied the responsive behavior of regenerated cellulose (RC) in hydrolysis under microwave radiation. Four types of RC with different crystallinity (Cr) and degree of polymerization (DP) are produced to evaluate the reactivity of RC by step-by-step hydrolysis. Results show Cr is the key factor to affect the reactivity of RCs. With hydrolysis of amorphous region and the formation of recrystallization, the Cr of RC reaches a high value and thus weakens the reactivity. As a result, the increment of cellulose conversion and sugar yield gradually reduces. Decrease of the DP of RC is helpful to increase the speed at the onset of hydrolysis and produce high sugar yield. But, there is no direct influence with the reactivity of RC to prolong the time of pretreatment. This research provides an accurate understanding to guide the RC preparation for sugar formation with relative high efficiency under mild reaction conditions. PMID:24971946

Ni, Jinping; Na, Haining; She, Zhen; Wang, Jinggang; Xue, Wenwen; Zhu, Jin

2014-09-01

307

ESTIMATION OF CARBOXYLIC ACID ESTER HYDROLYSIS RATE CONSTANTS  

EPA Science Inventory

SPARC chemical reactivity models were extended to calculate hydrolysis rate constants for carboxylic acid esters from molecular structure. The energy differences between the initial state and the transition state for a molecule of interest are factored into internal and external...

308

Preparation of monodisperse titania by titanium alkoxide hydrolysis  

SciTech Connect

A process for the production of monodisperse titania particles is described comprising the steps of: (a) dissolving titanium tetraalkoxide in an alcoholic medium to form a solution of the alkoxide in the alcoholic medium; (b) providing a hydrolysis solution comprising alcohol and water in amounts sufficient to hydrolyze the alkoxide in the solution; (c) adding the hydrolysis solution to the solution of the alkoxide to hydrolyze the alkoxide at hydrolysis conditions to form a dispersion of monodisperse titania particles, the hydrolysis being conducted in the presence of a component selected from the group consisting of (1) monoalkyl amines, (2) dialkyl amines, (3) trialkyl amines in combination with hydroxypropylcellulose and (4) mixtures thereof, the alkyl substituent having from 1 to 7 carbon atoms; and (d) separating and recovering the monodisperse titania particles from the dispersion.

Olson, W.L.; Liss, W.E.

1988-03-22

309

Cellulase-lignin interactions in the enzymatic hydrolysis of lignocellulose.  

E-print Network

??Lignin, a major non-carbohydrate polymer in lignocellulosic plant biomass, restricts the action of hydrolytic enzymes in the enzymatic hydrolysis of lignocellulosic feedstocks. Non-productive enzyme adsorption… (more)

Rahikainen, Jenni

2013-01-01

310

Accelerating enzymatic hydrolysis of cornstarch and cellulose using cationic polymers.  

E-print Network

??The effect of cationic polymers on the rate of hydrolysis of cornstarch and cellulosic feedstocks was investigated. Poly(diallyldimethylammonium chloride) (p-DADMAC) and cationic polyacrylamides (c-PAMs) were… (more)

Mora, Sandeep

2013-01-01

311

Kinetics of the hydrolysis of guanosine 5'-phospho-2-methylimidazolide  

NASA Technical Reports Server (NTRS)

The hydrolysis kinetics of guanosine 5'-phospho-2-methylimidazolide (2-MeImpG) in aqueous buffered solutions of various pH's was studied at 75 and 37 C, using spectrophotometric and HPLC techniques. The hydrolysis was found to be very slow even at low pH. At 75 C and pH at or below l.0, two kinetic processes were observed: the more rapid one was attributed to the hydrolysis of the phosphoimidazolide P-N bond; the second, much slower one, was attributed to the cleavage of the glycosidic bond. It is noted that the P-N hydrolysis in phosphoimidazolides is very slow compared to other phosphoramidates, and that this might be one of the reasons why the phosphoimidazolides showed an extraordinary ability to form long oligomers under template-directed conditions.

Kanavarioti, Anastassia

1986-01-01

312

A General Approach for Teaching Hydrolysis of Salts.  

ERIC Educational Resources Information Center

Presented is a general approach and equation for teaching the hydrolysis of salts. This general equation covers many more sets of conditions than those currently in textbooks. The simplifying assumptions leading to the known limiting equations are straightforward. (RH)

Aguirre-Ode, Fernando

1987-01-01

313

Mechanistic insights into the hydrolysis of organophosphorus compounds by  

E-print Network

Mechanistic insights into the hydrolysis of organophosphorus compounds by paraoxonase-1: exploring in the online version of this paper. Keywords: structure­activity relationships; paraoxonase; organophosphorus esters and organophosphorus (OP) compounds; however, its physiological role remains enigmatic

Magliery, Thomas J.

314

Energetic approach of biomass hydrolysis in supercritical water.  

PubMed

Cellulose hydrolysis can be performed in supercritical water with a high selectivity of soluble sugars. The process produces high-pressure steam that can be integrated, from an energy point of view, with the whole biomass treating process. This work investigates the integration of biomass hydrolysis reactors with commercial combined heat and power (CHP) schemes, with special attention to reactor outlet streams. The innovation developed in this work allows adequate energy integration possibilities for heating and compression by using high temperature of the flue gases and direct shaft work from the turbine. The integration of biomass hydrolysis with a CHP process allows the selective conversion of biomass into sugars with low heat requirements. Integrating these two processes, the CHP scheme yield is enhanced around 10% by injecting water in the gas turbine. Furthermore, the hydrolysis reactor can be held at 400°C and 23MPa using only the gas turbine outlet streams. PMID:25536511

Cantero, Danilo A; Vaquerizo, Luis; Mato, Fidel; Bermejo, M Dolores; Cocero, M José

2015-03-01

315

Enzymatic hydrolysis of steryl glycosides for their analysis in foods.  

PubMed

Steryl glycosides (SG) contribute significantly to the total intake of phytosterols. The standard analytical procedure involving acid hydrolysis fails to reflect the correct sterol profile of SG due to isomerization of some of the labile sterols. Therefore, various glycosylases were evaluated for their ability to hydrolyse SG under milder conditions. Using a pure SG mixture in aqueous solution, the highest glycolytic activity, as demonstrated by the decrease in SG and increase in free sterols was achieved using inulinase preparations (decrease of >95%). High glycolytic activity was also demonstrated using hemicellulase (63%). The applicability of enzymatic hydrolysis using inulinase preparations was further verified on SG extracted from foods. For example in potato peel ?(5)-avenasteryl glucoside, a labile SG, was well preserved and contributed 26.9% of the total SG. Therefore, enzymatic hydrolysis is suitable for replacing acid hydrolysis of SG in food lipid extracts to accurately determine the sterol profile of SG. PMID:24912717

Münger, Linda H; Nyström, Laura

2014-11-15

316

Site-specific acetylation of ISWI by GCN5  

Microsoft Academic Search

BACKGROUND: The tight organisation of eukaryotic genomes as chromatin hinders the interaction of many DNA-binding regulators. The local accessibility of DNA is regulated by many chromatin modifying enzymes, among them the nucleosome remodelling factors. These enzymes couple the hydrolysis of ATP to disruption of histone-DNA interactions, which may lead to partial or complete disassembly of nucleosomes or their sliding on

Roger Ferreira; Anton Eberharter; Tiziana Bonaldi; Mariacristina Chioda; Axel Imhof; Peter B Becker

2007-01-01

317

PCAF acetylates Runx2 and promotes osteoblast differentiation.  

PubMed

Osteoblasts play a crucial role in bone formation. However, the molecular mechanisms involved in osteoblast differentiation remain largely unclear. Runt-related gene 2 (Runx2) is a master transcriptional factor for osteoblast differentiation. Here we reported that p300/CBP-associated factor (PCAF) directly binds to Runx2 and acetylates Runx2, leading to an increase in its transcriptional activity. Upregulation of PCAF in MC3T3-E1 cells increases the expression of osteogenic marker genes including alkaline phosphatase (ALP), osteocalcin (Ocn), and Osteopontin (Opn), and ALP activity was stimulated as well. Consequently, the mineralization of MC3T3-E1 cells was remarkably improved by PCAF. In contrast, PCAF knockdown decreases the mRNA levels of ALP, Ocn, and Opn. ALP activity and the mineralized area were attenuated under PCAF knockdown conditions. These results indicate that PCAF is an important regulator for promoting osteoblast differentiation via acetylation modification of Runx2. PMID:23468178

Wang, Chao-Yang; Yang, Shu-Feng; Wang, Zhong; Tan, Jun-Ming; Xing, Shun-Min; Chen, De-Chun; Xu, Sheng-Ming; Yuan, Wen

2013-07-01

318

A SPECTROPHOTOMETRIC STUDY OF THE HYDROLYSIS OF PLUTONIUM(IV)  

Microsoft Academic Search

The hydrolysis of Pu(IV) in HâO and DâO was studied by ; means of spectrophotometric measurements at 3300 A and various acidities. The ; data were solved with the least squares method on an IBM computer (704) for the ; hydrolysis constant K = STAPuOH\\/sup 3+\\/!STAH\\/sup +\\/!\\/STAPu\\/sup 4+\\/!. ; Measurements were made at 15.4 and 25.0 deg C, and they

S. W. Rabideau; R. J. Kline

1960-01-01

319

Fully acetylated carbamate and hypotensive thiocarbamate glycosides from Moringa oleifera.  

PubMed

Six new and three synthetically known glycosides have been isolated from the leaves of Moringa oleifera, employing a bioassay-directed isolation method on the ethanolic extract. Most of these compounds, bearing thiocarbamate, carbamate or nitrile groups, are fully acetylated glycosides, which are very rare in nature. Elucidation of the structures was made using chemical and spectroscopic methods, including 2D NMR techniques. Thiocarbamates showed hypotensive activity. PMID:7766390

Faizi, S; Siddiqui, B S; Saleem, R; Siddiqui, S; Aftab, K; Gilani, A H

1995-03-01

320

Inhibition of acetyl cholinesterase by solanaceous glycoalkaloids and alkaloids  

Microsoft Academic Search

Seven solanaceous glycoalkaloids (?-chaconine, ?2-chaconine, ?-solanine, dehydrocommersonine, commersonine, demissine and tomatine) and three alkaloids (solanidine, tomatidine\\u000a and demissidine) were tested for their ability to inhibit acetyl cholinesterase in anin vitro system. Glycoalkaloids at concentrations of 33–41 parts per million (ppm) gave cholinesterase inhibition ranging from 4.2\\u000a to 26.8%. All three alkaloids had lower anticholinesterase (4.2 to 15.4%) than the seven

Rodney J. Bushway; Sharon A. Savage; Bruce S. Ferguson

1987-01-01

321

Acetylcholinesterase inhibition activity of acetylated depsidones from Lobaria pulmonaria  

Microsoft Academic Search

As part of our ongoing project of new acetylcholinesterase inhibitors from lower marine and terrestrial species, a phytochemical investigation was conducted on a foliose lichen, Lobaria pulmonaria (L.) Hoffm. (Lobariaceae), from Bosnia and Herzegovina. The study led to the isolation of a mixture of acetylated depsidones which showed a moderate activity (0.5?µg) in the acetylcholinesterase inhibition test on Thin-layer chromatography

Boris Pejin; Giuseppina Tommonaro; Carmine Iodice; Vele Tesevic; Vlatka Vajs

2012-01-01

322

Acetylcholinesterase inhibition activity of acetylated depsidones from Lobaria pulmonaria  

Microsoft Academic Search

As part of our ongoing project of new acetylcholinesterase inhibitors from lower marine and terrestrial species, a phytochemical investigation was conducted on a foliose lichen, Lobaria pulmonaria (L.) Hoffm. (Lobariaceae), from Bosnia and Herzegovina. The study led to the isolation of a mixture of acetylated depsidones which showed a moderate activity (0.5?µg) in the acetylcholinesterase inhibition test on Thin-layer chromatography

Boris Pejin; Giuseppina Tommonaro; Carmine Iodice; Vele Tesevic; Vlatka Vajs

2011-01-01

323

Acetyl l -carnitine reduces impulsive behaviour in adolescent rats  

Microsoft Academic Search

The attention deficit\\/hyperactivity disorder (ADHD) can affect human infants and adolescents. One important feature of this disorder is behavioural impulsivity. This study assessed the ability of chronic acetyl-l-carnitine (ALC, saline or 100 mg\\/kg SC, plus 50 mg\\/kg orally) to reduce impulsivity in a validated animal model for ADHD. Food-restricted rats were tested during adolescence (postnatal days, pnd, 30–45) in operant chambers with

Walter Adriani; Monica Rea; Marta Baviera; William Invernizzi; Mirjana Carli; Orlando Ghirardi; Antonio Caprioli; Giovanni Laviola

2004-01-01

324

Photodecomposition of acetyl chloride on the excited singlet state surface  

Microsoft Academic Search

We investigate the plausible mechanism of fast decomposition of acetyl chloride upon 1n?* (CO) excitation through the selective C–Cl bond-fission on the lowest excited singlet state surface using abinitio quantum chemical methods. Effects of zero point energy corrections and of electron correlation have been considered. The pathway involves dissociation, via a ?Cl?*CO and a ?Cl?*C–Cl configurations where ?’s stand for

R. Sumathi; A. K. Chandra

1993-01-01

325

Ethyl 2-acetyl­hydrazono-2-phenyl­acetate  

PubMed Central

The title compound, C12H14N2O3, was synthesized as an inter­mediate for the synthesis of metamitron. The benzene ring forms dihedral angles of 86.3?(2) and 10.0?(3)° with the ethyl group and the acetyl­imino plane, respectively. The crystal structure involves inter­molecular C—H?O and N—H?O hydrogen bonds. PMID:21200890

Xu, Liang-Zhong; Yi, Xu; An, Guang-Wei; Zhang, Gong-Sheng; Li, Chun-Fang

2008-01-01

326

2-Acetyl­hydrazono-2-phenyl­aceto­hydrazide  

PubMed Central

The title compound, C10H12N4O2, was prepared as an inter­mediate for the synthesis of metamitron. The benzene ring plane forms dihedral angles of 66.0?(1) and 3.5?(5)° with the hydrazine plane and the acetyl­imino plane, respectively. The crystal structure involves inter­molecular N—H?O hydrogen bonds. PMID:21201803

Feng, Bai-Cheng; Yang, Zhi; Yi, Xu

2008-01-01

327

Evaluation of abalone ?-glucuronidase substitution in current urine hydrolysis procedures.  

PubMed

This study examined the potential of abalone ?-glucuronidase as a viable and cost effective alternative to current hydrolysis procedures using acid, Helix pomatia ?-glucuronidase and Escherichia coli ?-glucuronidase. Abalone ?-glucuronidase successfully hydrolyzed oxazepam-glucuronide and lorazepam-glucuronide within 5% of the spiked control concentration. Benzodiazepines present in authentic urine specimens were within 20% of the concentrations obtained with the current hydrolysis procedure using H. pomatia ?-glucuronidase. JWH 018 N-(5-hydroxypentyl) ?-d-glucuronide was hydrolyzed within 10% of the control concentration. Authentic urine specimens showed improved glucuronide cleavage using abalone ?-glucuronidase with up to an 85% increase of drug concentration, compared with the results obtained using E. coli ?-glucuronidase. The JWH 018 and JWH 073 carboxylic acid metabolites also showed increased drug concentrations of up to 24%. Abalone ?-glucuronidase was able to completely hydrolyze a morphine-3-glucuronide control, but only 82% of total morphine was hydrolyzed in authentic urine specimens compared with acid hydrolysis results. Hydrolysis of codeine and hydromorphone varied between specimens, suggesting that abalone ?-glucuronidase may not be as efficient in hydrolyzing the glucuronide linkages in opioid compounds compared with acid hydrolysis. Abalone ?-glucuronidase demonstrates effectiveness as a low cost option for enzyme hydrolysis of benzodiazepines and synthetic cannabinoids. PMID:24488113

Malik-Wolf, Brittany; Vorce, Shawn; Holler, Justin; Bosy, Thomas

2014-04-01

328

Electron transfer precedes ATP hydrolysis during nitrogenase catalysis  

PubMed Central

The biological reduction of N2 to NH3 catalyzed by Mo-dependent nitrogenase requires at least eight rounds of a complex cycle of events associated with ATP-driven electron transfer (ET) from the Fe protein to the catalytic MoFe protein, with each ET coupled to the hydrolysis of two ATP molecules. Although steps within this cycle have been studied for decades, the nature of the coupling between ATP hydrolysis and ET, in particular the order of ET and ATP hydrolysis, has been elusive. Here, we have measured first-order rate constants for each key step in the reaction sequence, including direct measurement of the ATP hydrolysis rate constant: kATP = 70 s?1, 25 °C. Comparison of the rate constants establishes that the reaction sequence involves four sequential steps: (i) conformationally gated ET (kET = 140 s?1, 25 °C), (ii) ATP hydrolysis (kATP = 70 s?1, 25 °C), (iii) Phosphate release (kPi = 16 s?1, 25 °C), and (iv) Fe protein dissociation from the MoFe protein (kdiss = 6 s?1, 25 °C). These findings allow completion of the thermodynamic cycle undergone by the Fe protein, showing that the energy of ATP binding and protein–protein association drive ET, with subsequent ATP hydrolysis and Pi release causing dissociation of the complex between the Feox(ADP)2 protein and the reduced MoFe protein. PMID:24062462

Duval, Simon; Danyal, Karamatullah; Shaw, Sudipta; Lytle, Anna K.; Dean, Dennis R.; Hoffman, Brian M.; Antony, Edwin; Seefeldt, Lance C.

2013-01-01

329

ATP Hydrolysis in Water -A Density Functional Study J. Akola and R. O. Jones*  

E-print Network

ATP Hydrolysis in Water - A Density Functional Study J. Akola and R. O. Jones* Institut fu¨r Festko-dependent hydrolysis reaction. Two paths for ATP hydrolysis in water with Mg2+ are studied here using the density) in the triphosphate tail of the molecule as an energy-rich bond that releases energy upon hydrolysis due

330

Theoretical Analysis of Microtubules Dynamics Using a Physical-Chemical Description of Hydrolysis  

E-print Network

Theoretical Analysis of Microtubules Dynamics Using a Physical- Chemical Description of Hydrolysis. They can be viewed as dynamic polymers that function in nonequilibrium conditions stimulated by hydrolysis-chemical description of GTP hydrolysis is presented, in which the hydrolysis rate at a given monomer depends

331

Toxicology 212 (2005) 107115 Carbofuran and malathion inhibit nucleotide hydrolysis in  

E-print Network

Toxicology 212 (2005) 107­115 Carbofuran and malathion inhibit nucleotide hydrolysis in zebrafish and ADP hydrolysis in an uncompetitive manner, but no effect was observed on AMP hydrolysis. Malathion decreased ATP and ADP hydrolysis in competitive and an uncompetitive manner, respectively, but not altered

Eizirik, Eduardo

332

Enzymatic hydrolysis of corn stalk in a hollow fiber ultrafiltration membrane reactor  

Microsoft Academic Search

A hollow fiber ultrafiltration (UF) membrane reactor was set up to investigate the enzymatic hydrolysis of steam-exploded corn stalk. It was found that the hydrolysis rate, as well as the reducing sugar (RS) yield, could be markedly enhanced in the UF membrane reactor due to the continuous removal of inhibitory products. Compared with traditional batch hydrolysis, the hydrolysis rate and

Sen Yang; Wenyong Ding; Hongzhang Chen

2009-01-01

333

Adsorption and activity profiles of cellulases during the hydrolysis of two Douglas fir pulps  

Microsoft Academic Search

The adsorption and specific activities of various cellulases were evaluated during the hydrolysis of Avicel and Douglas fir-derived kraft and refiner mechanical pulps (RMP). Both the RMP and kraft pulps required higher enzyme loadings and longer hydrolysis times to achieve complete hydrolysis than did Avicel. Complete hydrolysis of a 2% kraft pulp required an enzyme loading of 60 FPU g?1

Abdellatif Boussaid; John N. Saddler

1999-01-01

334

Regulation of Acetyl Coenzyme A Synthetase in Escherichia coli  

PubMed Central

Cells of Escherichia coli growing on sugars that result in catabolite repression or amino acids that feed into glycolysis undergo a metabolic switch associated with the production and utilization of acetate. As they divide exponentially, these cells excrete acetate via the phosphotransacetylase-acetate kinase pathway. As they begin the transition to stationary phase, they instead resorb acetate, activate it to acetyl coenzyme A (acetyl-CoA) by means of the enzyme acetyl-CoA synthetase (Acs) and utilize it to generate energy and biosynthetic components via the tricarboxylic acid cycle and the glyoxylate shunt, respectively. Here, we present evidence that this switch occurs primarily through the induction of acs and that the timing and magnitude of this induction depend, in part, on the direct action of the carbon regulator cyclic AMP receptor protein (CRP) and the oxygen regulator FNR. It also depends, probably indirectly, upon the glyoxylate shunt repressor IclR, its activator FadR, and many enzymes involved in acetate metabolism. On the basis of these results, we propose that cells induce acs, and thus their ability to assimilate acetate, in response to rising cyclic AMP levels, falling oxygen partial pressure, and the flux of carbon through acetate-associated pathways. PMID:10894724

Kumari, Suman; Beatty, Christine M.; Browning, Douglas F.; Busby, Stephen J. W.; Simel, Erica J.; Hovel-Miner, Galadriel; Wolfe, Alan J.

2000-01-01

335

Investigation of acetylated chitosan microspheres as potential chemoembolic agents.  

PubMed

The aim was to investigate the potential of chitosan microspheres (CMs) with different acetylation using as a chemoembolic agent. Chitosan microspheres (CMs) were prepared via water-in-oil (W/O) emulsification cross-linking method, and acetylated chitosan microspheres (ACMs) were obtained by acetylation of CMs. Next, we characterized the morphology, size, composition and degrees of deacetylation using scanning electron microscopy (TEM), dynamic laser light scattering (DLS), and Fourier transform infrared spectrometer (FTIR). All microspheres had smooth surfaces and good mechanical flexibility, and all could pass through a 5F catheter. The swelling rate (SR) of CMs decreased significantly with the increase of pH (4.0-10.0) but ACMs did not change under the same conditions. Protein absorption assays suggested that albumin was more greatly adsorbed on CMs than on ACMs. Furthermore, CMs caused more blood clots than ACMs. ACMs caused hemolysis less than CMs (<5% of the time). Data indicated that ACMs had more hemocompatibility. Cytotoxicity tests indicated that ACMs initially had less cell attached proliferation but increased with incubation. In contrast, the relative growth rate of mouse embryo fibroblasts (MEFs) on CMs decreased gradually. The results suggested that ACMs could stimulate the growth of MEFs, and CMs were not cytotoxic to MEFs. Thus, ACMs were more biocompatible with greater potential to be used as chemoembolic material. PMID:25311962

Zhou, Xuan; Kong, Ming; Cheng, Xiaojie; Li, Jingjing; Li, Jing; Chen, Xiguang

2014-11-01

336

Selected properties of acetylated adipate of retrograded starch.  

PubMed

Native potato starch (NS) and retrograded starch (R - obtained via freezing and defrosting of a starch paste) were used to prepare starch acetates: NS-A and R-A, and then acetylated distarch adipates: NS-ADA and R-ADA. The chemically-modified preparations produced from retrograded starch (R-A; R-ADA) were characterized by a higher degree of esterification compared to the modified preparations produced under the same conditions from native potato starch (NS-A; NS-ADA). Starch resistance to amylolysis was observed to increase (to 30-40 g/100 g) as a result of starch retrogradation and acetylation. Starch cross-linking had a significant impact on the increased viscosity of the paste in the entire course of pasting characteristics and on the increased values of rheological coefficients determined from the equations describing flow curves. The produced preparation of acetylated retrograded starch cross-linked with adipic acid (R-ADA) may be deemed an RS3/4 preparation to be used as a food thickening agent. PMID:24274559

Zi?ba, T; Gryszkin, A; Kapelko, M

2014-01-01

337

Regulation of bacterial physiology by lysine acetylation of proteins.  

PubMed

Post-translational modification of proteins is a reversible mechanism of cellular adaptation to changing environmental conditions. In eukaryotes, the physiological relevance of N-?-lysine protein acetylation is well demonstrated. In recent times, important roles in the regulation of metabolic processes in bacteria are being uncovered, adding complexity to cellular regulatory networks. The aim of this mini-review is to sum up the current state-of-the-art in the regulation of bacterial physiology by protein acetylation. Current knowledge on the molecular biology aspects of known bacterial protein acetyltransferases and deacetylases will be summarized. Protein acetylation in Escherichia coli, Salmonella enterica, Bacillus subtilis, Rhodopseudomonas palustris and Mycobacterium tuberculosis, will be explained in the light of their physiological relevance. Progress in the elucidation of bacterial acetylomes and the emerging understanding of chemical acylation mechanisms will be discussed together with their regulatory and evolutionary implications. Fundamental molecular studies detailing this recently discovered regulatory mechanism pave the way for their prospective application for the construction of synthetic regulation networks. PMID:24636882

Bernal, Vicente; Castańo-Cerezo, Sara; Gallego-Jara, Julia; Écija-Conesa, Ana; de Diego, Teresa; Iborra, José Luis; Cánovas, Manuel

2014-12-25

338

Human tissue transglutaminase is inhibited by pharmacologic and chemical acetylation  

PubMed Central

Human tissue transglutaminase (TGM2) is implicated in the pathogenesis of several neurodegenerative disorders including Alzheimer's, Parkinson's and expanded polyglutamine (polyQ) diseases. TGM2 promotes formation of soluble and insoluble high molecular weight aggregates by catalyzing a covalent linkage between peptide-bound Q residues in polyQ proteins and a peptide-bound Lys residue. Therapeutic approaches to modulate the activity of TGM2 are needed to proceed with studies to test the efficacy of TGM2 inhibition in disease processes. We investigated whether acetylation of Lys-residues by sulfosuccinimidyl acetate (SNA) or aspirin (ASA) would alter the crosslinking activity of TGM2. Acetylation by either SNA and/or ASA resulted in a loss of >90% of crosslinking activity. The Lys residues that were critical for inhibition were identified by mass spectrometry as Lys444, Lys468, and Lys663. Hence, acetylation of Lys-residues may modulate the enzymatic function of TGM2 in vivo and offer a novel approach to treatment of TGM2 mediated disorders. PMID:19998405

Lai, Thung S; Davies, Christopher; Greenberg, Charles S

2010-01-01

339

Acetyl and butyryl cholinesterase inhibitory sesquiterpene lactones from Amberboa ramosa  

PubMed Central

Background Alzheimer’s disease (AD) is characterized by a progressive memory loss that leads to a profound emotional disturbance in later stages. As no safe and effective drug is yet available for the treatment of AD, secondary metabolites from plants may be instrumental in meeting this challenge. Keeping in view this point we evaluated sesquiterpenes of medicinal plant Amberboa ramosa for their cholinesterase inhibitory activity. Results Four sesquiterpene lactones have been isolated from the ethyl acetate soluble fraction of Amberboa ramosa. In which one compound Amberbin C (1) was found to be new while other three Amberin (2), Amberbin A (3), and Amberbin B (4) were previously reported ones. The structures of the isolated compounds were elucidated using different spectroscopic techniques. Isolated compounds were tested for their inhibitory potential against acetyl cholinesterase and butyryl cholinesterase enzymes. All compounds showed excellent inhibitory activities against acetyl cholinesterase and butyryl cholinesterase. Conclusions A new sesquiterpene lactone has been isolated and fully characterized, the sesquiterpene lactones from Amberboa ramosa showed good inhibitory activities against acetyl cholinesterase and butyryl cholinesterase enzymes, this study indicated that sesquiterpene lactone can become interesting lead molecules in drug development against Alzheimer’s disease (AD). PMID:23837557

2013-01-01

340

Acetylation of ?A-crystallin in the human lens: effects on structure and chaperone function.  

PubMed

?-Crystallin is a major protein in the human lens that is perceived to help to maintain the transparency of the lens through its chaperone function. In this study, we demonstrate that many lens proteins including ?A-crystallin are acetylated in vivo. We found that K70 and K99 in ?A-crystallin and, K92 and K166 in ?B-crystallin are acetylated in the human lens. To determine the effect of acetylation on the chaperone function and structural changes, ?A-crystallin was acetylated using acetic anhydride. The resulting protein showed strong immunoreactivity against a N(?)-acetyllysine antibody, which was directly related to the degree of acetylation. When compared to the unmodified protein, the chaperone function of the in vitro acetylated ?A-crystallin was higher against three of the four different client proteins tested. Because a lysine (residue 70; K70) in ?A-crystallin is acetylated in vivo, we generated a protein with an acetylation mimic, replacing Lys70 with glutamine (K70Q). The K70Q mutant protein showed increased chaperone function against three client proteins compared to the Wt protein but decreased chaperone function against ?-crystallin. The acetylated protein displayed higher surface hydrophobicity and tryptophan fluorescence, had altered secondary and tertiary structures and displayed decreased thermodynamic stability. Together, our data suggest that acetylation of ?A-crystallin occurs in the human lens and that it affects the chaperone function of the protein. PMID:22120592

Nagaraj, Ram H; Nahomi, Rooban B; Shanthakumar, Shilpa; Linetsky, Mikhail; Padmanabha, Smitha; Pasupuleti, Nagarekha; Wang, Benlian; Santhoshkumar, Puttur; Panda, Alok Kumar; Biswas, Ashis

2012-02-01

341

Proteome-wide Analysis of Lysine Acetylation Suggests its Broad Regulatory Scope in Saccharomyces cerevisiae*  

PubMed Central

Post-translational modification of proteins by lysine acetylation plays important regulatory roles in living cells. The budding yeast Saccharomyces cerevisiae is a widely used unicellular eukaryotic model organism in biomedical research. S. cerevisiae contains several evolutionary conserved lysine acetyltransferases and deacetylases. However, only a few dozen acetylation sites in S. cerevisiae are known, presenting a major obstacle for further understanding the regulatory roles of acetylation in this organism. Here we use high resolution mass spectrometry to identify about 4000 lysine acetylation sites in S. cerevisiae. Acetylated proteins are implicated in the regulation of diverse cytoplasmic and nuclear processes including chromatin organization, mitochondrial metabolism, and protein synthesis. Bioinformatic analysis of yeast acetylation sites shows that acetylated lysines are significantly more conserved compared with nonacetylated lysines. A large fraction of the conserved acetylation sites are present on proteins involved in cellular metabolism, protein synthesis, and protein folding. Furthermore, quantification of the Rpd3-regulated acetylation sites identified several previously known, as well as new putative substrates of this deacetylase. Rpd3 deficiency increased acetylation of the SAGA (Spt-Ada-Gcn5-Acetyltransferase) complex subunit Sgf73 on K33. This acetylation site is located within a critical regulatory domain in Sgf73 that interacts with Ubp8 and is involved in the activation of the Ubp8-containing histone H2B deubiquitylase complex. Our data provides the first global survey of acetylation in budding yeast, and suggests a wide-ranging regulatory scope of this modification. The provided dataset may serve as an important resource for the functional analysis of lysine acetylation in eukaryotes. PMID:22865919

Henriksen, Peter; Wagner, Sebastian A.; Weinert, Brian T.; Sharma, Satyan; Ba?inskaja, Giedr?; Rehman, Michael; Juffer, André H.; Walther, Tobias C.; Lisby, Michael; Choudhary, Chunaram

2012-01-01

342

New short and general synthesis of three key Maillard flavour compounds: 2-Acetyl-1-pyrroline, 6-acetyl-1,2,3,4-tetrahydropyridine and 5-acetyl-2,3-dihydro-4H-1,4-thiazine.  

PubMed

A new general synthetic route towards three key Maillard flavour compounds, namely 2-acetyl-1-pyrroline, 6-acetyl-1,2,3,4-tetrahydropyridine and 5-acetyl-2,3-dihydro-4H-1,4-thiazine, was developed. The key step in the process is the methylenation reaction of azaheterocyclic carboxylic esters by means of dimethyltitanocene, giving rise to intermediate vinyl ethers which can be considered as excellent and stable precursors for the title compounds, as a simple acidic treatment of these precursors suffices to release the characteristic Maillard flavours. PMID:25172717

Deblander, Jurgen; Van Aeken, Sam; Adams, An; De Kimpe, Norbert; Abbaspour Tehrani, Kourosch

2015-02-01

343

Distinct and predictive histone lysine acetylation patterns at promoters, enhancers, and gene bodies.  

PubMed

In eukaryotic cells, histone lysines are frequently acetylated. However, unlike modifications such as methylations, histone acetylation modifications are often considered redundant. As such, the functional roles of distinct histone acetylations are largely unexplored. We previously developed an algorithm RFECS to discover the most informative modifications associated with the classification or prediction of mammalian enhancers. Here, we used this tool to identify the modifications most predictive of promoters, enhancers, and gene bodies. Unexpectedly, we found that histone acetylation alone performs well in distinguishing these unique genomic regions. Further, we found the association of characteristic acetylation patterns with genic regions and association of chromatin state with splicing. Taken together, our work underscores the diverse functional roles of histone acetylation in gene regulation and provides several testable hypotheses to dissect these roles. PMID:25122670

Rajagopal, Nisha; Ernst, Jason; Ray, Pradipta; Wu, Jie; Zhang, Michael; Kellis, Manolis; Ren, Bing

2014-11-01

344

In silico analysis of protein Lys-N𝜀-acetylation in plants  

PubMed Central

Among post-translational modifications, there are some conceptual similarities between Lys-N𝜀-acetylation and Ser/Thr/Tyr O-phosphorylation. Herein we present a bioinformatics-based overview of reversible protein Lys-acetylation, including some comparisons with reversible protein phosphorylation. The study of Lys-acetylation of plant proteins has lagged behind studies of mammalian and microbial cells; 1000s of acetylation sites have been identified in mammalian proteins compared with only hundreds of sites in plant proteins. While most previous emphasis was focused on post-translational modifications of histones, more recent studies have addressed metabolic regulation. Being directly coupled with cellular CoA/acetyl-CoA and NAD/NADH, reversible Lys-N𝜀-acetylation has the potential to control, or contribute to control, of primary metabolism, signaling, and growth and development. PMID:25136347

Rao, R. Shyama Prasad; Thelen, Jay J.; Miernyk, Ján A.

2014-01-01

345

Distinct and Predictive Histone Lysine Acetylation Patterns at Promoters, Enhancers, and Gene Bodies  

PubMed Central

In eukaryotic cells, histone lysines are frequently acetylated. However, unlike modifications such as methylations, histone acetylation modifications are often considered redundant. As such, the functional roles of distinct histone acetylations are largely unexplored. We previously developed an algorithm RFECS to discover the most informative modifications associated with the classification or prediction of mammalian enhancers. Here, we used this tool to identify the modifications most predictive of promoters, enhancers, and gene bodies. Unexpectedly, we found that histone acetylation alone performs well in distinguishing these unique genomic regions. Further, we found the association of characteristic acetylation patterns with genic regions and association of chromatin state with splicing. Taken together, our work underscores the diverse functional roles of histone acetylation in gene regulation and provides several testable hypotheses to dissect these roles. PMID:25122670

Rajagopal, Nisha; Ernst, Jason; Ray, Pradipta; Wu, Jie; Zhang, Michael; Kellis, Manolis; Ren, Bing

2014-01-01

346

The N-terminal acetylation of Sir3 stabilizes its binding to the nucleosome core particle  

PubMed Central

The N-terminal acetylation of Sir3 is essential for heterochromatin establishment and maintenance in yeast, but its mechanism of action is unknown. The crystal structure of the N-terminal acetylated BAH domain of S.cerevisiae Sir3 bound to the nucleosome core particle revealed that the N-terminal acetylation stabilizes the interaction of Sir3 with the nucleosome. Additionally, we present a new method for the production of protein-nucleosome complexes for structural analysis. PMID:23934150

Arnaudo, Nadia; Fernández, Israel S.; McLaughlin, Stephen H.; Peak-Chew, Sew Y.; Rhodes, Daniela; Martino, Fabrizio

2013-01-01

347

Eaf3 Regulates the Global Pattern of Histone Acetylation in Saccharomyces cerevisiae  

Microsoft Academic Search

Saccharomyces cerevisiae has a global pattern of histone acetylation in which histone H3 and H4 acetylation levels are lower at protein-coding sequences than at promoter regions. The loss of Eaf3, a subunit of the NuA4 histone acetylase and Rpd3 histone deacetylase complexes, greatly alters the genomic profile of histone acetylation, with the effects on H4 appearing to be more pronounced

Juliet L. Reid; Zarmik Moqtaderi; Kevin Struhl

2004-01-01

348

Enzymatic hydrolysis of organophosphate insecticides, a possible pesticide disposal method.  

PubMed Central

A crude cell extract from a mixed bacterial culture growing on parathion, an organophosphate insecticide, hydrolyzed parathion (21 C) at a rate of 416 nmol/min per mg of protein. This rate of enzymatic hydrolysis, when compared with chemical hydrolysis by 0.1 N sodium hydroxide at 40 C, was 2, 450 times faster. Eight of 12 commonly used organophosphate insecticides were enzymatically hydrolyzed with this enzyme preparation at rates ranging from 12 to 1,360 nmol/min per mg of protein. Seven pesticides were hydrolyzed at rates significantly higher (40 to 1,005 times faster) than chemical hydrolysis. The pH optimum for enzymatic hydrolysis of the eight pesticides ranged from 8.5 to 9.5, with less than 50% of maximal activity expressed at pH 7.0. Maximal enzyme activity occurred at 35 C. The crude extract lost its activity at the rate of only 0.75%/day when stored at 6 C. Eight organic solvents, ranging from methanol to hexane, at low concentrations stimulated enzymatic hydrolysis by 3 to 20%, whereas at higher concentrations (1,000 mg/liter) they inhibited the reaction (9 to 50%). Parathion metabolites p-nitrophenol, hydroquinone, and diethylthiophosphoric acid, at up to 100-mg/liter concentrations, did not significantly influence enzyme activity. PMID:9901

Munnecke, D M

1976-01-01

349

Hydrolysis of aluminum dross material to achieve zero hazardous waste.  

PubMed

A simple method with high efficiency for generating high pure hydrogen by hydrolysis in tap water of highly activated aluminum dross is established. Aluminum dross is activated by mechanically milling to particles of about 45 ?m. This leads to removal of surface layer of the aluminum particles and creation of a fresh chemically active metal surface. In contact with water the hydrolysis reaction takes place and hydrogen is released. In this process a Zero Waste concept is achieved because the other product of reaction is aluminum oxide hydroxide (AlOOH), which is nature-friendly and can be used to make high quality refractory or calcium aluminate cement. For comparison we also used pure aluminum powder and alkaline tap water solution (NaOH, KOH) at a ratio similar to that of aluminum dross content. The rates of hydrogen generated in hydrolysis reaction of pure aluminum and aluminum dross have been found to be similar. As a result of the experimental setup, a hydrogen generator was designed and assembled. Hydrogen volume generated by hydrolysis reaction was measured. The experimental results obtained reveal that aluminum dross could be economically recycled by hydrolysis process with achieving zero hazardous aluminum dross waste and hydrogen generation. PMID:22326245

David, E; Kopac, J

2012-03-30

350

Starch hydrolysis modeling: application to fuel ethanol production.  

PubMed

Efficiency of the starch hydrolysis in the dry grind corn process is a determining factor for overall conversion of starch to ethanol. A model, based on a molecular approach, was developed to simulate structure and hydrolysis of starch. Starch structure was modeled based on a cluster model of amylopectin. Enzymatic hydrolysis of amylose and amylopectin was modeled using a Monte Carlo simulation method. The model included the effects of process variables such as temperature, pH, enzyme activity and enzyme dose. Pure starches from wet milled waxy and high-amylose corn hybrids and ground yellow dent corn were hydrolyzed to validate the model. Standard deviations in the model predictions for glucose concentration and DE values after saccharification were less than ± 0.15% (w/v) and ± 0.35%, respectively. Correlation coefficients for model predictions and experimental values were 0.60 and 0.91 for liquefaction and 0.84 and 0.71 for saccharification of amylose and amylopectin, respectively. Model predictions for glucose (R2 = 0.69-0.79) and DP4+ (R2 = 0.8-0.68) were more accurate than the maltotriose and maltose for hydrolysis of high-amylose and waxy corn starch. For yellow dent corn, simulation predictions for glucose were accurate (R2 > 0.73) indicating that the model can be used to predict the glucose concentrations during starch hydrolysis. PMID:21487699

Murthy, Ganti S; Johnston, David B; Rausch, Kent D; Tumbleson, M E; Singh, Vijay

2011-09-01

351

An experimental and theoretical study of the spin-orbit interaction for CO+(A 2?3/2,1/2, v+=0-41) and O2+(X 2?3/2,1/2g, v+=0-38)  

NASA Astrophysics Data System (ADS)

Accurate spin-orbit splitting constants (Av+) for the vibrational levels v+=0-41 of CO+(A 2?3/2,1/2) have been determined in a rotationally resolved pulsed field ionization photoelectron study. A change in slope is observed in the v+ dependence for Av+ at v+?19-20. This observation is attributed to perturbation of the CO+(A 2?) potential by the CO+(B 2?+) state. Theoretical Av+ values for CO+(A 2?3/2,1/2, v+=0-41) have also been obtained using a newly developed ab initio computational routine for spin-orbit coupling calculations. The theoretical Av+ predictions computed using this routine are found to be in agreement with the experimental Av+ values for CO+(A 2?3/2,1/2, v+=0-41). Similar Av+ calculations obtained for O2+(X 2?3/2,1/2g, v+=0-38) are also in accord with the recent experimental Av+ values reported by Song et al. [J. Chem. Phys. 111, 1905 (1999)].

Fedorov, D. G.; Evans, M.; Song, Y.; Gordon, M. S.; Ng, C. Y.

1999-10-01

352

Reduced Wall Acetylation Proteins Play Vital and Distinct Roles in Cell Wall O-Acetylation in Arabidopsis1[C][W][OPEN  

PubMed Central

The Reduced Wall Acetylation (RWA) proteins are involved in cell wall acetylation in plants. Previously, we described a single mutant, rwa2, which has about 20% lower level of O-acetylation in leaf cell walls and no obvious growth or developmental phenotype. In this study, we generated double, triple, and quadruple loss-of-function mutants of all four members of the RWA family in Arabidopsis (Arabidopsis thaliana). In contrast to rwa2, the triple and quadruple rwa mutants display severe growth phenotypes revealing the importance of wall acetylation for plant growth and development. The quadruple rwa mutant can be completely complemented with the RWA2 protein expressed under 35S promoter, indicating the functional redundancy of the RWA proteins. Nevertheless, the degree of acetylation of xylan, (gluco)mannan, and xyloglucan as well as overall cell wall acetylation is affected differently in different combinations of triple mutants, suggesting their diversity in substrate preference. The overall degree of wall acetylation in the rwa quadruple mutant was reduced by 63% compared with the wild type, and histochemical analysis of the rwa quadruple mutant stem indicates defects in cell differentiation of cell types with secondary cell walls. PMID:24019426

Manabe, Yuzuki; Verhertbruggen, Yves; Gille, Sascha; Harholt, Jesper; Chong, Sun-Li; Pawar, Prashant Mohan-Anupama; Mellerowicz, Ewa J.; Tenkanen, Maija; Cheng, Kun; Pauly, Markus; Scheller, Henrik Vibe

2013-01-01

353

Aurora B is regulated by acetylation/deacetylation during mitosis in prostate cancer cells  

PubMed Central

Protein acetylation has been implicated in playing an important role during mitotic progression. Aurora B kinase is known to play a critical role in mitosis. However, whether Aurora B is regulated by acetylation is not known. Using IP with an anti-acetyl lysine antibody, we identified Aurora B as an acetylated protein in PC3 prostate cancer cells. Knockdown of HDAC3 or inhibiting HDAC3 deacetylase activity led to a significant increase (P<0.01 and P<0.05, respectively) in Aurora B acetylation as compared to siLuc or vehicle-treated controls. Increased Aurora B acetylation is correlated with a 30% reduction in Aurora B kinase activity in vitro and resulted in significant defects in Aurora B-dependent mitotic processes, including kinetochore-microtubule attachment and chromosome congression. Furthermore, Aurora B transiently interacts with HDAC3 at the kinetochore-microtubule interface of congressing chromosomes during prometaphase. This window of interaction corresponded with a transient but significant reduction (P=0.02) in Aurora B acetylation during early mitosis. Together, these results indicate that Aurora B is more active in its deacetylated state and further suggest a new mechanism by which dynamic acetylation/deacetylation acts as a rheostat to fine-tune Aurora B activity during mitotic progression.—Fadri-Moskwik, M., Weiderhold, K. N., Deeraksa, A., Chuang, C., Pan, J., Lin, S.-H., Yu-Lee, L.-Y. Aurora B is regulated by acetylation/deacetylation during mitosis in prostate cancer cells. PMID:22751009

Fadri-Moskwik, Maria; Weiderhold, Kimberly N.; Deeraksa, Arpaporn; Chuang, Carol; Pan, Jing; Lin, Sue-Hwa; Yu-Lee, Li-Yuan

2012-01-01

354

Structural effects on the enantioselective acetylation of 4-hydroxychromans catalyzed by microbial lipases  

Microsoft Academic Search

Kinetic resolutions of a series of racemic 4-hydroxychromans by the Candida cylindracea lipase catalysed acetylation are described. Correlation between structure (conformation) and enantioselectivity is discussed.

Maja Majeri?; Mirjana Gelo-Puji?; Vitomir Šunji?; Albert Lévai; Peter Sebök; Tibor Timŕr

1995-01-01

355

Acetylation-defective mutants of Ppar? are associated with decreased lipid synthesis in breast cancer cells  

PubMed Central

In our prior publications we characterized a conserved acetylation motif (K(R)xxKK) of evolutionarily related nuclear receptors. Recent reports showed that peroxisome proliferator activated receptor gamma (PPAR?) deacetylation by SIRT1 is involved in delaying cellular senescence and maintaining the brown remodeling of white adipose tissue. However, it still remains unknown whether lysyl residues 154 and 155 (K154/155) of the conserved acetylation motif (RIHKK) in Ppar?1 are acetylated. Herein, we demonstrate that Ppar?1 is acetylated and regulated by both endogenous TSA-sensitive and NAD-dependent deacetylases. Acetylation of lysine 154 was identified by mass spectrometry (MS) while deacetylation of lysine 155 by SIRT1 was confirmed by in vitro deacetylation assay. An in vivo labeling assay revealed K154/K155 as bona fide acetylation sites. The conserved acetylation sites of Ppar?1 and the catalytic domain of SIRT1 are both required for the interaction between Ppar?1 and SIRT1. Sirt1 and Ppar?1 converge to govern lipid metabolism in vivo. Acetylation-defective mutants of Ppar?1 were associated with reduced lipid synthesis in ErbB2 overexpressing breast cancer cells. Together, these results suggest that the conserved lysyl residues K154/K155 of Ppar?1 are acetylated and play an important role in lipid synthesis in ErbB2-positive breast cancer cells. PMID:25229978

Tian, Lifeng; Wang, Chenguang; Hagen, Fred K.; Gormley, Michael; Addya, Sankar; Soccio, Raymond; Casimiro, Mathew C.; Zhou, Jie; Powell, Michael J.; Xu, Ping; Deng, Haiteng; Sauve, Anthony A.; Pestell, Richard G.

2014-01-01

356

Stereochemistry of chitin hydrolysis by a plant chitinase/lysozyme and X-ray structure of a complex with allosamidin: evidence for substrate assisted catalysis.  

PubMed

The plant enzyme hevamine has both chitinase and lysozyme activity. HPLC analysis of the products of the hydrolysis of chitopentaose shows that hevamine acts with retention of the configuration, despite the absence of a nucleophilic or stabilizing carboxylate. To analyze the stabilization of a putative oxocarbonium ion intermediate, the X-ray structure of hevamine complexed with the inhibitor allosamidin was determined at 1.85 A resolution. This structure supports the role of Glu127 as a proton donor. The allosamizoline group binds in the center of the active site, mimicking a reaction intermediate in which a positive charge at C1 is stabilized intramolecularly by the carbonyl oxygen of the N-acetyl group at C2. PMID:7495789

Terwisscha van Scheltinga, A C; Armand, S; Kalk, K H; Isogai, A; Henrissat, B; Dijkstra, B W

1995-12-01

357

Acetylation of Histones and Transcription-Related Factors  

PubMed Central

The state of chromatin (the packaging of DNA in eukaryotes) has long been recognized to have major effects on levels of gene expression, and numerous chromatin-altering strategies—including ATP-dependent remodeling and histone modification—are employed in the cell to bring about transcriptional regulation. Of these, histone acetylation is one of the best characterized, as recent years have seen the identification and further study of many histone acetyltransferase (HAT) proteins and their associated complexes. Interestingly, most of these proteins were previously shown to have coactivator or other transcription-related functions. Confirmed and putative HAT proteins have been identified from various organisms from yeast to humans, and they include Gcn5-related N-acetyltransferase (GNAT) superfamily members Gcn5, PCAF, Elp3, Hpa2, and Hat1: MYST proteins Sas2, Sas3, Esa1, MOF, Tip60, MOZ, MORF, and HBO1; global coactivators p300 and CREB-binding protein; nuclear receptor coactivators SRC-1, ACTR, and TIF2; TATA-binding protein-associated factor TAFII250 and its homologs; and subunits of RNA polymerase III general factor TFIIIC. The acetylation and transcriptional functions of these HATs and the native complexes containing them (such as yeast SAGA, NuA4, and possibly analogous human complexes) are discussed. In addition, some of these HATs are also known to modify certain nonhistone transcription-related proteins, including high-mobility-group chromatin proteins, activators such as p53, coactivators, and general factors. Thus, we also detail these known factor acetyltransferase (FAT) substrates and the demonstrated or potential roles of their acetylation in transcriptional processes. PMID:10839822

Sterner, David E.; Berger, Shelley L.

2000-01-01

358

Granular starch hydrolysis for fuel ethanol production  

NASA Astrophysics Data System (ADS)

Granular starch hydrolyzing enzymes (GSHE) convert starch into fermentable sugars at low temperatures (?48°C). Use of GSHE in dry grind process can eliminate high temperature requirements during cooking and liquefaction (?90°C). In this study, GSHE was compared with two combinations of commercial alpha-amylase and glucoamylase (DG1 and DG2, respectively). All three enzyme treatments resulted in comparable ethanol concentrations (between 14.1 to 14.2% v/v at 72 hr), ethanol conversion efficiencies and ethanol and DDGS yields. Sugar profiles for the GSHE treatment were different from DG1 and DG2 treatments, especially for glucose. During simultaneous saccharification and fermentation (SSF), the highest glucose concentration for the GSHE treatment was 7% (w/v); for DG1 and DG2 treatments, maximum glucose concentration was 19% (w/v). GSHE was used in one of the fractionation technologies (enzymatic dry grind) to improve recovery of germ and pericarp fiber prior to fermentation. The enzymatic dry grind process with GSHE was compared with the conventional dry grind process using GSHE with the same process parameters of dry solids content, pH, temperature, time, enzyme and yeast usages. Ethanol concentration (at 72 hr) of the enzymatic process was 15.5% (v/v), which was 9.2% higher than the conventional process (14.2% v/v). Distillers dried grains with solubles (DDGS) generated from the enzymatic process (9.8% db) was 66% less than conventional process (28.3% db). Three additional coproducts, germ 8.0% (db), pericarp fiber 7.7% (db) and endosperm fiber 5.2% (db) were produced. Costs and amounts of GSHE used is an important factor affecting dry grind process economics. Proteases can weaken protein matrix to aid starch release and may reduce GSHE doses. Proteases also can hydrolyze protein into free amino nitrogen (FAN), which can be used as a yeast nutrient during fermentation. Two types of proteases, exoprotease and endoprotease, were studied; protease and urea addition were evaluated in the dry grind process using GSHE (GSH process). Addition of proteases resulted in higher ethanol concentrations (15.2 to 18.0% v/v) and lower (DDGS) yields (32.9 to 45.8% db) compared to the control (no protease addition). As level of proteases and GSHE increased, ethanol concentrations increased and DDGS yields decreased. Proteases addition reduced required GSHE dose. Ethanol concentrations with protease addition alone were higher than with urea or with addition of both protease and urea. Corn endosperm consists of soft and hard endosperm. More exposed starch granules and rough surfaces produced from soft endosperm compared to hard endosperm will create more surface area which will benefit the solid phase hydrolysis as used in GSH process. In this study, the effects of protease, urea, endosperm hardness and GSHE levels on the GSH process were evaluated. Soft and hard endosperm materials were obtained by grinding and sifting flaking grits from dry milling pilot plant. Soft endosperm resulted in higher ethanol concentrations (at 72 hr) compared to ground corn or hard endosperm. Addition of urea increased ethanol concentrations (at 72 hr) for soft and hard endosperm. The effect of protease addition on increasing ethanol concentrations and fermentation rates was more predominant for soft endosperm, less for hard endosperm and least for ground corn. The GSH process with protease resulted in higher ethanol concentration than that with urea. For fermentation of soft endosperm, GSHE dose can be reduced. Ground corn fermented faster at the beginning than hard and soft endosperm due to the presence of inherent nutrients which enhanced yeast growth.

Wang, Ping

359

Tetra­ethyl­ammonium (acetyl­acetonato)bromidotricarbonyl­rhenate(I)  

PubMed Central

In the title compound, (C8H20N)[ReBr(C5H7O2)(CO)3], the ReI atom in the rhenate anion is surrounded by three carbonyl ligands orientated in a facial arrangement, a bromide ligand and an acetyl­acetonate ligand, leading to a distorted octa­hedral ReC3BrO2 coordination with a O—Re—O bite angle of 85.66?(7)°. An array of C—H?O and C—H?Br hydrogen-bonding inter­actions between the cations and the surrounding rhenate anions stabilize the crystal structure. PMID:21522557

Brink, Alice; Visser, Hendrik G.; Roodt, Andreas

2011-01-01

360

Sulfation of deoxynivalenol, its acetylated derivatives, and T2-toxin.  

PubMed

The synthesis of several sulfates of trichothecene mycotoxins is presented. Deoxynivalenol (DON) and its acetylated derivatives were synthesized from 3-acetyldeoxynivalenol (3ADON) and used as substrate for sulfation in order to reach a series of five different DON-based sulfates as well as T2-toxin-3-sulfate. These substances are suspected to be formed during phase-II metabolism in plants and humans. The sulfation was performed using a sulfuryl imidazolium salt, which was synthesized prior to use. All protected intermediates and final products were characterized via NMR and will serve as reference materials for further investigations in the fields of toxicology and bioanalytics of mycotoxins. PMID:25170180

Fruhmann, Philipp; Skrinjar, Philipp; Weber, Julia; Mikula, Hannes; Warth, Benedikt; Sulyok, Michael; Krska, Rudolf; Adam, Gerhard; Rosenberg, Erwin; Hametner, Christian; Fröhlich, Johannes

2014-08-26

361

Sulfation of deoxynivalenol, its acetylated derivatives, and T2-toxin?  

PubMed Central

The synthesis of several sulfates of trichothecene mycotoxins is presented. Deoxynivalenol (DON) and its acetylated derivatives were synthesized from 3-acetyldeoxynivalenol (3ADON) and used as substrate for sulfation in order to reach a series of five different DON-based sulfates as well as T2-toxin-3-sulfate. These substances are suspected to be formed during phase-II metabolism in plants and humans. The sulfation was performed using a sulfuryl imidazolium salt, which was synthesized prior to use. All protected intermediates and final products were characterized via NMR and will serve as reference materials for further investigations in the fields of toxicology and bioanalytics of mycotoxins. PMID:25170180

Fruhmann, Philipp; Skrinjar, Philipp; Weber, Julia; Mikula, Hannes; Warth, Benedikt; Sulyok, Michael; Krska, Rudolf; Adam, Gerhard; Rosenberg, Erwin; Hametner, Christian; Fröhlich, Johannes

2014-01-01

362

Acetylcholinesterase inhibition activity of acetylated depsidones from Lobaria pulmonaria.  

PubMed

As part of our ongoing project of new acetylcholinesterase inhibitors from lower marine and terrestrial species, a phytochemical investigation was conducted on a foliose lichen, Lobaria pulmonaria (L.) Hoffm. (Lobariaceae), from Bosnia and Herzegovina. The study led to the isolation of a mixture of acetylated depsidones which showed a moderate activity (0.5?µg) in the acetylcholinesterase inhibition test on Thin-layer chromatography plate. Our results indicate for the first time the significance of depsidones, highly specific metabolites from lichen species, in searching for these inhibitors which still represent the best drugs currently available for the management of Alzheimer's disease. PMID:21985528

Pejin, Boris; Tommonaro, Giuseppina; Iodice, Carmine; Tesevic, Vele; Vajs, Vlatka

2012-01-01

363

Uptake of acetyl- l -carnitine in the brain  

Microsoft Academic Search

Analysis in mouse brain slices of the uptake of acetyl-l-[N-methyl-14C]carnitine with time showed it to be concentrative, and kinetic analysis gave aK\\u000am of 1.92 mM and aV\\u000amax of 1.96 mol\\/min per ml, indicating the presence of a low-affinity carrier system. The uptake was energy-requiring and sodium-dependent, being inhibited in the presence of nitrogen (absence of O2), sodium cyanide,

Alessandro P. Burlina; Henry Sershen; Edmund A. Debler; Abel Lajtha

1989-01-01

364

Fundamental Reaction Pathway and Free Energy Profile for Butyrylcholinesterase-Catalyzed Hydrolysis of Heroin  

PubMed Central

The pharmacological function of heroin requires an activation process which transforms heroin into 6-monoacetylmorphine (6-MAM) which is the most active form. The primary enzyme responsible for this activation process in human plasma is butyrylcholinesterase (BChE). The detailed reaction pathway of the activation process via BChE-catalyzed hydrolysis has been explored computationally, for the first time, in the present study by performing molecular dynamics simulation and first-principles quantum mechanical/molecular mechanical free energy calculations. It has been demonstrated that the whole reaction process includes acylation and deacylation stages. The acylation consists of two reaction steps, i.e. the nucleophilic attack on the carbonyl carbon of 3-acetyl group of heroin by the hydroxyl oxygen of Ser198 side chain and the dissociation of 6-MAM. The deacylation also consists of two reaction steps, i.e. the nucleophilic attack on the carbonyl carbon of the acyl-enzyme intermediate by a water molecule and the dissociation of the acetic acid from Ser198. The calculated free energy profile reveals that the second transition state (TS2) should be rate-determining. The structural analysis reveals that the oxyanion hole of BChE plays an important role in the stabilization of the rate-determining transition state TS2. The free energy barrier (15.9±0.2 or 16.1±0.2 kcal/mol) calculated for the rate-determining step is in good agreement with the experimentally-derived activation free energy (~16.2 kcal/mol), suggesting that the mechanistic insights obtained from the present computational study are reliable. The obtained structural and mechanistic insights could be valuable for use in future rational design of a novel therapeutic treatment of heroin abuse. PMID:23992153

Qiao, Yan; Han, Keli; Zhan, Chang-Guo

2013-01-01

365

Hydrolysis of polycarbonate catalyzed by ionic liquid [Bmim][Ac].  

PubMed

Hydrolysis of polycarbonate (PC) was studied using ionic liquid 1-butyl-3-methylimidazolium acetate ([Bmim][Ac]) as a catalyst. The influences of temperature, time, water dosage and [Bmim][Ac] dosage on the hydrolysis reaction were examined. Under the conditions of temperature 140°C, reaction time 3.0 h, m([Bmim][Ac]):m(PC)=1.5:1 and m(H(2)O):m(PC)=0.35:1, the conversion of PC was nearly 100% and the yield of bisphenol A (BPA) was over 96%. The ionic liquid could be reused up to 6 times without apparent decrease in the conversion of PC and yield of BPA. The kinetics of the reaction was also investigated. The results showed that the hydrolysis of PC in [Bmim][Ac] was a first-order kinetic reaction with an activation energy of 228 kJ/mol. PMID:23246956

Song, Xiuyan; Liu, Fusheng; Li, Lei; Yang, Xuequn; Yu, Shitao; Ge, Xiaoping

2013-01-15

366

Monoolein production by triglycerides hydrolysis using immobilized Rhizopus oryzae lipase.  

PubMed

Lipase extracted from Rhizopus oryzae was immobilized in alginate gel beads. The effects of the immobilization conditions, such as, alginate concentration, CaCl2 concentration and amount of initial enzyme on retained activity (specific activity ratio of entrapped active lipase to free lipase) were investigated. The optimal conditions for lipase entrapment were determined: 2% (w/v) alginate concentration, 100mM CaCl2 and enzyme ratio of 2000IU/mL.In such conditions, immobilized lipase by inclusion in alginate showed a highest stability and activity, on olive oil hydrolysis reaction where it could be reused for 10 cycles. After 15min of hydrolysis reaction, the mass composition of monoolein, diolein and triolein were about 78%, 10% and 12%. Hydrolysis' products purification by column chromatography lead to a successful separation of reaction compounds and provide a pure fraction of monoolein which is considered as the widest used emulsifier in food and pharmaceutical industries. PMID:24755261

Ghattas, Nesrine; Abidi, Ferid; Galai, Said; Marzouki, M Nejib; Salah, Abderraouf Ben

2014-07-01

367

A 2-oxoglutarate-dependent dioxygenase from Ruta graveolens L. exhibits p-coumaroyl CoA 2'-hydroxylase activity (C2'H): a missing step in the synthesis of umbelliferone in plants.  

PubMed

Coumarins are important compounds that contribute to the adaptation of plants to biotic or abiotic stresses. Among coumarins, umbelliferone occupies a pivotal position in the plant phenylpropanoid network. Previous studies indicated that umbelliferone is derived from the ortho-hydroxylation of p-coumaric acid by an unknown biochemical step to yield 2,4-dihydroxycinnamic acid, which then undergoes spontaneous lactonization. Based on a recent report of a gene encoding a 2-oxoglutarate-dependent dioxygenase from Arabidopsis thaliana that exhibited feruloyl CoA 6'-hydroxylase activity (Bourgaud et al., 2006), we combined a bioinformatic approach and a cDNA library screen to identify an orthologous ORF (Genbank accession number JF799117) from Ruta graveolens L. This ORF shares 59% amino acid identity with feruloyl CoA 6'-hydroxylase, was functionally expressed in Escherichia coli, and converted feruloyl CoA into scopoletin and p-coumaroyl CoA into umbelliferone with equal activity. Its bi-functionality was further confirmed in planta: transient expression of JF799117 in Nicotiana benthamiana yielded plants with leaves containing high levels of umbelliferone and scopoletin when compared to control plants, which contained barely detectable traces of these compounds. The expression of JF799117 was also tightly correlated to the amount of umbelliferone that was found in UV-elicited R. graveolens leaves. Therefore, JF799117 encodes a p-coumaroyl CoA 2'-hydroxylase in R. graveolens, which represents a previously uncharacterized step in the synthesis of umbelliferone in plants. Psoralen, which is an important furanocoumarin in R. graveolens, was found to be a competitive inhibitor of the enzyme, and it may exert this effect through negative feedback on the enzyme at an upstream position in the pathway. PMID:22168819

Vialart, Guilhem; Hehn, Alain; Olry, Alexandre; Ito, Kyoko; Krieger, Celia; Larbat, Romain; Paris, Cedric; Shimizu, Bun-Ichi; Sugimoto, Yukihiro; Mizutani, Masaharu; Bourgaud, Frederic

2012-05-01

368

Soluble epoxide hydrolase regulates hydrolysis of vasoactive epoxyeicosatrienoic acids.  

PubMed

The cytochrome P450-derived epoxyeicosatrienoic acids (EETs) have potent effects on renal vascular reactivity and tubular sodium and water transport; however, the role of these eicosanoids in the pathogenesis of hypertension is controversial. The current study examined the hydrolysis of the EETs to the corresponding dihydroxyeicosatrienoic acids (DHETs) as a mechanism for regulation of EET activity and blood pressure. EET hydrolysis was increased 5- to 54-fold in renal cortical S9 fractions from the spontaneously hypertensive rat (SHR) relative to the normotensive Wistar-Kyoto (WKY) rat. This increase was most significant for the 14,15-EET regioisomer, and there was a clear preference for hydrolysis of 14, 15-EET over the 8,9- and 11,12-EETs. Increased EET hydrolysis was consistent with increased expression of soluble epoxide hydrolase (sEH) in the SHR renal microsomes and cytosol relative to the WKY samples. The urinary excretion of 14,15-DHET was 2.6-fold higher in the SHR than in the WKY rat, confirming increased EET hydrolysis in the SHR in vivo. Blood pressure was decreased 22+/-4 mm Hg (P:<0.01) 6 hours after treatment of SHRs with the selective sEH inhibitor N:, N:'-dicyclohexylurea; this treatment had no effect on blood pressure in the WKY rat. These studies identify sEH as a novel therapeutic target for control of blood pressure. The identification of a potent and selective inhibitor of EET hydrolysis will be invaluable in separating the vascular effects of the EET and DHET eicosanoids. PMID:11090543

Yu, Z; Xu, F; Huse, L M; Morisseau, C; Draper, A J; Newman, J W; Parker, C; Graham, L; Engler, M M; Hammock, B D; Zeldin, D C; Kroetz, D L

2000-11-24

369

A kinetic study on sesame cake protein hydrolysis by Alcalase.  

PubMed

In the present study, the hydrolysis of sesame cake protein was performed by Alcalase, a bacterial protease produced by Bacillus licheniformis, to investigate the reaction kinetics of sesame cake hydrolysis and to determine decay and product inhibition effects for Alcalase. The reactions were carried out for 10 min in 0.1 L of aqueous solutions containing 10, 15, 20, 25, and 30 g protein/L at various temperature and pH values. To determine decay and product inhibition effects for Alcalase, a series of inhibition experiments were conducted with the addition of various amounts of hydrolysate. The reaction kinetics was investigated by initial rate approach. The initial reaction rates were determined from the slopes of the linear models that fitted to the experimental data. The kinetic parameters, K(m) and V(max), were estimated as 41.17 g/L and 9.24 meqv/L x min. The Lineweaver-Burk plots showed that the type of inhibition for Alcalase determined as uncompetitive, and the inhibition constant, K(i), was estimated as 38.24% (hydrolysate/substrate mixture). Practical Application: Plant proteins are increasingly being used as an alternative to proteins from animal sources to perform functional roles in food formulation. Knowledge of the kinetics of the hydrolysis reaction is essential for the optimization of enzymatic protein hydrolysis and for increasing the utilization of plant proteins in food products. Therefore, in the present study, the hydrolysis of sesame cake protein was performed by Alcalase, a bacterial protease produced by B. licheniformis, to investigate the reaction kinetics of sesame cake hydrolysis and to determine decay and product inhibition effects for Alcalase. PMID:21535655

Demirhan, Elçin; Apar, Dilek K?l?ç; Özbek, Belma

2011-01-01

370

Hydrolysis and photolysis of oxytetracycline in aqueous solution.  

PubMed

Oxytetracycline ((2Z,4S,4aR,5S,5aR,6S,12aS)-2-(amino-hydroxy-methylidene)-4-dimethylamino-5,6,10,11,12a-pentahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione) is a member of tetracycline antibiotics family and is widely administered to farm animals for the purpose of therapeutical treatment and health protection. Increasing attention has been paid to the environmental fate of oxytetracycline and other veterinary antibiotics with the occurrence of these antibiotics in the environment. The hydrolysis and photolysis degradation of oxytetracycline was investigated in this study. Oxytetracycline hydrolysis was found to obey the first-order model and similar rate constant values ranging from 0.094 +/- 0.001 to 0.106 +/- 0.003 day(-1) were obtained at different initial concentration ranging from 10 to 230 microM. Solution pH and temperature were shown to have remarked effects on oxytetracycline hydrolysis. The hydrolysis in pH neutral solution appeared to be much faster than in both acidic and alkaline solutions. Oxytetracycline half-life decreased from 1.2 x 10(2) to 0.15 day with the increasing temperature from 4 +/- 0.8 to 60 +/- 1 degrees C. The presence of Ca(2+) made oxytetracycline hydrolytic degradation kinetics deviate from the simple first-order model to the availability-adjusted first-order model and greatly slowed down the hydrolysis. Oxytetracycline photolysis was found to be very fast with a degradation rate constant at 3.61 +/- 0.06 day(-1), which is comparable to that of hydrolysis at 60 degrees C. The presence of Ca(2+) accelerated oxytetracycline photolysis, implying that oxytetracycline become more vulnerable to sunlight irradiation after chelating with Ca(2+). The photolysis may be the dominant degradation pathway of oxytetracycline in shallow transparent water environment. PMID:20390934

Xuan, Richeng; Arisi, Lestley; Wang, Qiquan; Yates, Scott R; Biswas, Keka C

2010-01-01

371

The Mechanisms of Plant Cell Wall Deconstruction during Enzymatic Hydrolysis  

PubMed Central

Mechanical agitation during enzymatic hydrolysis of insoluble plant biomass at high dry matter contents is indispensable for the initial liquefaction step in biorefining. It is known that particle size reduction is an important part of liquefaction, but the mechanisms involved are poorly understood. Here we put forward a simple model based on mechanical principles capable of capturing the result of the interaction between mechanical forces and cell wall weakening via hydrolysis of glucosidic bonds. This study illustrates that basic material science insights are relevant also within biochemistry, particularly when it comes to up-scaling of processes based on insoluble feed stocks. PMID:25232741

Thygesen, Lisbeth G.; Thybring, Emil E.; Johansen, Katja S.; Felby, Claus

2014-01-01

372

Hydrolysis of xylan by an immobilized xylanase from Aureobasidium pullanans  

SciTech Connect

The beta-(1,4)-linked xylose residues that comprise the backbone of the abundant plant polymer xylan can be released by enzymic hydrolysis. Xylanase, which is produced in exceptionally high levels by the color-variant strain of A. pullulans, was immobilized onto a macroporous ceramic carrier. Despite a low coupling efficiency, it was possible to run the reactor under a wide range of conditions with flow rates of 3-10 bed volumes/minute of 1% soluble xylan with no detectable leaching of enzyme. The size distribution of products and rate of xylan hydrolysis were very similar for the immobilized and soluble enzymes. (Refs. 13).

Allenza, P.; Scherl, D.S.; Detroy, R.W.; Leathers, T.D.; Scott, C.D. (ed.)

1986-01-01

373

Hydrolysis of xylan by an immobilized xylanase from Aureobasidium pullulans  

SciTech Connect

The beta-(1,4)-linked xylose residues that comprise the backbone of the abundant plant polymer xylan can be released by enzymic hydrolysis. Xylanase, which is produced in exceptionally high levels by the color-variant strain Y-2311-1 of A. pullulans, was immobilized onto a macroporous ceramic carrier. Despite a low coupling efficiency, it was possible to run the reactor under a wide range of conditions with flow rates of 3-10 bed volumes/minute of 1% soluble xylan with no detectable leaching of enzyme. The size distribution of products and rate of xylan hydrolysis were very similar for the immobilized and soluble enzymes. (Refs. 13).

Allenza, P.; Scherl, D.S.; Detroy, R.W.; Leathers, T.D.; Scott, C.D. (ed.).

1986-01-01

374

Microwave-assisted hydrolysis of polysaccharides over polyoxometalate clusters.  

PubMed

Polyoxometalate (POM) clusters were utilized as recyclable acid catalysts and microwave-absorbing agents for the microwave-assisted hydrolysis of corn starch and crystalline cellulose. Phosphotungstic (PW) and silicotungstic (SiW) acids showed high hydrolyzing activity, while phosphomolybdic acid (PMo) showed lower glucose stability. The PW catalyst could be recycled by ether extraction at least 4 times without changing its catalytic activity. The addition of PW could reduce the energy demand required for running the hydrolysis by 17-23%. The dielectric property of the aqueous PW solution was important for increasing the microwave-absorption capability of the reaction system and reducing the energy consumption. PMID:23859983

Tsubaki, Shuntaro; Oono, Kiriyo; Ueda, Tadaharu; Onda, Ayumu; Yanagisawa, Kazumichi; Mitani, Tomohiko; Azuma, Jun-ichi

2013-09-01

375

Benzene/nitrous oxide flammability in the precipitate hydrolysis process  

SciTech Connect

The HAN (hydroxylamine nitrate) process for destruction of nitrite in precipitate hydrolysis produces nitrous oxide (N2O) gas as one of the products. N2O can form flammable mixtures with benzene which is also present due to radiolysis and hydrolysis of tetraphenylborate. Extensive flame modeling and explosion testing was undertaken to define the minimum oxidant for combustion of N2O/benzene using both nitrogen and carbon dioxide as diluents. The attached memorandum interprets and documents the results of the studies.

Jacobs, R A [Du Pont de Nemours (E.I.) and Co., Aiken, SC (USA). Savannah River Lab.

1989-09-18

376

Acetyl radical production by the methylglyoxal-peroxynitrite system: a possible route for L-lysine acetylation.  

PubMed

Methylglyoxal is an ?-oxoaldehyde putatively produced in excess from triose phosphates, aminoacetone, and acetone in some disorders, particularly in diabetes. Here, we investigate the nucleophilic addition of ONOO(-), known as a potent oxidant and nucleophile, to methylglyoxal, yielding an acetyl radical intermediate and ultimately formate and acetate ions. The rate of ONOO(-) decay in the presence of methylglyoxal [k(2,app) = (1.0 ± 0.1) × 10(3) M(-1) s(-1); k(2) ? 1.0 × 10(5) M(-1) s(-1)] at pH 7.2 and 25 °C was found to be faster than that reported with monocarbonyl substrates (k(2) < 10(3) M(-1) s(-1)), diacetyl (k(2) = 1.0 × 10(4) M(-1) s(-1)), or CO(2) (k(2) = 3-6 × 10(4) M(-1) s(-1)). The pH profile of the methylglyoxal-peroxynitrite reaction describes an ascendant curve with an inflection around pH 7.2, which roughly coincides with the pK(a) values of both ONOOH and H(2)PO(4)(-) ion. Electron paramagnetic resonance spin trapping experiments with 2-methyl-2-nitrosopropane revealed concentration-dependent formation of an adduct that can be attributed to 2-methyl-2-nitrosopropane-CH(3)CO(•) (a(N) = 0.83 mT). Spin trapping with 3,5-dibromo-4-nitrosobenzene sulfonate gave a signal that could be assigned to a methyl radical adduct [a(N) = 1.41 mT; a(H) = 1.35 mT; a(H(m)) = 0.08 mT]. The 2-methyl-2-nitrosopropane-CH(3)CO(•) adduct could also be observed by replacement of ONOO(-) with H(2)O(2), although at much lower yields. Acetyl radicals could be also trapped by added L-lysine as indicated by the presence of (?)N-acetyl-L-lysine in the spent reaction mixture. This raises the hypothesis that ONOO(-)/H(2)O(2) in the presence of methylglyoxal is endowed with the potential to acetylate proteins in post-translational processes. PMID:20923167

Massari, Júlio; Tokikawa, Rita; Zanolli, Luiz; Tavares, Marina Franco Maggi; Assunçăo, Nilson Antônio; Bechara, Etelvino José Henriques

2010-11-15

377

Two Arabidopsis proteins synthesize acetylated xylan in vitro.  

PubMed

Xylan is the third most abundant glycopolymer on earth after cellulose and chitin. As a major component of wood, grain and forage, this natural biopolymer has far-reaching impacts on human life. This highly acetylated cell wall polysaccharide is a vital component of the plant cell wall, which functions as a molecular scaffold, providing plants with mechanical strength and flexibility. Mutations that impair synthesis of the xylan backbone give rise to plants that fail to grow normally because of collapsed xylem cells in the vascular system. Phenotypic analysis of these mutants has implicated many proteins in xylan biosynthesis; however, the enzymes directly responsible for elongation and acetylation of the xylan backbone have not been unambiguously identified. Here we provide direct biochemical evidence that two Arabidopsis thaliana proteins, IRREGULAR XYLEM 10-L (IRX10-L) and ESKIMO1/TRICOME BIREFRINGENCE 29 (ESK1/TBL29), catalyze these respective processes in vitro. By identifying the elusive xylan synthase and establishing ESK1/TBL29 as the archetypal plant polysaccharide O-acetyltransferase, we have resolved two long-standing questions in plant cell wall biochemistry. These findings shed light on integral steps in the molecular pathways used by plants to synthesize a major component of the world's biomass and expand our toolkit for producing glycopolymers with valuable properties. PMID:25141999

Urbanowicz, Breeanna R; Peńa, Maria J; Moniz, Heather A; Moremen, Kelley W; York, William S

2014-10-01

378

Characterization of Maize Acetyl-Coenzyme A Carboxylase.  

PubMed Central

Maize (Zea mays L.) leaf acetyl-CoA carboxylase (ACCase) was purified about 500-fold by ammonium sulfate fractionation and gel filtration and blue Sepharose affinity and anion-exchange chromatography. Most ACCase activity (85%) recovered from the anion-exchange column was found in a highly purified fraction (specific activity 5.5 [mu]mol acid-stable product min-1 mg-1) that consisted primarily of a single 227-kD biotinylated polypeptide. The fraction represented 29% of the original activity and was designated ACCase I. A second partially purified ACCase activity (ACCase II) eluted earlier during anion-exchange chromatography, contained a single biotinylated polypeptide of 219 kD, was poorly recognized by antiserum raised against the ACCase I polypeptide, and was less inhibited by the herbicides haloxyfop or sethoxydim than was ACCase I. ACCase I and II both utilized propionyl-CoA as substrate about 50% as effectively as acetyl-CoA, and neither utilized methylcrotonyl-CoA. Immunoprecipitation with antiserum and protein blotting of crude extracts of leaf, embryo, and endosperm tissue and suspension cells indicated that most ACCase activity in these tissues was immunologically similar and consisted of ACCase I. Only leaves contained significant amounts of the ACCase II polypeptide; however, no ACCase II polypeptide was found in isolated mesophyll chloroplasts. The ACCase I and II polypeptides appear to be subunits of distinct ACCase isoforms. PMID:12231704

Egli, M. A.; Gengenbach, B. G.; Gronwald, J. W.; Somers, D. A.; Wyse, D. L.

1993-01-01

379

Structure of Alba: an archaeal chromatin protein modulated by acetylation  

PubMed Central

Eukaryotic DNA is packaged into nucleosomes that regulate the accessibility of the genome to replication, transcription and repair factors. Chromatin accessibility is controlled by histone modifications including acetylation and methylation. Archaea possess eukary otic-like machineries for DNA replication, transcription and information processing. The conserved archaeal DNA binding protein Alba (formerly Sso10b) interacts with the silencing protein Sir2, which regulates Alba’s DNA binding affinity by deacetylation of a lysine residue. We present the crystal structure of Alba from Sulfolobus solfataricus at 2.6 ? resolution (PDB code 1h0x). The fold is reminiscent of the N-terminal DNA binding domain of DNase I and the C-terminal domain of initiation factor IF3. The Alba dimer has two extended ?-hairpins flanking a central body containing the acetylated lysine, Lys16, suggesting three main points of contact with the DNA. Fluorescence, calorimetry and electrophoresis data suggest a final binding stoichiometry of ?5 bp DNA per Alba dimer. We present a model for the Alba–DNA interaction consistent with the available structural, biophysical and electron microscopy data. PMID:12198167

Wardleworth, B.N.; Russell, R.J.M.; Bell, S.D.; Taylor, G.L.; White, M.F.

2002-01-01

380

Total Levels of Hippocampal Histone Acetylation Predict Normal Variability in Mouse Behavior  

PubMed Central

Background Genetic, pharmacological, and environmental interventions that alter total levels of histone acetylation in specific brain regions can modulate behaviors and treatment responses. Efforts have been made to identify specific genes that are affected by alterations in total histone acetylation and to propose that such gene specific modulation could explain the effects of total histone acetylation levels on behavior — the implication being that under naturalistic conditions variability in histone acetylation occurs primarily around the promoters of specific genes. Methods/Results Here we challenge this hypothesis by demonstrating with a novel flow cytometry based technique that normal variability in open field exploration, a hippocampus-related behavior, was associated with total levels of histone acetylation in the hippocampus but not in other brain regions. Conclusions Results suggest that modulation of total levels of histone acetylation may play a role in regulating biological processes. We speculate in the discussion that endogenous regulation of total levels of histone acetylation may be a mechanism through which organisms regulate cellular plasticity. Flow cytometry provides a useful approach to measure total levels of histone acetylation at the single cell level. Relating such information to behavioral measures and treatment responses could inform drug delivery strategies to target histone deacetylase inhibitors and other chromatin modulators to places where they may be of benefit while avoiding areas where correction is not needed and could be harmful. PMID:24788142

Nesbitt, Addie May I.; McCurdy, Richard D.; Bryant, Sharell M.; Alter, Mark D.

2014-01-01

381

LAceP: Lysine Acetylation Site Prediction Using Logistic Regression Classifiers  

PubMed Central

Background Lysine acetylation is a crucial type of protein post-translational modification, which is involved in many important cellular processes and serious diseases. However, identification of protein acetylated sites through traditional experiment methods is time-consuming and laborious. Those methods are not suitable to identify a large number of acetylated sites quickly. Therefore, computational methods are still very valuable to accelerate lysine acetylated site finding. Result In this study, many biological characteristics of acetylated sites have been investigated, such as the amino acid sequence around the acetylated sites, the physicochemical property of the amino acids and the transition probability of adjacent amino acids. A logistic regression method was then utilized to integrate these information for generating a novel lysine acetylation prediction system named LAceP. When compared with existing methods, LAceP overwhelms most of state-of-the-art methods. Especially, LAceP has a more balanced prediction capability for positive and negative datasets. Conclusion LAceP can integrate different biological features to predict lysine acetylation with high accuracy. An online web server is freely available at http://www.scbit.org/iPTM/. PMID:24586884

Hou, Ting; Zheng, Guangyong; Zhang, Pingyu; Jia, Jia; Li, Jing; Xie, Lu; Wei, Chaochun; Li, Yixue

2014-01-01

382

Eaf3 regulates the global pattern of histone acetylation in Saccharomyces cerevisiae.  

PubMed

Saccharomyces cerevisiae has a global pattern of histone acetylation in which histone H3 and H4 acetylation levels are lower at protein-coding sequences than at promoter regions. The loss of Eaf3, a subunit of the NuA4 histone acetylase and Rpd3 histone deacetylase complexes, greatly alters the genomic profile of histone acetylation, with the effects on H4 appearing to be more pronounced than those on H3. Specifically, the loss of Eaf3 causes increases in H3 and H4 acetylation at coding sequences and decreases at promoters, such that histone acetylation levels become evenly distributed across the genome. Eaf3 does not affect the overall level of H4 acetylation, the recruitment of the NuA4 catalytic subunit Esa1 to target promoters, or the level of transcription of the genes analyzed for histone acetylation. Whole-genome transcriptional profiling indicates that Eaf3 plays a positive, but quantitatively modest, role in the transcription of a small subset of genes, whereas it has a negative effect on very few genes. We suggest that Eaf3 regulates the genomic profile of histone H3 and H4 acetylation in a manner that does not involve targeted recruitment and is independent of transcriptional activity. PMID:14701747

Reid, Juliet L; Moqtaderi, Zarmik; Struhl, Kevin

2004-01-01

383

Aberrant levels of histone H3 acetylation induce spermatid anomaly in mouse testis.  

PubMed

Histone acetylation is involved in the regulation of chromatin structure and gene function. We reported previously that histone H3 acetylation pattern is subject to dynamic changes and limited to certain stages of germ cell differentiation during murine spermatogenesis, suggesting a crucial role for acetylation in the process. In the present study, we investigated the effects of hyper- and hypo-acetylation on spermatogenesis. Changes in acetylation level were induced by either in vivo administration of sodium phenylbutyrate, a histone deacetylase inhibitor, or by knockdown of histone acetyltransferases using short hairpin RNA plasmids transfection. Administration of sodium phenylbutyrate induced accumulation of acetylated histone H3 at lysine 9 and lysine 18 in round spermatids, together with spermatid morphological abnormalities and induction of apoptosis through a Bax-related pathway. Knockdown of steroid receptor coactivator 1, a member of histone acetyltransferases, but not general control of amino acid synthesis 5 nor elongator protein 3 by in vivo electroporation of shRNA plasmids, reduced acetylated histone H3 at lysine 9 in round spermatids, and induced morphological abnormalities. We concluded that the proper regulation of histone H3 acetylation levels is important for spermatid differentiation and complex chromatin remodeling during spermiogenesis. PMID:25326673

Dai, Lei; Endo, Daisuke; Akiyama, Naotaro; Yamamoto-Fukuda, Tomomi; Koji, Takehiko

2015-02-01

384

Protein acetylation in prokaryotes increases stress resistance Qun Ma, Thomas K. Wood  

E-print Network

Protein acetylation in prokaryotes increases stress resistance Qun Ma, Thomas K. Wood Department of lysine residues is conserved in all three kingdoms; however, its role in prokaryotes is unknown. Here we of a specific environmental role of acetylation in prokaryotes. Ă? 2011 Elsevier Inc. All rights reserved. 1

Wood, Thomas K.

385

Protein acetylation affects acetate metabolism, motility and acid stress response in Escherichia coli  

PubMed Central

Although protein acetylation is widely observed, it has been associated with few specific regulatory functions making it poorly understood. To interrogate its functionality, we analyzed the acetylome in Escherichia coli knockout mutants of cobB, the only known sirtuin-like deacetylase, and patZ, the best-known protein acetyltransferase. For four growth conditions, more than 2,000 unique acetylated peptides, belonging to 809 proteins, were identified and differentially quantified. Nearly 65% of these proteins are related to metabolism. The global activity of CobB contributes to the deacetylation of a large number of substrates and has a major impact on physiology. Apart from the regulation of acetyl-CoA synthetase, we found that CobB-controlled acetylation of isocitrate lyase contributes to the fine-tuning of the glyoxylate shunt. Acetylation of the transcription factor RcsB prevents DNA binding, activating flagella biosynthesis and motility, and increases acid stress susceptibility. Surprisingly, deletion of patZ increased acetylation in acetate cultures, which suggests that it regulates the levels of acetylating agents. The results presented offer new insights into functional roles of protein acetylation in metabolic fitness and global cell regulation. PMID:25518064

Castańo-Cerezo, Sara; Bernal, Vicente; Post, Harm; Fuhrer, Tobias; Cappadona, Salvatore; Sánchez-Díaz, Nerea C; Sauer, Uwe; Heck, Albert JR; Altelaar, AF Maarten; Cánovas, Manuel

2014-01-01

386

Role of Alginate O Acetylation in Resistance of Mucoid Pseudomonas aeruginosa to Opsonic Phagocytosis  

Microsoft Academic Search

Establishment and maintenance of chronic lung infections with mucoid Pseudomonas aeruginosa in patients with cystic fibrosis (CF) require that the bacteria avoid host defenses. Elaboration of the extracellular, O-acetylated mucoid exopolysaccharide, or alginate, is a major microbial factor in resistance to immune effectors. Here we show that O acetylation of alginate maximizes the resistance of mucoid P. aeruginosa to antibody-independent

GERALD B. PIER; FADIE COLEMAN; MARTHA GROUT; MICHAEL FRANKLIN; DENNIS E. OHMAN

2001-01-01

387

Novel myelin penta- and hexa-acetyl-galactosyl-ceramides: structural characterization and immunoreactivity in cerebrospinal fluid.  

PubMed

Fast migrating cerebrosides (FMC) are derivatives of galactosylceramide (GalCer). The structures of the most hydrophobic FMC-5, FMC-6, and FMC-7 were determined by electrospray ionization linear ion-trap mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy complementing previous NMR spectroscopy and gas chromatography-mass spectrometry to be 3-O-acetyl-sphingosine-GalCer derivatives with galactose O-acetyl modifications. FMC-5 and FMC-6 are 3-O-acetyl-sphingosine-2,3,4,6-tetra-O-acetyl-GalCer with nonhydroxy and hydroxy-N-fatty-acids, while FMC-7 has an additional O-acetylation of the 2-hydroxy-fatty acid. The immuno-reactivity in human cerebrospinal fluid (CSF) to these acetylated glycolipids was examined in central nervous system (CNS) infectious disease, noninflammatory disorders, and multiple sclerosis (MS). Screening for lipid binding in MS and other neurological disease groups revealed that the greatest anti-hydrophobic FMC reactivity was observed in the inflammatory CNS diseases (meningitis, meningo-encephalitis, and subacute sclerosing panencephalitis). Some MS patients had increased reactivity with the hydrophobic FMCs and with glycoglycerophospholipid MfGL-II from Mycoplasma fermentans. The cross-reactivity of highly acetylated GalCer with microbial acyl-glycolipid raises the possibility that myelin-O-acetyl-cerebrosides, bacterial infection, and neurological disease are linked. PMID:20154333

Podbielska, Maria; Dasgupta, Somsankar; Levery, Steven B; Tourtellotte, Wallace W; Annuk, Heidi; Moran, Anthony P; Hogan, Edward L

2010-06-01

388

The Effect of Acetyl-L-Carnitine Administration on Persons with Down Syndrome  

ERIC Educational Resources Information Center

Since previous investigations reported improvements in cognition of patients with dementia after acetyl-L-carnitine therapy and since there is an increased risk for persons with Down syndrome to develop Alzheimer disease, this study was designed to investigate the effect of acetyl-L-carnitine administration on neurological, intellectual, and…

Pueschel, Siegfried M.

2006-01-01

389

Acetylation of yeast AMP-Activated Protein Kinase Controls Intrinsic Aging Independently of Caloric Restriction  

PubMed Central

SUMMARY (De)acetylation of histone and non-histone proteins is an important post-translational modification affecting many cellular processes. Here we report that NuA4 acetylation of Sip2, one of three regulatory ? subunits of Snf1 complex (yeast AMP-activated protein kinase), decreases as cells age. We used mutations at four acetylation sites, K12, 16, 17 and 256, to study acetyl-Sip2 function. Sip2 acetylation, controlled by antagonizing NuA4 acetyltransferase and Rpd3 deacetylase, enhances interaction with Snf1, the catalytic subunit of Snf1 complex. Sip2-Snf1 interaction inhibits Snf1 activity, thus decreasing phosphorylation of a downstream target, Sch9 (homolog of Akt/S6K), ultimately leads to slower growth but extends replicative lifespan. Sip2 acetylation mimetics are more resistant to oxidative stress. We further demonstrate that the anti-aging effect of Sip2 acetylation is independent of extrinsic nutrient availability and TORC1 activity. We propose a novel protein acetylation- phosphorylation cascade that regulates Sch9 activity, controls intrinsic aging and extends replicative lifespan in yeast. PMID:21906795

Lu, Jin-Ying; Lin, Yu-Yi; Sheu, Jin-Chuan; Wu, June-Tai; Lee, Fang-Jen; Chen, Yue; Lin, Min-I; Chiang, Fu-Tien; Tai, Tong-Yuan; Berger, Shelley L.; Zhao, Yingming; Tsai, Keh-Sung; Zhu, Heng; Chuang, Lee-Ming; Boeke, Jef D.

2011-01-01

390

Histone Acetylation is Recruited in Consolidation as a Molecular Feature of Stronger Memories  

ERIC Educational Resources Information Center

Gene expression is a key process for memory consolidation. Recently, the participation of epigenetic mechanisms like histone acetylation was evidenced in long-term memories. However, until now the training strength required and the persistence of the chromatin acetylation recruited are not well characterized. Here we studied whether histone…

Federman, Noel; Fustinana, Maria Sol; Romano, Arturo

2009-01-01

391

Per-O-acetylation of cellulose in dimethyl sulfoxide with catalyzed transesterification.  

PubMed

Cellulose acetylation was investigated in dimethyl sulfoxide (DMSO) with isopropenyl acetate (IPA) as acetylating reagent and 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as catalyst at 70-130 °C for 3-12 h. The degree of substitution (DS) of acetylated cellulose was comparatively determined by titration and ąH NMR and confirmed by FT-IR analysis. The results indicated that per-O-acetylation was achieved at >90 °C for a relatively long duration. The three well-resolved peaks of carbonyl carbons in ąłC NMR spectra also provided evidence of per-O-acetylation. The solubility of cellulose acetates in common organic solvents was examined, and the result showed that chloroform can be an alternative choice as a solvent for fully acetylated cellulose formed in this study besides DMSO. The intrinsic viscosity of acetylated cellulose solution implied almost no degradation of cellulose during acetylation in DMSO except at higher temperature (130 °C) for a long time. PMID:24678805

Chen, Chao-Yi; Chen, Ming-Jie; Zhang, Xue-Qin; Liu, Chuan-Fu; Sun, Run-Cang

2014-04-16

392

N??Lysine Acetylation of a Bacterial Transcription Factor Inhibits Its DNA-Binding Activity  

PubMed Central

Evidence suggesting that eukaryotes and archaea use reversible N?-lysine (N?-Lys) acetylation to modulate gene expression has been reported, but evidence for bacterial use of N?-Lys acetylation for this purpose is lacking. Here, we report data in support of the notion that bacteria can control gene expression by modulating the acetylation state of transcription factors (TFs). We screened the E. coli proteome for substrates of the bacterial Gcn5-like protein acetyltransferase (Pat). Pat acetylated four TFs, including the RcsB global regulatory protein, which controls cell division, and capsule and flagellum biosynthesis in many bacteria. Pat acetylated residue Lys180 of RcsB, and the NAD+-dependent Sir2 (sirtuin)-like protein deacetylase (CobB) deacetylated acetylated RcsB (RcsBAc), demonstrating that N?-Lys acetylation of RcsB is reversible. Analysis of RcsBAc and variant RcsB proteins carrying substitutions at Lys180 provided biochemical and physiological evidence implicating Lys180 as a critical residue for RcsB DNA-binding activity. These findings further the likelihood that reversible N?-Lys acetylation of transcription factors is a mode of regulation of gene expression used by all cells. PMID:21217812

Thao, Sandy; Chen, Chien-Sheng; Zhu, Heng; Escalante-Semerena, Jorge C.

2010-01-01

393

The Role of Histone Acetylation in Cocaine-Induced Neural Plasticity and Behavior  

E-print Network

The Role of Histone Acetylation in Cocaine-Induced Neural Plasticity and Behavior George A Rogge1 of abuse, such as cocaine, cause stable changes in neural plasticity that in turn drive long-term changes regulation via histone acetylation in cocaine action. Neuropsychopharmacology Reviews advance online

Wood, Marcelo A.

394

A dysregulated acetyl/SUMO switch of FXR promotes hepatic inflammation in obesity.  

PubMed

Acetylation of transcriptional regulators is normally dynamically regulated by nutrient status but is often persistently elevated in nutrient-excessive obesity conditions. We investigated the functional consequences of such aberrantly elevated acetylation of the nuclear receptor FXR as a model. Proteomic studies identified K217 as the FXR acetylation site in diet-induced obese mice. In vivo studies utilizing acetylation-mimic and acetylation-defective K217 mutants and gene expression profiling revealed that FXR acetylation increased proinflammatory gene expression, macrophage infiltration, and liver cytokine and triglyceride levels, impaired insulin signaling, and increased glucose intolerance. Mechanistically, acetylation of FXR blocked its interaction with the SUMO ligase PIASy and inhibited SUMO2 modification at K277, resulting in activation of inflammatory genes. SUMOylation of agonist-activated FXR increased its interaction with NF-?B but blocked that with RXR?, so that SUMO2-modified FXR was selectively recruited to and trans-repressed inflammatory genes without affecting FXR/RXR? target genes. A dysregulated acetyl/SUMO switch of FXR in obesity may serve as a general mechanism for diminished anti-inflammatory response of other transcriptional regulators and provide potential therapeutic and diagnostic targets for obesity-related metabolic disorders. PMID:25425577

Kim, Dong-Hyun; Xiao, Zhen; Kwon, Sanghoon; Sun, Xiaoxiao; Ryerson, Daniel; Tkac, David; Ma, Ping; Wu, Shwu-Yuan; Chiang, Cheng-Ming; Zhou, Edward; Xu, H Eric; Palvimo, Jorma J; Chen, Lin-Feng; Kemper, Byron; Kemper, Jongsook Kim

2014-11-25

395

Novel Family of Carbohydrate Esterases, Based on Identification of the Hypocrea jecorina Acetyl Esterase Gene  

Technology Transfer Automated Retrieval System (TEKTRAN)

Plant cell walls have been shown to contain acetyl groups in hemicelluloses and pectin. The gene, ae1, encoding the acetyl esterase (Ae1) of Hypocrea jecorina was identified by amino terminal sequencing, peptide mass spectrometry, and genomic sequence analyses. The coded polypeptide had 348 amino ...

396

Single Molecule Study of Cellulase Hydrolysis of Crystalline Cellulose  

SciTech Connect

This report seeks to elucidate the role of cellobiohydrolase-I (CBH I) in the hydrolysis of crystalline cellulose. A single-molecule approach uses various imaging techniques to investigate the surface structure of crystalline cellulose and changes made in the structure by CBH I.

Liu, Y.-S.; Luo, Y.; Baker, J. O.; Zeng, Y.; Himmel, M. E.; Smith, S.; Ding, S.-Y.

2009-12-01

397

Effect of particle size on enzymatic hydrolysis of pretreated Miscanthus  

Technology Transfer Automated Retrieval System (TEKTRAN)

Particle size reduction is a crucial factor in transportation logistics as well as cellulosic conversion. The effect of particle size on enzymatic hydrolysis of pretreated Miscanthus x giganteus was determined. Miscanthus was ground using a hammer mill equipped with screens having 0.08, 2.0 or 6.0...

398

ENZYMATIC HYDROLYSIS OF CLOVER-GRASS MIXTURES FOR ETHANOL  

E-print Network

ENZYMATIC HYDROLYSIS OF CLOVER- GRASS MIXTURES FOR ETHANOL PRODUCTION MARTÍN, C.1,2 , THOMSEN, M. H, Risø National Laboratory, P.O.Box 49, DK-4000 Roskilde, Denmark Clover (Trifolium repens L.)-grass.g. organic farming systems. Since clover and grass are rich in carbohydrates, mainly cellulose

399

Penicillin Hydrolysis: A Kinetic Study of a Multistep, Multiproduct Reaction.  

ERIC Educational Resources Information Center

Background, procedures used, and typical results are provided for an experiment in which students carry out the necessary measurements on the acid-catalysis of penicillin in two hours. By applying kinetic theory to the data obtained, the reaction pathways for the hydrolysis of potassium benzyl penicillin are elucidated. (JN)

McCarrick, Thomas A.; McLafferty, Fred W.

1984-01-01

400

ACID AND ENZYMATIC HYDROLYSIS OF SALINE BIOMASS FOR SUGAR PRODUCTION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Saline crops were evaluated for their potential to be used as feedstock for fermentable sugar production via dilute acid pretreatment and enzymatic hydrolysis. The saline crops included two woods, Athel (Tamarix aphylla L) and Eucalyptus (Eucalyptus camaldulensis), and two grasses, Jose Tall Wheatgr...

401

REVISED TREATMENT OF N2 O5 HYDROLYSIS IN CMAQ  

EPA Science Inventory

In this presentation, revised treatment of homogeneous and heterogeneous hydrolysis of dinitrogen pentoxide in the Community Multiscale Air Quality model version 4.6 are described. A series of model sensitivity tests are conducted and compared with observations of total atmosphe...

402

Hydrolysis Reactions of the Taccalonolides Reveal Structure Activity Relationships  

PubMed Central

The taccalonolides are microtubule stabilizers isolated from plants of the genus Tacca that show potent in vivo antitumor activity and the ability to overcome multiple mechanisms of drug resistance. The most potent taccalonolide identified to date, AJ, is a semisynthetic product generated from the major plant metabolite, taccalonolide A, in a two-step reaction. The first step involves hydrolysis of taccalonolide A to generate taccalonolide B and then this product is oxidized to generate an epoxide group at C22-23. To generate sufficient taccalonolide AJ for in vivo antitumor efficacy studies, the hydrolysis conditions for the conversion of taccalonolide A to B were optimized. During purification of the hydrolysis products, we identified the new taccalonolide, AO (1) along with taccalonolide I. When the same hydrolysis reaction was performed on a taccalonolide E-enriched fraction four new taccalonolides, assigned to AK, AL, AM, and AN (2–5), were obtained in addition to the expected product taccalonolide N. Biological assays were performed on each of the purified taccalonolides which allowed for increased refinement of the structure-activity relationship of this class of compounds. PMID:23855953

Li, Jing; Peng, Jiangnan; Risinger, April L.; Mooberry, Susan L.

2013-01-01

403

HYDROLYSIS OF CHLORPYRIFOS IN AQUEOUS AND COLLOIDAL SYSTEMS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Hydrolysis of chlorpyrifos [o,o-diethyl o-(3, 5, 6-trichloro-2-pyridyl) phosphorothioate] to TCP (3,5,6-trichloro-2-pyridinol) is an important degradation process influencing the fate of chlorpyrifos in aquatic environments. The effects of water chemistry and suspended colloids (smectites, humic ac...

404

Hydrolysis of ferric ion in water and conformational equilibrium  

E-print Network

Reported here are results of theoretical calculations on the hexaaquoferric complex and deprotonated products to investigate the molecular mechanisms of hydrolysis of ferric ion in water. The combination of density functional electronic structure techniques and a dielectric continuum model for electrostatic solvation applied to the Fe(H$_2$O)$_6

Martin, R L E; Pratt, L R; Martin, Richard L.; Pratt, Lawrence R.

1998-01-01

405

Optimization of the enzymatic hydrolysis of Blue shark skin.  

PubMed

Enzymatic hydrolysis of Blue shark skin using Protamex™ was evaluated seeking optimal process conditions. The influence of temperature (45 to 65 °C), pH (6.8 to 8), and enzyme/substrate ratio (E/S; 1% to 5%) on the responses of degree of hydrolysis and protein recovery were determined and process optimization was performed looking for maximum value of the responses. Optimum conditions were established (T = 51 °C, E/S = 4%, and pH = 7.1) and model validation was accomplished by triplicate. Under these conditions protein hydrolysates were prepared and characterized by their amino acid composition, peptide size distribution, and antioxidant capacity by ferric reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays. A degree of hydrolysis of 19.3% and protein recovery of 90.3% were obtained at optimal conditions. Chemical score indicated that the hydrolysate supplies minimal essential amino acid requirements for adults. Molecular weight of peptides on the hydrolysate was below 6.5 kDa. Enzymatic hydrolysis process was efficient for recovery of low molecular weight peptides with important nutritional content and antioxidant activity (FRAP = 12 ?mol eq. in FeSO(4).7H(2)O/g of protein, TEAC = 225.3 ?mol eq. in trolox/g of protein). PMID:22417547

Rodríguez-Díaz, Julio C; Kurozawa, Louise E; Netto, Flavia M; Hubinger, Miriam D

2011-09-01

406

Hydrolysis of lignocellulosic materials for ethanol production: a review  

Microsoft Academic Search

Lignocellulosic biomass can be utilized to produce ethanol, a promising alternative energy source for the limited crude oil. There are mainly two processes involved in the conversion: hydrolysis of cellulose in the lignocellulosic biomass to produce reducing sugars, and fermentation of the sugars to ethanol. The cost of ethanol production from lignocellulosic materials is relatively high based on current technologies,

Ye Sun; Jiayang Cheng

2002-01-01

407

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

408

Oxygen-17 NMR studies on uranium (VI) hydrolysis and gelation  

SciTech Connect

Hydrolysis and gelation processes in uranyl solutions are observed using the strong sharp uranyl oxygen-17 resonance. The ability to follow the hydrolysis of uranyl salts by observation of the sharp uranyl oxygen-17 resonance provides a clear indication of the dependence of uranyl hydrolysis on the counteranion (nitrate versus chloride) but not on the means of introducing hydroxide into the solution (Me{sub 4}NOH versus R{sub 3}N extraction). In addition, two different pathways for gelation are suggested. In the first pathway the uranyl hydrolysis is conducted with a base (HMTA in these studies) which preferentially forms trimeric (UO{sub 2}){sub 3} ({mu}{sub 3}-O) units which can then condense into the polymeric UO{sub 2}O{sub 6/3} layers of a gel based on the hexagonal structure of {proportional_to}UO{sub 2}(OH){sub 2}. In the second gelation pathway a uranyl derivative is treated with excess hydroxide in the absence of a metal or hydrogen-bonding ammonium cations which form insoluble solids uranates. Consensation of the resulting solution of soluble UO{sub 2}(OH)n{sup 2-n} anions can then lead to a similar polymer UO{sub 2}O{sub 4/2} or UO{sub 2}O{sub 6/3} structure of a gel. 9 refs., 2 figs.

King, R.B. [Georgia Univ., Athens, GA (United States). Dept. of Chemistry; King, C.M. [Westinghouse Savannah River Co., Aiken, SC (United States); Garber, A.R. [South Carolina Univ., Columbia, SC (United States). Dept. of Chemistry

1989-12-31

409

Oxygen-17 NMR studies on uranium (VI) hydrolysis and gelation  

SciTech Connect

Hydrolysis and gelation processes in uranyl solutions are observed using the strong sharp uranyl oxygen-17 resonance. The ability to follow the hydrolysis of uranyl salts by observation of the sharp uranyl oxygen-17 resonance provides a clear indication of the dependence of uranyl hydrolysis on the counteranion (nitrate versus chloride) but not on the means of introducing hydroxide into the solution (Me{sub 4}NOH versus R{sub 3}N extraction). In addition, two different pathways for gelation are suggested. In the first pathway the uranyl hydrolysis is conducted with a base (HMTA in these studies) which preferentially forms trimeric (UO{sub 2}){sub 3} ({mu}{sub 3}-O) units which can then condense into the polymeric UO{sub 2}O{sub 6/3} layers of a gel based on the hexagonal structure of {proportional to}UO{sub 2}(OH){sub 2}. In the second gelation pathway a uranyl derivative is treated with excess hydroxide in the absence of a metal or hydrogen-bonding ammonium cations which form insoluble solids uranates. Consensation of the resulting solution of soluble UO{sub 2}(OH)n{sup 2-n} anions can then lead to a similar polymer UO{sub 2}O{sub 4/2} or UO{sub 2}O{sub 6/3} structure of a gel. 9 refs., 2 figs.

King, R.B. (Georgia Univ., Athens, GA (United States). Dept. of Chemistry); King, C.M. (Westinghouse Savannah River Co., Aiken, SC (United States)); Garber, A.R. (South Carolina Univ., Columbia, SC (United States). Dept. of Chemistry)

1989-01-01

410

Ethanol production with dilute acid hydrolysis using partially dried lignocellulosics  

DOEpatents

A process of converting lignocellulosic biomass to ethanol, comprising hydrolyzing lignocellulosic materials by subjecting dried lignocellulosic material in a reactor to a catalyst comprised of a dilute solution of a strong acid and a metal salt to lower the activation energy (i.e., the temperature) of cellulose hydrolysis and ultimately obtain higher sugar yields.

Nguyen, Quang A. (Chesterfield, MO); Keller, Fred A. (Lakewood, CO); Tucker, Melvin P. (Lakewood, CO)

2003-12-09

411

DETERMINATION OF PENTACHLOROPHENOL IN URINE: THE IMPORTANCE OF HYDROLYSIS  

EPA Science Inventory

A gas chromatographic method for more reliable determination of pentachlorophenol (PCP) in urine has been developed. After hydrolysis and extraction the sample was reacted with diazomethane to produce the methyl ether of PCP prior to analysis by electron-capture gas chromatograph...

412

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

413

DFT STUDY OF THE HYDROLYSIS OF SOME S-TRIAZINES  

EPA Science Inventory

The acid-catalyzed hydrolysis of atrazine and related 2-chloro-s-triazines to the corresponding 2-hydroxy-s-triazines was investigated using the B3LYP hybrid density functional theory method. Gas-phase calculations were performed at the B3LYP/6-311++G(d,p)//B3LYP/6-31G* level of ...

414

Destruction of waste energetic materials using base hydrolysis  

SciTech Connect

In dismantling weapons from stockpile reduction, environmentally acceptable degradation of the associated high explosive (HE) waste to non-energetic forms is a critical objective. Base hydrolysis appears to be a simple, inexpensive method for converting propellants, explosives, and pyrotechnics (PEPS) into non-energetic materials that can be released directly or, if necessary, treated further. We have demonstrated that many PEPs can be hydrolyzed with aqueous sodium hydroxide or ammonia at temperatures ranging from 60 to 150[degree]C. Hydrolysis experiments have been performed on pure compounds as well as DOE and DoD formulations, such as plastic-bonded explosive (PBX) 9404, tritonal, and rocket motor propellant. Small particle size of the energetic material is desirable, but not necessary. We have decomposed molding powder, pressed charges up to two pounds in weight, and partially exposed, metal-encased pieces. The products formed are dependent on the starting material composition, but usually consist of organic and inorganic salts, e.g., sodium formate, acetate, nitrite and nitrate. The major gaseous product from the base hydrolysis of PEPs is nitrous oxide. The time required for complete destruction varies with the material being hydrolyzed, and is dependent on solubility and mass transfer. Hydrolysis rates can be increased by particle size reduction, efficient stirring, and addition of organic solvent to the alkaline solution. Rate enhancement by ultrasonic agitation is a possibility that we have just begun to study.

Benziger, T.M.; Buntain, G.A.; Sanchez, J.A.; Spontarelli, T.

1993-01-01

415

Hydrolysis of hemicellulose to produce fermentable monosaccharides by plasma acid.  

PubMed

In this paper, plasma acid was obtained by treating distilled water with dielectric barrier discharge to hydrolyze hemicellulose. The orthogonal experiment L??(5(6)) was used to optimize such hydrolysis conditions. The total reducing sugar (TRS) was measured by the DNS method. To determine whether the oligosaccharide existed in the hydrolysis products, it was hydrolyzed by sulfuric acid for a second time following the same procedure as reported earlier. The monosaccharide compositions of the hydrolyzed sample were analyzed by high-performance liquid chromatography (HPLC) and Fourier transformed infrared spectroscopy (FTIR). The results showed that pH 2.81 of plasma acid, 100 °C and 50 min were assigned as an optimal hydrolysis condition by plasma acid. Under this condition, the hemicellulose was hydrolyzed completely to produce monosaccharides including xylose, glucose, and galactose with the mole ratio being 17:3:1. The yields of xylose, glucose, and galactose were 38.67%, 9.28% and 3.09%, respectively. Compared with the hemicellulose hydrolysis results by sulfuric acid, it is concluded that plasma acid is an environmental-friendly and efficient method to explore and hydrolyze the hemicellulose existed in biomass. PMID:23911479

Wang, Ying; Yuan, Bo; Ji, Yingchao; Li, Hong

2013-09-12

416

A rapid microassay to evaluate enzymatic hydrolysis of lignocellulosic substrates.  

PubMed

Current attempts to produce ethanol from lignocellulosic biomass are focused on the optimization of pretreatment to reduce substrate recalcitrance and the improvement of enzymes for hydrolysis of the cellulose and hemicellulose components to produce fermentable sugars. Research aimed at optimizing both aspects of the bioconversion process involves assessment of the effects of multiple variables on enzyme efficiency, resulting in large factorial experiments with intensive assay requirements. A rapid assay for lignocellulose hydrolysis has been developed to address this need. Pretreated lignocellulose is formed into handsheets, which are then used to prepare small disks that are easily dispensed into microtiter plates. The hydrolysis of cellulose to glucose is estimated using an enzyme-coupled spectrophotometric assay. Using disks prepared from ethanol organosolv pretreated yellow poplar, it is shown that the assay generates data comparable with those produced by hydrolysis of pretreated yellow poplar pulp in Erlenmeyer flasks, followed by HPLC analysis of glucose. The assay shows considerable time and cost benefits over the standard assay protocol and is applicable to a broad range of lignocellulosic substrates. PMID:16345088

Berlin, Alex; Maximenko, Vera; Bura, Renata; Kang, Kyu-Young; Gilkes, Neil; Saddler, Jack

2006-04-01

417

Rapid method for detection of urea hydrolysis by yeasts.  

PubMed Central

A method is described for the rapid detection of urea hydrolysis by yeasts, using the Berthelot color reaction. The results could be determined within 30 to 50 min with this method, compared with 8 to 72 h usually required with Christensen urea agar. PMID:322609

Paliwal, D K; Randhawa, H S

1977-01-01

418

Evaluation of Cation Hydrolysis Schemes with a Pocket Calculator.  

ERIC Educational Resources Information Center

Described is the use of two models of pocket calculators. The Hewlett-Packard HP67 and the Texas Instruments TI59, to solve problems arising in connection with ionic equilibria in solution. A three-parameter regression program is described and listed as a specific example, the hydrolysis of hexavalent uranium, is provided. (BT)

Clare, Brian W.

1979-01-01

419

Investigation of acetylated kapok fibers on the sorption of oil in water.  

PubMed

Kapok fibers have been acetylated for oil spill cleanup in the aqueous environment. The structures of raw and acetylated kapok fiber were characterized using Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Without severe damage to the lumen structures, the kapok fibers were successfully acetylated and the resulting fibers exhibited a better oil sorption capacity than raw fibers for diesel and soybean oil. Compared with high viscosity soybean oil, low viscosity diesel shows a better affinity to the surface of acetylated fibers. Sorption kinetics is fitted well by the pseudo second-order model, and the equilibrium data can be described by the Freundlich isotherm model. The results implied that acetylated kapok fiber can be used as the substitute for non-biodegradable oil sorption materials. PMID:23596942

Wang, Jintao; Zheng, Yian; Wang, Aiqin

2013-02-01

420

Structural, morphological, and physicochemical properties of acetylated high-, medium-, and low-amylose rice starches.  

PubMed

The high-, medium-, and low-amylose rice starches were isolated by the alkaline method and acetylated by using acetic anhydride for 10, 30, and 90 min of reaction. The degree of substitution (DS), the Fourier-transformed infrared spectroscopy (FTIR), the X-ray diffractograms, the thermal, morphological, and pasting properties, and the swelling power and solubility of native and acetylated starches were evaluated. The DS of the low-amylose rice starch was higher than the DS of the medium- and the high-amylose rice starches. The introduction of acetyl groups was confirmed by FTIR spectroscopy. The acetylation treatment reduced the crystallinity, the viscosity, the swelling power, and the solubility of rice starch; however, there was an increase in the thermal stability of rice starch modified by acetylation. PMID:24528747

Colussi, Rosana; Pinto, Vania Zanella; El Halal, Shanise Lisie Mello; Vanier, Nathan Levien; Villanova, Franciene Almeida; Marques E Silva, Ricardo; da Rosa Zavareze, Elessandra; Dias, Alvaro Renato Guerra

2014-03-15

421

common and distinct specificities at different sites of hydrolysis. (3-lactoglobulin hydroly-  

E-print Network

common and distinct specificities at different sites of hydrolysis. (3-lactoglobulin hydroly- sis in allergenic protein hydrolysis in humans) are present as early as birth in both species. The early high level

Boyer, Edmond

422

ISOLATION AND UTILIZATION OF ACETYL-CoA CARBOXYLASE FROM OIL PALM (Elaeis guineensis) MESOCARP Keywords: acetyl-CoA carboxylase, gene isolation, biotin carboxylase, biodegradable plastics, oil palm.  

E-print Network

ISOLATION AND UTILIZATION OF ACETYL-CoA CARBOXYLASE FROM OIL PALM (Elaeis guineensis) MESOCARP 97 Keywords: acetyl-CoA carboxylase, gene isolation, biotin carboxylase, biodegradable plastics, oil palm; Accepted: 7 November 2007. ISOLATION AND UTILIZATION OF ACETYL-CoA CARBOXYLASE FROM OIL PALM (Elaeis

Sinskey, Anthony J.

423

System-wide Studies of N-Lysine Acetylation in Rhodopseudomonas palustris Reveals Substrate Specificity of Protein Acetyltransferases  

SciTech Connect

Background: Protein acetylation is widespread in prokaryotes. Results: Six new acyl-CoA synthetases whose activities are controlled by acetylation were identified, and their substrate preference established. A new protein acetyltransferase was also identified and its substrate specificity determined. Conclusion: Protein acetyltransferases acetylate a conserved lysine residue in protein substrates. Significance: The R. palustris Pat enzyme specifically acetylates AMP-forming acyl-CoA synthetases and regulates fatty acid metabolism.

Crosby, Heidi A [University of Wisconsin, Madison; Pelletier, Dale A [ORNL; Hurst, Gregory {Greg} B [ORNL; Escalante-Semerena, Jorge C [University of Wisconsin, Madison

2012-01-01

424

The acetyl group deficit at the onset of contraction in ischaemic canine skeletal muscle  

PubMed Central

Considerable debate surrounds the identity of the precise cellular site(s) of inertia that limit the contribution of mitochondrial ATP resynthesis towards a step increase in workload at the onset of muscular contraction. By detailing the relationship between canine gracilis muscle energy metabolism and contractile function during constant-flow ischaemia, in the absence (control) and presence of pyruvate dehydrogenase complex activation by dichloroacetate, the present study examined whether there is a period at the onset of contraction when acetyl-coenzyme A (acetyl-CoA) availability limits mitochondrial ATP resynthesis, i.e. whether a limitation in mitochondrial acetyl group provision exists. Secondly, assuming it does exist, we also aimed to identify the mechanism by which dichloroacetate overcomes this ‘acetyl group deficit’. No increase in pyruvate dehydrogenase complex activation or acetyl group availability occurred during the first 20 s of contraction in the control condition, with strong trends for both acetyl-CoA and acetylcarnitine to actually decline (indicating the existence of an acetyl group deficit). Dichloroacetate increased resting pyruvate dehydrogenase complex activation, acetyl-CoA and acetylcarnitine by ?20-fold (P < 0.01), ?3-fold (P < 0.01) and ?4-fold (P < 0.01), respectively, and overcame the acetyl group deficit at the onset of contraction. As a consequence, the reliance upon non-oxidative ATP resynthesis was reduced by ?40 % (P < 0.01) and tension development was increased by ?20 % (P < 0.05) following 5 min of contraction. The present study has demonstrated, for the first time, the existence of an acetyl group deficit at the onset of contraction and has confirmed the metabolic and functional benefits to be gained from overcoming this inertia. PMID:12381829

Roberts, Paul A; Loxham, Susan J G; Poucher, Simon M; Constantin-Teodosiu, Dumitru; Greenhaff, Paul L

2002-01-01

425

Furry promotes acetylation of microtubules in the mitotic spindle by inhibition of SIRT2 tubulin deacetylase.  

PubMed

The structure and function of microtubules (MTs) are regulated by post-translational modifications of tubulin subunits, such as acetylation of the Lys40 residue of ?-tubulin. Regulation of the organization and dynamics of MTs is essential for the precise formation of the mitotic spindle. Spindle MTs are highly acetylated, but the mechanism regulating this acetylation is largely unknown. Furry (Fry) is an evolutionarily conserved protein that binds to MTs and colocalizes with acetylated MTs in the mitotic spindle. In this study, we examined the role of Fry in the acetylation of MTs in the mitotic spindle. Depletion of Fry significantly reduced the level of MT acetylation in the mitotic spindle. Expression of the N-terminal fragment of Fry induced hyperacetylation of MTs in both mitotic and interphase cells. These results indicate that Fry promotes MT acetylation in the mitotic spindle. We also found that Fry binds to the tubulin deacetylase SIRT2, preferentially in mitotic cells. Cell-free experiments revealed that the N-terminal region of Fry is the domain responsible for binding to and inhibiting the tubulin-deacetylase activity of SIRT2. AGK2, a specific inhibitor of SIRT2, increased the level of MT acetylation in the mitotic spindle, indicating that SIRT2 is involved in the deacetylation of spindle MTs. Furthermore, AGK2 reversed the decrease in MT acetylation induced by Fry depletion. In summary, these results suggest that Fry plays a crucial role in promoting the level of MT acetylation in the mitotic spindle by inhibiting the tubulin-deacetylase activity of SIRT2. PMID:23886946

Nagai, Tomoaki; Ikeda, Masanori; Chiba, Shuhei; Kanno, Shin-Ichiro; Mizuno, Kensaku

2013-10-01

426

Acetylation of the Response Regulator RcsB Controls Transcription from a Small RNA Promoter  

PubMed Central

N?-lysine acetylation was recently discovered on many bacterial proteins that function in diverse cellular processes. Thus, many questions remain unanswered. For example, what mechanisms regulate lysine acetylation? Does acetylation affect physiology? To help answer these questions, we studied the Escherichia coli response regulator and transcription factor RcsB, which is reported to be acetylated in vitro. To characterize RcsB acetylation, we monitored transcription from the rprA promoter, which requires RcsB. The conventional view is that RcsB is activated by phosphorylation through either the Rcs phosphorelay or acetyl phosphate. We affirmed that rprA transcription requires phosphorylated RcsB and showed that acetyl-phosphate (AcP) is a phosphoryl group donor to RcsB. However, a mutant that accumulates AcP (ackA) exhibited a reduction in rprA transcription instead of the predicted increase. rprA transcription also diminished in the cobB mutant, which lacks the only known E. coli protein deacetylase. This suggests the existence of an inhibitory mechanism that involves lysine acetylation, a supposition supported by the observation that RcsB isolated from the ackA or cobB mutant was hyperacetylated. Finally, we used a genetic approach to identify an AckA- and CobB-sensitive lysine (Lys-154) that controls RcsB activity. We propose that acetylation inhibits RcsB activity and that some of this inhibition acts through the acetylation of Lys-154. PMID:23852870

Hu, Linda I.; Chi, Bui Khanh; Kuhn, Misty L.; Filippova, Ekaterina V.; Walker-Peddakotla, Arti J.; Bäsell, Katrin; Becher, Dörte; Anderson, Wayne F.; Antelmann, Haike

2013-01-01

427

Mechanism of the lysosomal membrane enzyme acetyl coenzyme A: alpha-glucosaminide N-acetyltransferase  

SciTech Connect

Acetyl-CoA:..cap alpha..-glucosaminide N-acetyltransferase is a lysosomal membrane enzyme, deficient in the genetic disease Sanfilippo C syndrome. The enzyme catalyzes the transfer of an acetyl group from cytoplasmic acetyl-CoA to terminal ..cap alpha..-glucosamine residues of heparan sulfate within the organelle. The reaction mechanism was examined using high purified lysosomal membranes from rat liver and human fibroblasts. The N-acetyltransferase reaction is optimal above pH 5.5 and a 2-3 fold stimulation of activity is observed in the presence of 0.1% taurodeoxycholate. Double reciprocal analysis and product inhibition studies indicate that the enzyme works by a Di-Iso Ping Pong Bi Bi mechanism. The binding of acetyl-CoA to the enzyme is measured by exchange label from (/sup 3/H)CoA to acetyl-CoA, and is optimal at pH's above 7.0. The acetyl-enzyme intermediate is formed by incubating membranes with (/sup 3/H)acetyl-CoA. The acetyl group can be transferred to glucosamine, forming (/sup 3/H)N-acetylglucosamine; the transfer is optimal between pH 4 and 5. Lysosomal membranes from Sanfilippo C fibroblasts confirm that these half reactions carried out by the N-acetyltransferase. The enzyme is inactivated by N-bromosuccinimide and diethylpyrocarbonate, indicating that a histidine is involved in the reaction. These results suggest that the histidine residue is at the active site of the enzyme. The properties of the N-acetyltransferase in the membrane, the characterization of the enzyme kinetics, the chemistry of a histidine mediated acetylation and the pH difference across the lysosomal membrane all support a transmembrane acetylation mechanism.

Bame, K.J.

1986-01-01

428

Hydrolysis of the energetic materials present in a composite modified double base solid rocket propellant  

Microsoft Academic Search

The aqueous hydrolysis of the nitroglycerin (NG), nitrocellulose (NC), and HMX present in CYH, a composite modified double base solid propellant, was successfully performed using either sodium hydroxide (NaOH) or ammonia (NH3) as hydrolyzing agents. The rate of hydrolysis was faster for NaOH compared to NH3. For both hydrolysis agents the rate of hydrolysis of NG was the fastest, followed

Louis F. Cannizzo; Glenn L. Mower; Lewis R. Hunstman; Walter R. Achatz; W. Wayne Edwards

1995-01-01

429

Enzymatic hydrolysis of cellulose materials treated with ionic liquid [BMIM] Cl  

Microsoft Academic Search

A new cellulose solvent ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was used to treat wheat straw and steam-exploded\\u000a wheat straw (SEWS) in order to improve the enzymatic hydrolysis rates, while the water was used as the control. The enzymatic\\u000a hydrolysis results showed that the hydrolysis rates of materials treated with [BMIM]Cl were improved. The hydrolysis rate\\u000a of treated wheat straw could

Liying Liu; Hongzhang Chen

2006-01-01

430

40 CFR 180.1089 - Poly-N-acetyl-D-glucosamine; exemption from the requirement of tolerance.  

...2014-07-01 false Poly-N-acetyl-D-glucosamine; exemption from the requirement of...1089 Poly-N -acetyl-D -glucosamine; exemption from the requirement of...nematicide poly-N -acetyl-D -glucosamine on a variety of agricultural...

2014-07-01

431

40 CFR 180.1089 - Poly-N-acetyl-D-glucosamine; exemption from the requirement of tolerance.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Poly-N-acetyl-D-glucosamine; exemption from the requirement of...1089 Poly-N -acetyl-D -glucosamine; exemption from the requirement of...nematicide poly-N -acetyl-D -glucosamine on a variety of agricultural...

2013-07-01

432

40 CFR 180.1089 - Poly-N-acetyl-D-glucosamine; exemption from the requirement of tolerance.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Poly-N-acetyl-D-glucosamine; exemption from the requirement of...1089 Poly-N -acetyl-D -glucosamine; exemption from the requirement of...nematicide poly-N -acetyl-D -glucosamine on a variety of agricultural...

2011-07-01

433

40 CFR 180.1089 - Poly-N-acetyl-D-glucosamine; exemption from the requirement of tolerance.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Poly-N-acetyl-D-glucosamine; exemption from the requirement of...1089 Poly-N -acetyl-D -glucosamine; exemption from the requirement of...nematicide poly-N -acetyl-D -glucosamine on a variety of agricultural...

2012-07-01

434

40 CFR 180.1089 - Poly-N-acetyl-D-glucosamine; exemption from the requirement of tolerance.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Poly-N-acetyl-D-glucosamine; exemption from the requirement of...1089 Poly-N -acetyl-D -glucosamine; exemption from the requirement of...nematicide poly-N -acetyl-D -glucosamine on a variety of agricultural...

2010-07-01

435

Structures of Bacillus subtilis PdaA, a family 4 carbohydrate esterase, and a complex with N-acetyl-glucosamine  

E-print Network

Structures of Bacillus subtilis PdaA, a family 4 carbohydrate esterase, and a complex with N-acetyl-glucosamine. A complex with the substrate analogue N-acetyl-glucosamine was refined to 2.25 A resolution, revealing by Elsevier B.V. All rights reserved. Keywords: Family 4 carbohydrate esterase; PdaA; N-Acetyl-glucosamine

van Aalten, Daan

436

Extensive lysine acetylation occurs in evolutionarily conserved metabolic pathways and parasite-specific functions during Plasmodium falciparum intraerythrocytic development  

PubMed Central

Summary Lysine acetylation has emerged as a major posttranslational modification involved in diverse cellular functions. Using a combination of immunoisolation and liquid chromatography coupled to accurate mass spectrometry, we determined the first acetylome of the human malaria parasite Plasmodium falciparum during its active proliferation in erythrocytes with 421 acetylation sites identified in 230 proteins. Lysine-acetylated proteins are distributed in the nucleus, cytoplasm, mitochondrion, and apicoplast. Whereas occurrence of lysine acetylation in a similarly wide range of cellular functions suggests conservation of lysine acetylation through evolution, the Plasmodium acetylome also revealed significant divergence from those of other eukaryotes and even the closely-related parasite Toxoplasma. This divergence is reflected in the acetylation of a large number of Plasmodium-specific proteins and different acetylation sites in evolutionarily conserved acetylated proteins. A prominent example is the abundant acetylation of proteins in the glycolysis pathway but relatively deficient acetylation of enzymes in the citrate cycle. Using specific transgenic lines and inhibitors, we determined that the acetyltransferase PfMYST and lysine deacetylases play important roles in regulating the dynamics of cytoplasmic protein acetylation. The Plasmodium acetylome provides an exciting start point for further exploration of functions of acetylation in the biology of malaria parasites. PMID:23796209

Miao, Jun; Lawrence, Matthew; Jeffers, Victoria; Zhao, Fangqing; Parker, Daniel; Ge, Ying; Sullivan, William J.; Cui, Liwang

2013-01-01

437

MATHEMATICAL MODELING OF ENZYMATIC HYDROLYSIS OF STARCH: APPLICATION TO FUEL ETHANOL PRODUCTION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Enzymatic hydrolysis of starch in corn is an important step that determines fermentation efficiency. Corn genetics, post harvest handling and process conditions are factors that affect starch hydrolysis. There is a lack of mathematical models for starch hydrolysis in the dry grind corn process tha...

438

A new class of inhibitors of 2-arachidonoylglycerol hydrolysis and invasion of prostate cancer cells q  

E-print Network

A new class of inhibitors of 2-arachidonoylglycerol hydrolysis and invasion of prostate cancer-independent prostate cancer cells. Blocking cellular hydrolysis of 2-AG to increase its endogenous concentration to inhibit 2-AG hydrolysis and prostate cancer cell invasion. Compounds containing a thioether b to a TFK

Hammock, Bruce D.

439

An Overview of Chemical Processes That Damage Cellular DNA: Spontaneous Hydrolysis, Alkylation, and Reactions with Radicals  

E-print Network

ReViews An Overview of Chemical Processes That Damage Cellular DNA: Spontaneous Hydrolysis damage under physiological conditions. Contents 1. Introduction 1747 2. Hydrolysis of DNA 1747 2.1. Spontaneous Hydrolysis of the Phosphodiester Backbone Is Very Slow 1747 2.2. Hydrolytic Deamination of DNA

Gates, Kent. S.

440

Changes in the Enzymatic Hydrolysis Rate of Avicel Cellulose With Conversion  

E-print Network

hydrolysis. Then, the solids were treated with proteinase to degrade the cellulase enzymes remaining with water, 1.0 M NaCl solution, and water. Next, fresh cellulase and buffer were added to the solids. Keywords: cellulase; cellulose; enzymatic hydrolysis; restarted hydrolysis; substrate reactivity

California at Riverside, University of

441

Toward an aggregated understanding of enzymatic hydrolysis of cellulose: Noncomplexed cellulase systems  

Microsoft Academic Search

Information pertaining to enzymatic hydrolysis of cellulose by noncomplexed cellulase enzyme systems is reviewed with a particular emphasis on development of aggregated understanding incorporating substrate features in addition to concentration and multiple cellulase compo- nents. Topics considered include properties of cellulose, adsorption, cellulose hydrolysis, and quantitative models. A classification scheme is proposed for quantitative models for enzymatic hydrolysis of cellulose

Yi-Heng Percival Zhang; Lee R. Lynd

2004-01-01

442

Organized Unidirectional Waves of ATP Hydrolysis within a RecA Filament  

E-print Network

Organized Unidirectional Waves of ATP Hydrolysis within a RecA Filament Julia M. Cox, Oleg V on opposite filament ends, with disassembly requiring ATP hydrolysis. When filaments form on duplex DNA, Rec. RecA filament state was monitored with a coupled spectrophotometric assay for ATP hydrolysis

Cox, Michael M.

443

Enzymatic Hydrolysis of Cellulose Coupled With Electricity Generation in a Microbial Fuel Cell  

E-print Network

ARTICLE Enzymatic Hydrolysis of Cellulose Coupled With Electricity Generation in a Microbial Fuel hydrolysis rates of the particles. Cellulases are used to achieve rapid conversion of cellulose to sugar%, likely as a result of rapid hydrolysis of cellulose in the reactor and biodegradation of the enzyme

444

Effects of Hydrolysis on Force Generation by Actin Filaments A. E. Carlsson  

E-print Network

Effects of Hydrolysis on Force Generation by Actin Filaments A. E. Carlsson Department of