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1

Regulation of the structure and activity of pyruvate carboxylase by acetyl CoA  

PubMed Central

In this review we examine the effects of the allosteric activator, acetyl CoA on both the structure and catalytic activities of pyruvate carboxylase. We describe how the binding of acetyl CoA produces gross changes to the quaternary and tertiary structures of the enzyme that are visible in the electron microscope. These changes serve to stabilize the tetrameric structure of the enzyme. The main locus of activation of the enzyme by acetyl CoA is the biotin carboxylation domain of the enzyme where ATP-cleavage and carboxylation of the biotin prosthetic group occur. As well as enhancing reaction rates, acetyl CoA also enhances the binding of some substrates, especially HCO3?, and there is also a complex interaction with the binding of the cofactor Mg2+. The activation of pyruvate carboxylase by acetyl CoA is generally a cooperative processes, although there is a large degree of variability in the degree of cooperativity exhibited by the enzyme from different organisms. The X-ray crystallographic holoenzyme structures of pyruvate carboxylases from Rhizobium etli and Staphylococcus aureus have shown the allosteric acetyl CoA binding domain to be located at the interfaces of the biotin carboxylation and carboxyl transfer and the carboxyl transfer and biotin carboxyl carrier protein domains.

Adina-Zada, Abdussalam; Zeczycki, Tonya N.; Attwood, Paul V.

2011-01-01

2

Expression of a yeast acetyl CoA hydrolase in the mitochondrion  

Microsoft Academic Search

Acetyl Coenzyme A (acetyl CoA) is required in the mitochondria to fuel the operation of the Krebs cycle and within the cytosolic, peroxisomal and plastidial compartments wherein it acts as the immediate precursor for a wide range of anabolic functions. Since this metabolite is impermeable to membranes it follows that discrete pathways both for its synthesis and for its utilization

Lilia Bender-machado; Michael Bäuerlein; Fernando Carrari; Nicolas Schauer; Anna Lytovchenko; Yves Gibon; Amelie kelly; Marcello loureiro; Bernd Müller-röber; lothar willmitzer; Alisdair fernie

2004-01-01

3

The capacity of plastids from developing pea cotyledons to synthesise acetyl CoA  

Microsoft Academic Search

In order to determine whether the enzymes required to convert triose phosphate to acetyl CoA were present in pea (Pisum sativum L.) seed plastids, a rapid, mechanical technique was used to isolate plastids from developing cotyledons. The plastids were intact and the extraplastidial contamination was low. The following glycolytic enzymes, though predominantly cytosolic, were found to be present in plastids:

Kay Denyer; Alison M. Smith

1988-01-01

4

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.

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

2010-01-01

5

Differential regulation of the yeast isozymes of pyruvate carboxylase and the locus of action of acetyl CoA.  

PubMed

Unlike other eukaryotes studied to date, yeast has two genes for pyruvate carboxylase coding for very similar, but not identical, isozymes (Pyc1 and Pyc2), both of which are located in the cytoplasm. We have found that there are marked differences in the kinetic properties of the isozymes potentially leading to differential regulation of Pyc1 and Pyc2 activity by both activators and substrates. For example, Pyc2 is only activated 3.7-fold by acetyl CoA, and 9.6-fold by NH(4)(+), whilst the figures for Pyc1 are 16 and 14.6-fold, respectively. Pyc1 and Pyc2 display different allosteric properties with respect to acetyl CoA activation and aspartate inhibition, with Pyc1 showing a higher degree of cooperativity than Pyc2, even in the absence of aspartate. We have investigated the locus of action in the amino acid sequence of the isozymes of this activator by measuring its regulation of various chimeric constructs of the two isozymes. In this way, we conclude that the main locus of action of acetyl CoA lies in the N-terminal half of the enzyme, within the biotin-carboxylation domain, between amino acids 99 and 478 of Pyc1. PMID:17478118

Jitrapakdee, Sarawut; Adina-Zada, Abdussalam; Besant, Paul G; Surinya, Kathy H; Cleland, W Wallace; Wallace, John C; Attwood, Paul V

2007-03-30

6

Enzymatic Carboxylation of Biotin: Molecular and Catalytic Properties of a Component Enzyme of Acetyl CoA Carboxylase*  

PubMed Central

The biotin carboxylase component of acetyl CoA carboxylase has been purified approximately 2000 times from Escherichia coli. This protein, which catalyzes the carboxylation of free d-biotin, is free of the biotin-containing carboxyl carrier protein, is homogeneous by polyacrylamide gel electrophoresis and analytical ultracentrifugation, and has been crystallized. Biotin carboxylase, with a molecular weight of approximately 100,000, is composed of two 50,000-dalton subunits. The catalytic capacity of biotin carboxylase is markedly enhanced by ethanol (11 times at 15% v/v), and certain other organic solvents; this may mimic an effector-mediated response. The kinetic effect is exclusively on the maximal velocity of the reaction. Activation by ethanol is reversible and not accompanied by aggregation or disaggregation of the enzyme. Images

Dimroth, Peter; Guchhait, Ras B.; Stoll, Erwin; Lane, M. Daniel

1970-01-01

7

The roles of Arg427 and Arg472 in the binding and allosteric effects of acetyl CoA in pyruvate carboxylase  

PubMed Central

Mutation of Arg427 and Arg472 in Rhizobium etli pyruvate carboxylase to serine or lysine greatly increased the activation constant (Ka) of acetyl CoA, with the increase being greater for the Arg472 mutants. These results indicate that while both these residues are involved in the binding of acetyl CoA to the enzyme, Arg472 is more important than Arg427. The mutations had substantially smaller effects on the kcat for pyruvate carboxylation. Part of the effects of the mutations was to increase the Km for MgATP and the Ka for activation by free Mg2+ determined at saturating acetyl CoA concentrations. The inhibitory effects of the mutations on the rates of the enzyme-catalysed bicarbonate-dependent ATP cleavage, carboxylation of biotin and phosphorylation of ADP by carbamoyl phosphate indicate that the major locus of the effects of the mutations was in the biotin carboxylase (BC) domain active site. Even though both Arg427 and Arg472 are distant from the BC domain active site, it is proposed that their contacts with other residues in the allosteric domain, either directly or through acetyl CoA, affect the positioning and orientation of the biotin-carboxyl carrier protein (BCCP) domain and thus the binding of biotin at the BC domain active site. Based on the kinetic analysis proposed here it is proposed that mutations of Arg427 and Arg472 perturb these contacts and consequently the binding of biotin at the BC domain active site. Inhibition of pyruvate carboxylation by the allosteric inhibitor, L-aspartate, was largely unaffected by the mutation of either Arg427 or Arg472.

Adina-Zada, Abdussalam; Sereeruk, Chutima; Jitrapakdee, Sarawut; Zeczycki, Tonya N.; St. Maurice, Martin; Cleland, W. Wallace; Wallace, John C.; Attwood, Paul V.

2012-01-01

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

Probing the allosteric activation of pyruvate carboxylase using 2?,3?-O-(2,4,6-trinitrophenyl) adenosine 5?-triphosphate as a fluorescent mimic of the allosteric activator acetyl CoA  

PubMed Central

2?,3?-O-(2,4,6-Trinitrophenyl) adenosine 5?-triphosphate (TNP-ATP) is a fluorescent analogue of ATP. MgTNP-ATP was found to be an allosteric activator of pyruvate carboxylase that exhibits competition with acetyl CoA in activating the enzyme. There is no evidence that MgTNP-ATP binds to the MgATP substrate binding site of the enzyme. At concentrations above saturating, MgATP activates bicarbonate-dependent ATP cleavage, but inhibits the overall reaction. The fluorescence of MgTNP-ATP increases by about 2.5 fold upon binding to the enzyme and decreases on addition of saturating acetyl CoA. However, not all the MgTNP-ATP is displaced by acetyl CoA, or with a combination of saturating concentrations of MgATP and acetyl CoA. The kinetics of the binding of MgTNP-ATP to pyruvate carboxylase have been measured and shown to be triphasic, with the two fastest phases having pseudo first-order rate constants that are dependent on the concentration of MgTNP-ATP. The kinetics of displacement from the enzyme by acetyl CoA have been measured and also shown to be triphasic. A model of the binding process is proposed that links the kinetics of MgTNP-ATP binding to the allosteric activation of the enzyme.

Adina-Zada, Abdussalam; Hazra, Rasmani; Sereeruk, Chutima; Jitrapakdee, Sarawut; Zeczycki, Tonya N.; Maurice, Martin St.; Cleland, W.Wallace; Wallace, John C.; Attwood, Paul V.

2011-01-01

10

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

11

Cardiac-specific deletion of acetyl CoA carboxylase 2 (ACC2) prevents metabolic remodeling during pressure-overload hypertrophy  

PubMed Central

Rationale Decreased fatty acid oxidation (FAO) with increased reliance on glucose are hallmarks of metabolic remodeling that occurs in pathological cardiac hypertrophy and is associated with decreased myocardial energetics and impaired cardiac function. To date, it has not been tested whether prevention of the metabolic switch that occurs during the development of cardiac hypertrophy has unequivocal benefits on cardiac function and energetics. Objectives Since malonyl CoA production via acetyl CoA carboxylase 2 (ACC2) inhibits mitochondrial fatty acid transport, we hypothesized that mice with a cardiac-specific deletion of ACC2 (ACC2H?/?) would maintain cardiac fatty acid oxidation (FAO) and improve function and energetics during the development of pressure-overload hypertrophy. Methods and Results ACC2 deletion led to a significant reduction in cardiac malonyl CoA levels. In isolated perfused heart experiments, left ventricular (LV) function and oxygen consumption were similiar in ACC2H?/? mice despite an ~60% increase in FAO compared to controls (CON). After 8 weeks of pressure-overload via transverse aortic constriction (TAC), ACC2H?/? mice exhibited a substrate utilization profile similar to sham animals while CON-TAC hearts had decreased FAO with increased glycolysis and anaplerosis. Myocardial energetics, assessed by 31P NMR spectroscopy, and cardiac function were maintained in ACC2H?/? after 8 weeks of TAC. Furthermore, ACC2H?/?-TAC demonstrated an attenuation of cardiac hypertrophy with a significant reduction in fibrosis relative to CON-TAC. Conclusions These data suggest that reversion to the fetal metabolic profile in chronic pathological hypertrophy is associated with impaired myocardial function and energetics and maintenance of the inherent cardiac metabolic profile and mitochondrial oxidative capacity is a viable therapeutic strategy.

Kolwicz, Stephen C.; Olson, David P.; Marney, Luke C.; Garcia-Menendez, Lorena; Synovec, Robert E.; Tian, Rong

2012-01-01

12

Stimulation of fat oxidation, but no sustained reduction of hepatic lipids by prolonged pharmacological inhibition of acetyl CoA carboxylase.  

PubMed

Acetyl CoA carboxylase isoforms 1 and 2 (ACC1/2) are key enzymes of fat metabolism and their inhibition has been postulated to be beneficial for the treatment of the metabolic syndrome by decreasing ectopic fat accumulation. In order to validate this approach pharmacologically, we characterized the chronic effect of the small molecule ACC1/2 inhibitor SAR210 in 2 rodent models of fatty liver. Chronic administration of SAR210 increased serum ketone levels in both diet-induced obese mice and female ZDF rats. The inhibitor neither reduced hepatic triglycerides nor influenced body weight in either diet-induced obese mice or female ZDF rats. Thus, chronic pharmacological inhibition of ACC1/2 stimulated fat oxidation, which was, however, not sufficient to reduce hepatic triglycerides. PMID:21823054

Glien, M; Haschke, G; Schroeter, K; Pfenninger, A; Zoller, G; Keil, S; Müller, M; Herling, A W; Schmoll, D

2011-08-05

13

The role of acetyl xylan esterase in the solubilization of xylan and enzymatic hydrolysis of wheat straw and giant reed  

PubMed Central

Background Due to the complexity of lignocellulosic materials, a complete enzymatic hydrolysis into fermentable sugars requires a variety of cellulolytic and xylanolytic enzymes. Addition of xylanases has been shown to significantly improve the performance of cellulases and to increase cellulose hydrolysis by solubilizing xylans in lignocellulosic materials. The goal of this work was to investigate the effect of acetyl xylan esterase (AXE) originating from Trichoderma reesei on xylan solubilization and enzymatic hydrolysis of cellulose. Results The solubilization of xylan in pretreated wheat straw and giant reed (Arundo donax) by xylanolytic enzymes and the impact of the sequential or simultaneous solubilization of xylan on the hydrolysis of cellulose by purified enzymes were investigated. The results showed that the removal of acetyl groups in xylan by AXE increased the accessibility of xylan to xylanase and improved the hydrolysis of xylan in pretreated wheat straw and giant reed. Solubilization of xylan led to an increased accessibility of cellulose to cellulases and thereby increased the hydrolysis extent of cellulose. A clear synergistic effect between cellulases and xylanolytic enzymes was observed. The highest hydrolysis yield of cellulose was obtained with a simultaneous use of cellulases, xylanase and AXE, indicating the presence of acetylated xylan within the cellulose matrix. Acetylated xylobiose and acetylated xylotriose were produced from xylan without AXE, as confirmed by atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry. Conclusions The results in this paper demonstrate that supplementation of xylanase with AXE enhances the solubilization of xylan to some extent and, consequently, increases the subsequent hydrolysis of cellulose. The highest hydrolysis yield was, however, obtained by simultaneous hydrolysis of xylan and cellulose, indicating a layered structure of cellulose and xylan chains in the cell wall substrate. AXE has an important role in the hydrolysis of lignocellulosic materials containing acetylated xylan.

2011-01-01

14

SpxB regulates O-acetylation-dependent resistance of Lactococcus lactis peptidoglycan to hydrolysis.  

PubMed

Endogenous peptidoglycan (PG)-hydrolyzing enzymes, the autolysins, are needed to relax the rigid PG sacculus to allow bacterial cell growth and separation. PGs of pathogens and commensal bacteria may also be degraded by hydrolases of animal origin (lysozymes), which act as antimicrobials. The genetic mechanisms regulating PG resistance to hydrolytic degradation were dissected in the Gram-positive bacterium Lactococcus lactis. We found that the ability of L. lactis to counteract PG hydrolysis depends on the degree of acetylation. Overexpression of PG O-acetylase (encoded by oatA) led to bacterial growth arrest, indicating the potential lethality of oatA and a need for its tight regulation. A novel regulatory factor, SpxB (previously denoted as YneH), exerted a positive effect on oatA expression. Our results indicate that SpxB binding to RNA polymerase constitutes a previously missing link in the multistep response to cell envelope stress, provoked by PG hydrolysis with lysozyme. We suggest that the two-component system CesSR responds to this stress by inducing SpxB, thus favoring its interactions with RNA polymerase. Induction of PG O-acetylation by this cascade renders it resistant to hydrolysis. PMID:17485463

Veiga, Patrick; Bulbarela-Sampieri, Carmen; Furlan, Sylviane; Maisons, Aurélie; Chapot-Chartier, Marie-Pierre; Erkelenz, Michael; Mervelet, Peggy; Noirot, Philippe; Frees, Dorte; Kuipers, Oscar P; Kok, Jan; Gruss, Alexandra; Buist, Girbe; Kulakauskas, Saulius

2007-05-07

15

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

2013-05-02

16

[3H]Indole-3-acetyl-myo-inositol hydrolysis by extracts of Zea mays L. vegetative tissue.  

PubMed

[3H]Indole-3-acetyl-myo-inositol was hydrolyzed by buffered extracts of acetone powders prepared from 4 day shoots of dark grown Zea mays L. seedlings. The hydrolytic activity was proportional to the amount of extract added and was linear for up to 6 hours at 37 degrees C. Boiled or alcohol denatured extracts were inactive. Analysis of reaction mixtures by high performance liquid chromatography demonstrated that not all isomers of indole-3-acetyl-myo-inositol were hydrolyzed at the same rate. Buffered extracts of acetone powders were prepared from coleoptiles and mesocotyls. The rates of hydrolysis observed with coleoptile extracts were greater than those observed with mesocotyl extracts. Active extracts also catalyzed the hydrolysis of esterase substrates such as alpha-naphthyl acetate and the methyl esters of indoleacetic acid and naphthyleneacetic acid. Attempts to purify the indole-3-acetyl-myo-inositol hydrolyzing activity by chromatographic procedures resulted in only slight purification with large losses of activity. Chromatography over hydroxylapatite allowed separation of two enzymically active fractions, one of which catalyzed the hydrolysis of both indole-3-acetyl-myo-inositol and esterase substrates. With the other enzymic hydrolysis of esterase substrates was readily demonstrated, but no hydrolysis of indole-3-acetyl-myo-inositol was ever detected. PMID:11539037

Hall, P J; Bandurski, R S

1986-01-01

17

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.

Neuberger, A.; Ratcliffe, Wendy A.

1972-01-01

18

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

PubMed

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

2013-09-11

19

Physicochemical properties of cross-linked and acetylated starches and products of their hydrolysis in continuous recycle membrane reactor.  

PubMed

The aim of the present work was to study the physicochemical properties of doubly modified, by cross-linking and acetylating, starches as well as the products of their enzymatic hydrolysis. A two step procedure of hydrolysis, including the batch and membrane reactors, were investigated. The second step of enzymatic processes were carried out in a continuous recycle membrane reactor (CRMR). Three kinds of commercial starches--two preparations of acetylated distarch adipate E1422 of different degrees of cross-linking, as well as one preparation of acetylated distarch phosphate E1414 were examined. It was found that the degree of substitution of acetyl groups in the macromolecules of starch did not influence the effectiveness of hydrolysis. However, the degree of cross-linking with adipate groups slightly decreased the efficiency of processing in the CRMR. Additionally, the relationship between the type of hydrocolloid and its adsorption activity in the air/water and oil/water systems was considered. All obtained derivatives revealed adsorption properties and reduced the surface/interface tension in the air/water and oil/water systems. The efficiency and effectiveness of adsorption of the investigated hydrocolloids were affected by the type of modification as well as the degree of substitution of acetyl groups in the macromolecules of starch. Particle size distributions formed in aqueous solutions for all investigated hydrolyses were determined and compared with results obtained for commercial products. PMID:19734024

Prochaska, Krystyna; Konowa?, Emilia; Sulej-Chojnacka, Joanna; Lewandowicz, Grazyna

2009-08-03

20

Reaction pathway and free energy profile for papain-catalyzed hydrolysis of N-acetyl-Phe-Gly 4-nitroanilide.  

PubMed

Possible reaction pathways for papain-catalyzed hydrolysis of N-acetyl-Phe-Gly 4-nitroanilide (APGNA) have been studied by performing pseudobond first-principles quantum mechanical/molecular mechanical-free energy (QM/MM-FE) calculations. The whole hydrolysis process includes two stages: acylation and deacylation. For the acylation stage of the catalytic reaction, we have explored three possible paths (A, B, and C) and the corresponding free energy profiles along the reaction coordinates. It has been demonstrated that the most favorable reaction path in this stage is path B consisting of two reaction steps: the first step is a proton transfer to form a zwitterionic form (i.e., Cys-S?/His-H? ion-pair), and the second step is the nucleophilic attack on the carboxyl carbon of the substrate accompanied by the dissociation of 4-nitroanilide. The deacylation stage includes the nucleophilic attack of a water molecule on the carboxyl carbon of the substrate and dissociation between the carboxyl carbon of the substrate and the sulfhydryl sulfur of Cys25 side chain. The free energy barriers calculated for the acylation and deacylation stages are 20.0 and 10.7 kcal/mol, respectively. Thus, the acylation is rate-limiting. The overall free energy barrier calculated for papain-catalyzed hydrolysis of APGNA is 20.0 kcal/mol, which is reasonably close to the experimentally derived activation free energy of 17.9 kcal/mol. PMID:23862626

Wei, Donghui; Huang, Xiaoqin; Liu, Junjun; Tang, Mingsheng; Zhan, Chang-Guo

2013-07-17

21

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 2h, 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; Sárka, Evžen; Kolá?ek, Jaroslav; Netopilík, Miloš; Walterová, Zuzana; Kruliš, Zden?k; Synytsya, Andrey; Hrušková, Kate?ina

2013-05-13

22

COAs: Behind the Masks.  

ERIC Educational Resources Information Center

|Provides information on alcoholism and codependency to help teachers identify and respond to children of alcoholics (COAs). Discusses characteristics of alcoholic homes and problems encountered by children and adult COAs. Examines survival "masks" of COAs, including hero, rebel, adjustor, clown, and caretaker. Lists organizational, print, and…

Birke, Szifra

1993-01-01

23

Increased cardiac fatty acid uptake with dobutamine infusiQn in swine is accompanied by a decrease in malonyl CoA levels  

Microsoft Academic Search

Objetive: Malonyl CoA is an important regulator of fatty acid oxidation in the heart secondary to its ability to inhibit camitine palmitoyltransferase 1 (CFT 1). Malonyl CoA is produced from acetyl CoA in a reaction catalyzed by acetyl CoA carboxylase (ACC). In this study we determined if alterations in malonyl CoA regulation of fatty acid metabolism are involved in the

Jennifer L. Hall; Gary D. Lopaschuk; Amy Barr; John Bringas; Robert D. Pizzurro; William C. Stanley

24

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.

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

2013-01-01

25

Modification of bovine kidney pyruvate dehydrogenase kinase activity by CoA esters and their mechanism of action  

SciTech Connect

The activation of pyruvate dehydrogenasea kinase activity by CoA esters has been further characterized. Half-maximal activation of kinase activity was achieved with about 1.0 microM acetyl-CoA after a 20-s preincubation in the presence of NADH. More than 80% of the acetyl-CoA was consumed during this period in acetylating sites in the pyruvate dehydrogenase complex as a result of the transacetylation reaction proceeding to equilibrium. At 1.0 microM acetyl-CoA, this resulted in more than a 4-fold higher level of CoA than residual acetyl-CoA. Activation of kinase activity could result either from acetylation of specific sites in the complex or tight binding of acetyl-CoA. Removal of CoA enhanced both acetylation and activation, suggesting acetylation mediates activation. For allosteric binding of acetyl-CoA to elicit activation, an activation constant, Ka, less than 50 nM would be required. To further distinguish between those mechanisms, the effects of other CoA esters as well as the reactivity of most of the effective CoA esters were characterized. Several short-chain CoA esters enhanced kinase activity including (in decreasing order of effectiveness) malonyl-CoA, acetoacetyl-CoA, propionyl-CoA, and methylmalonyl-CoA. Butyryl-CoA inhibited kinase activity as did high concentrations of long-chain acyl-CoAs.

Rahmatullah, M.; Roche, T.E.

1985-08-25

26

Stimulation of CoA biosynthesis by P-aminobenzoate and benzoate in cultured rat hepatocytes  

SciTech Connect

The effects of paraminobenzoate (PABA) and benzoate (BA) on CoA metabolism were studied in intact hepatocytes to elucidate the role of CoASH and acetyl-CoA in the regulation of CoA biosynthesis. CoASH and acetyl-CoA inhibit isolated pantothenate kinase, a cytosolic enzyme. PABA is N-acetylated (cytosol), and PABA and BA form acyl-CoA's which add glycine to form hippurates. Primary cultures of rat hepatocytes were incubated 6 h with (/sup 14/C)-pantothenate and radioactivity in CoA determined. PABA and BA stimulated (/sup 14/C)-pantothenate conversion to CoA 13-fold and 6-fold respectively. Glycine reversed stimulation by BA, but only partially reversed that by PABA. PABA decreased the CoASH and acetyl-CoA contents by > 90% and 66%, respectively. These changes were also partially reversed by glycine. In freshly isolated hepatocytes PABA decreased both cytosolic and mitochondrial acetyl-CoA levels. The results suggested that mitochondrial PABA-CoA formation, utilization of acetyl-CoA for PABA acetylation, and activation of pantothenate kinase by decreased cytosolic acetyl-CoA CoASH are involved in stimulation of (/sup 14/C)-pantothenate conversion to CoA by PABA.

Roitman, K.J.; Smith, C.M.

1987-05-01

27

Redox-dependent acetyl transfer partial reaction of the acetyl-CoA decarbonylase/synthase complex: kinetics and mechanism.  

PubMed

Acetyl-CoA decarbonylase/synthase (ACDS) is a multienzyme complex that plays a central role in energy metabolism in Methanosarcina barkeri grown on acetate. The ACDS complex carries out an unusual reaction involving net cleavage of the acetyl C-C and thioester bonds of acetyl-CoA. The overall reaction is composed of several partial reactions, one of which involves catalysis of acetyl group transfer. To gain insight into the overall reaction, a study was carried out on the kinetics and mechanism of the acetyltransferase partial reaction. Analysis by HPLC was used to quantify rates of acetyl transfer from acetyl-CoA both to 3'-dephospho-CoA and, by isotope exchange, to 14C-labeled CoA. Acetyl transfer activity was observed only under strongly reducing conditions, and was half-maximal at -486 mV at pH 6.5. The midpoint activation potential became increasingly more negative as the pH was increased, indicating the involvement of a protonation step. Cooperative dependence on acetyl-CoA concentration was exhibited in reactions that contained incompletely reduced enzyme; however, under redox conditions supporting maximum activity, hyperbolic kinetics were found. A ping-pong steady state kinetic mechanism was established, consistent with formation of an acetyl-enzyme intermediate. Analysis of the inhibitory effects of CoA on acetyl transfer to 3'-dephospho-CoA provided values for KiCoA of 6.8 microM and for Kiacetyl-CoA of 45 microM; isotope exchange analyses yielded values of 32 and 120 microM, respectively. Two separate measures of stability yielded values for the free energy of hydrolysis of the acetyl-enzyme intermediate of -9.6 and -9.3 kcal/mol, an indication of a high-energy bonding interaction in the acetyl-enzyme species. Implications for the mechanism of C-C bond cleavage are discussed. PMID:9772177

Bhaskar, B; DeMoll, E; Grahame, D A

1998-10-13

28

A Multisubunit Acetyl Coenzyme A Carboxylase from Soybean1  

Microsoft Academic Search

A multisubunit form of acetyl coenzyme A (CoA) carboxylase (ACCase) from soybean (Glycine max) was characterized. The en- zyme catalyzes the formation of malonyl CoA from acetyl CoA, a rate-limiting step in fatty acid biosynthesis. The four known com- ponents that constitute plastid ACCase are biotin carboxylase (BC), biotin carboxyl carrier protein (BCCP), and the a- and b-subunits of carboxyltransferase

Sergei Reverdatto; Vadim Beilinson; Niels C. Nielsen

1999-01-01

29

Molecular Cloning, Characterization, and Elicitation of AcetylCoA Carboxylase from Alfalfa  

Microsoft Academic Search

Acetyl-CoA carboxylase [ACCase; acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] catalyzes the ATP-dependent carboxylation of acetyl CoA to produce malonyl CoA. In plants, malonyl CoA is needed for plastid localized fatty acid biosynthesis and for a variety of pathways in the cytoplasm including flavonoid biosynthesis. We have determined the full nucleotide sequence of an ACCase from alfalfa, which appears to represent a

Basil S. Shorrosh; Richard A. Dixon; John B. Ohlrogge

1994-01-01

30

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

31

Modification of bovine kidney pyruvate dehydrogenase kinase activity by CoA esters and their mechanism of action  

Microsoft Academic Search

The activation of pyruvate dehydrogenasea kinase activity by CoA esters has been further characterized. Half-maximal activation of kinase activity was achieved with about 1.0 microM acetyl-CoA after a 20-s preincubation in the presence of NADH. More than 80% of the acetyl-CoA was consumed during this period in acetylating sites in the pyruvate dehydrogenase complex as a result of the transacetylation

M. Rahmatullah; T. E. Roche

1985-01-01

32

Acetyl coenzyme A synthetase catalyzed reactions of coenzyme A with. cap alpha. -. beta. -unsaturated carboxylic acids  

SciTech Connect

..cap alpha..,..beta..-Unsaturated coenzyme A(CoA) thioesters including acrylyl CoA, methacrylyl CoA, and propiolyl CoA were synthesized by catalysis with acetyl CoA synthetase. After isolation from the enzymatic reactions, the products were found to be the result of 1,4 addition of CoASH to the double bond and addition of water to the triple bond of the initial acyl CoA adducts. Structural determinations of these products by /sup 1/H NMR, /sup 13/C NMR, and the chemical reaction leading to their formation are described.

Patel, S.S.; Walt, D.R.

1988-05-01

33

Lipid Acetylation Reactions and the Metabolism of Platelet-Activating Factor  

Microsoft Academic Search

In this review properties of lipid acetyltransferase enzymes are outlined. The three activities of interest are lyso PAF acetyltransferase (acetyl CoA: 1-alkyl-sn-glycero-3-phosphocholine acetyltransferase), AGP acetyltransferase (acetyl CoA: 1-alkyl sn-glycero-3-phosphate acetyltransferase) and a transacetylase activity that can transfer acetyl groups from PAF to lipid acceptors in the formation of 1-alkenyl-2-acetyl-sn-glycero-3-phosphoethanolamine and N-acetyl sphingosine (C2 ceramide). This review focuses on the role

R. Roy Baker

2000-01-01

34

Amidase Activity of Acetyl- and Butylryl-Cholinesterases.  

National Technical Information Service (NTIS)

The report describes the hydrolysis of amides by acetyl- and butyryl-cholinesterases. The structure-activity pattern is quite different from that of the more conventional carboxylic ester substrates. Thus, quaternary amides resist hydrolysis. All of the a...

G. M. Steinberg M. L. Mednick N. C. Thomas

1973-01-01

35

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

PubMed

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 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 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

2013-06-01

36

Synthesis of radiolabeled acetyl-coenzyme A from sodium acetate  

SciTech Connect

The synthesis of high specific radioactivity (/sup 14/C)-acetyl-Coenzyme A from (/sup 14/C)sodium acetate, 2,6-dichlorobenzoic acid, 1,1'-carbonyldiimidazole, and CoA is reported. Starting with 1 mumol of (/sup 14/C)sodium acetate, this method yields pure (/sup 14/C)acetyl-CoA in yields approaching 40%. Chromatography on a reversed-phase ODS column was used to separate acetyl-CoA from Coenzyme A and side products. The acetylating agent is apparently a reaction intermediate, acetylimidazole.

Clough, R.C.; Barnum, S.R.; Jaworski, J.G.

1989-01-01

37

Exploration of possible mechanisms for 4-chlorobenzoyl CoA dehalogenase: Evidence for an aryl-enzyme intermediate  

SciTech Connect

4-chlorobenzoyl CoA dehalogenase catalyzes the replacement of the chlorine substituent on 4-chlorobenzoyl CoA with a hydroxyl group. We have explored alternative mechanisms for the enzymic dehalogenation reaction. The dehalogenation reaction appears to occur via an S{sub N}Ar mechanism. Further investigations suggested that the reaction proceeds by displacement of chloride by an enzymic carboxylate, followed by hydrolysis of an aryl-enzyme intermediate. When an alternative nucleophile hydroxylamine was included in reaction mixtures, no product derived from direct attack of hydroxylamine upon 4-chlorobenzoyl CoA could be detected. However inclusion of higher concentrations of hydroxylamine (100 mM) resulted in inactivation of the enzyme. These data are consistent with the formation of an aryl-enzyme intermediate that is converted to a hydroxamic acid upon attack by hydroxylamine. 26 refs., 2 figs., 2 tabs.

Crooks, G.P.; Xu, L.; Barkley, R.M.; Copley, S.D. [Univ. of Colorado, Boulder, CO (United States)

1995-11-08

38

Acetyl Coenzyme A-Glutamate Acetyltransferase and N2-Acetylornithine-Glutamate Acetyltransferase of Chlorella  

PubMed Central

The enzymic formation of acetylglutamate has been studied in Chlorella vulgaris extracts. Acetyl CoA and N2-acetyl-l-ornithine served as substrates for glutamate acetylation whereas acetylphosphate, N5-acetyl-l-ornithine, and N2-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. Images

Morris, Clayton J.; Thompson, John F.

1975-01-01

39

Inhibition of neutral lipase from castor bean lipid bodies by coenzyme A (CoA) and Oleoyl-CoA  

SciTech Connect

The neutral lipase (EC 3.1.1.3) in lipid body membranes isolated from the endosperm of 4 day old castor (Ricinus communis L.) seedlings catalyzes the hydrolysis of ({sup 14}C)trioleoylglycerol, releasing ({sup 14}C)oleic acid for up to 4 hours. However, the addition of Mg-ATP and coenzyme A (CoA), which are present in the cytoplasm of plant cells, caused a progressive inhibition of the neutral lipase such that after 15 minutes, release of ({sup 14}C)oleic acid was almost undetectable. A fatty acyl CoA synthetase was found in the lipid body membrane which converts ({sup 14}C)oleic acid produced from the lipase reaction to ({sup 14}C)oleoyl-CoA under these conditions. The concentration of free oleoyl-CoA in the reaction mixture when the lipase was inhibited by 50% was calculated to be about 21 micromolar. It was found that a mixture of exogenously added oleoyl-CoA and CoA was most effective in causing lipase inhibition. Little inhibition of lipase was detected in the presence of CoA alone. It is possible that this effect is important in vivo in coordinating lipase activity with fatty acid oxidation.

Not Available

1989-03-01

40

Biotinoyl domain of human acetylCoA carboxylase: Structural insights into the carboxyl transfer mechanism  

Microsoft Academic Search

Acetyl-CoA carboxylase (ACC) catalyzes the first step in fatty acid biosynthesis: the synthesis of malonyl-CoA from acetyl- CoA. As essential regulators of fatty acid biosynthesis and metabolism, ACCs are regarded as therapeutic targets for the treatment of metabolic diseases such as obesity. In ACC, the biotinoyl domain performs a critical function by transferring an activated carboxyl group from the biotin

Chung-Kyung Lee; Hae-Kap Cheong; Kyoung-Seok Ryu; Jae Il Lee; Weontae Lee; Young Ho Jeon; Chaejoon Cheong

2008-01-01

41

Acetyl coenzyme A carboxylase in species of Triticum of different ploidy  

Microsoft Academic Search

The cellular amounts and cellular activities of acetyl CoA carboxylase (ACC; EC 6.4.1.2.) were determined in the first leaves of diploid, tetraploid and hexaploid species of Triticum (wheat). Per leaf the ACC activities were very similar in T. monococcum (2 ?), T. dicoccum (4 ?) and T. aestivum (6 ?). The ACC activity per chloroplast also showed little variation between

J. C. Hawke; R. M. Leech

1990-01-01

42

Investigation of the photo-oxidative chemistry of acetylated softwood lignin  

Microsoft Academic Search

Lignin was isolated from a spruce bleached chemithermomechanical pulp (BCTMP) with a mild acid hydrolysis and acetylated. Nonacetylated and acetylated lignins were impregnated onto cellulosic testsheets and photolyzed by two different light sources. Optical reflective studies indicated that the irradiated lignin underwent a two-phase photodiscoloration process with the acetylated lignin exhibiting reduced color formation. To examine the chemical processes initiated

Yunqiao Pu; Sean Anderson; Lucian Lucia; Arthur J. Ragauskas

2004-01-01

43

Self-Assembled CoAs Nanostructures  

SciTech Connect

At low coverages, the codeposition of Co and As on the GaAs(100)c(4×4) surface results in the formation of two different types of self-assembled nanostructures; one has a "mesa" configuration, and the other a large aspect ratio "nanostripe" configuration. Minimum-energy calculations have been performed on several possible surface reconstructions for the latter configuration. The favored structure has a rather small unit that repeats essentially endlessly along the [10] direction. This unit contains one Co atom substituted between adjacent c(4×4) As dimers that straddle a misfit dislocation in the two-dimensional c(4×4) lattice. The distorted octahedral bonding around these Co atoms is completed by the addition of three As atoms to the repeat unit. A dip or a valley is formed on each side of the nanostripe by removing As atoms from the substrate. This valley partially relieves the compressive strain along the [110] direction across the nanostripes, and it helps to insure that each Co atom is surrounded by the requisite 18 valence electrons. The detailed atomic structure of the mesas was not determined. However, it is suggested that they are CoAs crystallites with a specific orientation relative to the substrate.

Helen H. Farrell

2003-07-01

44

Molecular Characterization of a Heteromeric ATP-Citrate Lyase That Generates Cytosolic Acetyl-Coenzyme A in Arabidopsis1(w)  

Microsoft Academic Search

Acetyl-coenzyme A (CoA) is used in the cytosol of plant cells for the synthesis of a diverse set of phytochemicals including waxes, isoprenoids, stilbenes, and flavonoids. The source of cytosolic acetyl-CoA is unclear. We identified two Arabidopsis cDNAs that encode proteins similar to the amino and carboxy portions of human ATP-citrate lyase (ACL). Coexpression of these cDNAs in yeast (Saccharomyces

Beth L. Fatland; Jinshan Ke; Marc D. Anderson; Wieslawa I. Mentzen; Li Wei Cui; C. Christy Allred; Jerry L. Johnston; Basil J. Nikolau; Eve Syrkin Wurtele

2002-01-01

45

Role of reversible phosphorylation of acetylCoA carboxylase in long-chain fatty acid synthesis  

Microsoft Academic Search

Acetyl-C0A carboxylase, the rate-limiting enzyme in the biogenesis of long-chain fatty acids, is regulated by phos- phorylation and dephosphorylation. The major phos- phorylation sites that affect carboxylase activity and the specific protein kinases responsible for phosphorylation of different sites have been identified. A form of acetyl- CoA carboxylase that is independent of citrate for ac- tivity occurs in vivo. This

KI-HAN KIM; F. LOPEZ-CASILLAS; D. H. BAI; X. LUO; M. E. PAPE

46

Hydrolysis of carnosine and related compounds by mammalian carnosinases  

Microsoft Academic Search

Comparative study of hydrolysis of carnosine and a number of its natural derivatives by human serum and rat kidney carnosinase was carried out. The rate of carnosine hydrolysis was 3–4-fold higher then for anserine and ophidine. The rate of homocarnosine, N-acetylcarnosine and carcinine hydrolysis was negligible by either of the enzymes used. Our data show that methylation, decarboxylation or acetylation

Anna Pegova; Hiroki Abe; Alexander Boldyrev

2000-01-01

47

Acetyl CoA, a central intermediate of autotrophic CO 2 fixation in Methanobacterium thermoautotrophicum  

Microsoft Academic Search

The pathway of autotrophic CO2 fixation in Methanobacterium thermoautotrophicum has been investigated by long term labelling of the organism with isotopic acetate and pyruvate while exponentially growing on H2 plus CO2. Maximally 2% of the cell carbon were derived from exogeneous tracer, 98% were synthesized from CO2. Since growth was obviously autotrophic the labelled compounds functioned as tracers of the

Georg Fuchs; Erhard Stupperich

1980-01-01

48

Acetylator Phenotype in Psoriasis  

Microsoft Academic Search

Acetylator phenotype has been determined with sulfamethazine in 64 psoriatic patients and in 157 normal control subjects. Forty patients (62.5%) versus 90 control subjects (57.3%) were slow acetylators (p = NS). However, 81 % of the 27 patients with psoriatic siblings were slow acetylators (p < 0.05). Slow acetylator phenotype may be a genetic risk factor for the development of

L. C. Jiménez-Nieto; J. M. Ladero; M. J. Fernández-Gundin; A. Robledo

1989-01-01

49

COA based robust output feedback UPFC controller design  

Microsoft Academic Search

In this paper, a novel method for the design of output feedback controller for unified power flow controller (UPFC) using chaotic optimization algorithm (COA) is developed. Chaotic optimization algorithms, which have the features of easy implementation, short execution time and robust mechanisms of escaping from the local optimum, is a promising tool for the engineering applications. The selection of the

H. Shayeghi; H. A. Shayanfar; S. Jalilzadeh; A. Safari

2010-01-01

50

Yersinia YopJ Acetylates and Inhibits Kinase Activation by Blocking Phosphorylation  

Microsoft Academic Search

Yersinia species use a variety of type III effector proteins to target eukaryotic signaling systems. The effector YopJ inhibits mitogen-activated protein kinase (MAPK) and the nuclear factor kappaB (NFkappaB) signaling pathways used in innate immune response by preventing activation of the family of MAPK kinases (MAPKK). We show that YopJ acted as an acetyltransferase, using acetyl-coenzyme A (CoA) to modify

Sohini Mukherjee; Gladys Keitany; Yan Li; Yong Wang; Haydn L. Ball; Elizabeth J. Goldsmith; Kim Orth

2006-01-01

51

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

52

Molecular cloning, characterization, and elicitation of acetyl-CoA carboxylase from alfalfa.  

PubMed

Acetyl-CoA carboxylase [ACCase; acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] catalyzes the ATP-dependent carboxylation of acetyl CoA to produce malonyl CoA. In plants, malonyl CoA is needed for plastid localized fatty acid biosynthesis and for a variety of pathways in the cytoplasm including flavonoid biosynthesis. We have determined the full nucleotide sequence of an ACCase from alfalfa, which appears to represent a cytoplasmic isozyme. Partial cDNAs were isolated from a cDNA library of suspension culture cells that had been elicited for isoflavonoid phytoalexin synthesis. The full-length sequence was obtained by primer extension and amplification of the cDNA with synthetic primers. The sequence codes for a protein of 2257 amino acids with a calculated M(r) of 252,039. The biotin carboxylase, biotin carboxyl carrier protein, and carboxyltransferase domains, respectively, show approximately 72%, 50%, and 65% sequence similarity to those of animal, diatom, and yeast ACCase sequences. ACCase enzyme activity and transcripts are induced severalfold upon addition of yeast or fungal elicitors to alfalfa cell cultures. PMID:7910406

Shorrosh, B S; Dixon, R A; Ohlrogge, J B

1994-05-10

53

Molecular cloning, characterization, and elicitation of acetyl-CoA carboxylase from alfalfa.  

PubMed Central

Acetyl-CoA carboxylase [ACCase; acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] catalyzes the ATP-dependent carboxylation of acetyl CoA to produce malonyl CoA. In plants, malonyl CoA is needed for plastid localized fatty acid biosynthesis and for a variety of pathways in the cytoplasm including flavonoid biosynthesis. We have determined the full nucleotide sequence of an ACCase from alfalfa, which appears to represent a cytoplasmic isozyme. Partial cDNAs were isolated from a cDNA library of suspension culture cells that had been elicited for isoflavonoid phytoalexin synthesis. The full-length sequence was obtained by primer extension and amplification of the cDNA with synthetic primers. The sequence codes for a protein of 2257 amino acids with a calculated M(r) of 252,039. The biotin carboxylase, biotin carboxyl carrier protein, and carboxyltransferase domains, respectively, show approximately 72%, 50%, and 65% sequence similarity to those of animal, diatom, and yeast ACCase sequences. ACCase enzyme activity and transcripts are induced severalfold upon addition of yeast or fungal elicitors to alfalfa cell cultures. Images

Shorrosh, B S; Dixon, R A; Ohlrogge, J B

1994-01-01

54

Effect of (L-Carnitine) on acetyl-L-carnitine production by heart mitochondria  

SciTech Connect

The authors recently reported a large efflux of acetyl-L-carnitine from rat heart mitochondria during state 3 respiration with pyruvate as substrate both in the presence and absence of malate. In this series of experiments, the effect of the concentration of L-carnitine on the efflux of acetyl-L-carnitine and on the production of /sup 14/CO/sub 2/ from 2-/sup 14/C-pyruvate was determined. Maximum acetylcarnitine production (approximately 25 n moles/min/mg protein) was obtained at 3-5 mM L-carnitine in the absence of added malate. /sup 14/CO/sub 2/ production decreased as the concentration of L-carnitine increased; it plateaued at 3-5 mM L-carnitine. These data indicate carnitine can stimulate flux of pyruvate through pyruvate dehydrogenase and can reduce flux of acetyl CoA through the Krebs cycle by acting as an acceptor of the acetyl moieties of acetyl CoA generated by pyruvate dehydrogenase.

Bieber, L.L.; Lilly, K.; Lysiak, W.

1986-05-01

55

Regulation of spinach chloroplast acetyl-CoA carboxylase.  

PubMed

We have investigated several factors which influence acetyl-CoA carboxylase (ACCase) activity in lysed spinach chloroplasts. (1) When assayed after rapid lysis of light-incubated chloroplasts, ACCase activity was 2-fold higher than activity from dark-incubated chloroplasts. Within 5 min after lysis, activity from dark-incubated chloroplasts increased, suggesting a transient inactivation or inhibition of ACCase in the dark. (2) When lysed chloroplast suspensions were incubated with 30 to 100 microM acetyl-CoA before starting assays, activity was 4-fold higher than if suspensions were not preincubated with acetyl-CoA. CoA, malonyl-CoA, propionyl-CoA, and butyryl-CoA also activated ACCase. Full acetyl-CoA activation required MgATP and was essentially complete after 8 min. ACCase activity decreased upon removal of acetyl-CoA by gel filtration and was partially restored by readdition of acetyl-CoA. Thus, ACCase activation by acetyl-CoA was reversible. (3) Dithiothreitol and thioredoxin stimulated ACCase activity, but only in preparations where ACCase activity was low. (4) ACCase was assayed in concentrations of ATP, ADP, NADPH, NADP+, Mg2+, and CO2/HCO-3, which are estimated to occur in the stroma of chloroplasts under illumination or darkness. ACCase activity from lysed chloroplast suspensions was 10-fold higher when illuminated conditions were used. However, this activity was still 5-fold to 10-fold lower than the rates required to sustain known in vivo rates of fatty acid synthesis and in vitro rates achieved under optimum assay conditions with saturating substrates. PMID:9808758

Hunter, S C; Ohlrogge, J B

1998-11-15

56

A multisubunit acetyl coenzyme A carboxylase from soybean.  

PubMed

A multisubunit form of acetyl coenzyme A (CoA) carboxylase (ACCase) from soybean (Glycine max) was characterized. The enzyme catalyzes the formation of malonyl CoA from acetyl CoA, a rate-limiting step in fatty acid biosynthesis. The four known components that constitute plastid ACCase are biotin carboxylase (BC), biotin carboxyl carrier protein (BCCP), and the alpha- and beta-subunits of carboxyltransferase (alpha- and beta-CT). At least three different cDNAs were isolated from germinating soybean seeds that encode BC, two that encode BCCP, and four that encode alpha-CT. Whereas BC, BCCP, and alpha-CT are products of nuclear genes, the DNA that encodes soybean beta-CT is located in chloroplasts. Translation products from cDNAs for BC, BCCP, and alpha-CT were imported into isolated pea (Pisum sativum) chloroplasts and became integrated into ACCase. Edman microsequence analysis of the subunits after import permitted the identification of the amino-terminal sequence of the mature protein after removal of the transit sequences. Antibodies specific for each of the chloroplast ACCase subunits were generated against products from the cDNAs expressed in bacteria. The antibodies permitted components of ACCase to be followed during fractionation of the chloroplast stroma. Even in the presence of 0.5 M KCl, a complex that contained BC plus BCCP emerged from Sephacryl 400 with an apparent molecular mass greater than about 800 kD. A second complex, which contained alpha- and beta-CT, was also recovered from the column, and it had an apparent molecular mass of greater than about 600 kD. By mixing the two complexes together at appropriate ratios, ACCase enzymatic activity was restored. Even higher ACCase activities were recovered by mixing complexes from pea and soybean. The results demonstrate that the active form of ACCase can be reassembled and that it could form a high-molecular-mass complex. PMID:10069834

Reverdatto, S; Beilinson, V; Nielsen, N C

1999-03-01

57

PanM, an Acetyl-Coenzyme A Sensor Required for Maturation of l-Aspartate Decarboxylase (PanD)  

PubMed Central

ABSTRACT Coenzyme A (CoA) is essential for cellular chemistry in all forms of life. The pantothenate moiety of CoA is generated from the condensation of pantoate and ?-alanine. ?-Alanine is formed by decarboxylation of l-aspartate catalyzed by PanD, a pyruvoyl enzyme that is synthesized by the cell as an inactive precursor (pro-PanD). Maturation of pro-PanD into PanD occurs via a self-cleavage event at residue Ser25, which forms the catalytic pyruvoyl moiety. We recently reported that Salmonella enterica PanM was necessary for pro-PanD maturation, both in vitro and in vivo. Notably, PanM is annotated as a Gcn5-like N-acetyltransferase (GNAT), which suggested that lysine acetylation might be part of the mechanism of maturation. Here we show that PanM lacks acetyltransferase activity and that acetyl-CoA stimulates its activity. Results of experiments with nonhydrolyzable ethyl-CoA and genetically encoded acetyl-lysine-containing PanD support the conclusion that PanM-dependent pro-PanD maturation does not involve an acetyl transfer event. We also show that CoA binding to PanM is needed for in vivo activity and that disruption of CoA binding prevents PanM from interacting with PanD. We conclude that PanM is a GNAT homologue that lost its acetyltransferase activity and evolved a new function as an acetyl-CoA sensor that can trigger the maturation of pro-PanD.

Stuecker, Tara N.; Tucker, Alex C.; Escalante-Semerena, Jorge C.

2012-01-01

58

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

59

Lovastatin and Simvastatin - Inhibitors of HMG CoA Reductase and Cholesterol Biosynthesis  

Microsoft Academic Search

The microsomal enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase is a key rate-controlling step early in the cholesterol biosynthetic pathway that catalyzes the conversion of HMG CoA to mevalonic acid. Since this enzyme plays a significant role in regulating cholesterol synthesis, it is a rational target for pharmacologic intervention. The first potent, specific inhibitor of HMG CoA was mevastatin (compactin,

Alfred W. Alberts

1990-01-01

60

SIRT3 deacetylates mitochondrial 3-hydroxy-3-methylglutaryl CoA synthase 2 and regulates ketone body production.  

PubMed

The mitochondrial sirtuin SIRT3 regulates metabolic homeostasis during fasting and calorie restriction. We identified mitochondrial 3-hydroxy-3-methylglutaryl CoA synthase 2 (HMGCS2) as an acetylated protein and a possible target of SIRT3 in a proteomics survey in hepatic mitochondria from Sirt3(-/-) (SIRT3KO) mice. HMGCS2 is the rate-limiting step in ?-hydroxybutyrate synthesis and is hyperacetylated at lysines 310, 447, and 473 in the absence of SIRT3. HMGCS2 is deacetylated by SIRT3 in response to fasting in wild-type mice, but not in SIRT3KO mice. HMGCS2 is deacetylated in vitro when incubated with SIRT3 and in vivo by overexpression of SIRT3. Deacetylation of HMGCS2 lysines 310, 447, and 473 by incubation with wild-type SIRT3 or by mutation to arginine enhances its enzymatic activity. Molecular dynamics simulations show that in silico deacetylation of these three lysines causes conformational changes of HMGCS2 near the active site. Mice lacking SIRT3 show decreased ?-hydroxybutyrate levels during fasting. Our findings show SIRT3 regulates ketone body production during fasting and provide molecular insight into how protein acetylation can regulate enzymatic activity. PMID:21109197

Shimazu, Tadahiro; Hirschey, Matthew D; Hua, Lan; Dittenhafer-Reed, Kristin E; Schwer, Bjoern; Lombard, David B; Li, Yu; Bunkenborg, Jakob; Alt, Frederick W; Denu, John M; Jacobson, Matthew P; Verdin, Eric

2010-12-01

61

Itinerant electronic ferromagnetism in Sr2ScO3CoAs with largely spaced CoAs conduction layers  

NASA Astrophysics Data System (ADS)

We studied magnetism of Sr2ScO3CoAs, a member of the group of layered compound with CoAs conducting layers, by using successfully synthesized polycrystalline sample. As a result of magnetic and electric resistivity measurements, Sr2ScO3CoAs was revealed to be an itinerant electronic ferromagnet with the Curie temperature TC = 48 K. We discussed the magnetism of this compound within the spin fluctuation theory for three-dimensional itinerant electronic ferromagnets in the ordered state and also pointed out possible quasi-two-dimensional behavior observed in magnetism.

Ohta, Hiroto; Noguchi, Daisuke; Nabetani, Koichiro; Katori, Hiroko Aruga

2013-09-01

62

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

Microsoft Academic Search

Plastidic acetyl-coenzyme A (CoA) carboxylase (ACCase) cata- lyzes the first committed reaction of de novo fatty acid biosynthe- sis. This heteromeric enzyme is composed of one plastid-coded subunit (b-carboxyltransferase) and three nuclear-coded subunits (biotin carboxy-carrier, biotin carboxylase, and a-carboxyltrans- ferase). We report the primary structure of the Arabidopsis a- carboxyltransferase and b-carboxyltransferase subunits deduced from nucleotide sequences of the respective

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

2000-01-01

63

Development of a new transformant selection system for Penicillium chrysogenum : isolation and characterization of the P. chrysogenum acetyl-coenzyme A synthetase gene ( facA ) and its use as a homologous selection marker  

Microsoft Academic Search

A new transformation system for the filamentous fungus Penicillium chrysogenum is described, based on the use of the homologous acetyl-coenzyme A synthetase (facA) gene as a selection marker. Acetate-non-utilizing (Fac-) strains of P. chrysogenum were obtained by positive selection for spontaneous resistance to fluoroacetate. Among these fac mutants putative facA strains were selected for a loss of acetyl-coenzyme A (CoA)

Robin J. Gouka; Wim van Hartingsveldt; Roel A. L. Bovenberg; Cora M. J. van Zeijl; Cees A. M. J. J. van den Hondel; Robert F. M. van Gorcom I

1993-01-01

64

Hypophagic effects of propionate increase with elevated hepatic acetyl coenzyme A concentration for cows in the early postpartum period.  

PubMed

Thirty multiparous lactating dairy cows were used in a randomized block design experiment to evaluate factors related to the degree of hypophagia from intraruminal infusion of propionate. Cows between 3 and 40 d postpartum at the start of the experiment were blocked by calving date and randomly assigned to treatment. Treatments were 1.0 mol/L propionic acid or 1.0 mol/L acetic acid adjusted to pH 6 with sodium hydroxide and infused at 0.5 mol of volatile fatty acid/h from 6h before feeding until 12h after feeding. Propionate infusion decreased dry matter intake by 20.0%, total metabolizable energy intake by 22.5%, and plasma ?-hydroxybutyrate concentration by 54.3% compared with acetate infusion. Effects of treatment on dry matter intake were related to concentration of acetyl coenzyme A (CoA) in the liver; hypophagic effects of propionate compared with acetate increased as liver acetyl CoA concentration increased. Hypophagic effects of propionate are greater for cows with elevated concentrations of acetyl CoA in the liver. PMID:22612960

Stocks, S E; Allen, M S

2012-06-01

65

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

Microsoft Academic Search

Late adolescent children of alcoholics (COAs) were interviewed about their relationship with a natural mentor. Comparisons in social and emotional functioning were made to a matched sample of COAs who did not have a natural mentor. Results showed that a typical mentor was a same-sex relative who had been responsible for initiating the mentor-like relationship. Mentors' familiarity with adolescents' parents

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

2002-01-01

66

A method of COA based on multi-agent evolutionary algorithm  

Microsoft Academic Search

Planning detailed military course of action (COA) is very complex and time consuming. In this paper, a method based on multi-agent evolutionary algorithm was presented to solve COA' resource management and scheduling problems. Each individual can be seen as an agent, in order to realize the local perceptivity of agents, the environment is organized as a latticelike structure. Each agent

Xin Yu; Hui Wang; Licheng Jiao

2009-01-01

67

Acid Hydrolysis of Wood.  

National Technical Information Service (NTIS)

A series of investigations into the acid hydrolysis of pinus radiata (Monterey pine) and the results therefrom are described. Main objectives of the investigation were to establish, using the most promising routes, the conditions of hydrolysis that would ...

A. L. Titchener B. K. Guha

1981-01-01

68

Hydrolysis of Bromodifluoromethyltriphenylphosphonium Bromide.  

National Technical Information Service (NTIS)

Hydrolysis of Ph3P(+)CFBr2Br(-) afforded a high yield of dibromofluoromethane and triphenylphosphine oxide. Hydrolysis in the presence of a radioactive isotope of bromine gave evidence that the mechanism of this reaction proceeds via the dibromofluorometh...

R. M. Flynn R. G. Manning R. M. Kessler

1981-01-01

69

Molecular biology of cytosolic acetyl-CoA generation.  

PubMed

ATP citrate lyase (ACL) catalyses the ATP-dependent reaction between citrate and CoA to form oxaloacetate and acetyl-CoA. Our molecular characterizations of the cDNAs and genes coding for the Arabidopsis ACL indicate that the plant enzyme is heteromeric, consisting of two dissimilar subunits. The A subunit is homologous to the N-terminal third of the animal ACL, and the B subunit is homologous to C-terminal two-thirds of the animal ACL. Using both ACL-A- and ACL-B-specific antibodies and activity assays we have shown that ACL is located in the cytosol, and is not detectable in the plastids, mitochondria or peroxisomes. During seed development, ACL-A and ACL-B mRNA accumulation is co-ordinated with the accumulation of the cytosolic homomeric acetyl-CoA carboxylase mRNA. Antisense Arabidopsis plants reduced in ATP citrate lyase activity show a complex phenotype, with miniaturized organs, small cell size, aberrant plastid morphology and reduced cuticular wax. Our results indicate that ACL generates the cytosolic pool of acetyl-CoA, which is the substrate required for the biosynthesis of a variety of phytochemicals, including cuticular waxes and flavonoids. PMID:11171137

Fatland, B; Anderson, M; Nikolau, B J; Wurtele, E S

2000-12-01

70

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

71

Acetylation Goes Global: The Emergence of Acetylation Biology  

PubMed Central

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.

Norris, Kristi L.; Lee, Joo-Yong; Yao, Tso-Pang

2010-01-01

72

Turnover and transformation of mitochondrial acetyl-CoA acetyltransferase into CoA-modified forms.  

PubMed

Rat liver mitochondrial acetyl-CoA acetyltransferase (acetoacetyl-CoA thiolase, EC 2.3.1.9) exists additionally in the CoA-modified forms A1 and A2. After a pulse of radioactivity using [35S]methionine in hepatocytes, the highest radioactivity was obtained in the unmodified enzyme. Over the chase time, the radioactivity in the unmodified enzyme decreased, but simultaneously increased in both CoA-modified forms, thus proving that the fully active unmodified enzyme exists before the partially active modified forms A1 and A2. Also, the specific radioactivity (ratio % radioactivity/% immunoreactive area) of A1 > A2 demonstrates a sequential CoA modification of form A1 to form A2. Acetyl-CoA acetyltransferase was degraded with an apparent half-life of 38.0 h: the modified forms A1 and A2 have half-lives of 24.5 and 7.2 h. The physiological meaning of the CoA modification of acetyl-CoA acetyltransferase is not yet understood. PMID:8100417

Schwerdt, G; Huth, W

1993-06-15

73

Histone H3 tail acetylation modulates ATP-dependent remodeling through multiple mechanisms  

PubMed Central

There is a close relationship between histone acetylation and ATP-dependent chromatin remodeling that is not fully understood. We show that acetylation of histone H3 tails affects SWI/SNF (mating type switching/ sucrose non fermenting) and RSC (remodels structure of chromatin) remodeling in several distinct ways. Acetylation of the histone H3 N-terminal tail facilitated recruitment and nucleosome mobilization by the ATP-dependent chromatin remodelers SWI/SNF and RSC. Tetra-acetylated H3, but not tetra-acetylated H4 tails, increased the affinity of RSC and SWI/SNF for nucleosomes while also changing the subunits of SWI/SNF that interact with the H3 tail. The enhanced recruitment of SWI/SNF due to H3 acetylation is bromodomain dependent, but is not further enhanced by additional bromodomains found in RSC. The combined effect of H3 acetylation and transcription activators is greater than either separately which suggests they act in parallel to recruit SWI/SNF. Besides enhancing recruitment, H3 acetylation increased nucleosome mobilization and H2A/H2B displacement by RSC and SWI/SNF in a bromodomain dependent manner and to a lesser extent enhanced ATP hydrolysis independent of bromodomains. H3 and H4 acetylation did not stimulate disassembly of adjacent nucleosomes in short arrays by SWI/SNF or RSC. These data illustrate how histone acetylation modulates RSC and SWI/SNF function, and provide a mechanistic insight into their collaborative efforts to remodel chromatin.

Chatterjee, Nilanjana; Sinha, Divya; Lemma-Dechassa, Mekonnen; Tan, Song; Shogren-Knaak, Michael A.; Bartholomew, Blaine

2011-01-01

74

Determination of the structure of lecithins via the formation of acetylated 1,2-diglycerides  

Microsoft Academic Search

A detailed procedure for quantitative determinations of molecular species of lecithins is described and applied to several\\u000a lecithins isolated from natural sources. The method is based on the conversion of lecithin to acetylated 1,2-diglycerides\\u000a and analysis of these compounds by methodology used for the determination of triglyceride structure.\\u000a \\u000a The preparation of the acetylated 1,2-diglycerides was carried out via hydrolysis with

O. S. Privett; L. J. Nutter

1967-01-01

75

Importance of product inhibition in the kinetics of the acylase hydrolysis reaction by differential stopped flow microcalorimetry  

Microsoft Academic Search

The hydrolysis of N-acetyl-l-methionine, N-acetylglycine, N-acetyl-l-phenylalanine, and N-acetyl-l-alanine at 298.35K by porcine kidney acylase I (EC 3.5.1.14) was monitored by the heat released upon mixing of the substrate and enzyme in a differential stopped flow microcalorimeter. Values for the Michaelis constant (Km) and the catalytic constant (kcat) were determined from the progress of the reaction curve employing the integrated form

Magnus Stödeman; Frederick P. Schwarz

2002-01-01

76

Acetylation and Nuclear Receptor Action  

PubMed Central

Acetylation is an essential post-translational modification featuring an acetyl group that is covalently conjugated to a protein substrate. Histone acetylation was first proposed nearly half a century ago by Dr. Vincent Allfrey. Subsequent studies have shown that the acetylated core histones are often associated with transcriptionally active chromatin. Acetylation at lysine residues of histone tails neutralizes the positive charge, which decreases their binding ability to DNA and increases the accessibility of transcription factors and coactivators to the chromatin template. In addition to histones, a number of non-histone substrates are acetylated. Acetylation of non-histone proteins governs biological processes, such as cellular proliferation and survival, transcriptional activity, and intracellular trafficking. We demonstrated that acetylation of transcription factors can regulate cellular growth. Furthermore, we showed that nuclear receptors (NRs) are acetylated at a phylogenetically conserved motif. Since our initial observations with the estrogen and androgen receptors, more than a dozen NRs have been shown to function as substrates for acetyltransferases with diverse functional consequences. This review focuses on the acetylation of NRs and the effect of acetylation on NR function. We discuss the potential role of acetylation in disease initiation and progression with an emphasis on tumorigenesis.

Wang, Chenguang; Tian, Lifeng; Popov, Vladimir M.; Pestell, Richard G.

2011-01-01

77

The diversity of acetylated proteins  

Microsoft Academic Search

Acetylation of proteins, either on various amino-terminal residues or on the ?-amino group of lysine residues, is catalyzed by a wide range of acetyltransferases. Amino-terminal acetylation occurs on the bulk of eukaryotic proteins and on regulatory peptides, whereas lysine acetylation occurs at different positions on a variety of proteins, including histones, transcription factors, nuclear import factors, and ?-tubulin.

Bogdan Polevoda; Fred Sherman

2002-01-01

78

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.

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

2011-01-01

79

Genetics Home Reference: Succinyl-CoA:3-ketoacid CoA transferase deficiency  

MedlinePLUS

... made in the energy-producing centers of cells (mitochondria). The enzyme plays a role in the breakdown ... CoA ; coma ; deficiency ; enzyme ; fasting ; gene ; ketosis ; lethargy ; mitochondria ; prevalence ; recessive ; transferase You may find definitions for ...

80

A method of COA based on multi-agent co-evolutionary algorithm  

NASA Astrophysics Data System (ADS)

In the complex situation of the battlefield, COA (course of action) places an important role. It is required to coordinate many resources in some actions to achieve the desired purpose in the battle. The main goal of COA is to arrange the action in the right order and to put the right resource in the right action. The task which is composed of many actions is always extremely complex. Therefore, COA is actually NP-Hard and a multi-objective optimization problem. It is difficult to solve this problem by common methods. In this paper, a mechanism of co-evolutionary is introduced to solve the problem of COA. It deals well with the problems of resource management and action scheduling.

Yu, Xin; Dong, Shuaijun; Wang, Hui

2011-11-01

81

Measurement of Refractive Errors in Young Myopes Using the COAS Shack-Hartmann Aberrometer  

Microsoft Academic Search

Purpose. To evaluate the Complete Ophthalmic Analysis System (COAS; WaveFront Science) for accuracy, repeatability, and instrument myopia when measuring myopic refractive errors. Methods. We measured the refractive errors of 20 myopic subjects (0.25 to 10 D sphere; 0 to 1.75 D cylinder) with a COAS, a phoropter, and a Nidek ARK-2000 autorefractor. Measurements were made for right and left eyes,

THOMAS O. SALMON; ROGER W. WEST; WAYNE GASSER; TODD KENMORE

2003-01-01

82

Identification and Characterisation of the ? and ? Subunits of Succinyl CoA Ligase of Tomato  

Microsoft Academic Search

Despite the central importance of the TCA cycle in plant metabolism not all of the genes encoding its constituent enzymes have been functionally identified. In yeast, the heterodimeric protein succinyl CoA ligase is encoded for by two single-copy genes. Here we report the isolation of two tomato cDNAs coding for ?- and one coding for the ?-subunit of succinyl CoA

Claudia Studart-Guimarães; Yves Gibon; Nicolás Frankel; Craig C. Wood; María Inés Zanor; Alisdair R. Fernie; Fernando Carrari

2005-01-01

83

Molecular cloning and characterization of the cDNA coding for the biotin-containing subunit of the chloroplastic acetyl-coenzyme A carboxylase  

Microsoft Academic Search

We report the molecular cloning and sequence of the cDNA coding for the biotin-containing subunit of the chloroplastic acetyl- coenzyme A (COA) carboxylase (ACCase) of Arabidopsis tbaliana (CAC7). lhe 3' end of the CAC7 sequence, coding for a peptide of 94 amino acids, which includes a putative biotinylation motif, was expressed in Escbericbia coli as a glutathione-S-transferase (CST) fusion protein.

Joong-Kook Choi; Fei Yu; Eve Syrkin Wurtele; Basil J. Nikolau

1995-01-01

84

3-Hydroxy-3-methylglutaryl CoA lyase (HL): Mouse and human HL gene (HMGCL) cloning and detection of large gene deletions in two unrelated HL-deficient patients  

SciTech Connect

3-hydroxy-3-methylglutaryl CoA lyase (HL, EC 4.1.3.4) catalyzes the cleavage of 3-hydroxy-3-methylglutaryl CoA to acetoacetic acid and acetyl CoA, the final reaction of both ketogenesis and leucine catabolism. Autosomal-recessive HL deficiency in humans results in episodes of hypoketotic hypoglycemia and coma. Using a mouse HL cDNA as a probe, we isolated a clone containing the full-length mouse HL gene that spans about 15 kb of mouse chromosome 4 and contains nine exons. The promoter region of the mouse HL gene contains elements characteristic of a housekeeping gene: a CpG island containing multiple Sp1 binding sites surrounds exon 1, and neither a TATA nor a CAAT box are present. We identified multiple transcription start sites in the mouse HL gene, 35 to 9 bases upstream of the translation start codon. We also isolated two human HL genomic clones that include HL exons 2 to 9 within 18 kb. The mouse and human HL genes (HGMW-approved symbol HMGCL) are highly homologous, with identical locations of intron-exon junctions. By genomic Southern blot analysis and exonic PCR, was found 2 of 33 HL-deficient probands to be homozygous for large deletions in the HL gene. 26 refs., 4 figs., 2 tabs.

Wang, S.P.; Robert, M.F.; Mitchell, G.A. [Hopital Sainte-Justine, Quebec (Canada)] [and others

1996-04-01

85

Acetylation of wood causes photobleaching  

Microsoft Academic Search

This paper deals with the photobleaching of acetylated wood. The acetylated spruce wood was irradiated by artificial sunlight emitted from xenon lamp with covering several kinds of band-pass filter. The lightness (L*) of acetylated wood increased with integral irradiance. The chroma (?C*) decreased by light-irradiation with wavelength from 430nm to 500nm. However, the light-irradiation including ultraviolet ray region made it

Katsuya Mitsui

2010-01-01

86

ATP-dependent remodeling and acetylation as regulators of chromatin fluidity  

Microsoft Academic Search

It has become widely accepted that modification of nucleosome structure is an important regulatory mecha- nism. The hypothesis that the acetylation of histones is involved in regulation was first formed over thirty years ago by Allfrey and colleagues (Allfrey et al. 1964). Sub- sequent genetic studies suggested that complexes that utilize ATP hydrolysis to alter chromatin structure might also play

Robert E. Kingston; Geeta J. Narlikar

1999-01-01

87

Molecular cloning of a 10-deacetylbaccatin III-10-O-acetyl transferase cDNA from Taxus and functional expression in Escherichia coli  

PubMed Central

The cDNA clone for a 10-deacetylbaccatin III-10-O-acetyl transferase, which catalyzes formation of the last diterpene intermediate in the Taxol biosynthetic pathway, has been isolated from Taxus cuspidata. By using consensus sequences from an assembly of transacylases of plant origin and from many deduced proteins of unknown function, a homology-based PCR cloning strategy was employed to amplify initially a 911-bp gene fragment of the putative taxane C-10 hydroxyl acetyl transferase from Taxus. This amplicon was used to screen a cDNA library constructed from mRNA isolated from methyl jasmonate-induced Taxus cells, from which the full-length 10-deacetylbaccatin III-10-O-transacetylase sequence was obtained. Expression of the ORF from pCWori+ in Escherichia coli JM109 afforded a functional enzyme, as determined by 1H-NMR and MS verification of the product baccatin III derived from 10-deacetylbaccatin III and acetyl CoA. The full-length cDNA has an ORF of 1,320 bp corresponding to a deduced protein of 440 residues with a calculated molecular weight of 49,052, consistent with the size of the operationally soluble, monomeric, native acetyl transferase. The recombinant acetyl transferase has a pH optimum of 7.5, has Km values of 10 ?M and 8 ?M for 10-deacetylbaccatin III and acetyl CoA, respectively, and is apparently regiospecific toward the 10-hydroxyl group of the taxane ring. Amino acid sequence comparison of 10-deacetylbaccatin III-10-O-acetyl transferase with taxadienol-5-O-acetyl transferase and with other known acyl transferases of plant origin indicates a significant degree of similarity between these enzymes (80% and 64–67%, respectively).

Walker, Kevin; Croteau, Rodney

2000-01-01

88

CoA Synthase is in complex with p85?PI3K and affects PI3K signaling pathway  

Microsoft Academic Search

The complex interplay between cellular signaling and metabolism in eukaryotic cells just start to emerge. Coenzyme A (CoA) and its derivatives play a key role in cell metabolism and also participate in regulatory processes. CoA Synthase (CoASy) is a mitochondria-associated enzyme which mediates two final stages of de novo CoA biosynthesis. Here, we report that CoASy is involved in signaling

Oksana Breus; Ganna Panasyuk; Ivan T. Gout; Valeriy Filonenko; Ivan Nemazanyy

2009-01-01

89

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

90

Accelerated Degradation of HMG CoA Reductase Mediated by Binding of Insig-1 to Its Sterol-Sensing Domain  

Microsoft Academic Search

Sterols accelerate degradation of the ER enzyme 3-hydroxy-3-methylglutaryl CoA reductase (HMG CoA reductase), which catalyzes a rate-controlling step in cholesterol biosynthesis. This degradation contributes to feedback inhibition of synthesis of cholesterol and nonsterol isoprenoids. Here, we show that degradation of HMG CoA reductase is accelerated by the sterol-induced binding of its sterol-sensing domain to the ER protein insig-1. Accelerated degradation

Navdar Sever; Tong Yang; Michael S. Brown; Joseph L. Goldstein; Russell A. DeBose-Boyd

2003-01-01

91

Use of Coagulase Gene (coa) Repeat Region Nucleotide Sequences for Typing of Methicillin-Resistant Staphylococcus aureus Strains  

PubMed Central

Coagulase gene (coa) short sequence repeat region sequencing was used to measure relatedness among a collection of temporally and geographically diverse methicillin-resistant Staphylococcus aureus isolates. The results show that coa polymorphism is free of strong selective pressure and has a low index of variation that may be useful for long-term epidemiological investigations. coa typing is a useful addition to spa typing for analysis of S. aureus, including methicillin-resistant strains.

Shopsin, B.; Gomez, M.; Waddington, M.; Riehman, M.; Kreiswirth, B. N.

2000-01-01

92

Progressing batch hydrolysis process  

DOEpatents

A progressive batch hydrolysis process is disclosed for producing sugar from a lignocellulosic feedstock. It comprises passing a stream of dilute acid serially through a plurality of percolation hydrolysis reactors charged with feed stock, at a flow rate, temperature and pressure sufficient to substantially convert all the cellulose component of the feed stock to glucose. The cooled dilute acid stream containing glucose, after exiting the last percolation hydrolysis reactor, serially fed through a plurality of pre-hydrolysis 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. The dilute acid stream containing glucose is cooled after it exits the last prehydrolysis reactor.

Wright, J.D.

1985-01-10

93

Enzymatic hydrolysis of molasses  

Microsoft Academic Search

Kinetic studies of the enzymatic hydrolysis of molasses were conducted using glucoamylase. Central Sugar Refinery SDN BHD contains 13–20% glucose. The molasses was diluted and the kinetic experiments were conducted at 67 °C with 100–1000 mg\\/l of glucoamylase. The glucose contents of the molasses were enhanced after hydrolysis of molasses solution with 1000 mg\\/l glucoamylase. A Lineweaver–Burk plot was obtained

Ghasem D. Najafpour; Cheong Poi Shan

2003-01-01

94

Structural and docking studies of Leucaena leucocephala Cinnamoyl CoA reductase.  

PubMed

Lignin, a major constituent of plant call wall, is a phenolic heteropolymer. It plays a major role in the development of plants and their defense mechanism against pathogens. Therefore Lignin biosynthesis is one of the critical metabolic pathways. In lignin biosynthesis, the Cinnamoyl CoA reductase is a key enzyme which catalyzes the first step in the pathway. Cinnamoyl CoA reductase provides the substrates which represent the main transitional molecules of lignin biosynthesis pathway, exhibits a high in vitro kinetic preference for feruloyl CoA. In present study, the three-dimensional model of cinnamoyl CoA reductase was constructed based on the crystal structure of Grape Dihydroflavonol 4-Reductase. Furthermore, the docking studies were performed to understand the substrate interactions to the active site of CCR. It showed that residues ARG51, ASN52, ASP54 and ASN58 were involved in substrate binding. We also suggest that residue ARG51 in CCR is the determinant residue in competitive inhibition of other substrates. This structural and docking information have prospective implications to understand the mechanism of CCR enzymatic reaction with feruloyl CoA, however the approach will be applicable in prediction of substrates and engineering 3D structures of other enzymes as well. PMID:20512516

Prasad, Nirmal K; Vindal, Vaibhav; Kumar, Vikash; Kabra, Ashish; Phogat, Navneet; Kumar, Manoj

2010-05-29

95

CRYSTALLINE ACETYL DERIVATIVES OF PEPSIN  

PubMed Central

Crystalline pepsin has been acetylated by the action of ketene in aqueous solution at pH 4.07–5.5. As acetylation proceeds the activity decreases, the decrease being more rapid at pH 5.0–5.5 than at 4.0–4.5. Three acetyl derivatives have been isolated from the reaction mixture and obtained in crystalline form. The crystal form of these derivatives is similar to that of pepsin. Fractionation and solubility determinations show that these preparations are not mixtures or solid solutions of the original pepsin with an inactive derivative. A compound which contains three or four acetyl groups and which has lost all of its original primary amino groups can be isolated after short acetylation. It has the same activity as the original pepsin. A second derivative containing six to eleven acetyl groups has also been isolated. It has about 60 per cent of the activity of the original pepsin. A third derivative having twenty to thirty acetyl groups and about 10 per cent of the activity of original pepsin can be isolated after prolonged acetylation. The 60 per cent active derivative on standing in strong acid solution loses some of its acetyl groups and at the same time regains the activity of the original pepsin. The compound obtained in this way is probably the same as the completely active three acetyl derivative obtained by mild acetylation. These results show that acetylation of three or four of the primary amino groups of pepsin causes no change in the specific activity of the enzyme but that the introduction of acetyl groups in other parts of the molecule results in a marked loss in activity. The solubilities, amino nitrogen content, acetyl content, isoelectric point, and the specific activity have been determined by a variety of methods and found to be different from the corresponding properties of crystalline pepsin. The pH-activity curves, acid and alkali inactivation, and titration curves were not significantly different from the same respective properties of pepsin.

Herriott, Roger M.; Northrop, John H.

1934-01-01

96

Structure of succinyl-CoA:3-ketoacid CoA transferase from Drosophila melanogaster.  

PubMed

Succinyl-CoA:3-ketoacid CoA transferase (SCOT) plays a crucial role in ketone-body metabolism. SCOT from Drosophila melanogaster (DmSCOT) was purified and crystallized. The crystal structure of DmSCOT was determined at 2.64?Å resolution and belonged to space group P212121, with unit-cell parameters a = 76.638, b = 101.921, c = 122.457?Å, ? = ? = ? = 90°. Sequence alignment and structural analysis identified DmSCOT as a class I CoA transferase. Compared with Acetobacter aceti succinyl-CoA:acetate CoA transferase, DmSCOT has a different substrate-binding pocket, which may explain the difference in their substrate specificities. PMID:24100554

Zhang, Min; Xu, Han Yang; Wang, Yi Cui; Shi, Zhu Bing; Zhang, Nan Nan

2013-09-28

97

An efficient Amano PS-catalyzed chemo-, regio- and enantioselective hydrolysis of (±)-2,3-di- O-acetyl-2- C-methyl- d-erythrono-1,4-lactone: a facile preparation of bioactive natural products (?)-saccharinic acid lactone and potassium (2 R,3 R)-2,3,4-trihydroxy-2-methylbutanoate  

Microsoft Academic Search

Saccharinic acid lactone (?)-1a is a suitable building block for the synthesis of many bioactive natural products. Amano PS-induced chemo-, regio- and enantioselective hydrolysis of diacetyl lactone (±)-3 has been carried out to obtain (?)-1a in 46% yield with 99% ee and diacetyl lactone (+)-3 in 49% yield with 99% ee. The Amano PS-catalyzed enantioselective acylation of (±)-1a with vinyl

Sanjib Gogoi; Narshinha P. Argade

2006-01-01

98

Acid hydrolysis and quantitative determination of total hexosamines of an exopolysaccharide produced by Citrobacter sp  

Microsoft Academic Search

During the hydrolysis of an exopolysaccharide (EPS) produced by Citrobacter sp., the maximum liberation of hexosamine was obtained with 6 m HCl at 115 °C in an autoclave for 1 h. The glycosidic bond energy and degree of acetylation of the hexosamine in EPS were approximately 77 kJ mol–1 and 61%, respectively. Thermal destruction of the hexosamines and the effect

Jin-Ho Jang; Hui Ching Hia; Michihiko Ike; Chiyo Inoue; Masanori Fujita; Toshiomi Yoshida

2005-01-01

99

Acetylation of wood causes photobleaching.  

PubMed

This paper deals with the photobleaching of acetylated wood. The acetylated spruce wood was irradiated by artificial sunlight emitted from xenon lamp with covering several kinds of band-pass filter. The lightness (L(*)) of acetylated wood increased with integral irradiance. The chroma (?C(*)) decreased by light-irradiation with wavelength from 430nm to 500nm. However, the light-irradiation including ultraviolet ray region made it decrease after increase with integral irradiance. The visible light made hue angle (h°) increase, however, the ultraviolet ray made it decrease. The lignin degradation and the production of carbonyl groups were observed by light-irradiation including ultraviolet ray. However, no remarkable changes in IR spectra were observed by visible light-irradiation. Photobleaching of acetylated wood was caused by mainly visible light without modifying the IR spectra of lignin. PMID:20696591

Mitsui, Katsuya

2010-07-25

100

Coenzyme A esters of 2-aryloxyphenoxypropionate herbicides and 2-arylpropionate antiinflammatory drugs are potent and stereoselective inhibitors of rat liver acetyl-CoA carboxylase.  

PubMed

The CoA esters of diclofop, haloxyfop and fluazifop are up to 425-fold more potent than the corresponding unconjugated herbicides as inhibitors of rat liver acetyl-CoA carboxylase (EC 6.4.1.2); the most potent inhibitor is (R)-fluazifopyl-CoA2 (Ki = 0.03 microM). The binding site is stereoselective for (R)-diclofop, the herbicidally active enantiomer, and for (R)-diclofopyl-CoA. The CoA esters of the antiinflammatory drugs ibuprofen and fenoprofen also strongly inhibit this carboxylase. (S)-Ibuprofenyl-CoA (Ki = 0.7 microM), the CoA ester of the enantiomer with antiinflammatory activity, is 15-fold more potent as an inhibitor than (R)-ibuprofenyl-CoA. These results suggest that some of the biological effects of these herbicides and antiinflammatory drugs in animals may be due to the inhibition of acetyl-CoA carboxylase by their acyl-CoA derivatives. PMID:1347398

Kemal, C; Casida, J E

1992-01-01

101

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

102

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

103

Methanogenesis from acetate in cell extracts of Methanosarcina barkeri : Isotope exchange between CO 2 and the carbonyl group of acetylCoA, and the role of H 2  

Microsoft Academic Search

From our previous studies on the mechanism of methane formation from acetate it was known that cell extracts of acetate-grown Methanosarcina barkeri (100 000 × g supernatant) catalyze the conversion of acetyl-CoA plus tetrahydromethanopterin (=H4MPT) to methyl-H4MPT, CoA, CO2 and presumably H2. We report here that these extracts, in the absence of H4MPT, mediated an isotope exchange between CO2 ([S]0.5

Reinhard Fischer; Rudolf K. Thauer

1990-01-01

104

Acetylation of chicken feathers for thermoplastic applications.  

PubMed

Poultry feathers are renewable resources, inexpensive and abundantly available, but have limited applications. Although keratin extracted from feathers has been chemically modified, there are no reports on the chemical modification or development of thermoplastics from poultry feathers. Acetylation is an inexpensive and environmentally friendly approach to make biopolymers thermoplastic. Several biopolymers have been acetylated and used to produce fibers, films, and extrudates. In this research, chicken feathers were acetylated, and the structure and properties of the acetylated feathers were studied. Acetylation conditions such as concentration of chemicals and catalyst and time and temperature of acetylation were optimized. Acetylation of feathers was confirmed using Fourier transform infrared (FTIR) and pyrolysis-gas chromatography-mass spectrometry (P-GC-MS). The acetylated feathers were analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to understand their thermal behavior. Acetylated feathers were thermoplastic and could be compression molded to form transparent films despite the relatively low percentage of acetyl content. PMID:21882886

Hu, Chunyan; Reddy, Narendra; Yan, Kelu; Yang, Yiqi

2011-09-14

105

Mining simulation data for insights about a decision space: application to an urban combat COA  

NASA Astrophysics Data System (ADS)

We start with a vision of an integrated decision architecture to assist in the various stages and subtasks of decisionmaking. We briefly describe how the Seeker-Filter-Viewer (S-F-V) architecture for multi-criterial decision support helps realize many components of that vision. The rest of the paper is devoted to one of the components: developing insights about the course of action (COA) decision space from COA simulations. We start with data obtained from multiple simulation executions of an urban combat COA in a specified scenario, where the stochastic nature of different executions produce a range of intermediate events and final outcomes. The Viewer in the S-F-V decision architecture is used to make and visually test hypotheses about how sensitive different events and outcomes are to different aspects of the COA and to various intermediate events. The analyst engages in a cycle of hypothesis making, visually evaluating the hypothesis, and making further hypotheses. A set of snapshots illustrates an investigational sequence of abstractions in an example of iterating on hypotheses. The synergy of data mining tools, high performance computing, and advanced high-resolution combat simulation has the potential to assist battle planners to make better decisions for imminent combat.

Chandrasekaran, B.; Josephson, John R.; O'May, Janet; Heilman, Eric; Kaste, Richard C.

2004-08-01

106

The COA360: a tool for assessing the cultural competency of healthcare organizations.  

PubMed

The U.S. Census Bureau projects that by 2050, non-Hispanic whites will be in the numerical minority. This rapid diversification requires healthcare organizations to pay closer attention to cross-cultural issues if they are to meet the healthcare needs of the nation and continue to maintain a high standard of care. Although scorecards and benchmarking are widely used to gauge healthcare organizations' performance in various areas, these tools have been underused in relation to cultural preparedness or initiatives. The likely reason for this is the lack of a validated tool specifically designed to examine cultural competency. Existing validated cultural competency instruments evaluate individuals, not organizations. In this article, we discuss a study to validate the Cultural Competency Organizational Assessment--360 or the COA360, an instrument designed to appraise a healthcare organization's cultural competence. The Office of Minority Health and the Joint Commission have each developed standards for measuring the cultural competency of organizations. The COA360 is designed to assess adherence to both of these sets of standards. For this validation study, we enlisted a panel of national experts. The panel rated each dimension of the COA360, and the combination of items for each of the scale's 14 dimensions was rated above 4.13 (on 5-point scale). Our conclusion points to the validity of the COA360. As such, it is a valuable tool not only for assessing a healthcare organization's cultural readiness but also for benchmarking its progress in addressing cultural and diversity issues. PMID:18720687

LaVeist, Thomas A; Relosa, Rachel; Sawaya, Nadia

107

Hydrolysis of CL-20.  

National Technical Information Service (NTIS)

The Energetics and Warheads Division of the U.S. Army Armament Research, Development and Engineering Center has been involved in the development of CL-20. An aqueous hydrolysis study was performed to better understand the fate and transport of CL-20 throu...

J. Pavlov M. Sidhoum C. Christodoulatos W. Balas S. Nicolich

2005-01-01

108

Evidence that carbon monoxide is an obligatory intermediate in anaerobic acetyl-CoA synthesis.  

PubMed

Carbon monoxide is produced by several biological reactions. It is proposed to act as an intracellular signaling molecule and can serve as the carbon and electon source for certain bacteria. Direct evidence for a new biological role for CO is presented here. The results strongly indicate that CO is produced as an obligatory intermediate during growth of the acetogenic bacterium Clostridium thermoaceticum on glucose, H2/CO2, or aromatic carboxylic acids. Our results are consistent with earlier hypotheses of the intermediacy of CO during growth of acetogenic bacteria on CO2 and hexoses [Diekert, G., & Ritter, M. (1983) FEMS Microbiol. Lett. 17, 299-302] and methanogenic Archaea on CO2 [Stupperich, E., Hammel, K. E., Fuchs, G., & Thauer, R. K. (1983) FEBS Lett. 152, 21-23]. Therefore, CO production is a key step in the Wood-Ljungdahl pathway of acetyl-CoA synthesis. The carbonyl group of acetyl-CoA is shown to be formed from the carboxyl group of pyruvate by the following steps. (i) Pyruvate undergoes decarboxylation by pyruvate:ferredoxin oxidoreductase to form acetyl-CoA and CO2. (ii) CO2 is reduced to CO by the CODH site of the bifunctional enzyme CO dehydrogenase/acetyl-CoA synthase (CODH/ACS). (iii) CO generated in situ combines with the ACS active site to form a paramagnetic adduct that has been called the NiFeC species, and (iv) the bound carbonyl group combines with a bound methyl group and CoA to generate acetyl-CoA. To our knowledge, this paper represents the first demonstration of a pathway in which CO is produced and then used as a metabolic intermediate. PMID:8810918

Menon, S; Ragsdale, S W

1996-09-17

109

Aminoacyl-coenzyme A synthesis catalyzed by a CoA ligase from Penicillium chrysogenum.  

PubMed

Coenzyme A ligases play an important role in metabolism by catalyzing the activation of carboxylic acids. In this study we describe the synthesis of aminoacyl-coenzyme As (CoAs) catalyzed by a CoA ligase from Penicillium chrysogenum. The enzyme accepted medium-chain length fatty acids as the best substrates, but the proteinogenic amino acids L-phenylalanine and L-tyrosine, as well as the non-proteinogenic amino acids D-phenylalanine, D-tyrosine and (R)- and (S)-?-phenylalanine were also accepted. Of these amino acids, the highest activity was found for (R)-?-phenylalanine, forming (R)-?-phenylalanyl-CoA. Homology modeling suggested that alanine 312 is part of the active site cavity, and mutagenesis (A312G) yielded a variant that has an enhanced catalytic efficiency with ?-phenylalanines and D-?-phenylalanine. PMID:21334330

Koetsier, Martijn J; Jekel, Peter A; Wijma, Hein J; Bovenberg, Roel A L; Janssen, Dick B

2011-02-18

110

Structural and Functional Similarities between Mitochondrial Malate Dehydrogenase and L-3-Hydroxyacyl CoA Dehydrogenase  

Microsoft Academic Search

Pig heart mitochondrial malate dehydrogenase (EC 1.1.1.37), which has been obtained free of electrophoretic subforms, has been shown to have a molecular weight of 67,000 and to be composed of two polypeptide chains. Comparison of these and other properties, such as amino-acid composition, isoelectric point, and keto-substrate inhibition, with those of L-3-hydroxyacyl CoA dehydrogenase (EC 1.1.1.35), another NAD+-dependent dehydrogenase of

Barbara E. Noyes; Beat E. Glatthaar; John S. Garavelli; Ralph A. Bradshaw

1974-01-01

111

Prehospital HMG CoA reductase inhibitor use and reduced mortality in hemorrhagic shock due to trauma  

Microsoft Academic Search

Introduction  3-Hydroxy-3-methyl-glutaryl Co-A reductase inhibitors (HMG Co-A reductase inhibitors, statins) are commonly used medications\\u000a for the control of serum cholesterol. Recent data suggests that these medications also modify the inflammatory pathways in\\u000a sepsis, septic shock, and hemorrhagic shock due to ruptured abdominal aortic aneurysms. Statin use in hemorrhagic shock due\\u000a to trauma, however, has conflicting data, with one study showing improvement,

J. M. Feeney; V. Jayaraman; J. Spilka; D. S. Shapiro; S. Ellner; W. T. Marshall; L. M. Jacobs

112

Germline Deletion of Pantothenate Kinases 1 and 2 Reveals the Key Roles for CoA in Postnatal Metabolism  

PubMed Central

Pantothenate kinase (PanK) phosphorylates pantothenic acid (vitamin B5) and controls the overall rate of coenzyme A (CoA) biosynthesis. Pank1 gene deletion in mice results in a metabolic phenotype where fatty acid oxidation and gluconeogenesis are impaired in the fasted state, leading to mild hypoglycemia. Inactivating mutations in the human PANK2 gene lead to childhood neurodegeneration, but Pank2 gene inactivation in mice does not elicit a phenotype indicative of the neuromuscular symptoms or brain iron accumulation that accompany the human disease. Pank1/Pank2 double knockout (dKO) mice were derived to determine if the mild phenotypes of the single knockout mice are due to the ability of the two isoforms to compensate for each other in CoA biosynthesis. Postnatal development was severely affected in the dKO mice. The dKO pups developed progressively severe hypoglycemia and hyperketonemia by postnatal day 10 leading to death by day 17. Hyperketonemia arose from impaired whole-body ketone utilization illustrating the requirement for CoA in energy generation from ketones. dKO pups had reduced CoA and decreased fatty acid oxidation coupled with triglyceride accumulation in liver. dKO hepatocytes could not maintain the NADH levels compared to wild-type hepatocytes. These results revealed an important link between CoA and NADH levels, which was reflected by deficiencies in hepatic oleate synthesis and gluconeogenesis. The data indicate that PanK1 and PanK2 can compensate for each other to supply tissue CoA, but PanK1 is more important to CoA levels in liver whereas PanK2 contributes more to CoA synthesis in the brain.

Garcia, Matthew; Leonardi, Roberta; Zhang, Yong-Mei; Rehg, Jerold E.; Jackowski, Suzanne

2012-01-01

113

Acetyl Coenzyme A Carboxylase Activity in Developing Seedlings and Chloroplasts of Barley and Its Virescens Mutant 1  

PubMed Central

Acetyl coenzyme A (CoA) carboxylase activity of whole tissue homogenates and chloroplast preparations was analyzed as the acetyl-CoA-dependent incorporation of [14C]bicarbonate into an acid-stable product. The absolute requirement for ATP and MgCl2, the complete inhibition with avidin, and end-product analysis were consistent with the presence of acetyl-CoA carboxylase activity. Little difference was found between the mutant and normal tissue homogenates from the 1- to 3-day growth stages, during which period both showed a 3-fold increase. However, by 4 days, the activity of the mutant exceeded that of the normal. Fractionation studies showed that the enzyme was a soluble protein present in the stromal fraction of chloroplasts. The biotin content was also highest in the stroma, although it was found in the lamellar fraction as well. For both the mutant and the normal, the highest acetyl-CoA carboxylase activities were obtained in the stromal preparations from 4-day seedlings (54 and 31 nmoles per milligram protein per minute for the mutant and the normal, respectively) with a progressive decline by 6 and 8 days. The difference between the mutant and the normal was not due to the accumulation of an inhibitor in the normal.

Thomson, Lawrence W.; Zalik, Saul

1981-01-01

114

Receptor-coupled phosphoinositide hydrolysis in human retinal pigment epithelium.  

PubMed

Carbachol and histamine stimulated phosphoinositide (PPI) hydrolysis in cultured human retinal pigment epithelium (RPE), as reflected by an accumulation of 3H-inositol phosphates in the presence of 10 mM Li+. Carbachol increased PPI hydrolysis to greater than 600% of basal with an EC50 of 60 microM; stimulation was linear up to 60 min. This activation likely occurred via the M3 muscarinic cholinergic receptor based on the IC50 values for 4-diphenylacetoxy-N-methylpiperidine methiodide (0.47 nM), pirenzepine (280 nM), and 11-[[2-[(diethylamino)methyl]-1-piperidinyl]-acetyl]-5,11- dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one (1.4 microM). Carbachol-mediated PPI hydrolysis was decreased by 80% in the absence of extracellular Ca2+. Histamine stimulated PPI turnover in a linear manner by 180% with an EC50 of 20 microM by the H1 histaminergic receptor. Serotonin, glutamate, norepinephrine, and dopamine were inactive. In human RPE, the resting cytoplasmic Ca2+ concentration, as determined by fura-2 fluorescence, was 138 +/- 24 nM. On the addition of carbachol, there was a 180% increase in peak intracellular Ca2+; addition of histamine increased intracellular Ca2+ by 187%. These results suggest receptor-mediated, inositol lipid hydrolysis is coupled to intracellular Ca2+ flux in human RPE. PMID:1851211

Feldman, E L; Randolph, A E; Johnston, G C; DelMonte, M A; Greene, D A

1991-06-01

115

hCOA3 stabilizes cytochrome c oxidase 1 (COX1) and promotes cytochrome c oxidase assembly in human mitochondria.  

PubMed

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

2013-01-29

116

Kinetic studies on two isoforms of acetyl-CoA carboxylase from maize leaves.  

PubMed

The steady-state kinetics of two multifunctional isoforms of acetyl-CoA carboxylase (ACCase) from maize leaves (a major isoform, ACCase1 and a minor isoform, ACCase2) have been investigated with respect to reaction mechanism, inhibition by two graminicides of the aryloxyphenoxypropionate class (quizalofop and fluazifop) and some cellular metabolites. Substrate interaction and product inhibition patterns indicated that ADP and P(i) products from the first partial reaction were not released before acetyl-CoA bound to the enzymes. Product inhibition patterns did not match exactly those predicted for an ordered Ter Ter or a random Ter Ter mechanism, but were close to those postulated for an ordered mechanism. ACCase2 was about 1/2000 as sensitive as ACCase1 to quizalofop but only about 1/150 as sensitive to fluazifop. Fitting inhibition data to the Hill equation indicated that binding of quizalofop or fluazifop to ACCase1 was non-cooperative, as shown by the Hill constant (n(app)) values of 0.86 and 1.16 for quizalofop and fluazifop respectively. Apparent inhibition constant values (K' from the Hill equation) for ACCase1 were 0.054 microM for quizalofop and 21.8 microM for fluazifop. On the other hand, binding of quizalofop or fluazifop to ACCase2 exhibited positive co-operativity, as shown by the (napp) values of 1.85 and 1.59 for quizalofop and fluazifop respectively. K' values for ACCase2 were 1.7 mM for quizalofop and 140 mM for fluazifop. Kinetic parameters for the co-operative binding of quizalofop to maize ACCase2 were close to those of another multifunctional ACCase of limited sensitivity to graminicide, ACC220 from pea. Inhibition of ACCase1 by quizalofop was mixed-type with respect to acetyl-CoA or ATP, but the concentration of acetyl-CoA had the greater effect on the level of inhibition. Neither ACCase1 nor ACCase2 was appreciably sensitive to CoA esters of palmitic acid (16:0) or oleic acid (18:1). Approximate IC50 values were 10 microM (ACCase2) and 50 microM (ACCase1) for both CoA esters. Citrate concentrations up to 1 mM had no effect on ACCase1 activity. Above this concentration, citrate was inhibitory. ACCase2 activity was slightly stimulated by citrate over a broad concentration range (0.25-10 mM). The significance of possible effects of acyl-CoAs or citrate in vivo is discussed. PMID:8836149

Herbert, D; Price, L J; Alban, C; Dehaye, L; Job, D; Cole, D J; Pallett, K E; Harwood, J L

1996-09-15

117

Kinetic studies on two isoforms of acetyl-CoA carboxylase from maize leaves.  

PubMed Central

The steady-state kinetics of two multifunctional isoforms of acetyl-CoA carboxylase (ACCase) from maize leaves (a major isoform, ACCase1 and a minor isoform, ACCase2) have been investigated with respect to reaction mechanism, inhibition by two graminicides of the aryloxyphenoxypropionate class (quizalofop and fluazifop) and some cellular metabolites. Substrate interaction and product inhibition patterns indicated that ADP and P(i) products from the first partial reaction were not released before acetyl-CoA bound to the enzymes. Product inhibition patterns did not match exactly those predicted for an ordered Ter Ter or a random Ter Ter mechanism, but were close to those postulated for an ordered mechanism. ACCase2 was about 1/2000 as sensitive as ACCase1 to quizalofop but only about 1/150 as sensitive to fluazifop. Fitting inhibition data to the Hill equation indicated that binding of quizalofop or fluazifop to ACCase1 was non-cooperative, as shown by the Hill constant (n(app)) values of 0.86 and 1.16 for quizalofop and fluazifop respectively. Apparent inhibition constant values (K' from the Hill equation) for ACCase1 were 0.054 microM for quizalofop and 21.8 microM for fluazifop. On the other hand, binding of quizalofop or fluazifop to ACCase2 exhibited positive co-operativity, as shown by the (napp) values of 1.85 and 1.59 for quizalofop and fluazifop respectively. K' values for ACCase2 were 1.7 mM for quizalofop and 140 mM for fluazifop. Kinetic parameters for the co-operative binding of quizalofop to maize ACCase2 were close to those of another multifunctional ACCase of limited sensitivity to graminicide, ACC220 from pea. Inhibition of ACCase1 by quizalofop was mixed-type with respect to acetyl-CoA or ATP, but the concentration of acetyl-CoA had the greater effect on the level of inhibition. Neither ACCase1 nor ACCase2 was appreciably sensitive to CoA esters of palmitic acid (16:0) or oleic acid (18:1). Approximate IC50 values were 10 microM (ACCase2) and 50 microM (ACCase1) for both CoA esters. Citrate concentrations up to 1 mM had no effect on ACCase1 activity. Above this concentration, citrate was inhibitory. ACCase2 activity was slightly stimulated by citrate over a broad concentration range (0.25-10 mM). The significance of possible effects of acyl-CoAs or citrate in vivo is discussed.

Herbert, D; Price, L J; Alban, C; Dehaye, L; Job, D; Cole, D J; Pallett, K E; Harwood, J L

1996-01-01

118

Catalysis of acetyl-CoA cleavage and tetrahydrosarcinapterin methylation by a carbon monoxide dehydrogenase-corrinoid enzyme complex.  

PubMed

An enzyme complex containing carbon monoxide dehydrogenase and a corrinoid protein has been isolated from Methanosarcina barkeri. Sodium dodecyl sulfate-gel electrophoresis revealed five polypeptides of molecular masses alpha = 19,700, beta = 84,500, gamma = 63,200, delta = 53,000, and epsilon = 51,400 Da in equimolar amounts. One mol of cobamide cofactor was found per minimal alpha beta gamma delta epsilon unit. The molecular mass of the native complex was 1,600,000 Da by high pressure liquid chromatography (HPLC) gel filtration, which suggested an alpha 6 beta 6 gamma 6 delta 6 epsilon 6 oligomeric structure. Catalysis of a reaction involving cleavage of acetyl-CoA and methylation of tetrahydrosarcinapterin was indicated by spectrophotometric analyses; a time-dependent absorption decrease in the 300-320 nm region was observed in the complete reaction mixture which contained acetyl-CoA, tetrahydrosarcinapterin, and the enzyme complex. In control samples lacking any one of the these components the absorption spectrum remained virtually unaltered. Reversed-phase HPLC analysis confirmed that tetrahydrosarcinapterin was converted to a product that co-eluted with authentic methyltetrahydrosarcinapterin. The product also exhibited the UV-visible absorption spectrum expected for methyltetrahydrosarcinapterin. Free CoA was identified as an additional product of the reaction. The carbonyl group of acetyl-CoA was oxidized to carbon dioxide. Spectral changes indicated concomitant Fe/S center reduction. Production of CoA was essentially stoichiometric with methyltetrahydrosarcinapterin formation and tetrahydrosarcinapterin consumption. Analyses during purification showed that catalytic activity was restricted exclusively to the fractions that contained the carbon monoxide dehydrogenase-corrinoid enzyme complex. PMID:1939246

Grahame, D A

1991-11-25

119

Catalytic hydrolysis of carbonyl sulfide  

SciTech Connect

Hydrolysis of COS in gas streams to H/sub 2/S and CO/sub 2/ can be improved by using certain bicyclo tertiary amine catalysts. Bicyclo tertiary amine catalysts can enhance COS hydrolysis in an acid gas removal solvent in the liquid phase or on a solid support system in the gas phase.

Chen, M. S.; Edwards, T. J.; Ernst, W. R.

1985-06-18

120

Acetyl-coenzyme A synthesis from methyltetrahydrofolate, CO, and coenzyme A by enzymes purified from Clostridium thermoaceticum: attainment of in vivo rates and identification of rate-limiting steps.  

PubMed Central

Many anaerobic bacteria fix CO2 via the acetyl-coenzyme A (CoA) (Wood) pathway. Carbon monoxide dehydrogenase (CODH), a corrinoid/iron-sulfur protein (C/Fe-SP), methyltransferase (MeTr), and an electron transfer protein such as ferredoxin II play pivotal roles in the conversion of methyltetrahydrofolate (CH3-H4folate), CO, and CoA to acetyl-CoA. In the study reported here, our goals were (i) to optimize the method for determining the activity of the synthesis of acetyl-CoA, (ii) to evaluate how closely the rate of synthesis of acetyl-CoA by purified enzymes approaches the rate at which whole cells synthesize acetate, and (iii) to determine which steps limit the rate of acetyl-CoA synthesis. In this study, CODH, MeTr, C/Fe-SP, and ferredoxin were purified from Clostridium thermoaceticum to apparent homogeneity. We optimized conditions for studying the synthesis of acetyl-CoA and found that when the reaction is dependent upon MeTr, the rate is 5.3 mumol min-1 mg-1 of MeTr. This rate is approximately 10-fold higher than that reported previously and is as fast as that predicted on the basis of the rate of in vivo acetate synthesis. When the reaction is dependent upon CODH, the rate of acetyl-CoA synthesis is approximately 0.82 mumol min-1 mg-1, approximately 10-fold higher than that observed previously; however, it is still lower than the rate of in vivo acetate synthesis. It appears that at least two steps in the overall synthesis of acetyl-CoA from CH3-H4folate, CO, and CoA can be partially rate limiting. At optimal conditions of low pH (approximately 5.8) and low ionic strength, the rate-limiting step involves methylation of CODH by the methylated C/Fe-SP. At higher pH values and/or higher ionic strength, transfer of the methyl group of CH3-H4folate to the C/Fe-SP becomes rate limiting. Images

Roberts, J R; Lu, W P; Ragsdale, S W

1992-01-01

121

A propionate CoA-transferase of Ralstonia eutropha H16 with broad substrate specificity catalyzing the CoA thioester formation of various carboxylic acids.  

PubMed

In this study, we have investigated a propionate CoA-transferase (Pct) homologue encoded in the genome of Ralstonia eutropha H16. The corresponding gene has been cloned into the vector pET-19b to yield a histidine-tagged enzyme which was expressed in Escherichia coli BL21 (DE3). After purification, high-performance liquid chromatography/mass spectrometry (HPLC/MS) analyses revealed that the enzyme exhibits a broad substrate specificity for carboxylic acids. The formation of the corresponding CoA-thioesters of acetate using propionyl-CoA as CoA donor, and of propionate, butyrate, 3-hydroxybutyrate, 3-hydroxypropionate, crotonate, acrylate, lactate, succinate and 4-hydroxybutyrate using acetyl-CoA as CoA donor could be shown. According to the substrate specificity, the enzyme can be allocated in the family I of CoA-transferases. The apparent molecular masses as determined by gel filtration and detected by SDS polyacrylamide gel electrophoresis were 228 and 64 kDa, respectively, and point to a quaternary structure of the native enzyme (?4). The enzyme exhibited similarities in sequence and structure to the well investigated Pct of Clostridium propionicum. It does not contain the typical conserved (S)ENG motif, but the derived motif sequence EXG with glutamate 342 to be, most likely, the catalytic residue. Due to the homo-oligomeric structure and the sequence differences with the subclasses IA-C of family I CoA-transferases, a fourth subclass of family I is proposed, comprising - amongst others - the Pcts of R. eutropha H16 and C. propionicum. A markerless precise-deletion mutant R. eutropha H16?pct was generated. The growth and accumulation behaviour of this mutant on gluconate, gluconate plus 3,3'-dithiodipropionic acid (DTDP), acetate and propionate was investigated but resulted in no observable phenotype. Both, the wild type and the mutant showed the same growth and storage behaviour with these carbon sources. It is probable that R. eutropha H16 is upregulating other CoA-transferase(s) or CoA-synthetase(s), thereby compensating for the lacking Pct. The ability of R. eutropha H16 to substitute absent enzymes by isoenzymes has been already shown in different other studies in the past. PMID:23250223

Lindenkamp, Nicole; Schürmann, Marc; Steinbüchel, Alexander

2012-12-19

122

Classification of Sugar Chains of Glycoproteins by Analyzing Reducing End Oligosaccharides Obtained by Partial Acid Hydrolysis  

Microsoft Academic Search

Sugar chain types were classified on the basis of reducing end di- and trisaccharide structures. Sugar chains liberated from glycoproteins by the hydrazinolysis–N-acetylation method were pyridylaminated, and pyridylamino (PA-) sugar chains were purified by HPLC. The PA-sugar chains thus purified were partially hydrolyzed with 1Mtrifluoroacetic acid. The acid hydrolysis conditions were investigated with the object of obtaining PA-di- and trisaccharides

Yasushi Makino; Nahoki Kuraya; Kaoru Omichi; Sumihiro Hase

1996-01-01

123

Measurement of bile acid synthesis by 14CO2: the metabolism of propionyl CoA.  

PubMed

The relationship between 14CO2 evolution from the catabolism of [26 or 2714C] cholesterol to bile acids was studied in rats with biliary fistulae. When equal quantities of [26 or 2714C] cholesterol and [414C] cholesterol were administered, there was a significant linear relationship between 14CO2 expiration in the breath and [414C] bile acid excreted in the bile. Bile acid synthesis calculated as the ratio of 14CO2: molar specific activity of biliary cholesterol correlated highly with biliary bile acid excretion in the bile acid depleted rat. Phenobarbital, a known inducer of gamma-amino levulenic acid formation from succinyl CoA did not alter the relationship between the 14CO2 estimation of bile acid synthesis and biliary bile acid excretion, indicating that the relationship between [26 or 2714C] cholesterol side chain cleavage and 14CO2 formation was not altered. Phenobarbital, however, did cause a reduction in bile acid synthesis measured by 14CO2 evolution and by biliary bile acid excretion. The 14CO2 method underestimated bile acid excretion. 8.7% in untreated and phenobarbital treated rats respectively. Since 11% of the radioactivity which was expired as 14CO2 was isolated as bile acids, radioactivity cleaved as [1 or 314C] propionyl CoA may enter cholesterol-bile acid biosynthesis resulting in the underestimation of bile acid synthesis. To test whether radioactivity from propionyl CoA enters steroid biosynthesis [114C] propionate and [214C] propionate were given to untreated biliary fistula rats and the biliary lipids excreted in 60 hours were analyzed. Incorporation of radioactivity into cholesterol and bile acids was greater after the administration of [214C] propionate than after [114C] propionate than after [114C] propionate, suggesting that radioactivity from propionyl CoA may enter steroid biosynthesis by metabolic events in which the methylene and carboxyl carbon atoms are differentiated. Although the use of 14CO2 expiration from [26 or 2714C] cholesterol catabolism underestimates the rate of bile acid synthesis, it should have many applications because of the constant relationship between 14CO2 formation and cholesterol side chain cleavage. PMID:1202660

Davis, R A; Showalter, P; Kern, F

1975-10-01

124

A quantum chemical study of the reaction mechanism of acetyl-coenzyme a synthase.  

PubMed

Recent experimental and theoretical studies have focused on the mechanism of the A-cluster active site of acetyl-CoA synthase that produces acetyl-CoA from a methyl group, carbon monoxide, and CoA. Several proposals have been made concerning the redox states of the (Ni-Ni) bimetallic center and the iron-sulfur cluster connected to one of the metals. Using hybrid density functional theory, we have investigated putative intermediate states from the catalytic cycle. Among our conclusions are the following: (i) the zerovalent state proposed for the proximal metal is unlikely if the charge on the iron-sulfur cluster is +2; (ii) a mononuclear mechanism in which both CO and CH(3) bind the proximal nickel is favored over the binuclear mechanism in which CO and CH(3) bind the proximal and distal nickel ions, respectively; (iii) the formation of a disulfide bond in the active site could provide the two electrons necessary for the reaction but only if methylation occurs simultaneously; and (iv) the crystallographic closed form of the active site needs to open to accommodate ligands in the equatorial site. PMID:15725036

Amara, Patricia; Volbeda, Anne; Fontecilla-Camps, Juan Carlos; Field, Martin J

2005-03-01

125

The fluorescence-based acetylation assay using thiol-sensitive probes.  

PubMed

Lysine acetyltransferases (KATs) catalyze the acetylation of specific lysine residues in histone and nonhistone proteins. The enzymatic activities of KATs are involved in a broad spectrum of cellular processes. Thus far, the reaction of KAT catalysis has been studied by various bioanalytical methods such as radioisotopic labeling, spectrophotometric and fluorometric measurements, and antibody-dependent immunosorbent assays. In particular, the fluorescent method has the advantage of simplicity for implementation, fast assay speed, fine signal to noise ratio, and superior sensitivity. We describe here the technical protocols of using thiol-sensitive fluorogenic probes for the fluorescent analysis of enzymatic activities of KATs, with males on the first (MOF) as an exemplary KAT enzyme. 7-Diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin (CPM) is selected as the KAT probe owing to its fast reaction kinetics with coenzyme A (CoA) and excellent fluorogenicity upon thiol conjugation. The fluorescence-based acetylation assay is well suited for both kinetic characterization of KAT catalysis and KAT inhibitor investigation. PMID:23381866

Gao, Tielong; Yang, Chao; Zheng, Yujun George

2013-01-01

126

COA Workshop  

Center for Drug Evaluation (CDER)

Text Version... 15 the effects of the medical products that we approve ... 12 information on the effect of the therapy on the ... 11 a look at your calendar and I know you're ... More results from www.fda.gov/downloads/drugs/newsevents

127

Metabolism is regulated by protein acetylation  

Microsoft Academic Search

Lysine acetylation, first identified in histones, was initially thought to be a posttranslational modification occuring only\\u000a in eukaryotic cells that controlled gene transcription either via remodeling chromatin or altering the transcriptional machinery.\\u000a Recent studies, however, have shown that acetylation is a well-conserved metabolic regulatory mechanism that plays critical\\u000a roles in regulating and coordinating cell metabolism. Acetylation regulates metabolism through controlling

Wei Xu; Shimin Zhao

2011-01-01

128

Lysosomal Cholesterol Accumulation Inhibits Subsequent Hydrolysis Of Lipoprotein Cholesteryl Ester  

PubMed Central

Human macrophages incubated for prolonged periods with mildly oxidized LDL (oxLDL) or cholesteryl ester-rich lipid dispersions (DISP) accumulate free and esterified cholesterol within large, swollen lysosomes similar to those in foam cells of atherosclerosis. The cholesteryl ester (CE) accumulation is, in part, the result of inhibition of lysosomal hydrolysis due to increased lysosomal pH mediated by excessive lysosomal free cholesterol (FC). To determine if the inhibition of hydrolysis was long lived and further define the extent of the lysosomal defect, we incubated THP-1 macrophages with oxLDL or DISP to produce lysosome sterol engorgement and then chased with acetylated LDL (acLDL). Unlike oxLDL or DISP, CE from acLDL normally is hydrolyzed rapidly. Three days of incubation with oxLDL or DISP produced an excess of CE in lipid-engorged lysosomes, indicative of inhibition. After prolonged oxLDL or DISP pretreatment, subsequent hydrolysis of acLDL CE was inhibited. Coincident with the inhibition, the lipid-engorged lysosomes failed to maintain an acidic pH during both the initial pretreatment and subsequent acLDL incubation. This indicates that the alterations in lysosomes were general, long-lived and affected subsequent lipoprotein metabolism. This same phenomenon, occurring within atherosclerotic foam cells, could significantly affect lesion progression.

Jerome, W. Gray; Cox, Brian E.; Griffin, Evelyn E.; Ullery, Jody C.

2010-01-01

129

Acetylation regulates Jun protein turnover in Drosophila.  

PubMed

C-Jun is a major transcription factor belonging to the activating protein 1 (AP-1) family. Phosphorylation has been shown to be critical for c-Jun activation and stability. Here, we report that Jra, the Drosophila Jun protein, is acetylated in vivo. We demonstrate that the acetylation of Jra leads to its rapid degradation in response to osmotic stress. Intriguingly, we also found that Jra phosphorylation antagonized its acetylation, indicating the opposite roles of acetylation and phosphorylation in Jra degradation process under osmotic stress. Our results provide new insights into how c-Jun proteins are precisely regulated by the interplay of different posttranslational modifications. PMID:23891849

Zhang, Daoyong; Suganuma, Tamaki; Workman, Jerry L

2013-07-25

130

A method of COA based on multi-agent evolutionary algorithm  

NASA Astrophysics Data System (ADS)

Planning detailed military course of action (COA) is very complex and time consuming. In this paper, a method based on multi-agent evolutionary algorithm was presented to solve COA' resource management and scheduling problems. Each individual can be seen as an agent, in order to realize the local perceptivity of agents, the environment is organized as a latticelike structure. Each agent is fixed on a lattice point and it can only interact with its neighbors .Two agent behaviors which are competition behavior and self-learning behavior are designed. In this work, constraint functions are considered as functions to be optimized like the objectives and then added in competition strategy to deal with the multi-objective aspect of resource-constrained project scheduling problems. This approach avoids the use of a penalty function to deal with constraints. At the same time, the added constraint functions could make the whole algorithm evolving feasible. The simulation results demonstrated that this approach could improve searching ability of this algorithm, and the precision of this method.

Yu, Xin; Wang, Hui; Jiao, Licheng

2009-10-01

131

Characterization and Prediction of Lysine (K)-Acetyl-Transferase Specific Acetylation Sites*  

PubMed Central

Lysine acetylation is a well-studied post-translational modification on both histone and nonhistone proteins. More than 2000 acetylated proteins and 4000 lysine acetylation sites have been identified by large scale mass spectrometry or traditional experimental methods. Although over 20 lysine (K)-acetyl-transferases (KATs) have been characterized, which KAT is responsible for a given protein or lysine site acetylation is mostly unknown. In this work, we collected KAT-specific acetylation sites manually and analyzed sequence features surrounding the acetylated lysine of substrates from three main KAT families (CBP/p300, GCN5/PCAF, and the MYST family). We found that each of the three KAT families acetylates lysines with different sequence features. Based on these differences, we developed a computer program, Acetylation Set Enrichment Based method to predict which KAT-families are responsible for acetylation of a given protein or lysine site. Finally, we evaluated the efficiency of our method, and experimentally detected four proteins that were predicted to be acetylated by two KAT families when one representative member of the KAT family is over expressed. We conclude that our approach, combined with more traditional experimental methods, may be useful for identifying KAT families responsible for acetylated substrates proteome-wide.

Li, Tingting; Du, Yipeng; Wang, Likun; Huang, Lei; Li, Wenlin; Lu, Ming; Zhang, Xuegong; Zhu, Wei-Guo

2012-01-01

132

Characterization and prediction of lysine (K)-acetyl-transferase specific acetylation sites.  

PubMed

Lysine acetylation is a well-studied post-translational modification on both histone and nonhistone proteins. More than 2000 acetylated proteins and 4000 lysine acetylation sites have been identified by large scale mass spectrometry or traditional experimental methods. Although over 20 lysine (K)-acetyl-transferases (KATs) have been characterized, which KAT is responsible for a given protein or lysine site acetylation is mostly unknown. In this work, we collected KAT-specific acetylation sites manually and analyzed sequence features surrounding the acetylated lysine of substrates from three main KAT families (CBP/p300, GCN5/PCAF, and the MYST family). We found that each of the three KAT families acetylates lysines with different sequence features. Based on these differences, we developed a computer program, Acetylation Set Enrichment Based method to predict which KAT-families are responsible for acetylation of a given protein or lysine site. Finally, we evaluated the efficiency of our method, and experimentally detected four proteins that were predicted to be acetylated by two KAT families when one representative member of the KAT family is over expressed. We conclude that our approach, combined with more traditional experimental methods, may be useful for identifying KAT families responsible for acetylated substrates proteome-wide. PMID:21964354

Li, Tingting; Du, Yipeng; Wang, Likun; Huang, Lei; Li, Wenlin; Lu, Ming; Zhang, Xuegong; Zhu, Wei-Guo

2011-09-30

133

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

134

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

135

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.

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

2009-01-01

136

A functional Ni-Ni-[4Fe-4S] cluster in the monomeric acetyl-CoA synthase from Carboxydothermus hydrogenoformans.  

PubMed

In anaerobic microorganisms employing the acetyl-CoA pathway, acetyl-CoA synthase (ACS) and CO dehydrogenase (CODH) form a complex (ACS/CODH) that catalyzes the synthesis of acetyl-CoA from CO, a methyl group, and CoA. Previously, a [4Fe-4S] cubane bridged to a copper-nickel binuclear site (active site cluster A of the ACS component) was identified in the ACS(Mt)/CODH(Mt) from Moorella thermoacetica whereas another study revealed a nickel-nickel site in the open form of ACS(Mt), and a zink-nickel site in the closed form. The ACS(Ch) of the hydrogenogenic bacterium Carboxydothermus hydrogenoformans was found to exist as an 82.2-kDa monomer as well as in a 1:1 molar complex with the 73.3-kDa CODHIII(Ch). Homogeneous ACS(Ch) and ACS(Ch)/CODHIII(Ch) catalyzed the exchange between [1-(14)C]acetyl-CoA and (12)CO with specific activities of 2.4 or 5.9 micromol of CO per min per mg, respectively, at 70 degrees C and pH 6.0. They also catalyzed the synthesis of acetyl-CoA from CO, methylcobalamin, corrinoid iron-sulfur protein, and CoA with specific activities of 0.14 or 0.91 micromol of acetyl-CoA formed per min per mg, respectively, at 70 degrees C and pH 7.3. The functional cluster A of ACS(Ch) contains a Ni-Ni-[4Fe-4S] site, in which the positions proximal and distal to the cubane are occupied by Ni ions. This result is apparent from a positive correlation of the Ni contents and negative correlations of the Cu or Zn contents with the acetyl-CoA/CO exchange activities of different preparations of monomeric ACS(Ch), a 2.2-A crystal structure of the dithionite-reduced monomer in an open conformation, and x-ray absorption spectroscopy. PMID:14699043

Svetlitchnyi, Vitali; Dobbek, Holger; Meyer-Klaucke, Wolfram; Meins, Thomas; Thiele, Bärbel; Römer, Piero; Huber, Robert; Meyer, Ortwin

2003-12-29

137

Reverse genetic characterization of two paralogous acetoacetyl CoA thiolase genes in Arabidopsis reveals their importance in plant growth and development  

SciTech Connect

Acetoacetyl CoA thiolase (AACT, EC 2.3.1.9) catalyzes the condensation of two acetyl?CoA molecules to form acetoacetyl?CoA. Two AACT?encoding genes, At5g47720 (AACT1) and At5g48230 (AACT2), were functionally identified in the Arabidopsis genome by direct enzymological assays and functional expression in yeast. Promoter::GUS fusion experiments indicated that AACT1 is primarily expressed in the vascular system and AACT2 is highly expressed in root tips, young leaves, top stems and anthers. Characterization of T?DNA insertion mutant alleles at each AACT locus established that AACT2 function is required for embryogenesis and for normal male gamete transmission. In contrast, plants lacking AACT1 function are completely viable and show no apparent growth phenotypes, indicating that AACT1 is functionally redundant with respect to AACT2 function. RNAi lines that express reduced levels of AACT2 show pleiotropic phenotypes, including reduced apical dominance, elongated life span and flowering duration, sterility, dwarfing, reduced seed yield and shorter root length. Microscopic analysis reveals that the reduced stature is caused by a reduction in cell size and fewer cells, and male sterility is caused by loss of the pollen coat and premature degeneration of the tapetal cells. Biochemical analyses established that the roots of AACT2 RNAi plants show quantitative and qualitative alterations in phytosterol profiles. These phenotypes and biochemical alterations are reversed when AACT2 RNAi plants are grown in the presence of mevalonate, which is consistent with the role of AACT2 in generating the bulk of the acetoacetyl?CoA precursor required for the cytosol?localized, mevalonate?derived isoprenoid biosynthetic pathway.

Jin, Huanan; Song, Zhihong; Nikolau, Basil J.

2012-03-31

138

Dapsone Acetylation and the Treatment of Leprosy  

Microsoft Academic Search

DAPSONE (4,4'-diaminodiphenyl sulphone, DDS) continues to be the standard drug for the treatment of leprosy. Recent studies1 have shown that DDS is converted in man to monoacetyldapsone (MADDS) in a polymorphic fashion by the same enzyme system that acetylates isoniazid and sulphamethazine. Unlike acetylisoniazid and acetylsulphamethazine, however, MADDS is rapidly deacetylated in man. Consequently, constant plasma ratios of acetylated to

G. A. Ellard; Patricia T. Gammon

1972-01-01

139

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)

2012-03-27

140

40 CFR 721.10520 - Acetylated fatty acid glycerides (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Acetylated fatty acid glycerides (generic). 721.10520 Section...721.10520 Acetylated fatty acid glycerides (generic). (a) Chemical substance...generically as acetylated fatty acid glycerides (PMN P-11-160) is...

2013-07-01

141

Method of controlling acetylation of metabolic enzymes  

US Patent & Trademark Office Database

A method for modulating the activity of an AMP-forming enzyme (AFE) is disclosed. The method is based upon the novel observation that the activity of these enzymes is controlled by acetylation of the enzymes to inactivate them and de-acetylation of the enzymes to re-activate them. The acetylation of the enzyme occurs at a characteristic lysine residue. Various polypeptides, nucleic acids and other molecules that are related to modulating the AFE activity are also disclosed. Further disclosed are methods of modulating cellular acetyl-CoA or propionyl-CoA levels in bacterial hosts, methods of identifying agents that can modulate the activity of AFE acetylases, and methods of identifying AFE mutants that are insensitive to acetylation regulation.

Escalante-Semerena; Jorge C. (Madison, WI); Starai; Vincent J. (Madison, WI)

2009-05-12

142

Metabolic stress regulates basic transcription through acetyl-coenzyme A  

Microsoft Academic Search

.  The acetylation and auto-acetylation of general transcription factors has recently been demonstrated, but the functional significance\\u000a of these modifications is unclear. The presence of acetyl-coenzyme A activates basal transcription, and acetylation of transcription\\u000a factor IIB (TFIIB) has been shown to activate transcription in several contexts. If auto-acetylation is an important pathway\\u000a in eukaryotes, the regulatory pathways for acetyl-coenzyme A should

C. H. Choi; A. Zimon; A. Usheva

2005-01-01

143

Acetylation-Mediated Suppression of Transcription-Independent Memory: Bidirectional Modulation of Memory by Acetylation  

PubMed Central

Learning induced changes in protein acetylation, mediated by histone acetyl transferases (HATs), and the antagonistic histone deacetylases (HDACs) play a critical role in memory formation. The status of histone acetylation affects the interaction between the transcription-complex and DNA and thus regulates transcription-dependent processes required for long-term memory (LTM). While the majority of studies report on the role of elevated acetylation in memory facilitation, we address the impact of both, increased and decreased acetylation on formation of appetitive olfactory memory in honeybees. We show that learning-induced changes in the acetylation of histone H3 at aminoacid-positions H3K9 and H3K18 exhibit distinct and different dynamics depending on the training strength. A strong training that induces LTM leads to an immediate increase in acetylation at H3K18 that stays elevated for hours. A weak training, not sufficient to trigger LTM, causes an initial increase in acetylation at H3K18, followed by a strong reduction in acetylation at H3K18 below the control group level. Acetylation at position H3K9 is not affected by associative conditioning, indicating specific learning-induced actions on the acetylation machinery. Elevating acetylation levels by blocking HDACs after conditioning leads to an improved memory. While memory after strong training is enhanced for at least 2 days, the enhancement after weak training is restricted to 1 day. Reducing acetylation levels by blocking HAT activity after strong training leads to a suppression of transcription-dependent LTM. The memory suppression is also observed in case of weak training, which does not require transcription processes. Thus, our findings demonstrate that acetylation-mediated processes act as bidirectional regulators of memory formation that facilitate or suppress memory independent of its transcription-requirement.

Merschbaecher, Katja; Haettig, Jakob; Mueller, Uli

2012-01-01

144

Acetylation-mediated suppression of transcription-independent memory: bidirectional modulation of memory by acetylation.  

PubMed

Learning induced changes in protein acetylation, mediated by histone acetyl transferases (HATs), and the antagonistic histone deacetylases (HDACs) play a critical role in memory formation. The status of histone acetylation affects the interaction between the transcription-complex and DNA and thus regulates transcription-dependent processes required for long-term memory (LTM). While the majority of studies report on the role of elevated acetylation in memory facilitation, we address the impact of both, increased and decreased acetylation on formation of appetitive olfactory memory in honeybees. We show that learning-induced changes in the acetylation of histone H3 at aminoacid-positions H3K9 and H3K18 exhibit distinct and different dynamics depending on the training strength. A strong training that induces LTM leads to an immediate increase in acetylation at H3K18 that stays elevated for hours. A weak training, not sufficient to trigger LTM, causes an initial increase in acetylation at H3K18, followed by a strong reduction in acetylation at H3K18 below the control group level. Acetylation at position H3K9 is not affected by associative conditioning, indicating specific learning-induced actions on the acetylation machinery. Elevating acetylation levels by blocking HDACs after conditioning leads to an improved memory. While memory after strong training is enhanced for at least 2 days, the enhancement after weak training is restricted to 1 day. Reducing acetylation levels by blocking HAT activity after strong training leads to a suppression of transcription-dependent LTM. The memory suppression is also observed in case of weak training, which does not require transcription processes. Thus, our findings demonstrate that acetylation-mediated processes act as bidirectional regulators of memory formation that facilitate or suppress memory independent of its transcription-requirement. PMID:23028801

Merschbaecher, Katja; Haettig, Jakob; Mueller, Uli

2012-09-19

145

Enhanced sensitivity for the determination of ambiphilic polyaromatic amines by LC-MS/MS after acetylation.  

PubMed

A new method for the analysis of aminonitropyrenes and diaminopyrenes was developed for urine and hemoglobin samples using LC-MS/MS. A good separation by LC was only achieved after derivatization of the amino group, which also increased sensitivity to a limit of detection (LOD) of 0.1 pg (on column) for diaminopyrene and 5 pg for aminonitropyrene using electrospray ionization (ESI). Compared to a derivatization with pentafluorobenzoyl chloride yielding only one sensitive MS/MS transition, acetylation offers the advantages of a higher selectivity with two sensitive MS/MS transitions and the possibility of a direct detection of acetylated aminonitropyrenes and diaminopyrenes formed metabolically in vivo. Acetylated diaminopyrene was detected in urine and after hydrolysis of the corresponding hemoglobin adducts followed by acetylation in blood samples of rats after administration of dinitropyrene but not in controls. A method based on GC-MS with negative chemical ionization of the electrophore labelled metabolites was non-selective since only one major ion [M - HF]- was formed and some isobaric peaks were observed preventing unequivocal analyte identification at concentrations close to the LOD. PMID:15844523

Straube, Ellen; Dekant, Wolfgang; Völkel, Wolfgang

2005-03-01

146

Effect of ketanserin tartrate on HMG CoA reductase and LDL receptor activity in cultured human skin fibroblasts  

Microsoft Academic Search

In man ketanserin tartrate reduces plasma LDL cholesterol. To clarify the mechanism of this effect the effect of ketanserin on 3-hydroxy-3-methylglutaryl (HMG) CoA reductase and LDL receptor activity in cultured human skin fibroblasts has been examined.

M. Suzukawa; H. Nakamura

1990-01-01

147

5? end of hmg CoA reductase gene contains sequences responsible for cholesterol-mediated inhibition of transcription  

Microsoft Academic Search

Summary Cholesterol homeostasis is maintained by feedback inhibition of transcription of the gene encoding HMG CoA reductase. To study this mechanism, we joined the 5' end of the hamster reductase gene to the coding region for chloramphenicol acetyltransferase (CAT). The chimeric gene produced high levels of CAT activ- ity in mouse L cells; sterols suppressed expression by 70% to 90%.

Timothy F. Osborne; Joseph L. Goldstein; Michael S. Brown

1985-01-01

148

Identification and characterization of a succinyl-coenzyme A (CoA):benzoate CoA transferase in Geobacter metallireducens.  

PubMed

Geobacter metallireducens is a Fe(III)-respiring deltaproteobacterium and serves as a model organism for aromatic compound-degrading, obligately anaerobic bacteria. In this study, a genetic system was established for G. metallireducens using nitrate as an alternative electron acceptor. Surprisingly, disruption of the benzoate-induced bamY gene, encoding a benzoate coenzyme A (CoA) ligase, reproducibly showed an increased biomass yield in comparison to the wild type during growth with benzoate but not during growth with acetate. Complementation of bamY in trans converted the biomass yield back to the wild-type level. Growth of the bamY mutant with benzoate can be rationalized by the identification of a previously unknown succinyl-CoA:benzoate CoA transferase activity; it represents an additional, energetically less demanding mode of benzoate activation. The activity was highly enriched from extracts of cells grown on benzoate, yielding a 50-kDa protein band; mass spectrometric analysis identified the corresponding benzoate-induced gene annotated as a CoA transferase. It was heterologously expressed in Escherichia coli and characterized as a specific succinyl-CoA:benzoate CoA transferase. The newly identified enzyme in conjunction with a benzoate-induced succinyl-CoA synthetase links the tricarboxylic acid cycle to the upper benzoyl-CoA degradation pathway during growth on aromatic growth substrates. PMID:22408161

Oberender, Jana; Kung, Johannes W; Seifert, Jana; von Bergen, Martin; Boll, Matthias

2012-03-09

149

Carnitine palmitoyl transferase activity in Morris Hepatoma 7777 mitochondria and its sensitivity to malonyl CoA inhibition  

SciTech Connect

Earlier reports in the literature have indicated no detectable Carnitine Palymitoyl Transferase (CPT) activity in homogenates prepared from Morris Hepatoma 7777. In its study CPT activity in isolated mitochondria (mito) was measured by butanol extraction of the (/sup 3/H)palmitoyl carnitine formed as outlined by Bremer et al. Contrary to the earlier work where no appreciable activity of CPT was observed the authors find significant levels of CPT (2.6 nMol/min/mg protein) in isolated mito from Morris Hepatoma 7777 (MH 7777). The level of CPT activity observed in MH 7777 mito was, however, 36% lower compared to the host liver CPT activity (4.1 nMol/min/mg protein). The enzyme in MH 7777 mito showed 83% inhibition in the presence of 10 ..mu..M malonyl CoA, in agreement with the degree of sensitivity observed with the host liver isolated mito. On freeze thawing host mito, total CPT activity increased and the sensitivity of the enzyme to malonyl CoA decreased. Frozen thawed MH 7777 mito showed a similar response to malonyl CoA but no change in the total CPT level was observed. The authors results establish for the first time the presence of a malonyl CoA sensitive CPT in MH 7777 mito, which may have slightly different properties from normal due to the membrane environment of the enzyme.

Woldegiorgis, G.; Shrago, E.

1986-05-01

150

The hydrolysis and alkylation activities of S-(2-haloethyl)-L-cysteine analogs--evidence for extended half-life.  

PubMed

A series of S-(2-haloethyl)-L-cysteine derivatives, which are analogs of the proposed glutathione half-mustard metabolites of dihaloethanes, were synthesized and studied with respect to their hydrolysis and alkylation rates in aqueous solution. The trend of relative hydrolysis rates, Br greater than Cl much greater than F, paralleled their respective leaving group abilities; however, a dramatic rate increase was seen at pH 8 versus pH's 6 or 4. Hydrolysis of S-(2-chloroethyl)-L-cysteine analogs, where the ionizable groups were blocked (carboxyl esterified and/or N-acetylated), revealed that the amine moiety was responsible for the increased hydrolysis of mustard gas (beta, beta'-dichlorodiethyl sulfide) gave similar results with S-(2-chloroethyl)-L-cysteine, a finding which is consistent with the reaction intermediate being a highly charged species. The alkylation rates with 4-(p-nitrobenzyl)-pyridine were not affected by blocking the ionizable groups. A mechanism of internal cyclization is proposed to explain the accelerated alkaline hydrolysis rates noted with S-(2-haloethyl)-L-cysteines but not with the N-acetylated analogs (mercapturic acids). This scheme proposes the formation of 3-(thiomorpholine)-carboxylic acid as an alternative pathway to the generally accepted hydrolysis reaction. This compound and not S-(2-hydroxyethyl)-L-cysteine was the identified product following pH 10 hydrolysis. Increased hydrolysis half-time of amine-blocked cysteine analogs versus parent cysteine analogs may exist with S-(2-haloethyl)-glutathione derivatives which may explain the substantial nucleic acid alkylation seen with S-(2-haloethyl) derivatives of glutathione. PMID:6636172

Schasteen, C S; Reed, D J

1983-09-30

151

Impairment of mitochondrial acetoacetyl CoA thiolase activity in the colonic mucosa of patients with ulcerative colitis  

PubMed Central

Background and aims Butyrate oxidation by colonocytes is impaired in ulcerative colitis. This study examined the activity of enzymes involved in butyrate oxidation in ulcerative colitis. Methods Activities of mitochondrial acetoacetyl coenzyme A (CoA) thiolase, crotonase and ??hydroxy butyryl CoA dehydrogenase were estimated spectrophotometrically in rectosigmoid mucosal biopsies from patients with ulcerative colitis and Crohn's colitis, and control subjects undergoing colonoscopy for colon cancer or rectal bleeding. Results The activity of mitochondrial acetoacetyl CoA thiolase was decreased by 80% in ulcerative colitis (3.4 (0.58) ?mol/min/g wet weight, n?=?30) compared with control (16.9 (3.5), n?=?18) and with Crohn's colitis (17.6 (3.1), n?=?12) (p<0.0001). The activity of two other mitochondrial butyrate oxidation enzymes—crotonase and ??hydroxy butyryl CoA dehydrogenase—as well as of cytoplasmic thiolase was normal in ulcerative colitis. Mitochondrial thiolase activity in ulcerative colitis did not correlate with clinical, endoscopic or histological indices of disease severity. Mitochondrial thiolase activity was reduced in the normal right colon mucosa of patients with left?sided ulcerative colitis. Enzyme kinetic studies revealed a lowered Vmax, suggesting inhibition at a site distinct from the catalytic site. Reduced thiolase activity in ulcerative colitis was returned to normal by exposure to 0.3?mM ??mercaptoethanol, a reductant. Using normal colon mucosal biopsies, redox modulation of thiolase activity by hydrogen peroxide, a mitochondrial oxidant, could be shown. A significant increase in hydrogen peroxide formation was observed in ulcerative colitis biopsies. Conclusion A defect of mitochondrial acetoacetyl CoA thiolase occurs in ulcerative colitis. Increased reactive oxygen species generation in mitochondria of epithelial cells in ulcerative colitis may underlie this defect.

Santhanam, Srikanth; Venkatraman, Aparna; Ramakrishna, Balakrishnan S

2007-01-01

152

Acetyl-phosphate is a critical determinant of lysine acetylation in E. coli.  

PubMed

Lysine acetylation is a frequently occurring posttranslational modification in bacteria; however, little is known about its origin and regulation. Using the model bacterium Escherichia coli (E. coli), we found that most acetylation occurred at a low level and accumulated in growth-arrested cells in a manner that depended on the formation of acetyl-phosphate (AcP) through glycolysis. Mutant cells unable to produce AcP had significantly reduced acetylation levels, while mutant cells unable to convert AcP to acetate had significantly elevated acetylation levels. We showed that AcP can chemically acetylate lysine residues in vitro and that AcP levels are correlated with acetylation levels in vivo, suggesting that AcP may acetylate proteins nonenzymatically in cells. These results uncover a critical role for AcP in bacterial acetylation and indicate that most acetylation in E. coli occurs at a low level and is dynamically affected by metabolism and cell proliferation in a global, uniform manner. PMID:23830618

Weinert, Brian T; Iesmantavicius, Vytautas; Wagner, Sebastian A; Schölz, Christian; Gummesson, Bertil; Beli, Petra; Nyström, Thomas; Choudhary, Chunaram

2013-07-03

153

Competition between acetate and oleate for the formation of malonyl-CoA and mitochondrial acetyl-CoA in the perfused rat heart  

PubMed Central

We previously showed that in the perfused rat heart, the capacity of n-fatty acids to generate mitochondrial acetyl-CoA decreases as their chain length increases. In the present study, we investigated whether the oxidation of a long-chain fatty acid, oleate, is inhibited by short-chain fatty acids, acetate or propionate (which do and do not generate mitochondrial acetyl-CoA, respectively). We perfused rat hearts with buffer containing 4 mM glucose, 0.2 mM pyruvate, 1 mM lactate, and various concentrations of either (i) [U-13C]acetate, (ii) [U-13C]acetate plus [1-13C]oleate, or (iii) unlabeled propionate plus [1-13C]oleate. Using mass isotopomer analysis, we determined the contributions of the labeled substrates to the acetyl moiety of citrate (a probe of mitochondrial acetyl-CoA) and to malonyl-CoA. We found that acetate, even at low concentration, markedly inhibits the oxidation of [1-13C]oleate in the heart, without change in malonyl-CoA concentration. We also found that propionate, at a concentration higher than 1 mM, decreases (i) the contribution of [1-13C]oleate to mitochondrial acetyl-CoA, and (ii) malonyl-CoA concentration. The inhibition by acetate or propionate of acetyl-CoA production from oleate probably results from a competition for mitochondrial CoA between the CoA-utilizing enzymes.

Bian, Fang; Kasumov, Takhar; Jobbins, Kathryn A.; Minkler, Paul E.; Anderson, Vernon E.; Kerner, Janos; Hoppel, Charles L.; Brunengraber, Henri

2007-01-01

154

Synthesis of Benz[d]oxazolones Involving Concomitant Acetyl Migration from Oxygen to Nitrogen  

Microsoft Academic Search

Heating of o-acetoxybenzoyl azides 6–10 in toluene leads to the Curtius reaction, which, when followed by closure of oxazolone ring with concomitant migration of acetyl group from oxygen to nitrogen, produces 3-acetoxybenz[d]oxazol-2(3H)-ones 11–15, which undergo hydrolysis with hot dilute hydrochloric acid to furnish benz[d]oxazol-2(3H)-ones 17–21. Thermal reaction of 2-hydroxy-5-nitrobenzoyl azide (22) in toluene finally yields a mixture of 5-nitrobenz[d]oxazol-2(3H)-one (20)

Sibdas Ray; Sukla Ghosh

2010-01-01

155

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

156

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...

157

Alkaline Hydrolysis of CL-20.  

National Technical Information Service (NTIS)

The Energetics and Warheads Division of the U.S. Army Armament Research, Development and Engineering Center has been involved in the development of CL-20. An alkaline hydrolysis study was performed to better understand the fate and transport of CL-2O thro...

P. Karakaya M. Sidhourn C. Christodoulatos W. Balas S. Nicolich

2005-01-01

158

Abiotic Hydrolysis of Sorbed Pesticides.  

National Technical Information Service (NTIS)

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...

D. L. Macalady N. L. Wolfe

1984-01-01

159

Nucleosome structural changes due to acetylation.  

PubMed

We have measured the helical repeat of acetylated nucleosomes reconstituted with HeLa cell histone octamers and the 5 S RNA gene positioning sequence from Xenopus borealis. The hydroxyl radical footprinting experiments show that the helical repeat of nucleosome-bound DNA is unchanged upon acetylation, and that the extent of DNA-protein contacts remains unaltered. These results, combined with previous determinations of the linking number change in minichromosomes as a function of the extent of acetylation, are analyzed with surface linking theory. We demonstrate that the shape of the nucleosome changes upon acetylation, in such a way as to decrease the number of times the DNA winds around the nucleosome central axis. PMID:8114086

Bauer, W R; Hayes, J J; White, J H; Wolffe, A P

1994-02-25

160

Regulation of RAS oncogenicity by acetylation.  

PubMed

Members of the RAS small GTPase family regulate cellular responses to extracellular stimuli by mediating the flux through downstream signal transduction cascades. RAS activity is strongly dependent on its subcellular localization and its nucleotide-binding status, both of which are modulated by posttranslational modification. We have determined that RAS is posttranslationally acetylated on lysine 104. Molecular dynamics simulations suggested that this modification affects the conformational stability of the Switch II domain, which is critical for the ability of RAS to interact with guanine nucleotide exchange factors. Consistent with this model, an acetylation-mimetic mutation in K-RAS4B suppressed guanine nucleotide exchange factor-induced nucleotide exchange and inhibited in vitro transforming activity. These data suggest that lysine acetylation is a negative regulatory modification on RAS. Because mutations in RAS family members are extremely common in cancer, modulation of RAS acetylation may constitute a therapeutic approach. PMID:22711838

Yang, Moon Hee; Nickerson, Seth; Kim, Eric T; Liot, Caroline; Laurent, Gaelle; Spang, Robert; Philips, Mark R; Shan, Yibing; Shaw, David E; Bar-Sagi, Dafna; Haigis, Marcia C; Haigis, Kevin M

2012-06-18

161

Reversible Acetylation Of Non Histone Proteins  

Microsoft Academic Search

Post-translational modifications of nonhistone proteins play a significant role in regulating the chromatin structure, dynamics\\u000a and thereby gene regulation. Among the different posttranslational modifications, reversible acetylation of non-histone proteins\\u000a has profound functional implications on wide range of cellular processes. The acetylation status of these proteins is regulated\\u000a by several cellular and non-cellular factors like viruses, physiological stresses, DNA damaging agents

Kiran Batta; Chandrima Das; Shrikanth Gadad; Jayasha Shandilya; Tapas Kundu

162

Levels of histone acetylation in thyroid tumors.  

PubMed

Histone acetylation is a major mechanism to regulate gene transcription. This post-translational modification is modified in cancer cells. In various tumor types the levels of acetylation at several histone residues are associated to clinical aggressiveness. By using immunohistochemistry we show that acetylated levels of lysines at positions 9-14 of H3 histone (H3K9-K14ac) are significantly higher in follicular adenomas (FA), papillary thyroid carcinomas (PTC), follicular thyroid carcinomas (FTC) and undifferentiated carcinomas (UC) than in normal tissues (NT). Similar data have been obtained when acetylated levels of lysine 18 of H3 histone (H3K18ac) were evaluated. In this case, however, no difference was observed between NT and UC. When acetylated levels of lysine 12 of H4 histone (H4K12ac) were evaluated, only FA showed significantly higher levels in comparison with NT. These data indicate that modification histone acetylation is an early event along thyroid tumor progression and that H3K18 acetylation is switched off in the transition between differentiated and undifferentiated thyroid tumors. By using rat thyroid cell lines that are stably transfected with doxycyclin-inducible oncogenes, we show that the oncoproteins RET-PTC, RAS and BRAF increase levels of H3K9-K14ac and H3K18ac. In the non-tumorigenic rat thyroid cell line FRTL-5, TSH increases levels of H3K18ac. However, this hormone decreases levels of H3K9-K14ac and H4K12ac. In conclusion, our data indicate that neoplastic transformation and hormonal stimulation can modify levels of histone acetylation in thyroid cells. PMID:21763277

Puppin, Cinzia; Passon, Nadia; Lavarone, Elisa; Di Loreto, Carla; Frasca, Francesco; Vella, Veronica; Vigneri, Riccardo; Damante, Giuseppe

2011-07-03

163

Acetylation inactivates the transcriptional repressor BCL6  

Microsoft Academic Search

The proto-oncogene BCL6 encodes a BTB\\/POZ-zinc finger transcriptional repressor that is necessary for germinal-center formation and has been implicated in the pathogenesis of B-cell lymphomas. Here we show that the co-activator p300 binds and acetylates BCL6 in vivo and inhibits its function. Acetylation disrupts the ability of BCL6 to recruit histone deacetylases (HDACs), thereby hindering its capacity to repress transcription

Oksana R. Bereshchenko; Wei Gu; Riccardo Dalla-Favera

2002-01-01

164

Bromodomain: an acetyl-lysine binding domain  

Microsoft Academic Search

Bromodomains, an extensive family of evolutionarily conserved protein modules originally found in proteins associated with chromatin and in nearly all nuclear histone acetyltransferases, have been recently discovered to function as acetyl-lysine binding domains. More recent structural studies of bromodomain\\/peptide ligand complexes have enriched our understanding of differences in ligand selectivity of bromodomains. These new findings demonstrate that bromodomain\\/acetyl-lysine recognition can

Lei Zeng; Ming-Ming Zhou

2002-01-01

165

Hydrolysis of Dibromo fluoromethyl triphenylpho sphonium Bromide.  

National Technical Information Service (NTIS)

Hydrolysis of (Ph3PCFBr2)Br(-) afforded a high yield of dibromofluoromethane and triphenylphosphine oxide. Hydrolysis in the presence of a radioactive isotope of bromine gave evidence that the mechanism of this reaction proceeds via the dibromofluoromethi...

D. J. Burton R. M. Flynn R. G. Manning R. M. Kessler

1982-01-01

166

Molecular cloning, and characterization of a modular acetyl xylan esterase from the edible straw mushroom Volvariella volvacea.  

PubMed

A new Volvariella volvacea gene encoding an acetyl xylan esterase (designated as Vvaxe1) was cloned and expressed in Pichia pastoris. The cDNA contained an ORF of 1047 bp encoding 349 amino acids with a calculated mass of 39 990 Da. VvAXE1 is a modular enzyme consisting of an N-terminal signal peptide, a catalytic domain, and a cellulose-binding domain. The amino acid sequence of the enzyme exhibited a high degree of similarity to cinnamoyl esterase B from Penicillium funiculosum, and acetyl xylan esterases from Aspergillus oryzae, Penicillium purpurogenum, and Aspergillus ficuum. Recombinant acetyl xylan esterase released acetate from several acetylated substrates including beta-d-xylose tetraacetate and acetylated xylan. No activity was detectable on p-nitrophenyl acetate. Enzyme-catalyzed hydrolysis of 4-methylumbelliferyl acetate was maximal at pH 8.0 and 60 degrees C, and reciprocal plots revealed an apparent K(m) value of 307.7 microM and a V(max) value of 24 733 IU micromol(-1) protein. ReAXE1 also exhibited a capacity to bind to Avicel and H(3)PO(4) acid-swollen cellulose. PMID:17623028

Ding, Shaojun; Cao, Jie; Zhou, Rui; Zheng, Fei

2007-07-09

167

Purification and Characterization of Acetyl-Coenzyme A Carboxylase from Diclofop-Resistant and -Susceptible Lolium multiflorum.  

PubMed Central

Acetyl-coenzyme A carboxylase (ACCase) was purified >100-fold (specific activity 3.5 units mg-1) from leaf tissue of diclofopresistant and -susceptible biotypes of Lolium multiflorum. As determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified fractions from both biotypes contained a single 206-kD biotinylated polypeptide. The molecular mass of the native enzyme from both biotypes was approximately 520 kD. In some cases the native dimer from both biotypes dissociated during gel filtration to form a subunit of approximately 224 kD. The inclusion of 5% (w/v) polyethylene glycol 3350 (PEG) in the elution buffer prevented this dissociation. Steady-state substrate kinetics were analyzed in both the presence and absence of 5% PEG. For ACCase from both biotypes, addition of PEG increased the velocity 22% and decreased the apparent Km values for acetyl-coenzyme A (acetyl-CoA), but increased the Km values for bicarbonate and ATP. In the presence of PEG, the Km values for bicarbonate and ATP were approximately 35% higher for the enzyme from the susceptible biotype compared with the resistant enzyme. In the absence of PEG, no differences in apparent Km values were observed for the enzymes from the two biotypes. Inhibition constants (Ki app) were determined for CoA, malonyl-CoA, and diclofop. CoA was an S-hyperbolic (slope replots)-I-hyperbolic (intercept replots) noncompetitive inhibitor with respect to acetyl-CoA, with Ki app values of 711 and 795 [mu]M for enzymes from the resistant and susceptible biotypes, respectively. Malonyl-CoA competitively inhibited both enzymes (versus acetyl-CoA) with Ki app values of 140 and 104 [mu]M for ACCase from resistant and susceptible biotypes, respectively. Diclofop was a linear noncompetitive inhibitor of ACCase from the susceptible biotype and a nonlinear, or S-hyperbolic-I-hyperbolic, noncompetitive inhibitor of ACCase from the resistant biotype. For ACCase from the susceptible biotype the slope (Kis) and intercept (Kii) inhibition constants for diclofop versus acetyl-CoA were 0.08 and 0.44 [mu]M, respectively. ACCase from the resistant biotype had a Ki app value of 6.5 [mu]M. At a subsaturating acetyl-CoA concentration of 50 [mu]M, the Hill coefficients for diclofop binding were 0.61 and 1.2 for ACCase from the resistant and susceptible biotypes, respectively. The Hill coefficients for diclofop binding and the inhibitor replots suggest that the resistant form of ACCase exhibits negative cooperativity in binding diclofop. However, the possibility that the nonlinear inhibition of ACCase activity by diclofop in the enzyme fraction isolated from the resistant biotype is due to the presence of both resistant and susceptible forms of ACCase cannot be excluded.

Evenson, K. J.; Gronwald, J. W.; Wyse, D. L.

1994-01-01

168

?-Amylase inactivation during corn starch hydrolysis process  

Microsoft Academic Search

The effects of operating conditions on the enzymatic hydrolysis of corn starch were investigated. A commercial ?-amylase produced by Bacillus sp. was used for the hydrolysis experiments. The degree of starch hydrolysis (%) and residual ?-amylase activity (%) was investigated versus process variables, including pH, temperature, viscosity, impeller speed, processing time and some materials added such as hydrolysate, maltose, glucose,

Dilek K?l?ç Apar; Belma Özbek

2004-01-01

169

?-Amylase inactivation during wheat starch hydrolysis process  

Microsoft Academic Search

The work reported here investigates the effects of operating conditions on enzymic hydrolysis of wheat starch. A commercial ?-amylase enzyme (Gemsize 4A, produced by Bacillus subtilis) was used for the hydrolysis experiments. The degree of hydrolysis (%) and ?-amylase activity (%) were investigated versus the process variables, pH, temperature, viscosity, amount of enzyme preparation added, impeller speed, amount of hydrolysate

Belma Özbek; Semra Yüceer

2001-01-01

170

Specific interaction between S6K1 and CoA synthase: a potential link between the mTOR\\/S6K pathway, CoA biosynthesis and energy metabolism  

Microsoft Academic Search

Ribosomal protein S6 kinase (S6K) is a key regulator of cell size and growth. It is regulated via phosphoinositide 3-kinases (PI3K) and the mammalian target of rapamycin (mTOR) signaling pathways. We demonstrate for the first time that CoA synthase associates specifically with S6K1. The association was observed between native and transiently overexpressed proteins in vivo, as well as by BIAcore

Ivan Nemazanyy; Ganna Panasyuk; Alexander Zhyvoloup; George Panayotou; Ivan T. Gout; Valeriy Filonenko

2004-01-01

171

Kinetic studies of enzymatic hydrolysis of insoluble cellulose: (II) analysis of extended hydrolysis times  

Microsoft Academic Search

The kinetics of enzymatic hydrolysis of pure insoluble cellulose by means of unpurified culture filtrate of Trichoderma reesei was studied, emphasizing the kinetic characteristics associated wit the extended hydrolysis times. The changes in the hydrolysis rate and extent of soluble protein ad sorption during the progress of reaction, either apparent or intrinsic, were investigated. The hydrolysis rate declined drastically during

Yong-Hyun Lee; L. T. Fan

1983-01-01

172

ATP-Citrate Lyase Links Cellular Metabolism to Histone Acetylation  

Microsoft Academic Search

Histone acetylation in single-cell eukaryotes relies on acetyl coenzyme A (acetyl-CoA) synthetase enzymes that use acetate to produce acetyl-CoA. Metazoans, however, use glucose as their main carbon source and have exposure only to low concentrations of extracellular acetate. We have shown that histone acetylation in mammalian cells is dependent on adenosine triphosphate (ATP)-citrate lyase (ACL), the enzyme that converts glucose-derived

Kathryn E. Wellen; Georgia Hatzivassiliou; Uma M. Sachdeva; Thi V. Bui; Justin R. Cross; Craig B. Thompson

2009-01-01

173

Hydrolysis of an acetylthiocholine by pralidoxime iodide (2-PAM).  

PubMed

Pralidoxime iodide (2-PAM), an antidote approved for the reactivation of inhibited acetylcholinesterase (AChE) in organophosphate poisoning, dose-dependently hydrolyzed an acetylthiocholine iodide (ASCh). The AChE (0.3 U) activity inhibited by VX analog (ENMP, 0.1 microM) increased to approximately 200% of normal levels after a dosage of 5 mM 2-PAM (control 0.132+/-0.012 U/ml, 5 mM 0.253+/-0.026 U/ml). This result indicates that 2-PAM produced a thiocholine from the ASCh by hydrolysis. High-performance liquid chromatography (HPLC) analysis was then performed to further clarify the hydrolysis of ASCh with 2-PAM. It was clear that 2-PAM was converted to acetylated 2-PAM with acetic acid produced from ASCh by hydrolysis. Next, we tried to compare this esterase-like activity of 2-PAM with that of obidoxime, which is known as a strong reactivator of inhibited AChE, and with diacetylmonoxime, known as a weak reactivator. All of these oximes showed esterase-like activity, and their strengths were consistent with those of known reactivators of inhibited AChE. These results indicate that a great deal of the data obtained previously with ASCh relating to the effects of oximes must be rechecked. It is clear that oximes easily hydrolyze ASCh. We therefore strongly caution that the method of determining AChE activity with ASCh is not suitable for examining the effects of oximes. PMID:16971069

Sakurada, Koichi; Ikegaya, Hiroshi; Ohta, Hikoto; Akutsu, Tomoko; Takatori, Takehiko

2006-08-12

174

Molecular characterization of a heteromeric ATP-citrate lyase that generates cytosolic acetyl-coenzyme A in Arabidopsis.  

PubMed

Acetyl-coenzyme A (CoA) is used in the cytosol of plant cells for the synthesis of a diverse set of phytochemicals including waxes, isoprenoids, stilbenes, and flavonoids. The source of cytosolic acetyl-CoA is unclear. We identified two Arabidopsis cDNAs that encode proteins similar to the amino and carboxy portions of human ATP-citrate lyase (ACL). Coexpression of these cDNAs in yeast (Saccharomyces cerevisiae) confers ACL activity, indicating that both the Arabidopsis genes are required for ACL activity. Arabidopsis ACL is a heteromeric enzyme composed of two distinct subunits, ACLA (45 kD) and ACLB (65 kD). The holoprotein has a molecular mass of 500 kD, which corresponds to a heterooctomer with an A(4)B(4) configuration. ACL activity and the ACLA and ACLB polypeptides are located in the cytosol, consistent with the lack of targeting peptides in the ACLA and ACLB sequences. In the Arabidopsis genome, three genes encode for the ACLA subunit (ACLA-1, At1g10670; ACLA-2, At1g60810; and ACLA-3, At1g09430), and two genes encode the ACLB subunit (ACLB-1, At3g06650 and ACLB-2, At5g49460). The ACLA and ACLB mRNAs accumulate in coordinated spatial and temporal patterns during plant development. This complex accumulation pattern is consistent with the predicted physiological needs for cytosolic acetyl-CoA, and is closely coordinated with the accumulation pattern of cytosolic acetyl-CoA carboxylase, an enzyme using cytosolic acetyl-CoA as a substrate. Taken together, these results indicate that ACL, encoded by the ACLA and ACLB genes of Arabidopsis, generates cytosolic acetyl-CoA. The heteromeric organization of this enzyme is common to green plants (including Chlorophyceae, Marchantimorpha, Bryopsida, Pinaceae, monocotyledons, and eudicots), species of fungi, Glaucophytes, Chlamydomonas, and prokaryotes. In contrast, all known animal ACL enzymes have a homomeric structure, indicating that a evolutionary fusion of the ACLA and ACLB genes probably occurred early in the evolutionary history of this kingdom. PMID:12376641

Fatland, Beth L; Ke, Jinshan; Anderson, Marc D; Mentzen, Wieslawa I; Cui, Li Wei; Allred, C Christy; Johnston, Jerry L; Nikolau, Basil J; Wurtele, Eve Syrkin

2002-10-01

175

Molecular Characterization of a Heteromeric ATP-Citrate Lyase That Generates Cytosolic Acetyl-Coenzyme A in Arabidopsis1[w  

PubMed Central

Acetyl-coenzyme A (CoA) is used in the cytosol of plant cells for the synthesis of a diverse set of phytochemicals including waxes, isoprenoids, stilbenes, and flavonoids. The source of cytosolic acetyl-CoA is unclear. We identified two Arabidopsis cDNAs that encode proteins similar to the amino and carboxy portions of human ATP-citrate lyase (ACL). Coexpression of these cDNAs in yeast (Saccharomyces cerevisiae) confers ACL activity, indicating that both the Arabidopsis genes are required for ACL activity. Arabidopsis ACL is a heteromeric enzyme composed of two distinct subunits, ACLA (45 kD) and ACLB (65 kD). The holoprotein has a molecular mass of 500 kD, which corresponds to a heterooctomer with an A4B4 configuration. ACL activity and the ACLA and ACLB polypeptides are located in the cytosol, consistent with the lack of targeting peptides in the ACLA and ACLB sequences. In the Arabidopsis genome, three genes encode for the ACLA subunit (ACLA-1, At1g10670; ACLA-2, At1g60810; and ACLA-3, At1g09430), and two genes encode the ACLB subunit (ACLB-1, At3g06650 and ACLB-2, At5g49460). The ACLA and ACLB mRNAs accumulate in coordinated spatial and temporal patterns during plant development. This complex accumulation pattern is consistent with the predicted physiological needs for cytosolic acetyl-CoA, and is closely coordinated with the accumulation pattern of cytosolic acetyl-CoA carboxylase, an enzyme using cytosolic acetyl-CoA as a substrate. Taken together, these results indicate that ACL, encoded by the ACLA and ACLB genes of Arabidopsis, generates cytosolic acetyl-CoA. The heteromeric organization of this enzyme is common to green plants (including Chlorophyceae, Marchantimorpha, Bryopsida, Pinaceae, monocotyledons, and eudicots), species of fungi, Glaucophytes, Chlamydomonas, and prokaryotes. In contrast, all known animal ACL enzymes have a homomeric structure, indicating that a evolutionary fusion of the ACLA and ACLB genes probably occurred early in the evolutionary history of this kingdom.

Fatland, Beth L.; Ke, Jinshan; Anderson, Marc D.; Mentzen, Wieslawa I.; Cui, Li Wei; Allred, C. Christy; Johnston, Jerry L.; Nikolau, Basil J.; Wurtele, Eve Syrkin

2002-01-01

176

Hydroxymethylglutaryl CoA reductase and the modulation of microsomal cholesterol content by the nonspecific lipid transfer protein  

Microsoft Academic Search

The influence of membrane cholesterol content on 3-hYdroxY-3-methYlglutarYl CoA reductase (HMG-CoA reduc- tase, EC 1.1.1.34) in rat liver microsomes was investigated. Mi- crosomes were enriched in cholesterol by incubation with egg phosphatidylcholine-cholesterol vesicles and the nonspecific lipid transfer protein from rat liver. By this method, the microsomal cholesterol content was 2.5-fold enhanced up to final concen- either a normal or

G. Paul; H. van Heusden; Karel W. A. Wirtz

177

Cellulase hydrolysis of unsorted MSW.  

PubMed

A recent development in waste management and engineering has shown that the cellulase can be used for the liquefaction of organic fractions in household waste. The focus of this study was to optimize the enzyme hydrolysis of thermally treated municipal solid waste (MSW) by the addition of surfactant. Concurrently, the enzyme performance was analysed on pure cellulose in a solution of MSW wastewater. Results showed no effect of surfactant addition to the hydrolysis media as measured by viscosity and particle size distribution. MSW treatment wastewater was found to contain a high amount of calcium, potassium, sodium, chloride and others that may affect cellulolytic enzymes. Cellulase performance showed no effect of adding the metal ion-chelating agent EDTA to the solution. The cellulases were stable, tolerated and functioned in the presence of several contaminants. PMID:21989799

Jensen, Jacob Wagner; Felby, Claus; Jørgensen, Henning

2011-10-12

178

Yeast Phospholipase C Is Required for Normal Acetyl-CoA Homeostasis and Global Histone Acetylation.  

PubMed

Phospholipase C (Plc1p) is required for the initial step of inositol polyphosphate (InsP) synthesis, and yeast cells with deletion of the PLC1 gene are completely devoid of any InsPs and display aberrations in transcriptional regulation. Here we show that Plc1p is required for a normal level of histone acetylation; plc1? cells that do not synthesize any InsPs display decreased acetylation of bulk histones and global hypoacetylation of chromatin histones. In accordance with the role of Plc1p in supporting histone acetylation, plc1? mutation is synthetically lethal with mutations in several subunits of SAGA and NuA4 histone acetyltransferase (HAT) complexes. Conversely, the growth rate, sensitivity to multiple stresses, and the transcriptional defects of plc1? cells are partially suppressed by deletion of histone deacetylase HDA1. The histone hypoacetylation in plc1? cells is due to the defect in degradation of repressor Mth1p, and consequently lower expression of HXT genes and reduced conversion of glucose to acetyl-CoA, a substrate for HATs. The histone acetylation and transcriptional defects can be partially suppressed and the overall fitness improved in plc1? cells by increasing the cellular concentration of acetyl-CoA. Together, our data indicate that Plc1p and InsPs are required for normal acetyl-CoA homeostasis, which, in turn, regulates global histone acetylation. PMID:23913687

Galdieri, Luciano; Chang, Jennifer; Mehrotra, Swati; Vancura, Ales

2013-08-02

179

Hydrolysis of Hexanitrohexaazaisowurtzitane (CL20)  

Microsoft Academic Search

The hydrolysis of the ?, ?, and ? polymorphs of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20) was investigated in dilute buffered aqueous solutions over a pH range of 4–10 and at 35, 43, 50, 58 and 65°C, with starting concentrations of CL-20 at one half the solubility limit for the respective temperature. In all cases, an overall first-order kinetic behavior was observed. The rate constants,

Julius Pavlov; Christos Christodoulatos; Mohammed Sidhoum; Steven Nicolich; Wendy Balas; Agamemnon Koutsospyros

2007-01-01

180

The chlorination of hydrolysis lignin  

Microsoft Academic Search

Summary 1.Technical hydrolysis lignin is easily chlorinated at 20° by solutions of chlorine in carbon tetrachloride or by chlorine water. When 25–27% of chlorine is introduced, the latter is quantitatively removed from the solution by the lignin.2.The chlorine content of products chlorinated in carbon tetrachloide is very close to that required by calculation for the substitution reaction.3.When lignin is chlorinated

N. N. Shorygina; L. I. Kolotova

1953-01-01

181

Hydrolysis of titanium sulphate compounds  

Microsoft Academic Search

The influence of TiOSO4 and free sulphuric acid concentrations in the starting solution on the degree of titanyl sulphate conversion to hydrated\\u000a titanium dioxide and post-hydrolytic sulphuric acid was studied. Titanyl sulphate solution, an intermediate product in the\\u000a commercial preparation of titanium dioxide pigments by sulphate route, was used. It was found that the degree of hydrolysis\\u000a markedly depends on

Barbara U. Grzmil; Daniel Grela; Bogumi? Kic

2008-01-01

182

Contribution of CoA ligases to benzenoid biosynthesis in petunia flowers.  

PubMed

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

2012-05-30

183

Cloning and characterization of the human mitochondrial 3-hydroxy-3-methylglutaryl CoA synthase gene.  

PubMed

We report the characterization of lambda and P1 phage clones containing the entire human mitochondrial 3-hydroxy-3-methylglutaryl CoA synthase (mHS) gene. The human mHS locus (HMGCS2) on chromosome 1p12-13 spans 25 kb and contains 10 exons. Exon 1 contains most of the mitochondrial leader, consistent with a recent hypothesis of the evolution of the ketogenic pathway. By primer extension and cDNA amplification (RACE-PCR) we localized the transcription start point (tsp) to 60 bp upstream of the initiation codon. Nine blocks of conserved sequence were identified by comparing the 5' flanking regions of the mHS genes of human and rat. The 5' flanking region contains potential binding sites for TATA-binding protein, Sp1, nuclear factor 1 (NF1), CAAT-box binding protein (C/EBP), hepatocyte nuclear factors 1 and 5 (HNF1, HNF5) and activator proteins 1 and 2 (AP1, AP2). PMID:9305755

Boukaftane, Y; Mitchell, G A

1997-08-22

184

Cloning, Expression and Purification of an Acetoacetyl CoA Thiolase from Sunflower Cotyledon  

PubMed Central

Thiolase I and II coexist as part of the glyoxysomal ?-oxidation system in sunflower (Helianthus annuus L.) cotyledons, the only system shown to have both forms. The importance of thiolases can be underscored not only by their ubiquity, but also by their involvement in a wide variety of processes in plants, animals and bacteria. Here we describe the cloning, expression and purification of acetoacetyl CoA thiolase (AACT) in enzymatically active form. Use of the extensive amount of sequence information from the databases facilitated the efficient generation of the gene-specific primers used in the RACE protocols. The recombinant AACT (1233 bp) shares 75% similarity with other plant AACTs. Comparison of specific activity of this recombinant AACT to a previously reported enzyme purified from primary sunflower cotyledon tissue was very similar (263 nkat/mg protein vs 220 nkat/mg protein, respectively). Combining the most pure fractions from the affinity column, the enzyme was purified 88-fold with a 55% yield of the enzymatically active, 47 kDa AACT.

Dyer, James H.; Maina, Anthony; Gomez, Iris D.; Cadet, Melissa; Oeljeklaus, Silke; Schiedel, Anke C.

2009-01-01

185

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.

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

2012-01-01

186

Expression and Characterization of ?-Methylacyl CoA Racemase from Anisakis simplex Larvae  

PubMed Central

Larval excretory-secretory products of Anisakis simplex are known to cause allergic reactions in humans. A cDNA library of A. simplex 3rd-stage larvae (L3) was immunoscreened with polyclonal rabbit serum raised against A. simplex L3 excretory-secretory products to identify an antigen that elicits the immune response. One cDNA clone, designated as ?-methylacyl CoA racemase (Amacr) contained a 1,412 bp cDNA transcript with a single open reading frame that encoded 418 amino acids. A. simplex Amacr showed a high degree of homology compared to Amacr orthologs from other species. Amacr mRNA was highly and constitutively expressed regardless of temperature (10-40?) and time (24-48 hr). Immunohistochemical analysis revealed that Amacr was expressed mainly in the ventriculus of A. simplex larvae. The Amacr protein produced in large quantities from the ventriculus is probably responsible for many functions in the development and growth of A. simplex larvae.

Kim, Bong Jin; Kim, Sun Mi; Cho, Min Kyung; Yu, Hak Sun; Lee, Yong Seok; Cha, Hee Jae

2012-01-01

187

Expression and characterization of ?-methylacyl CoA racemase from Anisakis simplex larvae.  

PubMed

Larval excretory-secretory products of Anisakis simplex are known to cause allergic reactions in humans. A cDNA library of A. simplex 3rd-stage larvae (L3) was immunoscreened with polyclonal rabbit serum raised against A. simplex L3 excretory-secretory products to identify an antigen that elicits the immune response. One cDNA clone, designated as ?-methylacyl CoA racemase (Amacr) contained a 1,412 bp cDNA transcript with a single open reading frame that encoded 418 amino acids. A. simplex Amacr showed a high degree of homology compared to Amacr orthologs from other species. Amacr mRNA was highly and constitutively expressed regardless of temperature (10-40?) and time (24-48 hr). Immunohistochemical analysis revealed that Amacr was expressed mainly in the ventriculus of A. simplex larvae. The Amacr protein produced in large quantities from the ventriculus is probably responsible for many functions in the development and growth of A. simplex larvae. PMID:22711931

Kim, Bong Jin; Kim, Sun Mi; Cho, Min Kyung; Yu, Hak Sun; Lee, Yong Seok; Cha, Hee Jae; Ock, Meesun

2012-05-24

188

The sleep inducing brain lipid cis-oleamide (cOA) does not modulate serotonergic transmission in the CA1 pyramidal neurons of the hippocampus in vitro  

Microsoft Academic Search

cis-Oleamide (cOA) is a novel sleep inducing brain lipid with an unknown mechanism of action. High affinity interactions with metabotropic 5-HT receptors (2A\\/C and 1A subtypes) in frog oocytes and expression systems have been reported, but functional in vitro evidence for the modulatory effect is still lacking. Here, we addressed the ability of cOA to modulate 5-HT-induced cellular actions in

Antonios Dougalis; George Lees; C. Robin Ganellin

2004-01-01

189

Acyl CoA profiles of transgenic plants that accumulate medium-chain fatty acids indicate inefficient storage lipid synthesis in developing oilseeds.  

PubMed

Several Brassica napus lines transformed with genes responsible for the synthesis of medium- or long-chain fatty acids were examined to determine limiting factor(s) for the subsequent accumulation of these fatty acids in seed lipids. Examination of a decanoic acid (10:0) accumulating line revealed a disproportionately high concentration of 10:0 CoA during seed development compared to long-chain acyl CoAs isolated from the same tissues, suggesting that poor incorporation of 10:0 CoA into seed lipids limits 10:0 fatty acid accumulation. This relationship was also seen for dodecanoyl (12:0) CoA and fatty acid in a high 12:0 line, but not for octadecanoic (18:0) CoA and fatty acid in a high 18:0 line. Comparison of 10:0 CoA and fatty acid proportions from seeds at different developmental stages for transgenic B. napus and Cuphea hookeriana, the source plant for the medium-chain thioesterase and 3-ketoacyl-ACP synthase transgenes, revealed that C. hookeriana incorporates 10:0 CoA into seed lipids more efficiently than transgenic B. napus. Furthermore, beta-oxidation and glyoxylate cycle activities were not increased above wild type levels during seed development in the 8:0/10:0 line, suggesting that lipid catabolism was not being induced in response to the elevated 10:0 CoA concentrations. Taken together, these data suggest that transgenic plants that are engineered to synthesize medium-chain fatty acids may lack the necessary mechanisms, such as specific acyltransferases, to incorporate these fatty acids efficiently into seed lipids. PMID:12445123

Larson, Tony R; Edgell, Teresa; Byrne, James; Dehesh, Katayoon; Graham, Ian A

2002-11-01

190

Biochemical characterization of recombinant cinnamoyl CoA reductase 1 (Ll-CCRH1) from Leucaena leucocephala.  

PubMed

Recombinant cinnamoyl CoA reductase 1 (Ll-CCRH1) protein from Leucaena leucocephala was overexpressed in Escherichia coli BL21 (DE3) strain and purified to apparent homogeneity. Optimum pH for forward and reverse reaction was found to be 6.5 and 7.8 respectively. The enzyme was most stable around pH 6.5 at 25°C for 90 min. The enzyme showed Kcat/Km for feruloyl, caffeoyl, sinapoyl, coumaroyl CoA, coniferaldehyde and sinapaldehyde as 4.6, 2.4, 2.3, 1.7, 1.9 and 1.2 (×10(6) M(-1) s(-1)), respectively, indicating affinity of enzyme for feruloyl CoA over other substrates and preference of reduction reaction over oxidation. Activation energy, Ea for various substrates was found to be in the range of 20-50 kJ/mol. Involvement of probable carboxylate ion, histidine, lysine or tyrosine at the active site of enzyme was predicted by pH activity profile. SAXS studies of protein showed radius 3.04 nm and volume 49.25 nm(3) with oblate ellipsoid shape. Finally, metal ion inhibition studies revealed that Ll-CCRH1 is a metal independent enzyme. PMID:23541561

Sonawane, Prashant; Vishwakarma, Rishi Kishore; Khan, Bashir M

2013-03-26

191

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

PubMed

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

2013-06-10

192

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

2013-02-08

193

Proteomic analysis of acetylation in thermophilic Geobacillus kaustophilus.  

PubMed

Recent analysis of prokaryotic N(?)-lysine-acetylated proteins highlights the posttranslational regulation of a broad spectrum of cellular proteins. However, the exact role of acetylation remains unclear due to a lack of acetylated proteome data in prokaryotes. Here, we present the N(?)-lysine-acetylated proteome of gram-positive thermophilic Geobacillus kaustophilus. Affinity enrichment using acetyl-lysine-specific antibodies followed by LC-MS/MS analysis revealed 253 acetylated peptides representing 114 proteins. These acetylated proteins include not only common orthologs from mesophilic Bacillus counterparts, but also unique G. kaustophilus proteins, indicating that lysine acetylation is pronounced in thermophilic bacteria. These data complement current knowledge of the bacterial acetylproteome and provide an expanded platform for better understanding of the function of acetylation in cellular metabolism. PMID:23696451

Lee, Dong-Woo; Kim, Dooil; Lee, Yong-Jik; Kim, Jung-Ae; Choi, Ji Young; Kang, Sunghyun; Pan, Jae-Gu

2013-07-11

194

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...

195

Molecular biology of acetyl-CoA metabolism.  

PubMed

We have characterized the expression of potential acetyl-CoA-generating genes (acetyl-CoA synthetase, pyruvate decarboxylase, acetaldehyde dehydrogenase, plastidic pyruvate dehydrogenase complex and ATP-citrate lyase), and compared these with the expression of acetyl-CoA-metabolizing genes (heteromeric and homomeric acetyl-CoA carboxylase). These comparisons have led to the development of testable hypotheses as to how distinct pools of acetyl-CoA are generated and metabolized. These hypotheses are being tested by combined biochemical, genetic and molecular biological experiments, which is providing insights into how acetyl-CoA metabolism is regulated. PMID:11171136

Nikolau, B J; Oliver, D J; Schnable, P S; Wurtele, E S

2000-12-01

196

HMG CoA Reductase Inhibitors, NSAIDs and Risk of Glioma  

PubMed Central

HMG Co-A reductase inhibitors (statins) have shown inverse associations with cancer risks, but the results have been inconsistent. Since there is no previous published data in brain tumors, we conducted a case-control study to investigate statin therapy and risk of glioma. We also further evaluated the use of nonsteriodal anti-inflammatory drugs (NSAIDs) in the risk of these tumors. We recruited newly diagnosed glioma cases and frequency matched controls at Columbia University and the University of California San Francisco. Standardized questions on statins and NSAIDs were used at both institutions. Intakes of these drugs were defined as > 6 months of at least twice weekly use versus less than this amount or never use. From July 2007 to January 2010, we recruited a total of 517 cases and 400 controls. Simvastatin and lovastatin showed significant inverse associations with glioma (OR = 0.49, 95% CI 0.30, 0.81 and OR = 0.47, 95% CI 0.24, 0.93, respectively). In NSAIDs, aspirin use was also inversely related to glioma risk (OR = 0.68, 95% CI 0.49, 0.96). Both statins and NSAIDs showed significant inverse trends between duration of drug use and glioma risks (trend tests p = 0.03 and p = 0.02, respectively), and drug intake > 120 months demonstrated the most significant associations for both types of medication. The inverse association between statin therapy and risk of glioma supports the roles of Ras/Rho GTPases or inflammatory cytokines in gliomagenesis, and similar relationship between NSAIDs and glioma highlights the importance of cyclo-oxygenase-2 in glioma pathogenesis.

Ferris, Jennifer; McCoy, Lucie; Neugut, Alfred I; Wrensch, Margaret; Lai, Rose

2012-01-01

197

4-coumarate: CoA ligase partitions metabolites for eugenol biosynthesis.  

PubMed

Biosynthesis of eugenol shares its initial steps with that of lignin, involving conversion of hydroxycinnamic acids to their corresponding coenzyme A (CoA) esters by 4-coumarate:CoA ligases (4CLs). In this investigation, a 4CL (OS4CL) was identified from glandular trichome-rich tissue of Ocimum sanctum with high sequence similarity to an isoform (OB4CL_ctg4) from Ocimum basilicum. The levels of OS4CL and OB4CL_ctg4-like transcripts were highest in O. sanctum trichome, followed by leaf, stem and root. The eugenol content in leaf essential oil was positively correlated with the expression of OS4CL in the leaf at different developmental stages. Recombinant OS4CL showed the highest activity with p-coumaric acid, followed by ferulic, caffeic and trans-cinnamic acids. Transient RNA interference (RNAi) suppression of OS4CL in O. sanctum leaves caused a reduction in leaf eugenol content and trichome transcript level, with a considerable increase in endogenous p-coumaric, ferulic, trans-cinnamic and caffeic acids. A significant reduction in the expression levels was observed for OB4CL_ctg4-related transcripts in suppressed trichome compared with transcripts similar to the other four isoforms (OB4CL_ctg1, 2, 3 and 5). Sinapic acid and lignin content were also unaffected in RNAi suppressed leaf samples. Transient expression of OS4CL-green fluorescent protein fusion protein in Arabidopsis protoplasts was associated with the cytosol. These results indicate metabolite channeling of intermediates towards eugenol by a specific 4CL and is the first report demonstrating the involvement of 4CL in creation of virtual compartments through substrate utilization and committing metabolites for eugenol biosynthesis at an early stage of the pathway. PMID:23677922

Rastogi, Shubhra; Kumar, Ritesh; Chanotiya, Chandan S; Shanker, Karuna; Gupta, Madan M; Nagegowda, Dinesh A; Shasany, Ajit K

2013-05-14

198

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

199

Low temperature hydrolysis for ethanol production  

SciTech Connect

Hydrolysis of corn was compared at two temperatures of 100/sup 0/C and 75/sup 0/C. Starch conversion to dextrose and then ethanol were determined. Yields were 10.69% ethanol in the fermented beer for 100/sup 0/C and 9.89% for 75/sup 0/C. The 75/sup 0/C hydrolysis required about 100 MJ less thermal energy than the 100/sup 0/C hydrolysis. The effects of contamination and respiration were also assessed.

Garcia, A.; Fischer, J.R.; Iannotti, E.L.

1982-12-01

200

Latest advancements in the acetylation of wood fibers to improve ...  

Treesearch

The acetylated fiber is then stripped in a first step with superheated vapor of ... more stable to dimensional changes in both high relative humidity and liquid water ... Keywords: Fibers, acetylation, dimensional stability, equilibrium moisture  ...

201

ATP-citrate lyase links cellular metabolism to histone acetylation  

PubMed Central

Histone acetylation in single cell eukaryotes relies on acetyl-CoA synthetase enzymes that utilize acetate to produce acetyl-CoA. Metazoans, however, use glucose as their main carbon source and have exposure to only low concentrations of extracellular acetate. We show that histone acetylation in mammalian cells is dependent on ATP-citrate lyase (ACL), the enzyme that converts glucose-derived citrate into acetyl-CoA. We find that ACL is required for increases in histone acetylation in response to growth factor stimulation and during differentiation, and that glucose availability can impact histone acetylation in an ACL-dependent manner. Together, these findings suggest that ACL activity is required to link growth-factor-induced increases in nutrient metabolism to the regulation of histone acetylation and gene expression.

Wellen, Kathryn E.; Hatzivassiliou, Georgia; Sachdeva, Uma M.; Bui, Thi V.; Cross, Justin R.; Thompson, Craig B.

2009-01-01

202

The Crystal Structure of N-Acetyl-L-glutamate Synthase from Neisseria gonorrhoeae Provides Insights into Mechanisms of Catalysis and Regulation  

SciTech Connect

The crystal structures of N-acetylglutamate synthase (NAGS) in the arginine biosynthetic pathway of Neisseria gonorrhoeae complexed with acetyl-CoA and with CoA plus N-acetylglutamate have been determined at 2.5- and 2.6-A resolution, respectively. The monomer consists of two separately folded domains, an amino acid kinase (AAK) domain and an N-acetyltransferase (NAT) domain connected through a 10-A linker. The monomers assemble into a hexameric ring that consists of a trimer of dimers with 32-point symmetry, inner and outer ring diameters of 20 and 100A, respectively, and a height of 110A(.) Each AAK domain interacts with the cognate domains of two adjacent monomers across two 2-fold symmetry axes and with the NAT domain from a second monomer of the adjacent dimer in the ring. The catalytic sites are located within the NAT domains. Three active site residues, Arg316, Arg425, and Ser427, anchor N-acetylglutamate in a position at the active site to form hydrogen bond interactions to the main chain nitrogen atoms of Cys356 and Leu314, and hydrophobic interactions to the side chains of Leu313 and Leu314. The mode of binding of acetyl-CoA and CoA is similar to other NAT family proteins. The AAK domain, although catalytically inactive, appears to bind arginine. This is the first reported crystal structure of any NAGS, and it provides insights into the catalytic function and arginine regulation of NAGS enzymes.

Shi, Dashuang; Sagar, Vatsala; Jin, Zhongmin; Yu, Xiaolin; Caldovic, Ljubica; Morizono, Hiroki; Allewell, Norma M.; Tuchman, Mendel (Maryland); (GWU); (Georgia)

2010-01-07

203

An acetylated bidesmosidic saponin from Schefflera octophylla.  

PubMed

A new acetylated bidesmosidic triterpenoid saponin has been isolated from the leaves of Schefflera octophylla and structurally elucidated as 3-epi-betulinic acid 3-O-beta-D-6'-acetylglucopyranoside 28-[alpha-L-rhamnopyranosyl(1----4)-O-beta-D-glucopyranosyl(1----6)]-bet a-D-0-glucopyranoside [1]. PMID:1512601

Tran, V S; Adam, G

1992-04-01

204

Degradation of Aromatics and Chloroaromatics by Pseudomonas sp. Strain B13: Purification and Characterization of 3-Oxoadipate:Succinyl-Coenzyme A (CoA) Transferase and 3-Oxoadipyl-CoA Thiolase  

PubMed Central

The degradation of 3-oxoadipate in Pseudomonas sp. strain B13 was investigated and was shown to proceed through 3-oxoadipyl-coenzyme A (CoA) to give acetyl-CoA and succinyl-CoA. 3-Oxoadipate:succinyl-CoA transferase of strain B13 was purified by heat treatment and chromatography on phenyl-Sepharose, Mono-Q, and Superose 6 gels. Estimation of the native molecular mass gave a value of 115,000 ± 5,000 Da with a Superose 12 column. Polyacrylamide gel electrophoresis under denaturing conditions resulted in two distinct bands of equal intensities. The subunit A and B values were 32,900 and 27,000 Da. Therefore it can be assumed that the enzyme is a heterotetramer of the type A2B2 with a molecular mass of 120,000 Da. The N-terminal amino acid sequences of both subunits are as follows: subunit A, AELLTLREAVERFVNDGTVALEGFTHLIPT; subunit B, SAYSTNEMMTVAAARRLKNGAVVFV. The pH optimum was 8.4. Km values were 0.4 and 0.2 mM for 3-oxoadipate and succinyl-CoA, respectively. Reversibility of the reaction with succinate was shown. The transferase of strain B13 failed to convert 2-chloro- and 2-methyl-3-oxoadipate. Some activity was observed with 4-methyl-3-oxoadipate. Even 2-oxoadipate and 3-oxoglutarate were shown to function as poor substrates of the transferase. 3-Oxoadipyl-CoA thiolase was purified by chromatography on DEAE-Sepharose, blue 3GA, and reactive brown-agarose. Estimation of the native molecular mass gave 162,000 ± 5,000 Da with a Superose 6 column. The molecular mass of the subunit of the denatured protein, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was 42 kDa. On the basis of these results, 3-oxoadipyl-CoA thiolase should be a tetramer of the type A4. The N-terminal amino acid sequence of 3-oxoadipyl-CoA thiolase was determined to be SREVYI-DAVRTPIGRFG. The pH optimum was 7.8. Km values were 0.15 and 0.01 mM for 3-oxoadipyl-CoA and CoA, respectively. Sequence analysis of the thiolase terminus revealed high percentages of identity (70 to 85%) with thiolases of different functions. The N termini of the transferase subunits showed about 30 to 35% identical amino acids with the glutaconate-CoA transferase of an anaerobic bacterium but only an identity of 25% with the respective transferases of aromatic compound-degrading organisms was found.

Kaschabek, Stefan R.; Kuhn, Bernd; Muller, Dagmar; Schmidt, Eberhard; Reineke, Walter

2002-01-01

205

Property enhancement of optically transparent bionanofiber composites by acetylation  

NASA Astrophysics Data System (ADS)

The authors studied acetylation of bacterial cellulose (BC) nanofibers to widen the applications of BC nanocomposites in optoelectronic devices. The slight acetylation of BC nanofibers significantly reduces the hygroscopicity of BC nanocomposites, while maintaining their high optical transparency and thermal stability. Furthermore, the degradation in optical transparency at elevated temperature (200 °C) was significantly reduced by acetylation treatment. Therefore, the acetylation of bionanofibers has an extraordinary potential as treatment for property enhancement of bionanofiber composites.

Nogi, Masaya; Abe, Kentaro; Handa, Keishin; Nakatsubo, Fumiaki; Ifuku, Shinsuke; Yano, Hiroyuki

2006-12-01

206

Structure and acetyl-lysine recognition of the bromodomain  

Microsoft Academic Search

Histone lysine acetylation is central to epigenetic control of gene transcription. The bromodomain, found in chromatin-associated proteins and histone acetyltranferases, functions as the sole protein module known to bind acetyl-lysine motifs. Recent structural and functional analyses of bromodomains' recognition of lysine-acetylated peptides derived from major acetylation sites in histones and cellular proteins provide new insights into differences in ligand binding

S Mujtaba; L Zeng; M-M Zhou

2007-01-01

207

Mechanisms of P\\/CAF auto-acetylation  

Microsoft Academic Search

P\\/CAF is a histone acetyltransferase enzyme which was originally identified as a CBP\\/p300-binding protein. In this manuscript we report that human P\\/CAF is acetylated in vivo. We find that P\\/CAF is acetylated by itself and by p300 but not by CBP. P\\/CAF acetylation can be an intra- or intermolecular event. The intermolecular acetylation requires the N-terminal domain of P\\/CAF. The

Helena Santos-Rosa; Ester Valls; Tony Kouzarides; Marian Martinez-Balbas

2003-01-01

208

The Caenorhabditis elegans Elongator Complex Regulates Neuronal ?-tubulin Acetylation  

Microsoft Academic Search

Although acetylated ?-tubulin is known to be a marker of stable microtubules in neurons, precise factors that regulate ?-tubulin acetylation are, to date, largely unknown. Therefore, a genetic screen was employed in the nematode Caenorhabditis elegans that identified the Elongator complex as a possible regulator of ?-tubulin acetylation. Detailed characterization of mutant animals revealed that the acetyltransferase activity of the

Jachen A. Solinger; Roberta Paolinelli; Holger Klöß; Francesco Berlanda Scorza; Stefano Marchesi; Ursula Sauder; Dai Mitsushima; Fabrizio Capuani; Stephen R. Stürzenbaum; Giuseppe Cassata

2010-01-01

209

Pantoate Kinase and Phosphopantothenate Synthetase, Two Novel Enzymes Necessary for CoA Biosynthesis in the Archaea*  

PubMed Central

Bacteria/eukaryotes share a common pathway for coenzyme A (CoA) biosynthesis. Although archaeal genomes harbor homologs for most of these enzymes, homologs of bacterial/eukaryotic pantothenate synthetase (PS) and pantothenate kinase (PanK) are missing. PS catalyzes the ATP-dependent condensation of pantoate and ?-alanine to produce pantothenate, whereas PanK catalyzes the ATP-dependent phosphorylation of pantothenate to produce 4?-phosphopantothenate. When we examined the cell-free extracts of the hyperthermophilic archaeon Thermococcus kodakaraensis, PanK activity could not be detected. A search for putative kinase-encoding genes widely distributed in Archaea, but not present in bacteria/eukaryotes, led to four candidate genes. Among these genes, TK2141 encoded a protein with relatively low PanK activity. However, higher levels of activity were observed when pantothenate was replaced with pantoate. Vmax values were 7-fold higher toward pantoate, indicating that TK2141 encoded a novel enzyme, pantoate kinase (PoK). A search for genes with a distribution similar to TK2141 led to the identification of TK1686. The protein product catalyzed the ATP-dependent conversion of phosphopantoate and ?-alanine to produce 4?-phosphopantothenate and did not exhibit PS activity, indicating that TK1686 also encoded a novel enzyme, phosphopantothenate synthetase (PPS). Although the classic PS/PanK system performs condensation with ?-alanine prior to phosphorylation, the PoK/PPS system performs condensation after phosphorylation of pantoate. Gene disruption of TK2141 and TK1686 led to CoA auxotrophy, indicating that both genes are necessary for CoA biosynthesis in T. kodakaraensis. Homologs of both genes are widely distributed among the Archaea, suggesting that the PoK/PPS system represents the pathway for 4?-phosphopantothenate biosynthesis in the Archaea.

Yokooji, Yuusuke; Tomita, Hiroya; Atomi, Haruyuki; Imanaka, Tadayuki

2009-01-01

210

Column cellulose hydrolysis reactor: Cellulase adsorption profile  

Microsoft Academic Search

A column cellulose hydrolysis reactor was set up using a single passage of cellulase enzyme which was followed with a continuous percolation of buffer. Hydrolysis rates were found to decline precipitously upon the removal of the non-adsorbed cellulase components. By comparing specific activities of the cellulase before and after adsorption on the cellulose column, it was concluded that the adsorption

Larry U. L. Tan; Ernest K. C. Yu; Paul Mayers; John N. Saddler

1986-01-01

211

Hydrolysis of Bromodifluoro-methyltriphenylphosphonium Bromide.  

National Technical Information Service (NTIS)

Hydrolysis of Ph3P(+)CF2BrBr(-) afforded a high yield of bromodifluoromethane and triphenylphosphine oxide. Hydrolysis in the presence of a radioactive isotope of bromine or sodium iodide gave unequivocal evidence that the mechanism for this reaction proc...

D. J. Burton R. M. Flynn R. G. Manning R. M. Kessler

1982-01-01

212

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...

213

?-Amylase inactivation during rice starch hydrolysis  

Microsoft Academic Search

The effects of operating conditions on the enzymatic hydrolysis of rice starch were investigated using a commercial ?-amylase produced by Bacillus spp. in a stirred batch reactor. The degree of starch hydrolysis (%) and residual ?-amylase activity (%) were investigated versus process variables including pH, temperature, viscosity, impeller speed, processing time and some materials added such as hydrolysate, maltose, glucose,

Dilek K?l?ç Apar; Belma Özbek

2005-01-01

214

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

215

In vitro effects of valproate and valproate metabolites on mitochondrial oxidations. Relevance of CoA sequestration to the observed inhibitions.  

PubMed

The inhibitory effects of valproate (VPA) and nine of its metabolites on mitochondrial oxidations have been investigated. Valproate, 4-ene-VPE, 2,4-diene-VPA and 2-propylglutaric acid inhibited the rate of oxygen consumption by rat liver mitochondrial fractions with long- and medium-chain fatty acids, glutamate (+/- malate), succinate, alpha-ketoglutarate (+ malate) and pyruvate (+ malate) as substrates. Sequestration of intramitochondrial free CoA by valproate and these three metabolites has been demonstrated and quantified. However, CoA trapping could not account for all the inhibitions observed. 2-ene-VPA and 3-oxo-VPA, metabolites formed during the beta-oxidation of valproate, were not capable of trapping intramitochondrial CoA although they were inhibitors of the beta-oxidation of decanoate, probably by inhibition of the medium-chain acyl-CoA synthetase. PMID:1610408

Ponchaut, S; van Hoof, F; Veitch, K

1992-06-01

216

Acetylation of ?-chitin in ionic liquids  

Microsoft Academic Search

Acetylation of ?-chitin using acetic anhydride in an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), was performed. First, a mixture of chitin and AMIMBr (2% w\\/w) was heated at 100°C for 24h for dissolution. Then, acetic anhydride (5–20equiv) was added to the solution and the mixture was heated with stirring at desired temperatures for 24h. The product was precipitated by the addition

Shozaburo Mine; Hironori Izawa; Yoshiro Kaneko; Jun-ichi Kadokawa

2009-01-01

217

Enthalpies of formation of acetyl radicals  

NASA Astrophysics Data System (ADS)

The database on the enthalpies of formation (?f H ?) of aliphatic acetyl radicals of the RC·(O) type is analyzed and extended. ?f H ? values are estimated for the first time for three compounds on the basis of experimental data. The data were analyzed using the additive group approach with the determination and correction of parameters. Good correspondence between the ?f H ?(RC·(O)) values calculated according to parameters with experimental data is observed.

Orlov, Yu. D.; Chernova, E. M.; Orlov, M. Yu.; Turovtsev, V. V.

2013-10-01

218

Effect of dietary di-2-ethylhexyl phthalate on oxidation of 14 C-palmitoyl CoA by mitochondria from mammalian heart and liver  

Microsoft Academic Search

Oxidation of [1-14C] palmitoyl CoA by heart and liver mitochondria from rats fed dietary di-2-ethylhexyl phthalate (DEHP) was investigated in\\u000a vitro. Oxidation of14C-palmitoyl CoA to14CO2 increased two- to threefold in hepatic mitochondria from rats fed 0.1% DEHP for 2 to 3 days; this increase appeared to be\\u000a a maximum response since similar data were obtained using hepatic mitochondria from rats

Frank P. Bell; Peter J. Gillies

1977-01-01

219

Modeling intrinsic kinetics of enzymatic cellulose hydrolysis.  

PubMed

A multistep approach was taken to investigate the intrinsic kinetics of the cellulase enzyme complex as observed with hydrolysis of noncrystalline cellulose (NCC). In the first stage, published initial rate mechanistic models were built and critically evaluated for their performance in predicting time-course kinetics, using the data obtained from enzymatic hydrolysis experiments performed on two substrates: NCC and alpha-cellulose. In the second stage, assessment of the effect of reaction intermediates and products on intrinsic kinetics of enzymatic hydrolysis was performed using NCC hydrolysis experiments, isolating external factors such as mass transfer effects, physical properties of substrate, etc. In the final stage, a comprehensive intrinsic kinetics mechanism was proposed. From batch experiments using NCC, the time-course data on cellulose, cello-oligosaccharides (COS), cellobiose, and glucose were taken and used to estimate the parameters in the kinetic model. The model predictions of NCC, COS, cellobiose, and glucose profiles show a good agreement with experimental data generated from hydrolysis of different initial compositions of substrate (NCC supplemented with COS, cellobiose, and glucose). Finally, sensitivity analysis was performed on each model parameter; this analysis provides some insights into the yield of glucose in the enzymatic hydrolysis. The proposed intrinsic kinetic model parametrized for dilute cellulose systems forms a basis for modeling the complex enzymatic kinetics of cellulose hydrolysis in the presence of limiting factors offered by substrate and enzyme characteristics. PMID:17465526

Peri, Suma; Karra, Srinivas; Lee, Y Y; Karim, M Nazmul

2007-04-28

220

Kinetics of chitinase production. I. Chitin hydrolysis.  

PubMed

As part of the development of a comprehensive mathematical model for chitinase production by Serratia marcescens QMB 1466 growing on chitin, the different mass transport and kinetic steps involved during chitin hydrolysis were studied. The experimental results for the hydrolysis of chitin by a crude preparation of chitinase show a system kinetically limited by the overall rate of chitin hydrolysis. This rate is linearly related to the concentration of enzyme adsorbed on the chitin particle. Adsorbed and bulk enzyme concentration were found to be related through a Langmuir type of isotherm. PMID:18553734

Young, M E; Bell, R L; Carroad, P A

1985-06-01

221

Cellulose hydrolysis by immobilized Trichoderma reesei cellulase  

Microsoft Academic Search

Cellulose hydrolysis by immobilized Trichoderma reesei cellulase in the presence of a low viscosity ionic liquid, 1-ethyl-3-methylimidazolium diethyl phosphate (EMIM-DEP), was\\u000a investigated. Preparation of the carrier-free immobilized cellulase was optimized with respect to concentration of the cross-linker\\u000a and the type of precipitant. The addition of 2% (v\\/v) EMIM-DEP during hydrolysis gave an initial reaction rate 2.7 times higher\\u000a than the hydrolysis

Paetrice O. Jones; Palligarnai T. Vasudevan

2010-01-01

222

Actin Polymerization and ATP Hydrolysis  

NASA Astrophysics Data System (ADS)

F-actin is the major component of muscle thin filaments and, more generally, of the microfilaments of the dynamic, multifunctional cytoskeletal systems of nonmuscle eukaryotic cells. Polymeric F-actin is formed by reversible noncovalent self-association of monomeric G-actin. To understand the dynamics of microfilament systems in cells, the dynamics of polymerization of pure actin must be understood. The following model has emerged from recent work. During the polymerization process, adenosine 5'-triphosphate (ATP) that is bound to G-actin is hydrolyzed to adenosine 5'-diphosphate (ADP) that is bound to F-actin. The hydrolysis reaction occurs on the F-actin subsequent to the polymerization reaction in two steps: cleavage of ATP followed by the slower release of inorganic phosphate (Pi). As a result, at high rates of filament growth a transient cap of ATP-actin subunits exists at the ends of elongating filaments, and at steady state a stabilizing cap of ADP \\cdot Pi-actin subunits exists at the barbed ends of filaments. Cleavage of ATP results in a highly stable filament with bound ADP \\cdot Pi, and release of Pi destabilizes the filament. Thus these two steps of the hydrolytic reaction provide potential mechanisms for regulating the monomer-polymer transition.

Korn, Edward D.; Carlier, Marie-France; Pantaloni, Dominique

1987-10-01

223

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

224

Molecular Bases for Sensitivity to Acetyl-Coenzyme A Carboxylase Inhibitors in Black-Grass1  

PubMed Central

In grasses, residues homologous to residues Ile-1,781 and Ile-2,041 in the carboxyl-transferase (CT) domain of the chloroplastic acetyl-coenzyme A (CoA) carboxylase (ACCase) from the grass weed black-grass (Alopecurus myosuroides [Huds.]) are critical determinants for sensitivity to two classes of ACCase inhibitors, aryloxyphenoxypropionates (APPs) and cyclohexanediones. Using natural mutants of black-grass, we demonstrated through a molecular, biological, and biochemical approach that residues Trp-2,027, Asp-2,078, and Gly-2,096 are also involved in sensitivity to ACCase inhibitors. In addition, residues Trp-2,027 and Asp-2,078 are very likely involved in CT activity. Using three-dimensional modeling, we found that the side chains of the five residues are adjacent, located at the surface of the inside of the cavity of the CT active site, in the vicinity of the binding site for APPs. Residues 1,781 and 2,078 are involved in sensitivity to both APPs and cyclohexanediones, whereas residues 2,027, 2,041, and 2,096 are involved in sensitivity to APPs only. This suggests that the binding sites for these two classes of compounds are overlapping, although distinct. Comparison of three-dimensional models for black-grass wild-type and mutant CTs and for CTs from organisms with contrasted sensitivity to ACCase inhibitors suggested that inhibitors fitting into the cavity of the CT active site of the chloroplastic ACCase from grasses to reach their active sites may be tight. The three-dimensional shape of this cavity is thus likely of high importance for the efficacy of ACCase inhibitors.

Delye, Christophe; Zhang, Xiao-Qi; Michel, Severine; Matejicek, Annick; Powles, Stephen B.

2005-01-01

225

Operation of the CO Dehydrogenase/Acetyl Coenzyme A Pathway in both Acetate Oxidation and Acetate Formation by the Syntrophically Acetate-Oxidizing Bacterium Thermacetogenium phaeum  

PubMed Central

Thermacetogenium phaeum is a homoacetogenic bacterium that can grow on various substrates, such as pyruvate, methanol, or H2/CO2. It can also grow on acetate if cocultured with the hydrogen-consuming methanogenic partner Methanothermobacter thermautotrophicus. Enzyme activities of the CO dehydrogenase/acetyl coenzyme A (CoA) pathway (CO dehydrogenase, formate dehydrogenase, formyl tetrahydrofolate synthase, methylene tetrahydrofolate dehydrogenase) were detected in cell extracts of pure cultures and of syntrophic cocultures. Mixed cell suspensions of T. phaeum and M. thermautotrophicus oxidized acetate rapidly and produced acetate after addition of H2/CO2 after a short time lag. CO dehydrogenase activity staining after native polyacrylamide gel electrophoresis exhibited three oxygen-labile bands which were identical in pure culture and coculture. Protein profiles of T. phaeum cells after sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the strain exhibited basically the same protein patterns in both pure and syntrophic culture. These results indicate that T. phaeum operates the CO dehydrogenase/acetyl-CoA pathway reversibly both in acetate oxidation and in reductive acetogenesis by using the same biochemical apparatus, although it has to couple this pathway to ATP synthesis in different ways.

Hattori, Satoshi; Galushko, Alexander S.; Kamagata, Yoichi; Schink, Bernhard

2005-01-01

226

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.

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

1996-01-01

227

Spectrophotometric assay for urinary N-acetyl-. beta. -d-glucosaminidase activity  

SciTech Connect

An improved assay for N-acetyl-..beta..-D-glucosaminidase activity in urine is described that involves (a) gel filtration to separate the enzyme from inhibitors in urine, (b) enzymic hydrolysis of p-nitrophenyl-N-acetyl-..beta..-D-glucosaminide at pH 4.4, and (c) spectrophotometry of the liberated p-nitrophenylate. Measurements of activity of the enzyme in 58 urine specimens correlated closely (r = 0.9998) with results by an established procedure. The within-run coefficient of variation (CV) was 3.7%; the between-run CV averaged 6.8%. Reference values for the activity were established by assays of urine specimens from 135 healthy persons, age two weeks to 52 years. Efficacy of the assay for detection of nephrotoxicity was demonstrated in rats after experimental induction of reversible renal insufficiency by intraperitoneal injection of nickel chloride. Clinical application of the assay in approximately 1000 patients corroborated its utility for detection and monitoring of renal disorders.

Horak, E.; Hopfer, S.M.; Sunderman, F.W. Jr.

1981-07-01

228

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

2013-03-26

229

Process design and optimization of cellulose hydrolysis  

SciTech Connect

The primary concern of this work is the economic optimization of a process for the hydrolysis of waste cellulosic material to fermentable sugars. Hydrolysis is performed enzymatically, utilizing the cellulase enzyme complex produced by Trichoderma viride. Using corn stover as a substrate, a system was designed to provide 14% hydrolyzate sugars (70% fermentable) at an estimated cost of 6.84 cents/pound of sugar, a 43% cost reduction over previous designs. Optimal residence time for hydrolysis was found to be 62 hours, resulting in a 34% conversion of raw material to sugars. Total fixed capital investment for the process is estimated to be $17.13 x 10/sup 6/. The kinetics of cellulose hydrolysis were modeled through the use of a modified Michaelis--Menten equation, making computer simulation of batch hydrolyses possible. Additional studies on the accessibility of cellulose were performed, and the feasibility of a counter-current processing scheme was investigated.

Lindsey, R.R.; Wilke, C.R.

1978-08-01

230

Cotton cellulose: enzyme adsorption and enzymic hydrolysis  

SciTech Connect

The adsorption of a crude cellulase complex from Trichoderma viride on variously pretreated cotton cellulose samples was studied in the framework of the Langmuir approach at 2-8 degrees. The saturation amount of adsorbed enzyme was related to the susceptibility of the substrates to hydrolysis. In every case the adsorption process was faster by 2-3 orders of magnitude than the hydrolysis step to give end products. For ZnCl/sub 2/-treated cotton cellulose the Langmuir parameters correlated fairly well with the value of the Michaelis constant, measured for its enzymic hydrolysis, and the adsorptive complex was indistinguishable from the complex of the Michaelis-Menten model for the hydrolysis.

Beltrame, P.L.; Carniti, P.; Focher, B.; Marzetti, A.; Cattaneo, M.

1982-01-01

231

Hydrolysis of Sucrose by Heterogeneous Catalysis  

Microsoft Academic Search

The reaction kinetics of the hydrolysis of sucrose by solid catalysts was investigated using polarimetry. Silica included heteropoly acid was used as a catalyst. At the optimizing conditions the activation parameters have been evaluated using the Arrhenius and Eyring plots.

H. Iloukhani; S. Azizian; N. Samadani

2002-01-01

232

Mechanisms of P/CAF auto-acetylation  

PubMed Central

P/CAF is a histone acetyltransferase enzyme which was originally identified as a CBP/p300-binding protein. In this manuscript we report that human P/CAF is acetylated in vivo. We find that P/CAF is acetylated by itself and by p300 but not by CBP. P/CAF acetylation can be an intra- or intermolecular event. The intermolecular acetylation requires the N-terminal domain of P/CAF. The intramolecular acetylation targets five lysines (416–442) at the P/CAF C-terminus, which are in the nuclear localisation signal (NLS). Finally, we show that acetylation of P/CAF leads to an increment of its histone acetyltransferase (HAT) activity. These findings identify a new post-translation modification on P/CAF which may regulate its function.

Santos-Rosa, Helena; Valls, Ester; Kouzarides, Tony; Martinez-Balbas, Marian

2003-01-01

233

Regulation of Cellular Metabolism by Protein Lysine Acetylation  

PubMed Central

Protein lysine acetylation has emerged as a key posttranslational modification in cellular regulation, in particular through the modification of histones and nuclear transcription regulators. We show that lysine acetylation is a prevalent modification in enzymes that catalyze intermediate metabolism. Virtually every enzyme in glycolysis, gluconeogenesis, the tricarboxylic acid (TCA) cycle, the urea cycle, fatty acid metabolism, and glycogen metabolism was found to be acetylated in human liver tissue. The concentration of metabolic fuels, such as glucose, amino acids, and fatty acids, influenced the acetylation status of metabolic enzymes. Acetylation activated enoyl–coenzyme A hydratase/3-hydroxyacyl–coenzyme A dehydrogenase in fatty acid oxidation and malate dehydrogenase in the TCA cycle, inhibited argininosuccinate lyase in the urea cycle, and destabilized phosphoenolpyruvate carboxykinase in gluconeogenesis. Our study reveals that acetylation plays a major role in metabolic regulation.

Zhao, Shimin; Xu, Wei; Jiang, Wenqing; Yu, Wei; Lin, Yan; Zhang, Tengfei; Yao, Jun; Zhou, Li; Zeng, Yaxue; Li, Hong; Li, Yixue; Shi, Jiong; An, Wenlin; Hancock, Susan M.; He, Fuchu; Qin, Lunxiu; Chin, Jason; Yang, Pengyuan; Chen, Xian; Lei, Qunying; Xiong, Yue; Guan, Kun-Liang

2011-01-01

234

Inhibitory kinetics of phenol on the enzyme activity of beta-N-acetyl-D-glucosaminidase from green crab (Scylla serrata).  

PubMed

Chemical pollution such as chromium and phenol in the sea water has been increasing in recent years in China sea. At the same time, marine shellfish such as prawn and crab are sensitive to this pollution. beta-N-acetyl-D-glucosaminidase (NAGase, EC.3.2.1.52) catalyzes the cleavage the oligomers of N-acetylglucosamine (NAG) into the monomer. In this paper, the effects of phenol on the enzyme activity from green crab (Scylla serrata) for the hydrolysis of p-nitrophenyl-N-acetyl-beta-D-glucosaminide (pNP-NAG) have been studied. The results showed that appropriate concentrations of phenol could lead to reversible inhibition on the enzyme and the inhibitor concentration leading to 50% activity lost, IC(50), was estimated to be 75.0+/-2.0 mM. The inhibitory kinetics of phenol on the enzyme in the appropriate concentrations of phenol has been studied using the kinetic method of substrate reaction. The time course of the enzyme for the hydrolysis of pNP-NAG in the presence of different concentrations of phenol showed that at each phenol concentration, the rate decreased with increasing time until a straight line was approached. The results show that the inhibition of the enzyme by phenol is a slow, reversible reaction with fractional remaining activity. The microscopic rate constants are determined for the reaction on phenol with the enzyme. PMID:17161862

Zhang, Ji-Ping; Yan, Ya-Wen; Xie, Jin-Jin; Wang, Qin; Chen, Qing-Xi

2006-07-01

235

Lipase-catalyzed hydrolysis of palm oil  

Microsoft Academic Search

The hydrolysis of palm oil, palm olein and palm stearin, soybean oil, corn oil and peanut oil by the commercial lipase fromCandida rugosa (formerly known asC. cylindracea) was studied. The optimal conditions for the hydrolysis of palm oil by the lipase were established. The lipase fromC. rugosa exhibits an optimal activity at 37 C and at pH 7.5. The optimal

H. T. Khor; N. H. Tan; C. L. Chua

1986-01-01

236

Lactose Utilization and Hydrolysis in Saccharomyces fragilis  

Microsoft Academic Search

SUMMARY Sodium azide, 2,4-dinitrophenol and iodoacetate did not inhibit hydrolysis of lactose by cell-free preparations of Sacchuromyces fragilis ,8-galactosidase, but with intact organisms fermentation and hydrolysis were inhibited to a similar extent. This suggests that these inhibitors may interfere with the transport of lactose into the cell. Galactose fermentation was inhibited by sodium azide and dinitrophenol to a much greater

R. DAVIES

1964-01-01

237

The Mechanism of Boron Mobility in Wheat and Canola Phloem1[C][OA  

PubMed Central

Low-molecular-weight borate complexes were isolated from canola (Brassica napus) and wheat (Triticum aestivum) phloem exudates, as well as the cytoplasm of the fresh-water alga Chara corallina, and identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Phloem exudate was collected from field-grown canola inflorescence stalks by shallow incision, while wheat phloem exudate was collected by aphid stylectomy. Chara cytoplasm was collected by careful manual separation of the cell wall, vacuole, and cytosolic compartments. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry showed the presence of isotopic borate complexes, at mass-to-charge ratio of 690.22/691.22 in the canola and wheat phloem and at 300.11/301.11 in canola phloem and Chara cytoplasm. Using reference compounds, the borate complexes with mass-to-charge ratio 690.22/691.22 was identified as a bis-sucrose (Suc) borate complex in which the 4,6-hydroxyl pairs from the two ?-glucopyranoside moieties formed an [L2B]?1 complex. Further investigation using liquid chromatography electrospray ionization triple quadrupole mass spectrometry analysis confirmed the presence of the bis-Suc borate complex in wheat phloem with a concentration up to 220 ?m. The 300.11/301.11 complex was putatively identified as a bis-N-acetyl-serine borate complex but its concentration was below the detection limits of the liquid chromatography electrospray ionization triple quadrupole mass spectrometer so could not be quantified. The presence of borate complexes in the phloem provides a mechanistic explanation for the observed phloem boron mobility in canola and wheat and other species that transport Suc as their primary photoassimilate.

Stangoulis, James; Tate, Max; Graham, Robin; Bucknall, Martin; Palmer, Lachlan; Boughton, Berin; Reid, Robert

2010-01-01

238

STRUCTURE AND FUNCTIONAL PROPERTIES OF ACETYLATED SORGHUM STARCH  

Microsoft Academic Search

Sorghum starch was modified using acetic anhydride at various levels (1.25-6.25 g\\/100g of starch) and evaluated for its structure and functional properties. The acetylated starches showed degree of substitution and acetyl content between 0.05 to 0.081 and 1.31 to 2.1%, respectively. Acetylation led to surface roughness, formation of cavities and fusion of few starch granules and slight change in amylose

Harinder Singh; Navdeep Singh Sodhi; Narpinder Singh

2011-01-01

239

G protein coupled-receptor signaling and reversible lysine acetylation.  

PubMed

Abstract Emerging data suggest that interaction with reversible protein acetylation is an important mediator of GPCR-initiated changes in transcription and other processes. Alteration of acetylation downstream of GPCR activation occurs through a variety of mechanisms, including kinase-dependent and -independent regulation of histone deacetylases (HDACs) and histone acetyltransferases (HATs). The prominence of both GPCR and acetylation in pathology and drug development efforts highlights the importance of understanding cross-talk between these two signaling mechanisms. PMID:23895385

Spiegelberg, Bryan D

2013-07-29

240

CoA Adducts of 4-Oxo-4-Phenylbut-2-enoates: Inhibitors of MenB from the M. tuberculosis Menaquinone Biosynthesis Pathway  

PubMed Central

A high-throughput screen led to the discovery of 2-amino-4-oxo-4-phenylbutanoate inhibitors of the 1,4-dihydroxy-2-naphthoyl-CoA synthase (MenB) from the menaquinone biosynthesis pathway in Mycobacterium tuberculosis. However, these compounds are unstable in solution and eliminate to form the corresponding 4-oxo-4-phenylbut-2-enoates that then react with CoA in situ to form nanomolar inhibitors of MenB. The potency of these compounds results from interaction of the CoA adduct carboxylate with the MenB oxyanion hole, a conserved structural motif in the crotonase superfamily. 4-Oxo-4-chlorophenylbutenoyl methyl ester has MICs of 0.6 and 1.5 ?g/ml against replicating and nonreplicating M. tuberculosis, respectively, and it is proposed that the methyl ester penetrates the cell where it is hydrolyzed and reacts with CoA to generate the active antibacterial. The CoA adducts thus represent an important foundation for the development of novel MenB inhibitors, and suggest a general approach to the development of potent inhibitors of acyl-CoA binding enzymes.

Li, Xiaokai; Liu, Nina; Zhang, Huaning; Knudson, Susan E.; Li, Huei-Jiun; Lai, Cheng-Tsung; Simmerling, Carlos; Slayden, Richard A.; Tonge, Peter J.

2011-01-01

241

HMG CoA Reductase Inhibitor-Induced Myotoxicity: Pravastatin and Lovastatin Inhibit the Geranylgeranylation of Low-Molecular-Weight Proteins in Neonatal Rat Muscle Cell Culture  

Microsoft Academic Search

In previous studies, inhibition of cholesterol synthesis by HMG CoA reductase inhibitors (HMGRI) was associated with myotoxicity in cultures of neonatal rat skeletal myotubes, and rhabdomyolysis in rats, rabbits, and humansin vivo. In vitromyotoxicity was directly related to HMGRI-induced depletion of mevalonate, farnesol, and geranylgeraniol, since supplementation with these intermediate metabolites abrogated the toxicity. Both farnesol and geranylgeraniol are required

Oliver P. Flint; Barbara A. Masters; Richard E. Gregg; Stephen K. Durham

1997-01-01

242

Coordinate regulation of the nuclear and plastidic genes coding for the subunits of the heteromeric acetyl-coenzyme A carboxylase.  

PubMed

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 (beta-carboxyltransferase) and three nuclear-coded subunits (biotin carboxy-carrier, biotin carboxylase, and alpha-carboxyltransferase). We report the primary structure of the Arabidopsis alpha-carboxyltransferase and beta-carboxyltransferase subunits deduced from nucleotide sequences of the respective genes and/or cDNA. Co-immunoprecipitation experiments confirm that the alpha-carboxyltransferase and beta-carboxyltransferase subunits are physically associated. The plant alpha-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, J; Wen, T N; Nikolau, B J; Wurtele, E S

2000-04-01

243

New Targets for Acetylation in Autophagy  

NSDL National Science Digital Library

Macroautophagy is an evolutionarily conserved homeostatic process that mediates the degradation of long-lived cytoplasmic components in eukaryotes, which allows cells to survive stresses such as inflammation, hypoxia, and deprivation of nutrients or growth factors. At least 30 members of the Atg (autophagy-related) protein family orchestrate this degradative process. Additional complexity resides in the signaling networks controlling the autophagic process, which include various posttranslational modifications of key components. Evidence is accumulating that protein acetylation represents an evolutionarily conserved mechanism tightly regulating macroautophagy.

Ahmed Hamai (Paris;INSERM REV); Patrice Codogno (Paris;INSERM REV)

2012-07-03

244

Sphingolipids and cellular cholesterol homeostasis. Effect of ceramide on cholesterol trafficking and HMG CoA reductase activity  

PubMed Central

We previously showed that degradation of cellular sphingomyelin (SM) by SMase C results in a greater stimulation of cholesterol translocation to endoplasmic reticulum, compared to its degradation by SMase D. Here we investigated the hypothesis that the effect of SMase C is partly due to the generation of ceramide, rather than due to depletion of SM alone. Inhibition of hydroxymethylglutaryl CoA reductase (HMGCR) activity was used as a measure of cholesterol translocation. Treatment of fibroblasts with SMase C resulted in a 90% inhibition of HMGCR, whereas SMase D treatment inhibited it by 29%. Treatment with exogenous ceramides, or increasing the endogenous ceramide levels also inhibited HMGCR by 60–80%. Phosphorylation of HMGCR was stimulated by SMase C or exogenous ceramide. The effects of ceramide and SMase D were additive, indicating the independent effects of SM depletion and ceramide generation. These results show that ceramide regulates sterol trafficking independent of cellular SM levels.

Subbaiah, Papasani V.; Sowa, Jennifer M.; Singh, Dev K.

2008-01-01

245

Non-histone lysine acetylated proteins in heart failure  

PubMed Central

Both histone-acetylations and histone deacetylases have been shown to play a key role in cardiac remodeling. Recently, it has become abundantly clear that many non-histone proteins are modified by post-translational lysine acetylations and that these acetylations regulate protein activity, conformation, and binding. In the present study, non-histone acetylated proteins associated with heart failure were identified. Global screening for lysine acetylated proteins was performed using 2-dimensional gel electrophoresis coupled with immunoblotting with a primary monoclonal anti-acetyl-lysine antibody. Lysine acetylated proteins were compared in two rodent models of hypertensive heart failure, the Dahl salt-sensitive (SS) and spontaneously hypertensive heart failure prone (SHHF) rats with those in corresponding controls, i.e., the Dahl salt-resistant (SR) and W (W) rat strains, respectively. Forty-one and 66 acetylated proteins were detected in SS and SHHF failing hearts, respectively, but either not detected or detected with less abundance in corresponding control hearts. Twelve of these acetylated proteins were common to both models of heart failure. These were identified using matrix-assisted laser desorption/ionization time of flight (MALDI-TOF/TOF) mass spectrometry followed by Mascot Analysis and included mitochondrial enzymes: ATP synthase, long-chain acyl-CoA dehydrogenase, creatine kinase, malate dehydrogenase, and pyruvate dehydrogenase. The abundance of NAD-dependent deacetylase sirtuin-3 (Sirt3), a mitochondrial deacetylase was reduced in SS and SHHF failing hearts. This is the first description of non-histone protein acetylations associated with heart failure and raises the prospect that acetylations of mitochondrial proteins linked to reduced Sirt3 mediate, in part, metabolic changes in heart failure.1

Grillon, Jean Michel; Johnson, Keven R.; Kotlo, Kumar; Danziger, Robert S.

2013-01-01

246

Non-histone lysine acetylated proteins in heart failure.  

PubMed

Both histone-acetylations and histone deacetylases have been shown to play a key role in cardiac remodeling. Recently, it has become abundantly clear that many non-histone proteins are modified by post-translational lysine acetylations and that these acetylations regulate protein activity, conformation, and binding. In the present study, non-histone acetylated proteins associated with heart failure were identified. Global screening for lysine acetylated proteins was performed using 2-dimensional gel electrophoresis coupled with immunoblotting with a primary monoclonal anti-acetyl-lysine antibody. Lysine acetylated proteins were compared in two rodent models of hypertensive heart failure, the Dahl salt-sensitive (SS) and spontaneously hypertensive heart failure prone (SHHF) rats with those in corresponding controls, i.e., the Dahl salt-resistant (SR) and W (W) rat strains, respectively. Forty-one and 66 acetylated proteins were detected in SS and SHHF failing hearts, respectively, but either not detected or detected with less abundance in corresponding control hearts. Twelve of these acetylated proteins were common to both models of heart failure. These were identified using matrix-assisted laser desorption/ionization time of flight (MALDI-TOF/TOF) mass spectrometry followed by Mascot Analysis and included mitochondrial enzymes: ATP synthase, long-chain acyl-CoA dehydrogenase, creatine kinase, malate dehydrogenase, and pyruvate dehydrogenase. The abundance of NAD-dependent deacetylase sirtuin-3 (Sirt3), a mitochondrial deacetylase was reduced in SS and SHHF failing hearts. This is the first description of non-histone protein acetylations associated with heart failure and raises the prospect that acetylations of mitochondrial proteins linked to reduced Sirt3 mediate, in part, metabolic changes in heart failure. PMID:22155497

Grillon, Jean Michel; Johnson, Keven R; Kotlo, Kumar; Danziger, Robert S

2011-12-03

247

Anisole hydrolysis in high temperature water.  

PubMed

We investigated the hydrolysis of anisole to phenol in high-temperature water with and without water-tolerant Lewis acid catalysis. With no catalyst present, anisole hydrolyzes to phenol in 97% yield after 24 hours at 365 °C, our experimentally determined optimal temperature and time. Experiments with varied water density and analysis of comparable literature data suggest that anisole hydrolysis is almost third order in water, when the S(N)2 mechanism dominates. Of the water-tolerant Lewis acid catalysts studied, In(OTf)(3) offered the best phenol yield. Anisole hydrolysis was first order in catalyst and first order in substrate. Introducing In(OTf)(3) catalysis lowered the activation energy for anisole hydrolysis to 31 ± 1 kcal mol(-1). Anisole hydrolysis in high-temperature water with In(OTf)(3) catalysis is competitive with other techniques in the literature based on rate and yield. In the presence of 5 mol% In(OTf)(3) catalyst, anisole hydrolyzes to phenol in 97% yield after 90 minutes at 300 °C. PMID:23381061

Rebacz, Natalie A; Savage, Phillip E

2013-02-04

248

Ethanol from biomass by enzymatic hydrolysis  

SciTech Connect

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

Wright, J.D.

1988-08-01

249

Globin Intergenic Transcription and Histone Acetylation Dependent on an Enhancer  

Microsoft Academic Search

Histone acetyltransferases are associated with the elongating RNA polymerase II (Pol II) complex, support- ing the idea that histone acetylation and transcription are intertwined mechanistically in gene coding se- quences. Here, we studied the establishment and function of histone acetylation and transcription in noncoding sequences by using a model locus linking the -globin HS2 enhancer and the embryonic -globin gene

A. Kim; H. Zhao; I. Ifrim; A. Dean

2007-01-01

250

Acetylation in hormone signaling and the cell cycle  

Microsoft Academic Search

The last decade has seen a substantial change in thinking about the role of acetylation in regulating diverse cellular processes. The correlation between histone acetylation and gene transcription has been known for many years. The cloning and biochemical characterization of the enzymes that regulate this post-translational modification has led to an understanding of the diverse role histone acetyltransferases (HATs) play

Maofu Fu; Chenguang Wang; Jian Wang; Brian T Zafonte; Michael P Lisanti; Richard G Pestell

2002-01-01

251

Functional Analysis of p53 Acetylation in Prostate Tumor Suppression.  

National Technical Information Service (NTIS)

The tumor suppressor p53 becomes acetylated upon its activation. We show that MDM2 can promote p53 deacetylation by recruiting a complex containing HDAC1. The HDAC1 complex binds MDM2 in a p53-independent manner and deacetylates p53 at all known acetylate...

T. Yao

2004-01-01

252

Functional Analysis of p53 Acetylation in Prostate Tumor Suppression.  

National Technical Information Service (NTIS)

The tumor suppressor p53 is stabilized and activated in response to cellular stress through post translational modifications including acetylation. p300/CBP-mediated acetylation of p53 is negatively regulated by MDM2. We show that MDM2 can promote p53 dea...

T. Yao

2003-01-01

253

Importance of product inhibition in the kinetics of the acylase hydrolysis reaction by differential stopped flow microcalorimetry.  

PubMed

The hydrolysis of N-acetyl-L-methionine, N-acetylglycine, N-acetyl-L-phenylalanine, and N-acetyl-L-alanine at 298.35K by porcine kidney acylase I (EC 3.5.1.14) was monitored by the heat released upon mixing of the substrate and enzyme in a differential stopped flow microcalorimeter. Values for the Michaelis constant (K(m)) and the catalytic constant (k(cat)) were determined from the progress of the reaction curve employing the integrated form of the Michaelis-Menten equation for each reaction mixture. When neglecting acetate product inhibition of the acylase, values for k(cat) were up to a factor of 2.3 larger than those values determined from reciprocal initial velocity-initial substrate concentration plots for at least four different reaction mixtures. In addition, values for K(m) were observed to increase linearly with an increase in the initial substrate concentration. When an acetate product inhibition constant of 600+/-31M(-1), determined by isothermal titration calorimetry, was used in the progress curve analysis, values for K(m) and k(cat) were in closer agreement with their values determined from the reciprocal initial velocity versus initial substrate concentration plots. The reaction enthalpies, Delta(r)H(cal), which were determined from the integrated heat pulse per amount of substrate in the reaction mixture, ranged from -4.69+/-0.09kJmol(-1) for N-acetyl-L-phenylalanine to -1.87+/-0.23kJmol(-1) for N-acetyl-L-methionine. PMID:12419341

Stödeman, Magnus; Schwarz, Frederick P

2002-09-15

254

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

255

Cancers with wrong HATs: the impact of acetylation.  

PubMed

Lysine N-?-acetylation is a post-translational modification that regulates the function of histone and non-histone proteins. In several malignancies, histone acetyltransferase (HAT) activities are disturbed as a consequence of various genetic or epigenetic alterations. In particular, HATs can function as tumor suppressors, helping cells control cellular proliferation and cell cycle, and also as oncogenes, because abnormal acetylation can activate malignant proteins and contribute to cancer. An impaired acetylation profile can be indicative of a pathological process, and thus evaluation of histone acetylation could be used as a predictive index of patient survival or therapy outcome. Therefore, epigenetic therapy might be a very effective strategy to defeat cancer. With the use of histone deacetylase inhibitors and acetylation modulators (e.g. HAT inhibitors, bromodomain inhibitors), we are paving the way for a future epigenetic drug control of human diseases. PMID:23325510

Di Cerbo, Vincenzo; Schneider, Robert

2013-01-15

256

Reversible acetylation regulates acetate and propionate metabolism in Mycobacterium smegmatis.  

PubMed

Carbon metabolic pathways are important to the pathogenesis of Mycobacterium tuberculosis, the causative agent of tuberculosis. However, extremely little is known about metabolic regulation in mycobacteria. There is growing evidence for lysine acetylation being a mechanism of regulating bacterial metabolism. Lysine acetylation is a post-translational modification in which an acetyl group is covalently attached to the side chain of a lysine residue. This modification is mediated by acetyltransferases, which add acetyl groups, and deacetylases, which remove the acetyl groups. Here we set out to test whether lysine acetylation and deacetylation impact acetate metabolism in the model mycobacteria Mycobacterium smegmatis, which possesses 25 candidate acetyltransferases and 3 putative lysine deacetylases. Using mutants lacking predicted acetyltransferases and deacetylases we showed that acetate metabolism in M. smegmatis is regulated by reversible acetylation of acetyl-CoA synthetase (Ms-Acs) through the action of a single pair of enzymes: the acetyltransferase Ms-PatA and the sirtuin deacetylase Ms-SrtN. We also confirmed that the role of Ms-PatA in regulating Ms-Acs regulation depends on cAMP binding. We additionally demonstrated a role for Ms-Acs, Ms-PatA and Ms-SrtN in regulating the metabolism of propionate in M. smegmatis. Finally, along with Ms-Acs, we identified a candidate propionyl-CoA synthetase, Ms5404, as acetylated in whole-cell lysates. This work lays the foundation for studying the regulatory circuit of acetylation and deacetylation in the cellular context of mycobacteria. PMID:23813678

Hayden, Jennifer D; Brown, Lanisha R; Gunawardena, Harsha P; Perkowski, Ellen F; Chen, Xian; Braunstein, Miriam

2013-06-27

257

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.

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

258

The biology of lysine acetylation integrates transcriptional programming and metabolism.  

PubMed

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 substrates of KATs are metabolic enzymes, cytoskeletal proteins, molecular chaperones, ribosomal proteins and nuclear import factors. Emerging studies demonstrate that no fewer than 2000 proteins in any particular cell type may undergo lysine acetylation. As described in this review, our analyses of cellular acetylated proteins using DAVID 6.7 bioinformatics resources have facilitated organization of acetylated proteins into functional clusters integral to cell signaling, the stress response, proteolysis, apoptosis, metabolism, and neuronal development. In addition, these clusters also depict association of acetylated proteins with human diseases. These findings not only support lysine acetylation as a widespread cellular phenomenon, but also impel questions to clarify the underlying molecular and cellular mechanisms governing target selectivity by KATs. Present challenges are to understand the molecular basis for the overlapping roles of KAT-containing co-activators, to differentiate between global versus dynamic acetylation marks, and to elucidate the physiological roles of acetylated proteins in biochemical pathways. In addition to discussing the cellular 'acetylome', a focus of this work is to present the widespread and dynamic nature of lysine acetylation and highlight the nexus that exists between epigenetic-directed transcriptional regulation and metabolism. PMID:21371315

Patel, Jigneshkumar; Pathak, Ravi R; Mujtaba, Shiraz

2011-03-03

259

Lysozyme-catalysed hydrolysis of some ?-aryl di-N-acetylchitobiosides  

PubMed Central

1. Four ?-aryl di-N-acetylchitobiosides and ?-S-phenyl di-N-acetylthiochitobioside have been prepared and shown to be substrates for hen's-egg-white lysozyme. 2. The lysozyme-catalysed hydrolysis of these substrates obeys Michaelis–Menten kinetics. 3. The Michaelis constants, Km, for the ?-aryl di-N-acetyl-chitobiosides are almost independent of the aglycone, whereas the catalytic constants, kcat., show a marked dependence, giving a Hammett reaction constant, ?, equal to 1·2; this suggests the rate-determining step involves concerted acid–base or acid–nucleophilic catalysis. 4. This conclusion is supported by the Michaelis–Menten constants found for ?-S-phenyl di-N-acetylthiochitobioside. 5. A three-step reaction pathway is proposed, and mechanisms are suggested that would account for the evidence currently available.

Lowe, G.; Sheppard, G.; Sinnott, M. L.; Williams, A.

1967-01-01

260

SIAH-mediated ubiquitination and degradation of acetyl-transferases regulate the p53 response and protein acetylation.  

PubMed

Posttranslational modification of proteins by lysine acetylation regulates many biological processes ranging from signal transduction to chromatin compaction. Here we identify the acetyl-transferases CBP/p300, Tip60 and PCAF as new substrates for the ubiquitin E3 ligases SIAH1 and SIAH2. While CBP/p300 can undergo ubiquitin/proteasome-dependent degradation by SIAH1 and SIAH2, the two other acetyl-transferases are exclusively degraded by SIAH2. Accordingly, SIAH-deficient cells show enhanced protein acetylation, thus revealing SIAH proteins as indirect regulators of the cellular acetylation status. Functional experiments show that Tip60/PCAF-mediated acetylation of the tumor suppressor p53 is antagonized by the p53 target gene SIAH2 which mediates ubiquitin/proteasome-mediated degradation of both acetyl-transferases and consequently diminishes p53 acetylation and transcriptional activity. The p53 kinase HIPK2 mediates hierarchical phosphorylation of SIAH2 at 5 sites, which further boosts its activity as a ubiquitin E3 ligase for several substrates and therefore dampens the late p53 response. PMID:23044042

Grishina, Inna; Debus, Katherina; García-Limones, Carmen; Schneider, Constanze; Shresta, Amit; García, Carlos; Calzado, Marco A; Schmitz, M Lienhard

2012-10-06

261

Hydrolysis of iodine: equilibria at high temperatures  

SciTech Connect

The hydrolysis (or disproportionation) of molecular iodine to form iodate and iodide ions has been studied by emf measurements over the temperature range, 3.8/sup 0/ to 209.0/sup 0/C. The interpretation of these results required a knowledge of the formation constant for triiodide ion and the acid dissociation constant of iodic acid, both of which were measured as a function of temperature. The resulting thermodynamic data have been incorporated into a general computer model describing the hydrolysis equilibria of iodine as a function of initial concentration, pH and temperature.

Palmer, D.A.; Ramette, R.W.; Mesmer, R.E.

1984-01-01

262

Computational Analysis of N-acetyl transferase in Tribolium castaneum.  

PubMed

N-acetyl transferase (NAT) is responsible to catalyze the transfer of acetyl groups to arylamines from acetyl-CoA. Aralkylamine Nacetyl transferase (AANAT), which belongs to GCN5-related N-acetyl transferase member, is a globular 23-kDa cytosolic protein that forms a reversible regulatory complex with 14-3-3 proteins, AANAT regulates the daily cycle of melatonin biosynthesis in mammals, making it an attractive target for therapeutic control of abnormal melatonin production in mood and sleep disorders. There is no evidence available regarding ? and ? subunits, active site and their ASA value in Dopamine N-acetyl transferase. Therefore, we describe the development of Dopamine N-acetyl transferase model in Tribolium castaneum. We further document the predicted active sites in the structural model with solvent exposed ASA residues. During this study, the model was built by CPH program and validated through PROCHECK, Verify 3D, ERRAT and ProSA for reliability. The active sites were predicted in the model with further ASA analysis of active site residues. The discussed information thus provides insight to the predicted active site and ASA values of Dopamine N-acetyl transferase model in Tribolium castaneum. PMID:23976826

Singh, Kailash; Mishra, Vineet Kumar; Nath, Karabi; Rashid, Naira; Parveen, Farzana

2013-08-07

263

Computational Analysis of N-acetyl transferase in Tribolium castaneum  

PubMed Central

N-acetyl transferase (NAT) is responsible to catalyze the transfer of acetyl groups to arylamines from acetyl-CoA. Aralkylamine Nacetyl transferase (AANAT), which belongs to GCN5-related N-acetyl transferase member, is a globular 23-kDa cytosolic protein that forms a reversible regulatory complex with 14-3-3 proteins, AANAT regulates the daily cycle of melatonin biosynthesis in mammals, making it an attractive target for therapeutic control of abnormal melatonin production in mood and sleep disorders. There is no evidence available regarding ? and ? subunits, active site and their ASA value in Dopamine N-acetyl transferase. Therefore, we describe the development of Dopamine N-acetyl transferase model in Tribolium castaneum. We further document the predicted active sites in the structural model with solvent exposed ASA residues. During this study, the model was built by CPH program and validated through PROCHECK, Verify 3D, ERRAT and ProSA for reliability. The active sites were predicted in the model with further ASA analysis of active site residues. The discussed information thus provides insight to the predicted active site and ASA values of Dopamine N-acetyl transferase model in Tribolium castaneum.

Singh, Kailash; Mishra, Vineet Kumar; Nath, Karabi; Rashid, Naira; Parveen, Farzana

2013-01-01

264

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

265

Acetylation of Tau Inhibits Its Degradation and Contributes to Tauopathy  

PubMed Central

Summary 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). Using two antibodies specific for acetylated tau, we 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 in vivo, likely 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.

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

2011-01-01

266

Alkaline Hydrolysis Conversion of Nitrocellulose Fines.  

National Technical Information Service (NTIS)

The conversion of 1,125,000 pounds of bone-dry nitrocellulose fines into a liquid fertilizer was documented. Alkaline hydrolysis was the conversion method using potassium hydroxide to dissolve the nitrocellulose, phosphoric acid to adjust the pH and then ...

F. E. Wolf

1997-01-01

267

Study on the hydrolysis of 2-chlorobenzamide.  

PubMed

It is reported that 2-chlorobenzamide, one of the chief degradation products of CCU (1-(2-chlorobenzoyl)-3-(4-chlorophenyl) urea), a new insect growth regulator, is a potential carcinogen, but few studies about its environmental stability have been found. This paper is concerned with the hydrolysis of 2-chlorobenzamide as part of the environmental study of CCU. The results showed that 2-chlorobenzamide is relatively stable in solutions of pH = 6 and 8, for which the rate constants are 0.00286 h(-)(1) (R = 99.13%, SD = 0. 0095) and 0.00109 h(-)(1) (R = 96.70%, SD = 0.0072), respectively. Hydrolysis was more rapid in acidic (pH = 5), alkaline (pH = 10), and neutral (pH = 7) environments, with hydrolytic rate constants of 0.00417h(-)(1) (R = 95.76%, SD = 0.0390), 0.00411h(-)(1) (R = 99.89%, SD = 0.0162) and 0.00408h(-)(1) (R = 98.29%, SD = 0.0237), respectively. The change of the rate of hydrolysis with pH showed two minima at 25 degrees C. Temperature has some impact on the hydrolysis, showing at higher temperature the larger rate of reaction. PMID:10888586

Qingxiang, Z; Wenying, L; Guoguang, L; Xiuling, X

2000-06-01

268

Microstructure of coke briquettes from hydrolysis lignin  

Microsoft Academic Search

The microstructure of pyrolyzed briquettes prepared from hydrolyzed lignins at different final heating temperatures has been investigated. The pore structure of the briquettes of hydrolysis lignins before the thermal treatment is dependent to a large extent upon the granulometric composition of the raw material. The initial structure of the lignins also played an important part on the effect of the

B. N. Zhitov; Yu. G. Korolev; G. N. Makarov; A. M. Myasoedov; I. A. Shimanskaya; V. P. Okladnikov

1984-01-01

269

Lipase-mediated hydrolysis of blackcurrant oil.  

PubMed

Four commercially available lipases, both free and immobilized, were tested for their ability to catalyze hydrolysis of blackcurrant (Ribes nigrum) oil using two different approaches. The lipase from Mucor miehei was studied free and immobilized in two different ways. The former series of enzymic reactions were performed in tap water at 40 degrees C, but the latter series of enzymic processes were carried out in mixtures of isooctane and phosphate buffer (in a typical 2/1 ratio of the components) at 30 degrees C. These conditions were optimized to increase and/or to maximize the yields of the products, which were priority targets in this study. A rate of hydrolysis and a selective preference of the hydrolytic enzymes towards fatty acids, with a special focus on enrichment of alpha-linolenic acid and/or gamma-linolenic acid, were studied. Higher rates of hydrolysis of the blackcurrant oil in the former series of reactions were observed with the immobilized lipase from Pseudomonas cepacia used as biocatalyst. In the latter approach, the most favorable results of the rate of hydrolysis of the target blackcurrant oil were achieved with the immobilized lipase from Mucor miehei employed as biocatalyst. Only three lipases, selected from a series of lipases tested during this investigation, displayed specificity towards alpha-linolenic acid and gamma-linolenic acid, i.e. the immobilized lipase from P. cepacia, lipase from M. miehei and lipase from P. fluorescens. PMID:10978776

Vacek; Zarevúcka; Wimmerb; Stránský; Koutek; Macková; Demnerová

2000-10-01

270

Storage oil hydrolysis during early seedling growth  

Microsoft Academic Search

Storage oil breakdown plays an important role in the life cycle of many plants by providing the carbon skeletons that support seedling growth immediately following germination. This metabolic process is initiated by lipases (EC: 3.1.1.3), which catalyze the hydrolysis of triacylglycerols (TAGs) to release free fatty acids and glycerol. A number of lipases have been purified to near homogeneity from

Anne-Laure Quettier; Peter J. Eastmond

2009-01-01

271

Interfacial charge effects during natural oil hydrolysis  

Microsoft Academic Search

This paper describes a novel laboratory scale catalytic bioreactor for the hydrolysis of natural oils in the presence of free lipase. The novelty of the reactor system is that it uses an electrostatic dispersion technique to both control the interfacial area available for the reaction and improve on the quality of that area. The system is shown to produce higher

L. R. Weatherley; D. W. Rooney; M. V. Niekerk

1997-01-01

272

Siloxanes from the hydrolysis of isopropyltrimethoxysilane  

Microsoft Academic Search

The behavior of isopropyltrimethoxysilane (1 in the presence one equivalent of water and a dibutyltin dilaurate catalyst has been investigated. Under these conditions, partial hydrolysis of the methoxy groups of 1 occurred, followed by condensation reactions leading to the formation of low molecular-weight oligomers. Disiloxane 4, trisiloxane 6 and cyclic siloxane 7 and 8 have been isolated and fully characterized.

Jack K. Crandall; Christophe Morel-Fourrier

1995-01-01

273

HD Hydrolysis/Biodegradation Toxicology and Kinetics.  

National Technical Information Service (NTIS)

One technology developed for potential use in the disposal of RD (2,2'-dichlorodiethyl sulfide) from the Aberdeen Proving Ground unitary chemical stockpile is hydrolysis followed by biodegradation. Stockpile RD (89.2% pure) was hydrolyzed in 90 deg C wate...

S. P. Harvey L. L. Szafraniec W. T. Beaudry M. V. Haley T. E. Rosso

1996-01-01

274

COMPUTERIZED EXTRAPOLATION OF HYDROLYSIS RATE DATA  

EPA Science Inventory

The program RATE was developed to aid in the extrapolation and interpretation of hydrolysis rate data to a format that is useful for environmental risk assessment. ydrolysis data typically are reported in the literature as pseudo-first-order rate constants at the temperature and ...

275

Kinetics of the alkaline hydrolysis of nitrocellulose.  

PubMed

Cellulose nitrate (nitrocellulose) is an explosive solid substance used in large quantities in various formulations of rocket and gun propellants. Safe destruction of nitrocellulose can be achieved by alkaline hydrolysis, which converts it to biodegradable products that can then be treated by conventional biological processes. The kinetics of the alkaline hydrolysis of munitions-grade nitrocellulose in sodium hydroxide solutions were investigated in completely mixed batch reactors. Experiments were conducted using solutions of alkaline strength ranging from 0.1 to 15% by mass and temperatures in the range of 30 to 90 degrees C. Regression analysis of the kinetic data revealed that alkaline hydrolysis of nitrocellulose is of the order 1.0 and 1.5 with respect to nitrocellulose and hydroxide concentration, respectively. The activation energy of the hydrolysis reaction was found to be 100.9 kJ/mol with a preexponential Arrhenius constant of 4.73 x 10(13). Nitrite and nitrate, in a 3:1 ratio, were the primary nitrogen species present in the posthydrolysis solution. The kinetic information is pertinent to the development and optimization of nitrocellulose chemical-biological treatment systems. PMID:11563378

Christodoulatos, C; Su, T L; Koutsospyros, A

276

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

277

3Hydroxy3-methylglutaryl CoA reductase inhibitors reduce serum triglyceride levels through modulation of apolipoprotein C-III and lipoprotein lipase  

Microsoft Academic Search

Statins are hypolipidemic drugs which not only improve cholesterol but also triglyceride levels. Whereas their cholesterol-reducing effect involves inhibition of de novo biosynthesis of cellular cholesterol through competitive inhibition of its rate-limiting enzyme 3-hydroxy-3-methylglutaryl CoA reductase, the mechanism by which they lower triglycerides remains unknown and forms the subject of the current study. Treatment of normal rats for 4 days

Kristina Schoonjans; Julia Peinado-Onsurbe; Jean-Charles Fruchart; Anne Tailleux; Catherine Fiévet; Johan Auwerx

1999-01-01

278

Incorporation of [2 14 C]malonyl CoA into fatty acids by a cell-free extract of Catharanthus roseus suspension culture cells  

Microsoft Academic Search

A cell-free extract containing the enzymes for de-novo synthesis, elongation and desaturation of fatty acids was prepared from cultured cells of Catharanthus roseus G. Don. 14C-Fatty acids synthesized by the extract from [2-14C]malonyl CoA substrate were palmitic (16:0), stearic (18:0) and oleic (18:1). Dialyzed extract was active and stable at room temperature and at 4° C, but was inactivated on

J. J. MacCarthy; P. K. Stumpf

1980-01-01

279

Studies of human 2,4-dienoyl CoA reductase shed new light on peroxisomal ?-oxidation of unsaturated fatty acids.  

PubMed

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 ? 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 K(m) 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. PMID:22745130

Hua, Tian; Wu, Dong; Ding, Wei; Wang, Jiangyun; Shaw, Neil; Liu, Zhi-Jie

2012-06-28

280

Polymorphisms in Cinnamoyl CoA Reductase (CCR) Are Associated With Variation in Microfibril Angle in Eucalyptus spp.  

PubMed Central

Linkage disequilibrium (LD) mapping using natural populations results in higher resolution of marker-trait associations compared to family-based quantitative trait locus (QTL) studies. Depending on the extent of LD, it is possible to identify alleles within candidate genes associated with a trait. Analysis of a natural mutant in Arabidopsis has shown that mutations in cinnamoyl CoA reductase (CCR), a key lignin gene, affect physical properties of the secondary cell wall such as stiffness and strength. Using this gene, we tested whether LD mapping could identify alleles associated with microfibril angle (MFA), a wood quality trait affecting stiffness and strength of wood. We identified 25 common single-nucleotide polymorphism (SNP) markers in the CCR gene in Eucalyptus nitens. Using single-marker and haplotype analyses in 290 trees from a E. nitens natural population, two haplotypes significantly associated with MFA were found. These results were confirmed in two full-sib families of E. nitens and Eucalyptus globulus. In an effort to understand the functional significance of the SNP markers, we sequenced the cDNA clones and identified an alternatively spliced variant from the significant haplotype region. This study demonstrates that LD mapping can be used to identify alleles associated with wood quality traits in natural populations of trees.

Thumma, Bala R.; Nolan, Maureen F.; Evans, Robert; Moran, Gavin F.

2005-01-01

281

Protein N-terminal acetylation: NAT 2007-2008 Symposia  

PubMed Central

Protein N-terminal acetylation is a very common modification, but has during the past decades received relatively little attention. In order to put this neglected field back on the scientific map, we have in May 2007 and September 2008 arranged two international NAT symposia in Bergen, Norway. This supplement contains selected proceedings from these symposia reflecting the current status of the field, including an overview of protein N-terminal acetylation in yeast and humans, a novel nomenclature system for the N-terminal acetyltransferases (NATs) and methods for studying protein N-terminal acetylation in vitro and in vivo.

Arnesen, Thomas

2009-01-01

282

Non-catalytic steam hydrolysis of fats  

SciTech Connect

Hydrolysis of fats and oils produces fatty acid and glycerol. The catalyzed, liquid phase Colgate-Emry process, state-of-the-art, produces impure products that require extensive energy investment for their purification to commercial grade. Non-catalytic steam hydrolysis may produce products more easily purified. A bench-scale hydrolyzer was designed and constructed to contact descending liquid fat or oil with rising superheated steam. Each of the five stages in the reactor was designed similar to a distillation column stage to promote intimate liquid-gas contact. Degree of hydrolysis achieved in continuous tests using tallow feed were 15% at 280C and 35% at 300C at a tallow-to-steam mass feed ratio of 4.2. At a feed ratio of 9.2, the degree of hydrolysis was 21% at 300C. Decomposition was strongly evident at 325C but not at lower temperatures. Soybean oil rapidly polymerized under reaction conditions. Batch tests at 320C produced degrees of hydrolyses of between 44% and 63% using tallow and palm oil feeds. Over 95% fatty acids were present in a clean, readily separated organic portion of the overhead product from most tests. The test reactor had serious hydraulic resistance to liquid down-flow which limited operation to very long liquid residence times. These times are in excess of those that tallow and palm oil are stable at the reaction temperature. Little glycerol and extensive light organics were produced indicating that unexplained competing reactions to hydrolysis occurred in the experimental system. Further tests using an improved reactor will be required.

Deibert, M.C.

1992-08-28

283

Design and Parametric Evaluation of an Enzymatic Hydrolysis Process (Separate Hydrolysis and Fermentation).  

National Technical Information Service (NTIS)

A separate fungal enzyme hydrolysis and fermentation process for converting lignocellulose to ethanol was evaluated. Although the current state-of-the-art process is expensive, research now under way has the potential to reduce projected selling prices by...

J. D. Wright A. J. Power L. J. Douglas

1986-01-01

284

Hydrolysis Study and Exposure Data on Trimethyl Phosphate Site.  

National Technical Information Service (NTIS)

As requested in Mr. F. D. Kovar's letter of September 23, 1981, we are enclosing information on trimethyl phosphite hydrolysis and on levels of trimethyl phosphate measured at our production site. Attachment No. 1 summarizes the hydrolysis studies. The da...

1981-01-01

285

Column cellulose hydrolysis reactor: An efficient cellulose hydrolysis reactor with continuous cellulase recycling  

Microsoft Academic Search

The use of a column cellulose hydrolysis reactor with continuous enzyme recycling was demonstrated by incorporating a continuous ultrafiltration apparatus at the effluent end of the column reactor. Using this setup, over 90% (w\\/v) cellulose hydrolysis was achieved, resulting in an average sugar concentration of 6.8% (w\\/v) in the effluent stream. The output of the system was 1.98 g of

Larry U. L. Tan; Ernest K. C. Yu; Nancy Campbell; John N. Saddler

1986-01-01

286

Muscarinic receptor activation of phosphatidylcholine hydrolysis. Relationship to phosphoinositide hydrolysis and diacylglycerol metabolism  

Microsoft Academic Search

We examined the relationship between phosphatidylcholine (PC) hydrolysis, phosphoinositide hydrolysis, and diacylglycerol (DAG) formation in response to muscarinic acetylcholine receptor (mAChR) stimulation in 1321N1 astrocytoma cells. Carbachol increases the release of (3H)choline and (3H)phosphorylcholine ((3H)Pchol) from cells containing (3H)choline-labeled PC. The production of Pchol is rapid and transient, while choline production continues for at least 30 min. mAChR-stimulated release of

E. A. Martinson; D. Goldstein; J. H. Brown

1989-01-01

287

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-CtrpbndN 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

288

Reduced wall acetylation proteins play vital and distinct roles in cell wall o-acetylation in Arabidopsis.  

PubMed

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

2013-09-09

289

Removing Hemicellulose from Pulps by Specific Enzymic Hydrolysis  

Microsoft Academic Search

The hemicellulose content (solubility in 18% NaOH) of a delignified mechanical aspen pulp was lowered from 23.4% to 18.2% by one-hour hydrolysis with xylanase isolated from the fungus Schizophpllum commune by fractional precipitation. After 24 h hydrolysis, the hemicellulose content was reduced further to 12.9%. The predominant hydrolysis products, xylose and xylobiose, confirmed the specificity of hydrolysis. A crude mixture

M. G. Paice; L. Jurasek

1984-01-01

290

Hydrolysis and oxidation of gaseous HCN over heterogeneous catalysts  

Microsoft Academic Search

The hydrolysis and oxidation of HCN, which is a potential toxic emission of automotive catalysts, were systematically examined with model gas experiments on typical hydrolysis, SCR and oxidation catalysts.TiO2-anatase showed the highest HCN hydrolysis activity among the hydrolysis catalysts, with approximately two times more activity than Al2O3. On Fe-ZSM-5, HCN was converted to NH3 to the same degree as on

O. Kröcher; M. Elsener

2009-01-01

291

Enzymatic hydrolysis of castor oil: Process intensification studies  

Microsoft Academic Search

The usual methods of castor oil hydrolysis give impure product, i.e. ricinoleic acid. An alternative technique for production is the enzymatic hydrolysis of castor oil where the product is available as a light colored and odorless product. Usually lipase catalyzed enzymatic hydrolysis has been carried out in oil in water emulsions, which require rather high quantities of enzymes limiting the

Meenal S. Puthli; Virendra K. Rathod; Aniruddha B. Pandit

2006-01-01

292

A review: Hydrogen generation from borohydride hydrolysis reaction  

Microsoft Academic Search

In this review, a convenient hydrogen generation technology based on sodium borohydride and water as hydrogen carriers has been summarized. The recent progresses in the development of the hydrogen generation from sodium borohydride hydrolysis are reviewed. The NaBH4 hydrolysis behavior is discussed in detail. From reported results, it is considered that hydrogen generation from sodium borohydride hydrolysis is a feasible

B. H. Liu; Z. P. Li

2009-01-01

293

Technical bases for precipitate hydrolysis process operating parameters  

SciTech Connect

This report provides the experimental data and rationale in support of the operating parameters for precipitate hydrolysis specified in WSRC-RP-92737. The report is divided into two sections, the first dealing with lab-scale precipitate hydrolysis experimentation while the second part addresses large-scale runs conducted to demonstrate the revised operating parameters in the Precipitate Hydrolysis Experimental Facility (PHEF).

Bannochie, C.J.

1992-10-05

294

21 CFR 172.372 - N-Acetyl-L-methionine.  

Code of Federal Regulations, 2013 CFR

...conditions: (a) N- Acetyl-L-methionine (Chemical Abstracts Service Registry No. 65-82-7) is the derivative of the...3) Adequate directions for use to provide a finished food meeting the limitations prescribed by paragraph (c) of this...

2013-04-01

295

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.

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

2012-01-01

296

Acetylation of Androgen Receptor Enhances Coactivator Binding and Promotes Prostate Cancer Cell Growth  

Microsoft Academic Search

Modification by acetylation occurs at -amino lysine residues of histones and transcription factors. Unlike phosphorylation, a direct link between transcription factor acetylation and cellular growth or apoptosis has not been established. We show that the nuclear androgen receptor (AR), a DNA-binding transcriptional regulator, is acetylated in vivo. The acetylation of the AR is induced by ligand dihydrotestosterone and by histone

Maofu Fu; Mahadev Rao; Chenguang Wang; Toshiyuki Sakamaki; Jian Wang; Dolores Di Vizio; Xueping Zhang; Chris Albanese; Steven Balk; Chawnshang Chang; Saijun Fan; Eliot Rosen; Jorma J. Palvimo; Olli A. Janne; Selen Muratoglu; Maria Laura Avantaggiati; Richard G. Pestell

2003-01-01

297

Effect of lime pre-treatment on the synergistic hydrolysis of sugarcane bagasse by hemicellulases.  

PubMed

Agricultural crop wastes are typically lignocellulosic in composition and thus partially recalcitrant to enzymatic degradation. The recalcitrant nature of plant biomass and the inability to obtain complete enzymatic hydrolysis has led to the establishment of various pre-treatment strategies. Alkaline pre-treatments increase the accessibility of the exposed surface to enzymatic hydrolysis through the removal of acetyl and uronic acid substituents on hemicelluloses. Unlike the use of steam and acid pre-treatments, alkaline pre-treatments (e.g. lime) solubilise lignin and a small percentage of the hemicelluloses. The most common alkaline pre-treatments that are employed make use of sodium hydroxide and lime. This study compared the synergistic degradation of un-treated and lime pre-treated sugarcane bagasse using cellulosomal and non-cellulosomal hemicellulases as free enzymes. The enzyme combination of 37.5% ArfA and 62.5% ManA produced the highest amount of reducing sugar of 91.834 micromol/min for the degradation of un-treated bagasse. This enzyme combination produced a degree of synergy of 1.87. The free enzymes displayed an approximately 6-fold increase in the enzyme activity, i.e. the total amount of reducing sugar released (593.65 micromol/min) with the enzyme combination of 37.5% ArfA, 25% ManA and 37.5% XynA for the lime pre-treated substrate and a degree of synergy of 2.14. To conclude, this study indicated that pre-treating the sugarcane bagasse is essential, in order to increase the efficiency of lignocellulose enzymatic hydrolysis by disruption of the lignin sheath, that the lime pre-treatment did not have any dramatic effect on the synergistic relationship between the free enzymes, and that time may play an important role in the establishment of synergistic relationships between enzymes. PMID:20156678

Beukes, Natasha; Pletschke, Brett I

2010-02-13

298

Towards a Functional Understanding of Protein N-Terminal Acetylation  

Microsoft Academic Search

Protein N-terminal acetylation is a major modification of eukaryotic proteins. Its functional implications include regulation of protein–protein interactions and targeting to membranes, as demonstrated by studies of a handful of proteins. Fifty years after its discovery, a potential general function of the N-terminal acetyl group carried by thousands of unique proteins remains enigmatic. However, recent functional data suggest roles for

Thomas Arnesen

2011-01-01

299

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.

2012-01-01

300

Acetylation Suppresses the Proapoptotic Activity of GD3 Ganglioside  

Microsoft Academic Search

GD3 synthase is rapidly activated in different cell types after specific apoptotic stimuli. De novo synthesized GD3 accumulates and contributes to the apoptotic program by relocating to mito- chondrial membranes and inducing the release of apoptogenic factors. We found that sialic acid acetylation suppresses the proapoptotic activity of GD3. In fact, unlike GD3, 9-O-acetyl-GD3 is completely ineffective in inducing cytochrome

Florence Malisan; Luigi Franchi; Barbara Tomassini; Natascia Ventura; Ivano Condò; Maria Rita Rippo; Alessandra Rufini; Laura Liberati; Claudia Nachtigall; Bernhard Kniep; Roberto Testi

2002-01-01

301

Clinical pharmacokinetics of procainamide infusions in relation to acetylator phenotype  

Microsoft Academic Search

The pharmacokinetics of procainamide was determined in 21 lidocaine-resistant patients who received the drug according to a pharmacokinetically designed double-infusion technique. Thirteen patients were phenotyped as slow acetylators, seven as fast, and one as intermediate. The total body clearances (ClT) of PA in slow and fast acetylators were 22.6 and 34.8 liters\\/hr, respectively. The fraction of PA cleared by the

John J. Lima; David R. Conti; Allen L. Goldfarb; William J. Tilstone; Lawrence H. Golden; William J. Jusko

1979-01-01

302

Comparison of the acetylation of procainamide and sulfadimidine in man  

Microsoft Academic Search

The acetylation of procainamide and sulfadimidine has been measured simultaneously in plasma and urine in 20 healthy human volunteers by a specific G.L.C. method, after single and multiple oral doses of procainamide retard tablets. A distinct bimodality (9 rapid and 11 slow acetylators) was apparent from the concentrations of procainamide and N-acetylprocainamide both in urine and plasma, which was in

K. Frislid; M. Berg; V. Hansteen; P. K. M. Lunde

1976-01-01

303

Alkylating antitumor agents reduce histone acetyl-transferase activity.  

PubMed

N-Mustard depresses the acetylation of histones in Ehrlich ascites and Walker carcinoma cells. It is demonstrated that this effect is not caused by an accelerated deacetylation but is due to an inhibition of the acetyl-transferase reaction. Employing 4-sulphonatoethylthio-cyclophosphamide it is demonstrated that the alkylating agent affects predominantly the acetylation of a chromatin fraction which is soluble in 0.1M NaCl after digestion with micrococcal nuclease. After removal of the alkylating agent, the recovery of histone acetylation is relatively slow and--in contrast to the repair of DNA cross-links--characterized by a 4-hr lag period. The reduction of histone acetylation by N-mustard is much less expressed in cells which are resistant to the drug than in the sensitive parental lines. This is in contrast to DNA-interstrand cross-links in Walker cells where both N-mustard sensitive and resistant cells inhibit the same cross-link frequency and identical repair rates. Based on these data it is concluded that the inhibition of histone acetylation may be an important part of the mechanism by which alkylating agents inhibit tumor growth. PMID:3643697

Grunicke, H; Helliger, W; Hermann, B J; Höck, W; Hofmann, J; Puschendorf, B

1986-01-01

304

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.

Kramer, Oliver H.; Knauer, Shirley K.; Greiner, Georg; Jandt, Enrico; Reichardt, Sigrid; Guhrs, Karl-Heinz; Stauber, Roland H.; Bohmer, Frank D.; Heinzel, Thorsten

2009-01-01

305

K-acetylation and its enzymes: overview and new developments.  

PubMed

Lysine (K) acetylation refers to transfer of the acetyl moiety from acetyl-CoA to the ?-amino group of a lysine residue. This is posttranslational and reversible, with its level dynamically maintained by lysine acetyltransferases (KATs) and deacetylases (KDACs). Traditionally, eukaryotic KDACs have been referred to as HDACs (histone deacetylases). Recent proteomic studies have revealed that hundreds of bacterial proteins and thousands of eukaryotic proteins contain acetyl-lysine (AcK) residues, indicating that K-acetylomes are comparable to phosphoproteomes. The current challenges are to assign enzymes that execute specific acetylation events, to determine the impact of these events, and to relate this modification to other posttranslational modifications, cell signaling networks, and pathophysiology under different cellular and developmental contexts. In this chapter, we provide a brief overview about the acetylomes, KATs, HDACs, AcK-recognizing protein domains, and acetylation-modulating therapeutics, and emphasize the latest developments in related areas. The remaining chapters of the book focus on and cover various aspects of HDACs (both the Rpd3/Hda1 and sirtuin families), which shall provide novel insights into how to utilize these enzymes for developing a new generation of HDAC-related therapeutics. PMID:21879443

Aka, Juliette Adjo; Kim, Go-Woon; Yang, Xiang-Jiao

2011-01-01

306

Genetic Construction of Truncated and Chimeric Metalloproteins Derived from the Alpha Subunit of Acetyl-CoA Synthase from Clostridium thermoaceticum  

SciTech Connect

In this study, a genetics-based method is used to truncate acetyl-coenzyme A synthase from Clostridium thermoaceticum (ACS), an alpha2beta2 tetrameric 310 kda bifunctional enzyme. ACS catalyzes the reversible reduction of CO2 to CO and the synthesis of acetyl-CoA from CO (or CO2 in the presence of low-potential reductants), CoA, and a methyl group bound to a corrinoid-iron sulfur protein (CoFeSP). ACS contains 7 metal-sulfur clusters of 4 different types called A, B, C, and D. The B, C, and D clusters are located in the 72 kda beta subunit while the A-cluster, a Ni-X-Fe4S4 cluster that serves as the active site for acetyl-CoA synthase activity, is located in the 82 kda alpha subunit. The extent to which the essential properties of the cluster, including catalytic, redox, spectroscopic, and substrate-binding properties, were retained as ACS was progressively truncated was determined. Acetyl-CoA synthase catalytic activity remained when the entire alpha subunit was removed, as long as CO, rather than CO2 and a low-potential reductant, was used as a substrate. Truncating an {approx} 30 kda region from the N-terminus of the alpha subunit yielded a 49 kda protein that lacked catalytic activity but exhibited A-cluster-like spectroscopic, redox, and CO binding properties. Further truncation afforded a 23 kda protein that lacked recognizable A-cluster properties except for UV-vis spectra typical of [Fe4S4]2+ clusters. Two chimeric proteins were constructed by fusing the gene encoding a ferredoxin from Chromatium vinosum to genes encoding the 49 kda and 82 kda fragments of the alpha subunit. The chimeric proteins exhibited EPR signals that were not the simple sum of the signals from the separate proteins, suggesting magnetic interactions between clusters. This study highlights the potential for using genetics to simplify the study of complex multi-centered metalloenzymes and to generate new complex metalloenzymes with interesting properties.

Huay-Keng Loke; Xiangshi Tan; Paul A. Lindahl

2002-06-28

307

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, HOOCCH2CH2?(NHCOCH3)COOH radical; and those in N?-acetyl L-glutamine single crystal to the NH2COCH2CH2?(NHCOCH3)COOH and NH2COCH2CH2CH(NHCOCH3)?OOH 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, ?.; Ucun, F.

1997-05-01

308

Hydrolysis of carbonyl sulfide over alumina  

SciTech Connect

The reaction rate for the hydrolysis of carbonyl sulfide in liquid petroleum hydrocarbons over alumina, such as propylene, is greatly increased by maintaining water in the hydrocarbons in an amount of one mole of water per mole of carbonyl sulfide to an upper limit of about ten moles of water per mole of carbonyl sulfide or about 30% of saturation of the hydrocarbons, whichever upper limit provides the lesser amount of water.

Polleck, R. E.; Ledley, R. E.; Scott, K. A.

1985-01-01

309

?-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.

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

2013-01-01

310

Enzymatic Hydrolysis of Cellulose in NMMO  

Microsoft Academic Search

In-situ hydrolysis of de-lignified cellulose pulp dissolved in N-methyl morpholine oxide (NMMO) by commercially available AccelleraseTM1000 was studied under various reaction conditions and reaction schemes. The yield of reducing sugars was followed as a function of time at different cellulose loadings predominantly at an enzyme loading of 122 FPU\\/g and a temperature of 50oC. A twin screw reactor was successfully

Brett S. Robbins

2010-01-01

311

Role of nucleotide hydrolysis in microtubule assembly  

Microsoft Academic Search

MICROTUBULE assembly in vitro requires (in normal conditions) that GTP be bound to the exchangeable nucleotide-binding site of tubulin1-3. The bound GTP is hydrolysed during polymerisation and the resulting GDP remains bound to the microtubule while the phosphate is released into the medium. Although hydrolysis normally occurs during polymerisation, microtubules will form in a non-hydrolysable analogue of GTP, guanylyl imidodiphosphate

R. C. Weisenberg; W. J. Deery

1976-01-01

312

Kinetics of hydrolysis of type I, II, and III collagens by the class I and II Clostridium histolyticum collagenases.  

PubMed

The kinetics of hydrolysis of rat tendon type I, bovine nasal septum type II, and human placental type III collagens by class I and class II Clostridium histolyticum collagenases (CHC) have been investigated. To facilitate this study, radioassays developed previously for the hydrolysis of these [3H]acetylated collagens by tissue collagenases have been adapted for use with the CHC. While the CHC are known to make multiple scissions in these collagens, the assays are shown to monitor the initial proteolytic events. The individual kinetic parameters kcat and KM have been determined for the hydrolysis of all three collagens by both class I and class II CHC. The specific activities of these CHC toward fibrillar type I and III collagens have also been measured. In contrast to human tissue collagenases, neither class of CHC exhibits a marked specificity toward any collagen type either in solution or in fibrillar form. The values of the kinetic parameters kcat and KM for the CHC are similar in magnitude to those of the human enzymes acting on their preferred substrates. Thus, the widely held view that the CHC are more potent collagenases is not strictly correct. As with the tissue collagenases, the local collagen structure at the cleavage sites is believed to play an important role in determining the rates of the reactions studied. PMID:1325155

Mallya, S K; Mookhtiar, K A; Van Wart, H E

1992-02-01

313

N-Acetyl-L-Aspartate is a Major Source of Acetyl Groups for Lipid Synthesis during Rat Brain Development  

Microsoft Academic Search

The function of N-acetyl-L-aspartate (NAA), a predominant substance in the CNS, has not yet been determined. To investigate the possible function of NAA as a lipid precursor [14C]-N-acetyl-L-aspartate (NAA) or [14C]-acetate (AcA) was injected intracerebrally into 8, 15- and 22-day-old rats. These time points were selected because NAA concentration and the activity of the NAA synthetizing enzyme L-aspartate-N-acetyltransferase (ANAT) were

R. Burri; C. Steffen; N. Herschkowitz

1991-01-01

314

Antibodies specific to acetylated histones document the existence of deposition- and transcription-related histone acetylation in Tetrahymena  

Microsoft Academic Search

In this study, we have constructed synthetic peptides which are identical to hyperacetylated amino termini of two Tetrahymena core histones (tetra-acet- ylated H4 and penta-acetylated hvl) and used them to generate polyclonal antibodies specific for acetylated forms (mono-, di-, tri-, etc.) of these histones. Neither of these antisera recognizes histone that is unacetyl- ated. Immunoblotting analyses demonstrate that both transcription-related

Rueyling Lin; Joseph W. Leone; Richard G. Cook; C. David Allis

1989-01-01

315

Palm Date Fibers: Analysis and Enzymatic Hydrolysis  

PubMed Central

Waste palm dates were subjected to analysis for composition and enzymatic hydrolysis of their flesh fibers. The fruit contained 32% glucose and 30% fructose, while the water-insoluble fibers of its flesh consisted of 49.9% lignin and 20.9% polysaccharides. Water-insoluble fibers were settled to 55% of its initial volume in 12 h. The presence of skin and flesh colloidal fibers results in high viscosity and clogging problems during industrial processes. The settling velocity of the fibers was improved by enzymatic hydrolysis. Hydrolysis resulted in 84.3% conversion of the cellulosic part of the fibers as well as reducing the settling time to 10 minutes and the final settled volume to 4% of the initial volume. It implies easier separation of the fibers and facilitates fermentation processes in the corresponding industries. Two kinds of high- and low-lignin fibers were identified from the water-insoluble fibers. The high-lignin fibers (75% lignin) settled easily, while the low-lignin fibers (41.4% lignin) formed a slurry suspension which settled very slowly. The hydrophilicity of these low-lignin fibers is the major challenge of the industrial processes.

Shafiei, Marzieh; Karimi, Keikhosro; Taherzadeh, Mohammad J.

2010-01-01

316

Thiogalactopyranosides are resistant to hydrolysis by ?-galactosidases.  

PubMed

Fluorescently tagged glycosides containing terminal ?(1?3) and ?(1?4)-linked thiogalactopyranosides have been prepared and tested for resistance to hydrolysis by ?-galactosidases. Eight fluorescent glycosides containing either galactose or 5-thiogalactose as the terminal sugar were enzymatically synthesized using galactosyltransferases, with lactosyl glycosides as acceptors and UDP-galactose or UDP-5'-thiogalactose, respectively, as donors. The glycosides were incubated with human ?-galactosidase A (CAZy family GH27, a retaining glycosidase), Bacteroides fragilis ?-1,3-galactosidase (GH110, an inverting glycosidase), or homogenates of MCF-7 human breast cancer cells or NG108-15 rat glioma cells. Substrate hydrolysis was monitored by capillary electrophoresis with fluorescence detection. All compounds containing terminal O-galactose were readily degraded. Their 5-thiogalactose counterparts were resistant to hydrolysis by human ?-galactosidase A and the enzymes present in the cell extracts. B. fragilis ?-1,3-galactosidase hydrolyzed both thio- and O-galactoside substrates; however, the thiogalactosides were hydrolyzed at only 1-3 % of the rate of O-galactosides. The hydrolytic resistance of 5-thiogalactose was also confirmed by an in vivo study using cells in culture. The results suggest that 5-thiogalactosides may be useful tools for the study of anabolic pathways in cell extracts or in single cells. PMID:22740420

Adlercreutz, Dietlind; Yoshimura, Yayoi; Mannerstedt, Karin; Wakarchuk, Warren W; Bennett, Eric P; Dovichi, Norman J; Hindsgaul, Ole; Palcic, Monica M

2012-06-27

317

Sugarcane bagasse hydrolysis using yeast cellulolytic enzymes.  

PubMed

Ethanol fuel production from lignocellulosic biomass is emerging as one of the most important technologies for sustainable development. To use this biomass, it is necessary to circumvent the physical and chemical barriers presented by the cohesive combination of the main biomass components, which hinders the hydrolysis of cellulose and hemicellulose into fermentable sugars. This study evaluated the hydrolytic capacity of enzymes produced by yeasts, isolated from the soils of the Brazilian Cerrado biome (savannah) and the Amazon region, on sugarcane bagasse pre-treated with H2SO4. Among the 103 and 214 yeast isolates from the Minas Gerais Cerrado and the Amazon regions, 18 (17.47%) and 11 (5.14%) isolates, respectively, were cellulase-producing. Cryptococcus laurentii was prevalent and produced significant ?- glucosidase levels, which were higher than the endo- and exoglucanase activities. In natura sugarcane bagasse was pre-treated with 2% H2SO4 for 30 min at 150oC. Subsequently, the obtained fibrous residue was subjected to hydrolysis using the Cryptococcus laurentii yeast enzyme extract for 72 h. This enzyme extract promoted the conversion of approximately 32% of the cellulose, of which 2.4% was glucose, after the enzymatic hydrolysis reaction, suggesting that C. laurentii is a good ?-glucosidase producer. The results presented in this study highlight the importance of isolating microbial strains that produce enzymes of biotechnological interest, given their extensive application in biofuel production. PMID:23851270

Souza, Angelica Cristina de; Carvalho, Fernanda Paula; Silva E Batista, Cristina Ferreira; Schwan, Rosane Freitas; Dias, Disney Ribeiro

2013-10-28

318

Hydrolysis of sulphonamides in aqueous solutions.  

PubMed

Hydrolysis is one of the most common reactions controlling abiotic degradation and is one of the main paths by which substances are degraded in the environment. Nevertheless, the available information on this process for many compounds, including sulphonamides (a group of antibiotic drugs widely used in veterinary medicine), is very limited. This is the first study investigating the hydrolytic stabilities of 12 sulphonamides, which were determined according to OECD guideline 111 (1st category reliability data on the basis of regulatory demands on data quality for the environmental risk assessment of pharmaceuticals). Hydrolysis behaviour was examined at pH values normally found in the environment. This was prefaced by a discussion of the acid-base properties of sulphonamides. All the sulphonamides tested were hydrolytically stable at pH 9.0, nine (apart from sulphadiazine, sulphachloropyridazine and sulphamethoxypyridazine) were stable in this respect at pH 7.0 and two (sulphadiazine and sulphaguanidine) at pH 4.0 (hydrolysis rate?10%; t(0.5 (25°C))>1 year). The degradation products were identified, indicating two independent mechanisms of this process. Our results show that under typical environmental conditions (pH and temperature) sulphonamides are hydrolytically stable with a long half-life; they thus contribute to the on-going assessment of their environmental fate. PMID:22579461

Bia?k-Bieli?ska, Anna; Stolte, Stefan; Matzke, Marianne; Fabia?ska, Aleksandra; Maszkowska, Joanna; Ko?odziejska, Marta; Liberek, Beata; Stepnowski, Piotr; Kumirska, Jolanta

2012-04-25

319

Biosynthesis of polylactic acid and its copolymers using evolved propionate CoA transferase and PHA synthase.  

PubMed

For the synthesis of polylactic acid (PLA) and its copolymers by one-step fermentation process, heterologous pathways involving Clostridium propionicum propionate CoA transferase (Pct(Cp)) and Pseudomonas sp. MBEL 6-19 polyhydroxyalkanoate (PHA) synthase 1 (PhaC1(Ps6-19)) were introduced into Escherichia coli for the generation of lactyl-CoA endogenously and incorporation of lactyl-CoA into the polymer, respectively. Since the wild-type PhaC1(Ps6-19) did not efficiently accept lactyl-CoA as a substrate, site directed mutagenesis as well as saturation mutagenesis were performed to improve the enzyme. The wild-type Pct(Cp) was not able to efficiently convert lactate to lactyl-CoA and was found to exert inhibitory effect on cell growth, random mutagenesis by error-prone PCR was carried out. By employing engineered PhaC1(Ps6-19) and Pct(Cp), poly(3-hydroxybutyrate-co-lactate), P(3HB-co-LA), containing 20-49 mol% lactate could be produced up to 62 wt% from glucose and 3HB. By controlling the 3HB concentration in the medium, PLA homopolymer and P(3HB-co-LA) containing lactate as a major monomer unit could be synthesized. Also, P(3HB-co-LA) copolymers containing various lactate fractions could be produced from glucose alone by introducing the Cupriavidus necator beta-ketothiolase and acetoacetyl-CoA reductase genes. Fed-batch cultures were performed to produce P(3HB-co-LA) copolymers having 9-64 mol% of lactate, and their molecular weights, thermal properties, and melt flow properties were determined. PMID:19937726

Yang, Taek Ho; Kim, Tae Wan; Kang, Hye Ok; Lee, Sang-Hyun; Lee, Eun Jeong; Lim, Sung-Chul; Oh, Sun Ok; Song, Ae-Jin; Park, Si Jae; Lee, Sang Yup

2010-01-01

320

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

321

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

PubMed

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

2012-06-04

322

Effect of Zn on acetyl coenzyme a synthase: evidence for a conformational change in the alpha subunit during catalysis.  

PubMed

Acetyl coenzyme A synthase (ACS) is an alpha2beta2 tetramer in which the active-site A-cluster, located in the alpha subunits, consists of an Fe4S4 cubane bridged to a {Nip Nid} binuclear site. The alpha subunits exist in two conformations. In the open conformation, Nip is surface-exposed, while the proximal metal is buried in the closed conformation. Nip is labile and can be replaced by Cu. In this study, the effects of Zn are reported. ACS in which Zn replaced Nip was inactive and did not exhibit the so-called NiFeC EPR signal nor the ability to accept a methyl group from the corrinoid-iron-sulfur protein (CoFeSP). Once Zn-bound, it could not be replaced by subsequently adding Ni. The Zn-bound A-cluster cannot be reduced and bound with CO or become methylated, probably because Zn (like Cu) is insufficiently nucleophilic for these functions. Unexpectedly, Zn replaced Nip only while ACS was engaged in catalysis. Under these conditions, replacement occurred with kapp approximately 0.6 min-1. Replacement was blocked by including EDTA in the assay mix. Zn appears to replace Nip when ACS is in an intermediate state (or states) of catalysis but this(these) state(s) must not be present when ACS is reduced in CO alone, or in the presence of CoA, CoFeSP, or reduced methyl viologen. Nip appears susceptible to Zn-attack when the alpha subunit is in the open conformation and protected from attack when it is in the closed conformation. This is the first evidence that the structurally-characterized conformations of the alpha subunit change during catalysis, indicating a mechanistic role for this conformational change. PMID:15137746

Tan, Xiangshi; Bramlett, Matthew R; Lindahl, Paul A

2004-05-19

323

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.

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

2012-01-01

324

O Acetylation of plant cell wall polysaccharides: identification and partial characterization of a rhamnogalacturonan O -acetyl-transferase from potato suspension-cultured cells  

Microsoft Academic Search

.  ?A microsomal preparation from suspension-cultured potato stem cells (Solanum tuberosum L. cv. AZY) was incubated with [14C]acetyl-CoA resulting in a precipitable radiolabeled product. Analysis of the product revealed that it consisted mostly of\\u000a acetylated proteins and cell wall polysaccharides, including xyloglucan, homogalacturonan and rhamnogalacturonan I. Thus,\\u000a acetyl-CoA is a donor-substrate for the O-acetylation of wall polysaccharides. A rhamnogalacturonan acetylesterase was

Markus Pauly; Henrik Vibe Scheller

2000-01-01

325

Laser enhanced hydrolysis of selected polypeptides  

NASA Astrophysics Data System (ADS)

This project serves as a preliminary examination of selectively enhancing bond cleavage during chemical reactions in biological molecules by using continuous wave infrared lasers. To analyze protein content, polypeptides are broken into their constituent amino acids through hydrolysis. The cleaving of the peptide bond has traditionally been accomplished under harsh conditions, 110°C in 6 N hydrochloric acid for 24 hours. In this project hydrolysis was strongly enhanced by irradiating the dipeptides, threonyl-aspartate and alanyl-alanine, for 30 minutes with coherent infrared radiation from a tunable carbon dioxide laser. The dipeptide tyrosyl-tyrosine, the chemical N- methylacetimide, and the protein BSA were successfully hydrolyzed with the laser. The effect of reaction parameters such as laser power and HCl concentration were studied, as well as the effect of the primary parameter, the beam wavelength. The samples were analyzed using standard biological methods for determining the amino acid concentration, thin layer chromatography and ion exchange chromatography. These methods gave consistent results for the irradiated samples as well as for standard amino acids and polypeptide samples. The results from these methods were used to create the hydrolysis spectra. The catalytic action of the laser was strongly wavelength dependent. The hydrolysis spectra of the molecules were compared to the absorption spectra of the samples. Laser enhanced hydrolysis occurred when the laser wavelength coincided with a line in the dipeptide spectra. This weak line in each of the dipeptide spectra is consistent both in position and strength with a line in NMA, which has been identified as a fundamental mode associated with the peptide bond. From the experimental results, the enhanced process appears to occur in the vapor phase. The initially liquid sample was progressively evaporated, and fully hydrolyzed material was carried to a collection trap by the vapor. It can, in principle, be extracted immediately and continuously, reducing the time involved and the degradation of the samples. If subsequent observations confirm that laser excited molecular resonance affects the reaction in vapor, the implications in physics will be numerous, including the study of atmospheric reactions and other light enhanced vapor phase reactions.

Ouzts, Mary Paige

326

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

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; Boll, Matthias

2013-05-10

327

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

328

Acetate Activation in Methanosaeta thermophila: Characterization of the Key Enzymes Pyrophosphatase and Acetyl-CoA Synthetase  

PubMed Central

The thermophilic methanogen Methanosaeta thermophila uses acetate as sole substrate for methanogenesis. It was proposed that the acetate activation reaction that is needed to feed acetate into the methanogenic pathway requires the hydrolysis of two ATP, whereas the acetate activation reaction in Methanosarcina sp. is known to require only one ATP. As these organisms live at the thermodynamic limit that sustains life, the acetate activation reaction in Mt. thermophila seems too costly and was thus reevaluated. It was found that of the putative acetate activation enzymes one gene encoding an AMP-forming acetyl-CoA synthetase was highly expressed. The corresponding enzyme was purified and characterized in detail. It catalyzed the ATP-dependent formation of acetyl-CoA, AMP, and pyrophosphate (PPi) and was only moderately inhibited by PPi. The breakdown of PPi was performed by a soluble pyrophosphatase. This enzyme was also purified and characterized. The pyrophosphatase hydrolyzed the major part of PPi (KM = 0.27 ± 0.05?mM) that was produced in the acetate activation reaction. Activity was not inhibited by nucleotides or PPi. However, it cannot be excluded that other PPi-dependent enzymes take advantage of the remaining PPi and contribute to the energy balance of the cell.

Berger, Stefanie; Welte, Cornelia; Deppenmeier, Uwe

2012-01-01

329

Endogenous apolipoprotein E modulates cholesterol efflux and cholesteryl ester hydrolysis mediated by high-density lipoprotein-3 and lipid-free apolipoproteins in mouse peritoneal macrophages  

Microsoft Academic Search

We investigated the effect of endogenous apolipoprotein (apo) E synthesis in mouse peritoneal macrophages on cholesterol efflux and intracellular cholesteryl ester hydrolysis mediated by high-density lipoprotein-3 (HDL3) and lipid-free apolipoproteins (apo). After loading with acetylated LDL (acLDL) peritoneal macrophages from wild-type (apoE+\\/+) and apoE-deficient (apoE-\\/-) mice were incubated with medium alone or with liposomes, HDL3, lipid-free apoA-I, or lipid-free apoE3.

Claus Langer; Yadong Huang; Paul Cullen; Bernd Wiesenhütter; Robert W. Mahley; Gerd Assmann; Arnold von Eckardstein

2000-01-01

330

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.

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

2000-01-01

331

Mycelium-bound carboxylesterase from Aspergillus oryzae: an efficient catalyst for acetylation in organic solvent.  

PubMed

Dry mycelium of a strain of Aspergillus oryzae efficiently catalyzed the esterification between free acetic acid and primary alcohols (geraniol and ethanol) in organic solvent. The growth conditions to obtain high activity of mycelium-bound enzymes were firstly evaluated. A medium containing Tween 80 as carbon source furnished mycelium with the highest activity in the hydrolysis of alpha-naphthyl esters (alpha-N-acetate, butyrate, caprylate). Dry mycelium was employed to select suited conditions for an efficient acetylation of ethanol and geraniol in heptane. Maximum productions were obtained using 30 g l(-)(1) of lyophilized cells: 12.4 g l(-)(1) of geranyl acetate were produced at 80 degrees C starting from 75 mM geraniol and acetic acid (84% molar conversion) and 4.1 g l(-)(1) of ethyl acetate at 50 degrees C from 50 mM ethanol and acetic acid (94% molar conversion) after 24 h. The stability of the mycelium-bound carboxylesterases are notable since only 10-30% loss of activity was observed after 14 days at temperatures between 30 and 50 degrees C. PMID:11024527

Molinari; Gandolfi; Converti; Zilli

2000-11-01

332

Acetylation-dependent regulation of Skp2 function.  

PubMed

Aberrant Skp2 signaling has been implicated as a driving event in tumorigenesis. Although the underlying molecular mechanisms remain elusive, cytoplasmic Skp2 correlates with more aggressive forms of breast and prostate cancers. Here, we report that Skp2 is acetylated by p300 at K68 and K71, which is a process that can be antagonized by the SIRT3 deacetylase. Inactivation of SIRT3 leads to elevated Skp2 acetylation, which leads to increased Skp2 stability through impairment of the Cdh1-mediated proteolysis pathway. As a result, Skp2 oncogenic function is increased, whereby cells expressing an acetylation-mimetic mutant display enhanced cellular proliferation and tumorigenesis in vivo. Moreover, acetylation of Skp2 in the nuclear localization signal (NLS) promotes its cytoplasmic retention, and cytoplasmic Skp2 enhances cellular migration through ubiquitination and destruction of E-cadherin. Thus, our study identifies an acetylation-dependent regulatory mechanism governing Skp2 oncogenic function and provides insight into how cytoplasmic Skp2 controls cellular migration. PMID:22770219

Inuzuka, Hiroyuki; Gao, Daming; Finley, Lydia W S; Yang, Wen; Wan, Lixin; Fukushima, Hidefumi; Chin, Y Rebecca; Zhai, Bo; Shaik, Shavali; Lau, Alan W; Wang, Zhiwei; Gygi, Steven P; Nakayama, Keiko; Teruya-Feldstein, Julie; Toker, Alex; Haigis, Marcia C; Pandolfi, Pier Paolo; Wei, Wenyi

2012-07-01

333

Relationship of histone acetylation to DNA topology and transcription.  

PubMed

An autonomously replicating plasmid constructed from bovine papiloma virus (BPV) and pBR322 was stably maintained as a nuclear episome in a mouse cell culture. Addition to a cell culture of sodium butyrate (5 mM) induced an increase in plasmid DNA supercoiling of 3-5 turns, an increase in acetylation of cellular histones, and a decrease in plasmid transcription by 2- to 4-fold. After withdrawal of butyrate, DNA supercoiling began to fluctuate in a wave-like manner with an amplitude of up to 3 turns and a period of 3-4 h. These waves gradually faded by 24 h. The transcription of the plasmid and acetylation of cellular histones also oscillated with the same period. The wave-like alterations were not correlated with the cell cycle, for there was no resumption of DNA replication after butyrate withdrawal for at least 24 h. In vitro chemical acetylation of histones with acetyl adenylate also led to an increase in the superhelical density of plasmid DNA. The parallel changes in transcription, histone acetylation, and DNA supercoiling in vivo may indicate a functional innerconnection. Also, the observed in vivo variation in the level of DNA supercoiling directly indicates the possibility of its natural regulation in eukaryotic cells. PMID:1662766

Krajewski, W A; Luchnik, A N

1991-12-01

334

Lysine acetylation in obesity, diabetes and metabolic disease.  

PubMed

Histone acetyltransferases (HATs) and histone deacetylases (HDACs) mediate acetylation and deacetylation of histone proteins and transcription factors. There is abundant evidence that these enzymes regulate the acetylation state of many cytoplasmic proteins, including lysine residues in important metabolic enzymes. Lysine acetylation regulates major cellular functions as a common post-transcriptional modification of proteins, conserved from prokaryotes to humans. In this article, we refer to HATs and HDACs broadly as lysine acetyltransferases (KATs) and deacetylases (KDACs). Lysine acetylation is vitally important in both immunological and metabolic pathways and may regulate the balance between energy storage and expenditure. Obesity, type II diabetes and cardiovascular disease (metabolic syndrome) are widely recognised as features of a chronic low-grade inflammatory state, involving significant alterations in primary immunometabolism. Identifying effective therapeutic and preventive options to treat this multi-factorial syndrome has proven to be very challenging, with an emerging focus on developing anti-inflammatory agents that can combat adiposity and metabolic disease. Here, we summarise current evidence and understanding of innate immune and metabolic pathways relevant to adiposity and metabolic disease regulated by lysine acetylation. Developing this understanding in greater detail may facilitate strategic development of novel and enzyme-specific lysine deacetylase modulators that regulate both metabolic and immune systems. PMID:22083525

Iyer, Abishek; Fairlie, David P; Brown, Lindsay

2011-11-15

335

Biochemical and Serological Characteristics of Natural 9-O-Acetyl GD3 from Human Melanoma and Bovine Buttermilk and Chemically O-Acetylated GD31  

Microsoft Academic Search

Because its expression appears to be largely restricted to human melanomas, 9-0-acetyl-GD3 is a candidate antigen for vaccine construc tion. Searching for potential sources, we compared chemically £>-acety- lated calf brain GD3 and 9-O-acetyl-GD3 extracted from bovine butter milk with 9-0-acetyl-GD3 from human melanoma. Three fractions (Fl- F3) of chemically O-acetylated GD3 differed in the number and position of O-acetyl

Gerd Ritter; Erika Boosfeld; Ellen Markstein; Robert K. Yu; Shunlin Ren; William B. Stallcup; F. Oettgen; Lloyd J. Old; Philip O. Livingston

336

Hydrolysis of ferric chloride in solution  

SciTech Connect

The Detox{trademark} process uses concentrated ferric chloride and small amounts of catalysts to oxidize organic compounds. It is under consideration for oxidizing transuranic organic wastes. Although the solution is reused extensively, at some point it will reach the acceptable limit of radioactivity or maximum solubility of the radioisotopes. This solution could be cemented, but the volume would be increased substantially because of the poor compatibility of chlorides and cement. A process has been developed that recovers the chloride ions as HCl and either minimizes the volume of radioactive waste or permits recycling of the radioactive chlorides. The process involves a two-step hydrolysis at atmospheric pressure, or preferably under a slight vacuum, and relatively low temperature, about 200{degrees}C. During the first step of the process, hydrolysis occurs according to the reaction below: FeCl{sub 3 liquid} + H{sub 2}O {r_arrow} FeOCl{sub solid} + 2 HCl{sub gas} During the second step, the hot, solid, iron oxychloride is sprayed with water or placed in contact with steam, and hydrolysis proceeds to the iron oxide according to the following reaction: 2 FeOCl{sub solid} + H{sub 2}O {r_arrow} Fe{sub 2}O{sub 3 solid} + 2 HCl{sub gas}. The iron oxide, which contains radioisotopes, can then be disposed of by cementation or encapsulation. Alternately, these chlorides can be washed off of the solids and can then either be recycled or disposed of in some other way.

Lussiez, G.; Beckstead, L.

1996-11-01

337

Nonenzymatic hydrolysis of creatine ethyl ester  

Microsoft Academic Search

The rate of the non-enzymatic hydrolysis of creatine ethyl ester (CEE) was studied at 37°C over the pH range of 1.6–7.0 using 1H NMR. The ester can be present in solution in three forms: the unprotonated form (CEE), the monoprotonated form (HCEE+), and the diprotonated form (H2CEE2+). The values of pKa1 and pKa2 of H2CEE2+ were found to be 2.30

Nicholas S. Katseres; David W. Reading; Luay Shayya; John C. DiCesare; Gordon H. Purser

2009-01-01

338

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.

339

Optimal enzymatic hydrolysis of urinary benzodiazepine conjugates.  

PubMed

Conditions for the enzymatic hydrolysis of benzodiazepine conjugates were systematically examined. Optimal recovery of the free drugs occurs when 1 mL of urine buffered to pH 4.5 is incubated with 5000 U of Helix pomatia beta-glucuronidase at 56 degrees C for 2 h. Urine specimens containing conjugates of temazepam, oxazepam, lorazepam, alpha-hydroxyalprazolam, 2-hydroxyethylflurazepam, and N-desalkyl-3-hydroxyflurazepam as targeted benzodiazepines were used. The freed drugs were quantitated by gas chromatography-mass spectrometry. PMID:7861750

Meatherall, R

340

Identification and preliminary characterization of acsF, a Putative Ni-insertase used in the biosynthesis of acetyl-CoA synthase from Clostridium thermoaceticum  

SciTech Connect

OAK-B135 The acsABCDE genes in the Clostridium thermoaceticum genome are used for autotrophic acetyl-CoA synthesis using the Wood/Ljungdahl pathway. A 2.8 kb region between acsC and acsD was cloned and sequenced. Two open reading frames, orf7 ({approx} 1.9 kb) and acsF ({approx} 0.7 kb) were identified. orf7 appears to encode an Fe-S protein, in that it contains 5 conserved cysteine residues, 3 of which are present in a motif (CXXXXXCXXC) commonly used to coordinate Fe-S clusters. However, Orf7 is probably not involved in autotrophic acetyl-CoA synthesis, as homologous genes are present in organisms that do not utilize this pathway and are absent in many that do. In contrast, acsF is probably involved in this pathway. Sequence alignment of AcsF and 11 homologs reveals a number of conserved regions, including a P-loop that binds nucleoside triphosphates and catalyzes their hydrolysis. One homolog is CooC, an ATPase/GTPase that inserts Ni into a precursor form of the C-cluster of the carbon monoxide dehydrogenase (CODH) from Rhodospirillum rubrum. Purified AcsF lacked Ni and Fe, and slowly catalyzed the hydrolysis of ATP. Such similarities to CooC suggest that AcsF may function to insert Ni into a Ni-deficient form of the bifunctional acetyl-CoA synthase/CODH from C. thermoaceticum (ACSCt). However, this could not be established, as expression of acsF did not effect activation of recombinant AcsAB expressed in E. coli. Also, E. coli cells defective in hypB retained the ability to synthesize active recombinant AcsAB. Rather, the concentration of extracellular Ni2+ ions was critical to activation.

Huay-Keng Loke; Paul A. Lindahl

2003-01-01

341

COA Roadmap Diagram  

Center for Drug Evaluation (CDER)

Text Version... Document content validity (qualitative or mixed methods research) • Evaluate cross-sectional measurement properties (reliability and construct ... More results from www.fda.gov/downloads/drugs/developmentapprovalprocess

342

COA workshop Panel Booklet  

Center for Drug Evaluation (CDER)

Text Version... Edward Cox, Sharon Hertz, John Jenkins, Lisa Kammerman, Elektra Papadopoulos, Anne Pariser, Bob Rappaport, Robert Temple, Ellis Unger ... More results from www.fda.gov/downloads/drugs/newsevents

343

COA workshop Panel Booklet  

Center for Drug Evaluation (CDER)

Text Version... by concepts and can be core, proximal, or ... and therefore are psychomodulated measures and not ... endpoint — An indirect outcome measure that is ... More results from www.fda.gov/downloads/drugs/newsevents

344

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

2013-07-15

345

Xylan as limiting factor in enzymatic hydrolysis of nanocellulose.  

PubMed

The role of xylan as a limiting factor in the enzymatic hydrolysis of cellulose was studied by hydrolysing nanocellulose samples prepared by mechanical fibrillation of birch pulp with varying xylan content. Analyzing the nanocelluloses and their hydrolysis residues with dynamic FT-IR spectroscopy revealed that a certain fraction of xylan remained tightly attached to cellulose fibrils despite partial hydrolysis of xylan with xylanase prior to pulp fibrillation and that this fraction remained in the structure during the hydrolysis of nanocellulose with cellulase mixture as well. Thus, a loosely bound fraction of xylan was predicted to have been more likely removed by purified xylanase. The presence of loosely bound xylan seemed to limit the hydrolysis of crystalline cellulose, indicated by an increase in cellulose crystallinity and by preserved crystal width measured with wide-angle X-ray scattering. Removing loosely bound xylan led to a proportional hydrolysis of xylan and cellulose with the cellulase mixture. PMID:23238342

Penttilä, Paavo A; Várnai, Anikó; Pere, Jaakko; Tammelin, Tekla; Salmén, Lennart; Siika-aho, Matti; Viikari, Liisa; Serimaa, Ritva

2012-11-19

346

The Hydrolysis of Carbonyl Sulfide at Low Temperature: A Review  

PubMed Central

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.

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

2013-01-01

347

Development of a PAN-specific, affinity-purified anti-acetylated lysine antibody for detection, identification, isolation, and intracellular localization of acetylated protein.  

PubMed

Acetylation on the lysine residue is an important event of posttranslational modification of proteins. In this study, we developed a simple method to produce and to affinity purify the specific anti-acetylated lysine polyclonal antibody, which is useful for the detection, identification, isolation, and intracellular localization of acetylated proteins on the lysine residues. We utilized the chemically acetylated hemocyanin of keyhole limpets (KLH) as an immunogen to raise the immune serum and to isolate the population of the acetylated lysine specific antibody using the immobilized acetylated lysine as immunoaffinity-ligand. The isolated antibody was tested to be useful for ELISA, immunoblotting detection, immunofluorescent localization, and affinity isolation of the acetylated proteins. PMID:15754801

Qiang, Liping; Xiao, Hao; Campos, Eric I; Ho, Vincent C; Li, Gang

2005-01-01

348

Influence of relativistic effects on hydrolysis of Ra 2+  

Microsoft Academic Search

Summary  Using 224Ra radiotracer the first hydrolysis constant (pK1h) of Ra2+ cations has been determined. The pK1h value of Ra2+ was compared with the pK1h values of other Group 2 cations. It has been shown that the electrostatic hydrolysis model based on assumption that pK1h is a linear function of reciprocal ionic radii (1\\/ri) does not describe well the hydrolysis of

B. Zieli?ska; A. Bilewicz

2005-01-01

349

Hydrolysis catalyst effect on sol–gel silica structure  

Microsoft Academic Search

Silica samples were prepared by the sol–gel process varying the hydrolysis catalyst. The samples were characterized by X-ray diffraction and the radial distribution function was determined (R.D.F.). Fourier transform infrared spectroscopy and thermal analysis were also used. It was found that OH-retention capacity as well as order in the material may be modified with hydrolysis catalysts. When the hydrolysis catalyst

M Asomoza; M. P Dom??nguez; S Sol??s; V. H Lara; P Bosch; T López

1998-01-01

350

Influence of carboxyl group on the acid hydrolysis of cellulose  

Microsoft Academic Search

Cellulose isolated from wood is more susceptible than cotton cellulose to homogeneous hydrolysis in phosphoric acid. The influence\\u000a of carboxyl group introduction at the C6 position on the hydrolysis rate of cellulose in 82.5% phosphoric acid was studied\\u000a as a model of the oxidation of cellulose during pulping. The rate constant of hydrolysis for dissolving pulp was larger than\\u000a that

Shuichi Hirosawa; Kazuya Minato; Fumiaki Nakatsubo

2001-01-01

351

Mechanism of cellobiose inhibition in cellulose hydrolysis by cellobiohydrolase  

Microsoft Academic Search

An experimental study of cellobiose inhibition in cellulose hydrolysis by synergism of cellobiohydrolyse I and endoglucanase\\u000a I is presented. Cellobiose is the structural unit of cellulose molecules and also the main product in enzymatic hydrolysis\\u000a of cellulose. It has been identified that cellobiose can strongly inhibit hydrolysis reaction of cellulase, whereas it has\\u000a no effect on the adsorption of cellulase

Yue Zhao; Bin Wu; Baixu Yan; Peiji Gao

2004-01-01

352

Technical bases for precipitate hydrolysis process operating parameters  

SciTech Connect

This report provides the experimental data and rationale in support of the operating parameters for tetraphenylborate precipitate hydrolysis specified in WSRC-RP-92-737. The report is divided into two sections, the first dealing with lab-scale precipitate hydrolysis experimentation while the second part addresses large-scale runs conducted to demonstrate the revised operating parameters in the Precipitate Hydrolysis Experimental Facility (PHEF). The program was in conjunction with reducing the nitrite ion level in DWPF feed.

Bannochie, C.J.; Lambert, D.P.

1992-11-09

353

Technical bases for precipitate hydrolysis process operating parameters. Revision 1  

SciTech Connect

This report provides the experimental data and rationale in support of the operating parameters for tetraphenylborate precipitate hydrolysis specified in WSRC-RP-92-737. The report is divided into two sections, the first dealing with lab-scale precipitate hydrolysis experimentation while the second part addresses large-scale runs conducted to demonstrate the revised operating parameters in the Precipitate Hydrolysis Experimental Facility (PHEF). The program was in conjunction with reducing the nitrite ion level in DWPF feed.

Bannochie, C.J.; Lambert, D.P.

1992-11-09

354

Abiotic degradation (photodegradation and hydrolysis) of imidazolinone herbicides  

Microsoft Academic Search

The abiotic degradation of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was investigated under controlled conditions. Hydrolysis, where it occurred, and photodegradation both followed first-order kinetics for all herbicides. There was no hydrolysis of any of the herbicides in buffer solutions at pH 3 or pH 7; however, slow hydrolysis occurred at pH 9. Estimated half-lives for the three herbicides

Mohammadkazem Ramezani; Danielle P. Oliver; Rai S. Kookana; Gurjeet Gill; Christopher Preston

2008-01-01

355

Investigation of the Acetylation Mechanism by GCN5 Histone Acetyltransferase  

PubMed Central

The histone acetylation of post-translational modification can be highly dynamic and play a crucial role in regulating cellular proliferation, survival, differentiation and motility. Of the enzymes that mediate post-translation modifications, the GCN5 of the histone acetyltransferase (HAT) proteins family that add acetyl groups to target lysine residues within histones, has been most extensively studied. According to the mechanism studies of GCN5 related proteins, two key processes, deprotonation and acetylation, must be involved. However, as a fundamental issue, the structure of hGCN5/AcCoA/pH3 remains elusive. Although biological experiments have proved that GCN5 mediates the acetylation process through the sequential mechanism pathway, a dynamic view of the catalytic process and the molecular basis for hGCN5/AcCoA/pH3 are still not available and none of theoretical studies has been reported to other related enzymes in HAT family. To explore the molecular basis for the catalytic mechanism, computational approaches including molecular modeling, molecular dynamic (MD) simulation and quantum mechanics/molecular mechanics (QM/MM) simulation were carried out. The initial hGCN5/AcCoA/pH3 complex structure was modeled and a reasonable snapshot was extracted from the trajectory of a 20 ns MD simulation, with considering post-MD analysis and reported experimental results. Those residues playing crucial roles in binding affinity and acetylation reaction were comprehensively investigated. It demonstrated Glu80 acted as the general base for deprotonation of Lys171 from H3. Furthermore, the two-dimensional QM/MM potential energy surface was employed to study the sequential pathway acetylation mechanism. Energy barriers of addition-elimination reaction in acetylation obtained from QM/MM calculation indicated the point of the intermediate ternary complex. Our study may provide insights into the detailed mechanism for acetylation reaction of GCN5, and has important implications for the discovery of regulators against GCN5 enzymes and related HAT family enzymes.

Liang, Zhongjie; Li, Lianchun; Ouyang, Sisheng; Kong, Xiangqian; Jiang, Hualiang; Shen, Bairong; Luo, Cheng

2012-01-01

356

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

357

Muscarinic receptor activation of phosphatidylcholine hydrolysis. Relationship to phosphoinositide hydrolysis and diacylglycerol metabolism  

SciTech Connect

We examined the relationship between phosphatidylcholine (PC) hydrolysis, phosphoinositide hydrolysis, and diacylglycerol (DAG) formation in response to muscarinic acetylcholine receptor (mAChR) stimulation in 1321N1 astrocytoma cells. Carbachol increases the release of (3H)choline and (3H)phosphorylcholine ((3H)Pchol) from cells containing (3H)choline-labeled PC. The production of Pchol is rapid and transient, while choline production continues for at least 30 min. mAChR-stimulated release of Pchol is reduced in cells that have been depleted of intracellular Ca2+ stores by ionomycin pretreatment, whereas choline release is unaffected by this pretreatment. Phorbol 12-myristate 13-acetate (PMA) increases the release of choline, but not Pchol, from 1321N1 cells, and down-regulation of protein kinase C blocks the ability of carbachol to stimulate choline production. Taken together, these results suggest that Ca2+ mobilization is involved in mAChR-mediated hydrolysis of PC by a phospholipase C, whereas protein kinase C activation is required for mAChR-stimulated hydrolysis of PC by a phospholipase D. Both carbachol and PMA rapidly increase the formation of (3H)phosphatidic acid ((3H)PA) in cells containing (3H)myristate-labeled PC. (3H)Diacylglycerol ((3H)DAG) levels increase more slowly, suggesting that the predominant pathway for PC hydrolysis is via phospholipase D. When cells are labeled with (3H)myristate and (14C)arachidonate such that there is a much greater 3H/14C ratio in PC compared with the phosphoinositides, the 3H/14C ratio in DAG and PA increases with PMA treatment but decreases in response to carbachol.

Martinson, E.A.; Goldstein, D.; Brown, J.H. (Univ. of California, San Diego, La Jolla (USA))

1989-09-05

358

Enzymatic hydrolysis of polysaccharide-rich particulate organic waste.  

PubMed

Hydrolysis of organic particulates in rapid fermentative processes can be inhibited. The volatile fatty acids (VFA) released during fermentation reduce pH. Whether VFA or the drop in pH inhibits hydrolysis is unclear. The effects of pH and acetate on the enzymatic hydrolysis of a potato sample that contains both carbohydrate and protein were studied at fixed pH (5-9) in the presence/absence of 20 g/L of acetate. Experimental results showed that the effects of pH and acetate on the hydrolysis of carbohydrate differed from those on the hydrolysis of protein. Numerous kinetic models fitted the hydrolysis data obtained during the first 40 h of hydrolysis when inhibitory effects were insignificant. The Chen-Hashimoto model was used herein to fit the hydrolysis data obtained during 144 h of reaction. Also, the non-competitive inhibition model of three inhibitors (H(+), OH(-), total/undissociated/dissociated acetate) successfully described the inhibition of the hydrolysis of both carbohydrate and protein. PMID:16444752

He, Pin-Jing; Lü, Fan; Shao, Li-Ming; Pan, Xiu-Jiang; Lee, Duu-Jong

2006-04-20

359

Water insoluble residue following acid hydrolysis of water soluble polysaccharides  

SciTech Connect

This paper illustrates a detailed procedure by which acid insoluble polymer residue can be determined. The procedure is quantitative and reproducible. Several water soluble polymers have been evaluated by this procedure. Values for insoluble residues at various hydrolysis times and temperatures for some common oilfield polymers are given. The insoluble residue content varies with the procedure used to do the polymer hydrolysis. During the hydrolysis reaction, the insoluble residue from a cellulosic polymer goes through a minimum, then increases depending upon hydrolysis time, temperature and acid strength. 11 refs.

Pober, K.W.; Hoff, M.H.; Darlington, R.K.

1982-01-01

360

Correlation of changes in rate of sterol synthesis with changes in HMG CoA reductase activity in cultured lens epithelial cells  

SciTech Connect

In the present study, the authors correlated changes in HMG CoA reductase activity with changes in relative rates of sterol synthesis measured from either /sup 3/H/sub 2/O or 1-/sup 14/C-acetate for bovine lens epithelial cells cultured in the presence or absence of lipoproteins. Enzyme activity and rates of incorporation of /sup 3/H/sub 2/O or 1-/sup 14/C-acetate into digitonin precipitable sterols were measured in cells on the 4th day of subculture in DMEM containing 9% whole calf serum (WM) or 9% lipoprotein deficient serum (LDM). In three experiments, HMG CoA reductase activity (U/10/sup 6/ cells) averaged 2.2 +/- 0.1 times greater for cells grown in LDM than WM. Sterol synthesis averaged 3.0 +/- 0.4 times greater when measured with /sup 3/H/sub 2/O and 4.0 +/- 1.1 times greater when measured with /sup 14/C-acetate. Thus, /sup 3/H/sub 2/O and /sup 14/C-acetate appear to be comparable substrates for estimating changes in relative rates of sterol synthesis by cultured cells. The larger increases in rates of sterol synthesis than in reductase activity in response to decreased cholesterol could reflect stimulation at additional metabolic steps in the cholesterol pathway beyond mevalonic acid.

Cenedella, R.J.; Hitchener, W.R.

1986-05-01

361

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

2007-06-22

362

Acetylation of glycerol catalyzed by different solid acids  

Microsoft Academic Search

This work describes the acetylation of glycerol with acetic acid catalyzed by different solid acids. Reactions were carried out in batch mode under reflux. The kinetics of glycerol transformation and selectivity to the products, notably mono, di and triacetyl esters, were determined within 30min of reaction time to observe the primary products. The results showed that the acid exchange resin,

Valter L. C. Gonçalves; Bianca P. Pinto; João C. Silva; Claudio J. A. Mota

2008-01-01

363

Selective Acetylation of Sterols in Imidazole-Functionalized Surfactant Vesicles.  

National Technical Information Service (NTIS)

In imidazole-functionalized surfactant coaggregates of 1 acetyl groups are stereoselectively transferred (via 1-Ac) from p-nitrophenyl acetate to 3 beta vs 3 alpha-cholestanol, and regioselectively transferred to 3 beta vs 6 beta-cholestanol. Keywords: Ve...

R. A. Moss Y. Okumura

1989-01-01

364

An Acetylation Switch Regulates SUMO-Dependent Protein Interaction Networks  

PubMed Central

SUMMARY The attachment of the SUMO modifier to proteins controls cellular signaling pathways through noncovalent binding to SUMO-interaction motifs (SIMs). Canonical SIMs contain a core of hydrophobic residues that bind to a hydrophobic pocket on SUMO. Negatively charged residues of SIMs frequently contribute to binding by interacting with a basic surface on SUMO. Here we define acetylation within this basic interface as a central mechanism for the control of SUMO-mediated interactions. The acetyl-mediated neutralization of basic charges on SUMO prevents binding to SIMs in PML, Daxx, and PIAS family members but does not affect the interaction between RanBP2 and SUMO. Acetylation is controlled by HDACs and attenuates SUMO- and PIAS-mediated gene silencing. Moreover, it affects the assembly of PML nuclear bodies and restrains the recruitment of the corepressor Daxx to these structures. This acetyl-dependent switch thus expands the regulatory repertoire of SUMO signaling and determines the selectivity and dynamics of SUMO-SIM interactions.

Ullmann, Rebecca; Chien, Christopher D.; Avantaggiati, Maria Laura; Muller, Stefan

2013-01-01

365

Regulation of Histone Acetylation during Memory Formation in the Hippocampus  

Microsoft Academic Search

Formation of long term memory begins with the acti- vation of many disparate signaling pathways that ulti- mately impinge on the cellular mechanisms regulating gene expression. We investigated whether mechanisms regulating chromatin structure were activated during the early stages of long term memory formation in the hippocampus. Specifically, we investigated hippocam- pal histone acetylation during the initial stages of con-

Jonathan M. Levenson; Kenneth J. O'Riordan; Karen D. Brown; Mimi A. Trinh; David L. Molfese; J. David Sweatt

2004-01-01

366

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

367

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

368

An acetylation switch regulates SUMO-dependent protein interaction networks.  

PubMed

The attachment of the SUMO modifier to proteins controls cellular signaling pathways through noncovalent binding to SUMO-interaction motifs (SIMs). Canonical SIMs contain a core of hydrophobic residues that bind to a hydrophobic pocket on SUMO. Negatively charged residues of SIMs frequently contribute to binding by interacting with a basic surface on SUMO. Here we define acetylation within this basic interface as a central mechanism for the control of SUMO-mediated interactions. The acetyl-mediated neutralization of basic charges on SUMO prevents binding to SIMs in PML, Daxx, and PIAS family members but does not affect the interaction between RanBP2 and SUMO. Acetylation is controlled by HDACs and attenuates SUMO- and PIAS-mediated gene silencing. Moreover, it affects the assembly of PML nuclear bodies and restrains the recruitment of the corepressor Daxx to these structures. This acetyl-dependent switch thus expands the regulatory repertoire of SUMO signaling and determines the selectivity and dynamics of SUMO-SIM interactions. PMID:22578841

Ullmann, Rebecca; Chien, Christopher D; Avantaggiati, Maria Laura; Muller, Stefan

2012-05-10

369

The Tale of Protein Lysine Acetylation in the Cytoplasm  

PubMed Central

Reversible posttranslational modification of internal lysines in many cellular or viral proteins is now emerging as part of critical signalling processes controlling a variety of cellular functions beyond chromatin and transcription. This paper aims at demonstrating the role of lysine acetylation in the cytoplasm driving and coordinating key events such as cytoskeleton dynamics, intracellular trafficking, vesicle fusion, metabolism, and stress response.

Sadoul, Karin; Wang, Jin; Diagouraga, Boubou; Khochbin, Saadi

2011-01-01

370

FUNCTIONAL PROPERTIES OF CROSSLINKED AND ACETYLATED BARLEY PROTEIN ISOLATE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Barley protein isolate (BPI) was prepared using defatted barley flour. BPI was extracted in 0.05 N NaOH in a 10:1 ratio solvent:flour, was precipitated by adjusting the pH to 4.5 and freeze-dried. Portion of the BPI sample was crosslinked using Transglutaminase and acetylated using acetic anhydrid...

371

N-Terminal Acetylation of Cellular Proteins Creates Specific Degradation Signals  

Microsoft Academic Search

The retained N-terminal methionine (Met) residue of a nascent protein is often N-terminally acetylated (Nt-acetylated). Removal of N-terminal Met by Met-aminopeptidases frequently leads to Nt-acetylation of the resulting N-terminal alanine (Ala), valine (Val), serine (Ser), threonine (Thr), and cysteine (Cys) residues. Although a majority of eukaryotic proteins (for example, more than 80% of human proteins) are cotranslationally Nt-acetylated, the function

Cheol-Sang Hwang; Anna Shemorry; Alexander Varshavsky

2010-01-01

372

RimJ is responsible for N ? -acetylation of thymosin ?1 in Escherichia coli  

Microsoft Academic Search

N\\u000a ?-Acetylation is one of the most common protein modifications in eukaryotes but a rare event in prokaryotes. Some endogenously\\u000a N\\u000a ?-acetylated proteins in eukaryotes are frequently reported not to be acetylated or only very partially when expressed in recombinant\\u000a Escherichia coli. Thymosin ?1 (T?1), an N\\u000a ?-acetylated peptide of 28 amino acids, displays a powerful general immunostimulating activity. Here,

Hongqing Fang; Xu Zhang; Lin Shen; Xinxi Si; Yuantao Ren; Hongmei Dai; Shulong Li; Changlin Zhou; Huipeng Chen

2009-01-01

373

Color changes in acetylated wood by the combined treatment of light and heat  

Microsoft Academic Search

This study investigated the change in color of acetylated wood by the combined treatment of light and heat. The color of acetylated\\u000a wood was stable against light, however, heat treatment after light-irradiation made it change greater. Furthermore, the acetylated\\u000a wood discolored greater than unacetylated one by light-irradiation after heat treatment. These results show that the acetylated\\u000a wood is not stable

Katsuya Mitsui; László Tolvaj

2005-01-01

374

Cloning and Expression of cDNA for O-Acetylation of GD3 Ganglioside  

Microsoft Academic Search

O-acetylated sialic acids of glycoproteins and gangliosides show cell type-specific and developmentally regulated expression in various systems and sometimes reappear as oncofetal antigens.O-acetylation of sialic acids may influence cell–cell interactions mediated by the sialic acid-binding lectins. Here we describe the molecular cloning and sequencing of a gene that producesO-acetyl disialoganglioside (O-acetyl GD3). Expression analysis showed that this gene product participates

Kiyoshi Ogura; Kiyomitsu Nara; Yumiko Watanabe; Kenji Kohno; Tadashi Tai; Yutaka Sanai

1996-01-01

375

Production of N?-acetylated thymosin ?1 in Escherichia coli  

PubMed Central

Background Thymosin ?1 (T?1), a 28-amino acid N?-acetylated peptide, has a powerful general immunostimulating activity. Although biosynthesis is an attractive means of large-scale manufacture, to date, T?1 can only be chemosynthesized because of two obstacles to its biosynthesis: the difficulties in expressing small peptides and obtaining N?-acetylation. In this study, we describe a novel production process for N?-acetylated T?1 in Escherichia coli. Results To obtain recombinant N?-acetylated T?1 efficiently, a fusion protein, T?1-Intein, was constructed, in which T?1 was fused to the N-terminus of the smallest mini-intein, Spl DnaX (136 amino acids long, from Spirulina platensis), and a His tag was added at the C-terminus. Because T?1 was placed at the N-terminus of the T?1-Intein fusion protein, T?1 could be fully acetylated when the T?1-Intein fusion protein was co-expressed with RimJ (a known prokaryotic N?-acetyltransferase) in Escherichia coli. After purification by Ni-Sepharose affinity chromatography, the T?1-Intein fusion protein was induced by the thiols ?-mercaptoethanol or d,l-dithiothreitol, or by increasing the temperature, to release T?1 through intein-mediated N-terminal cleavage. Under the optimal conditions, more than 90% of the T?1-Intein fusion protein was thiolyzed, and 24.5 mg T?1 was obtained from 1 L of culture media. The purity was 98% after a series of chromatographic purification steps. The molecular weight of recombinant T?1 was determined to be 3107.44 Da by mass spectrometry, which was nearly identical to that of the synthetic version (3107.42 Da). The whole sequence of recombinant T?1 was identified by tandem mass spectrometry and its N-terminal serine residue was shown to be acetylated. Conclusions The present data demonstrate that N?-acetylated T?1 can be efficiently produced in recombinant E. coli. This bioprocess could be used as an alternative to chemosynthesis for the production of T?1. The described methodologies may also be helpful for the biosynthesis of similar peptides.

2011-01-01

376

Functional ionic liquids for hydrolysis of lignocellulose.  

PubMed

An efficient system for hydrolysis of lignocellulosic materials to prepare reducing sugar in a series of functional acidic ionic liquids with low synthetic cost and excellent dissolved and catalytic activity was established. High yield of reducing sugar was obtained with the use of 1-H-3-methylimidazolium chloride ([HMIM]Cl). The use of ionic liquid under ultrasound irradiation greatly improved the yield of total reducing sugar. The optimum reaction conditions were as follows: ratio of water/sample was 5 (w/w), ratio of IL/sample was 25 (w/w), 70°C, 120 min and the yield of reducing sugar was up to 53.27 mg from 0.2g of soybean straw and 50.03 mg from 0.2g of corn straw. PMID:23769534

Hu, Xiaomei; Xiao, Yibo; Niu, Kun; Zhao, Yang; Zhang, Bixian; Hu, Baozhong

2013-04-30

377

Fermentable sugars by chemical hydrolysis of biomass  

PubMed Central

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.

Binder, Joseph B.; Raines, Ronald T.

2010-01-01

378

Defense waste processing facility precipitate hydrolysis process  

SciTech Connect

Sodium tetraphenylborate and sodium titanate are used to assist in the concentration of soluble radionuclide in the Savannah River Plant's high-level waste. In the Defense Waste Processing Facility, concentrated tetraphenylborate/sodium titanate slurry containing cesium-137, strontium-90 and traces of plutonium from the waste tank farm is hydrolyzed in the Salt Processing Cell forming organic and aqueous phases. The two phases are then separated and the organic phase is decontaminated for incineration outside the DWPF building. The aqueous phase, containing the radionuclides and less than 10% of the original organic, is blended with the insoluble radionuclides in the high-level waste sludge and is fed to the glass melter for vitrification into borosilicate glass. During the Savannah River Laboratory's development of this process, copper (II) was found to act as a catalyst during the hydrolysis reactions, which improved the organic removal and simplified the design of the reactor.

Doherty, J P; Eibling, R E; Marek, J C

1986-03-01

379

Kinetic study of the acid hydrolysis of sugar cane bagasse  

Microsoft Academic Search

Economic interest in xylitol production can be enhanced if the needed xylose solutions can be obtained from the hydrolysis of low-cost lignocellulosic wastes. Sugar cane bagasse is a renewable, cheap and widely available waste in tropical countries. The hydrolysis of sugar cane bagasse to obtain xylose solutions has a double consequence, the elimination of a waste and the generation of

R Aguilar; J. A Ram??rez; G Garrote; M Vázquez

2002-01-01

380

Hydrolysis of dietary fat by pancreatic lipase stimulates cholecystokinin release  

Microsoft Academic Search

Background & Aims: The hypothesis that cholecystokinin release requires adequate dietary fat digestion in the small intestine was investigated in 10 healthy volunteers, and the consequences of reduced fat hydrolysis on pancreaticobiliary secretions were assessed. Methods: Fat hydrolysis was inhibited by intraduodenal perfusion of tetrahydrolipstatin, an irreversible lipase inhibitor. An oil emulsion containing 0, 30, 60, or 120 mg tetrahydrolipstatin

Pius Hildebrand; Christophe Petrig; Beat Burckhardt; Silvia Ketterer; Hans Lengsfeld; André Fleury; Paul Hadváry; Christoph Beglinger

1998-01-01

381

Kinetics of hydrolysis of chloroform and bromoform in aqueous solutions  

Microsoft Academic Search

The base-catalyzed hydrolysis of chloroform (CF) and bromoform (BF) was examined in water-methanol solutions. The progress of reaction was determined by following the decrease in [OH?] and the increase in [halide] ions as function of time. The effects of temperature, [OH?] and the water: methanol ratio on the rates of reaction were tested in some detail. The hydrolysis of CF

A. M. Shams El Din; Rasheed A. Arain; A. A. Hammoud

1998-01-01

382

Effect of annealing on the hydrolysis of sago starch granules  

Microsoft Academic Search

Sago starch annealed at varying temperatures, time intervals and pH was used to study granule hydrolysis by a glucoamylase (AMG) and ?-amylase (Termamyl) mixture. Differential scanning calorimetry (DSC) indicated that there was a relationship between the extent of annealing and starch granule hydrolysis. Enthalpy of gelatinisation of annealed starch granules remained unchanged, suggesting that no gelatinisation had occurred. The degree

W. J. Wang; A. D. Powell; C. G. Oates

1997-01-01

383

The laccase-catalyzed modification of lignin for enzymatic hydrolysis  

Microsoft Academic Search

The efficient use of cellulases in the hydrolysis of pretreated lignocellulosic biomass is limited due to the presence of lignin. Lignin is known to bind hydrolytic enzymes nonspecifically, thereby reducing their action on carbohydrate substrates. The composition and location of residual lignin therefore seem to be important for optimizing the enzymatic hydrolysis of lignocellulosic substrates. The use of lignin-modifying enzymes

Ulla Moilanen; Miriam Kellock; Sari Galkin; Liisa Viikari

384

Enhanced functional properties of tannic acid after thermal hydrolysis  

Technology Transfer Automated Retrieval System (TEKTRAN)

Thermal hydrolysis processing of fresh tannic acid was carried out in a closed reactor at four different temperatures (65, 100, 150 and 200°C). Pressures reached in the system were 1.3 and 4.8 MPa at 150 and 200°C, respectively. Hydrolysis products (gallic acid and pyrogallol) were separated and qua...

385

Hydrolysis Kinetics of Secoisolariciresinol Diglucoside Oligomers from Flaxseed  

Microsoft Academic Search

Flaxseed is the richest dietary source of the lignan secoisolariciresinol diglucoside (SDG) and contains the largest amount of SDG oligomers, which are often hydrolyzed to break the ester linkages for the release of SDG and the glycosidic bonds for the release of secoisolariciresinol (SECO). The alkaline hydrolysis reaction kinetics of SDG oligomers from flaxseed and the acid hydrolysis process of

Jian-Ping Yuan; Xin Li; Shi-Ping Xu; Jiang-Hai Wang; Xin Liu

2008-01-01

386

Polymer-assisted dithane hydrolysis with minimum workup.  

PubMed

The first solid-phase-assisted protocol for the hydrolysis of dithioacetals is described using three different functionalized ion exchange resins. The hydrolysis and the purification proceed under milder conditions than common homogeneously employed reagents so that very reactive carbonyl compounds can be prepared. PMID:18271599

Luiken, Silke; Kirschning, Andreas

2008-02-14

387

Mechanism of hydrolysis of a novel indolocarbazole topoisomerase I inhibitor  

Microsoft Academic Search

The degradation kinetics and reaction product profile of the antitumor agent 1 in aqueous solution was studied. Hydrolysis of the pendant imide ring of 1 is the primary mode of thermal degradation in aqueous solution, and the pH rate profile of 1 has a V-shape indicating that hydrolysis of the imide ring can be catalyzed by either acid or base.

David Breslin; Yuichi Sato; Shyam B. Karki

2010-01-01

388

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...

389

THE MECHANISM OF THE HYDROLYSIS OF METHYLENE CHLORIDE  

Microsoft Academic Search

chloride with aqueous chloride solution and proposed the mechanism of the reaction!). The kinetics of the hydrolysis of methylene chloride has now been investigated over the pH range from ° to 12 under the same experimental conditions as those in the exchange reaction reported in the foregoing paper!). It has been found that the rate of the hydrolysis is approximately

Kozo TANABE; Masayuki MATSUDA

390

Preparation and Properties of Sirups Made by Hydrolysis of Lactose  

Microsoft Academic Search

Clear, nearly colorless sirups were prepared from lactose by hydrolysis with either lactase (~3-galactosidase) or hydrochloric acid, followed by decolor- ization, ion exchange demineralization, and concentration. Crystallization of sugars from the sirups was reduced by decreasing total solids from 66 to 60% and the degree of hydrolysis from 95 to 75%; however, overall stability of sirup with respect to both

E. J. Guy; L. F. Edmondson

1978-01-01

391

Acetylation at Lys-92 enhances signaling by the chemotaxis response regulator protein CheY  

PubMed Central

When Escherichia coli cells lacking all chemotaxis proteins except the response regulator CheY are exposed to acetate, clockwise flagellar rotation results, indicating the acetate stimulus has activated signaling by CheY. Acetate can be converted to acetyl-CoA by either of two different metabolic pathways, which proceed through acetyl phosphate or acetyl-AMP intermediates. In turn, CheY can be covalently modified by either intermediate in vitro, leading to phosphorylation or acetylation, respectively. Either pathway is sufficient to support the CheY-mediated response to acetate in vivo. Whereas phosphorylation of Asp-57 is a recognized mechanism for activation of CheY to stimulate clockwise flagellar rotation, acetylation of CheY is less well characterized. We found evidence for multiple CheY acetylation sites by mass spectrometry and directly identified Lys-92 and Lys-109 as acetylation sites by Edman degradation of peptides from [14C]acetate-labeled CheY. Replacement of CheY Lys-92, the preferred acetylation site, with Arg has little effect on chemotaxis but completely prevents the response to acetate via the acetyl-AMP pathway. Thus acetylation of Lys-92 activates clockwise signaling by CheY in vivo. The mechanism by which acetylation activates CheY apparently is not simple charge neutralization, nor does it involve enhanced binding to the FliM flagellar switch protein. Thus acetylation probably affects signal generation by CheY at a step after switch binding.

Ramakrishnan, Ranjani; Schuster, Martin; Bourret, Robert B.

1998-01-01

392

Nano-scale analyses of the chromatin decompaction induced by histone acetylation.  

PubMed

The acetylation of histone tails is a key factor in the maintenance of chromatin dynamics and cellular homeostasis. The hallmark of active chromatin is the hyper-acetylation of histones, which appears to result in a more open chromatin structure. Although short nucleosomal arrays have been studied, the structural dynamics of relatively long acetylated chromatin remain unclear. We have analyzed in detail the structure of long hyper-acetylated chromatin fibers using atomic force microscopy (AFM). Hyper-acetylated chromatin fibers isolated from nuclei that had been treated with Trichostatin A (TSA), an inhibitor of histone deacetylase, were found to be thinner than those from untreated nuclei. The acetylated chromatin fibers were more easily spread out of nuclei by high-salt treatment, implying that hyper-acetylation facilitates the release of chromatin fibers from compact heterochromatin regions. Chromatin fibers reconstituted in vitro from core histones and linker histone H1 became thinner upon acetylation. AFM imaging indicated that the gyration radius of the nucleosomal fiber increased after acetylation and that the hyper-acetylated nucleosomes did not aggregate at high salt concentrations, in contrast to the behavior of non-acetylated nucleosomal arrays, suggesting that acetylation increases long-range repulsions between nucleosomes. Based on these data, we considered a simple coarse grained model, which underlines the effect of remaining electric charges inside the chromatin fiber. PMID:22572182

Hizume, Kohji; Araki, Sumiko; Hata, Kosuke; Prieto, Eloise; Kundu, Tapas K; Yoshikawa, Kenichi; Takeyasu, Kunio

2010-01-01

393

Acetylome with Structural Mapping Reveals the Significance of Lysine Acetylation in Thermus thermophilus.  

PubMed

Lysine acetylation in proteins has recently been globally identified in bacteria and eukaryotes. Even though acetylproteins are known to be involved in various cellular processes, its physiological significance has not yet been resolved. Using a proteomics approach in combination with immunoprecipitation, we identified 197 lysine acetylation sites and 4 N-terminal acetylation sites from 128 proteins in Thermus thermophilus HB8, an extremely thermophilic eubacterium. Our analyses revealed that identified acetylproteins are well conserved across all three domains of life and are mainly involved in central metabolism and translation. To characterize the functional significance further, we successfully mapped 172 acetylation sites on their 59 authentic and 54 homologous protein structures. Although the percentage of acetylation on ordered structures was higher than that of the disordered structure, no tendency of acetylation in T. thermophilus was detected in secondary structures. However, the acetylated lysine was situated near the negatively charged glutamic acid residues. In tertiary structure analyses, 58 sites of 103 acetylations mapped on 59 authentic structures of T. thermophilus were located within a considerable distance that can disrupt electrostatic interactions and hydrogen bonding networks on protein surfaces, demonstrating the physiological significance of the acetylation that can directly alter the protein structure. In addition, we found 16 acetylation sites related to Schiff base formation, ligand binding, and protein-RNA and protein-protein interactions that involve the potential function of the proteins. The structural mapping of acetylation sites provides new molecular insight into the role of lysine acetylation in the proteins. PMID:23901841

Okanishi, Hiroki; Kim, Kwang; Masui, Ryoji; Kuramitsu, Seiki

2013-08-27

394

Selective Recognition of Acetylated Histones by Bromodomain Proteins Visualized in Living Cells  

Microsoft Academic Search

Acetylation and other modifications on histones comprise histone codes that govern transcriptional regulatory processes in chromatin. Yet little is known how different histone codes are translated and put into action. Using fluorescence resonance energy transfer, we show that bromodomain-containing proteins recognize different patterns of acetylated histones in intact nuclei of living cells. The bromodomain protein Brd2 selectively interacted with acetylated

Tomohiko Kanno; Yuka Kanno; Richard M Siegel; Moon Kyoo Jang; Michael J Lenardo; Keiko Ozato

2004-01-01

395

The hydrolysis of phosphatidylcholine by an immobilized lipase: Optimization of hydrolysis in organic solvents  

Microsoft Academic Search

The ability of a commercial immobilized lipase preparation (Lipozyme) to hydrolyze the fatty acyl ester bonds of soybean phosphatidylcholine\\u000a in organic media was investigated. Response surface methodology, based on a Modified Central Composite design, was employed\\u000a to examine the effects on hydrolysis of solvent polarity, water, pH, duration and temperature of incubation, and the amounts\\u000a of substrate and catalyst. A

M. J. Haas; D. J. Cichowicz; J. Phillips; R. Moreau

1993-01-01

396

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

397

Mechanism of hydrolysis of a novel indolocarbazole topoisomerase I inhibitor.  

PubMed

The degradation kinetics and reaction product profile of the antitumor agent 1 in aqueous solution was studied. Hydrolysis of the pendant imide ring of 1 is the primary mode of thermal degradation in aqueous solution, and the pH rate profile of 1 has a V-shape indicating that hydrolysis of the imide ring can be catalyzed by either acid or base. Hydrolysis of 1 to the anhydride derivative 3 or the dicarboxylic acid derivative 4 is stepwise and the intermediates 2a and 2b formed by initial hydrolytic attack have been observed under alkaline conditions. An overall mechanism for the hydrolysis of 1 in aqueous solution has been proposed. Extrapolating Arrhenius behavior to the hydrolysis reaction of 1 in aqueous solution maintained at a pH value of 4 suggests an aqueous buffered formulation has sufficient thermal stability to be considered a robust room temperature drug product. PMID:20025967

Breslin, David; Sato, Yuichi; Karki, Shyam B

2009-12-16

398

Waste activated sludge hydrolysis during ultrasonication: two-step disintegration.  

PubMed

In order to clearly describe the hydrolysis of waste activated sludge (WAS) during ultrasonication by a 2-step disintegration process, concentrations of ribonucleic acid (RNA) and bound extracellular polymeric substance (EPS) were measured. Apparently, different decreasing patterns of RNA and EPS concentrations during WAS hydrolysis made it possible to distinguish the floc disintegration (FD) and cell lysis (CL). Initially, FD and CL appear to take simultaneously, but the dominant hydrolytic process is shifted from FD to CL after 10 min of ultrasonication. Additional kinetic analysis of WAS hydrolysis was also conducted. A five-fold greater hydrolysis rate constant of FD relative to that of CL was observed, reflecting the different strengths of floc and cells. Therefore, different rates of increased solubilization during WAS hydrolysis appear to account for the initial disintegration of the rather loose part (sludge floc) and the subsequent disintegration of the rigid part (microbial cells). PMID:22850171

Cho, Si-Kyung; Shin, Hang-Sik; Kim, Dong-Hoon

2012-07-16

399

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

400

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

2005-09-30

401

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.

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

2011-01-01

402

Hydrolysis of glucosinolates to isothiocyanates after ingestion of raw or microwaved cabbage by human volunteers.  

PubMed

Cabbage contains the glucosinolate sinigrin, which is hydrolyzed by myrosinase to allyl isothiocyanate. Isothiocyanates are thought to inhibit the development of cancer cells by a number of mechanisms. The effect of cooking cabbage on isothiocyanate production from glucosinolates during and after their ingestion was examined in human subjects. Each of 12 healthy human volunteers consumed three meals, at 48-h intervals, containing either raw cabbage, cooked cabbage, or mustard according to a cross-over design. At each meal, watercress juice, which is rich in phenethyl isothiocyanate, was also consumed to allow individual and temporal variation in postabsorptive isothiocyanate recovery to be measured. Volunteers recorded the time and volume of each urination for 24 h after each meal. Samples of each urination were analyzed for N-acetyl cysteine conjugates of isothiocyanates as a measure of entry of isothiocyanates into the peripheral circulation. Excretion of isothiocyanates was rapid and substantial after ingestion of mustard, a source of preformed allyl isothiocyanate. After raw cabbage consumption, allyl isothiocyanate was again rapidly excreted, although to a lesser extent than when mustard was consumed. On the cooked cabbage treatment, excretion of allyl isothiocyanate was considerably less than for raw cabbage, and the excretion was delayed. The results indicate that isothiocyanate production is more extensive after consumption of raw vegetables but that isothiocyanates still arise, albeit to a lesser degree, when cooked vegetables are consumed. The lag in excretion on the cooked cabbage treatment suggests that the colon microflora catalyze glucosinolate hydrolysis in this case. PMID:14744743

Rouzaud, Gabrielle; Young, Sheila A; Duncan, Alan J

2004-01-01

403

in Silico mutagenesis and docking studies of active site residues suggest altered substrate specificity and possible physiological role of Cinnamoyl CoA Reductase 1 (Ll-CCRH1)  

PubMed Central

Cinnamoyl CoA reductase (CCR) carries out the first committed step in monolignol biosynthesis and acts as a first regulatory point in lignin formation. CCR shows multiple substrate specificity towards various cinnamoyl CoA esters. Here, in Silico mutagenesis studies of active site residues of Ll-CCRH1 were carried out. Homology modeling based modeled 3D structure of Ll-CCRH1 was used as template for in Silico mutant preparations. Docking simulations of Ll-CCRH1 mutants with CoA esters by AutoDock Vina tools showed altered substrate specificity as compared to wild type. The study evidences that conformational changes, and change in geometry or architecture of active site pocket occurred following mutations. The altered substrate specificity for active site mutants suggests the possible physiological role of CCR either in lignin formation or in defense system in plants. Abbreviations Ll-CCRH1 - Leucaena leucocephala cinnamoyl CoA reductase 1, OPLS - Optimized Potentials for Liquid Simulations, RMSD - Root Mean Square Deviation.

Sonawane, Prashant; Patel, Krunal; Vishwakarma, Rishi Kishore; Singh, Somesh; Khan, Bashir Mohammad

2013-01-01

404

Acetylation Increases EWS-FLI1 DNA Binding and Transcriptional Activity  

PubMed Central

Ewing Sarcoma (ES) is associated with a balanced chromosomal translocation that in most cases leads to the expression of the oncogenic fusion protein and transcription factor EWS-FLI1. EWS-FLI1 has been shown to be crucial for ES cell survival and tumor growth. However, its regulation is still enigmatic. To date, no functionally significant post-translational modifications of EWS-FLI1 have been shown. Since ES are sensitive to histone deacetylase inhibitors (HDI), and these inhibitors are advancing in clinical trials, we sought to identify if EWS-FLI1 is directly acetylated. We convincingly show acetylation of the C-terminal FLI1 (FLI1-CTD) domain, which is the DNA binding domain of EWS-FLI1. In vitro acetylation studies showed that acetylated FLI1-CTD has higher DNA binding activity than the non-acetylated protein. Over-expression of PCAF or treatment with HDI increased the transcriptional activity of EWS-FLI1, when co-expressed in Cos7 cells. However, our data that evaluates the acetylation of full-length EWS-FLI1 in ES cells remains unclear, despite creating acetylation specific antibodies to four potential acetylation sites. We conclude that EWS-FLI1 may either gain access to chromatin as a result of histone acetylation or undergo regulation by direct acetylation. These data should be considered when patients are treated with HDAC inhibitors. Further investigation of this phenomenon will reveal if this potential acetylation has an impact on tumor response.

Schlottmann, Silke; Erkizan, Hayriye V.; Barber-Rotenberg, Julie S.; Knights, Chad; Cheema, Amrita; Uren, Aykut; Avantaggiati, Maria L.; Toretsky, Jeffrey A.

2012-01-01

405

Centromere-specific acetylation of histone H4 in barley detected through three-dimensional microscopy.  

PubMed

Histone acetylation affects chromatin conformation and transcriptional activity. However, the structural role of histone acetylation at specific chromosomal regions, such as the centromere, is poorly understood. In this study, histone H4 acetylation and its localization in barley interphase nuclei are revealed by three-dimensional microscopy. The centromeres form a ring-like allocation near the nuclear membrane in barley. Immunofluorescence studies on non-fixed, interphase nuclei treatment revealed ring-like distribution of the highly acetylated histone H4, located near the nuclear membrane at one pole of the nucleus. This fluorescent structure was similar to the centromere cluster and referred to as hyperacetylated region (HAR). The distribution pattern of the acetylated histone H4 was similar to each of the K5, K8, K12 and K16 lysine residues, although H4 acetylated at K5, K8 and K12 residues was found in almost all nuclei, whereas H4 acetylated at K16 was weakly observed in only half of the nuclei. Each HAR consists of two strongly acetylated cores and a halo-like, less acetylated surrounding area. Fluorescence signals from centromere-specific repetitive sequences of barley, detected through three-dimensional fluorescence in situ hybridization (3D-FISH), co-localized with the HAR corresponding to the K5 residue acetylation, but the signals did not completely overlap each other. These findings indicate that histone acetylation specifically occurring at the centromeres likely have certain structural roles for the centromere. PMID:12650619

Wako, Toshiyuki; Houben, Andreas; Furushima-Shimogawara, Rieko; Belyaev, Nikolai D; Fukui, Kiichi

2003-03-01

406

Effect of hydrolysis on identifying prenatal cannabis exposure  

PubMed Central

Identification of prenatal cannabis exposure is important due to potential cognitive and behavioral consequences. A two-dimensional gas chromatography–mass spectrometry method for cannabinol, ?9-tetrahydrocannabinol (THC), 11-hydroxy-THC (11-OH-THC), 8?,11-dihydroxy-THC, and 11-nor-9-carboxy-THC (THCCOOH) quantification in human meconium was developed and validated. Alkaline, enzymatic, and enzyme–alkaline tandem hydrolysis conditions were optimized with THC- and THCCOOH-glucuronide reference standards. Limits of quantification ranged from 10 to 15 ng/g, and calibration curves were linear to 500 ng/g. Bias and intra-day and inter-day imprecision were <12.3%. Hydrolysis efficiencies were analyte-dependent; THC-glucuronide was effectively cleaved by enzyme, but not base. Conversely, THCCOOH-glucuronide was most sensitive to alkaline hydrolysis. Enzyme–alkaline tandem hydrolysis maximized efficiency for both glucuronides. Identification of cannabinoid-positive meconium specimens nearly doubled following alkaline and enzyme–alkaline hydrolysis. Although no 11-OH-THC glucuronide standard is available, enzymatic hydrolysis improved 11-OH-THC detection in authentic specimens. Maximal identification of cannabis-exposed neonates and the widest range of cannabis biomarkers are achieved with enzyme–alkaline tandem hydrolysis.

Gray, Teresa R.; Barnes, Allan J.

2011-01-01

407

Structural Basis for the Design of Potent and Species-specific Inhibitors of 3-hydroxy-3-methylglutaryl CoA Synthases  

SciTech Connect

3-Hydroxy-3-methylglutaryl CoA synthase (HMGS) catalyzes the first committed step in the mevalonate metabolic pathway for isoprenoid biosynthesis and serves as an alternative target for cholesterol-lowering and antibiotic drugs. We have determined a previously undescribed crystal structure of a eukaryotic HMGS bound covalently to a potent and specific inhibitor F-244 [(E,E)-11-[3-(hydroxymethyl)-4-oxo-2-oxytanyl]-3,5,7-trimethyl-2,4-undecadienenoic acid]. Given the accessibility of synthetic analogs of the F-244 natural product, this inhibited eukaryotic HMGS structure serves as a necessary starting point for structure-based methods that may improve the potency and species-specific selectivity of the next generation of F-244 analogs designed to target particular eukaryotic and prokaryotic HMGS.

Pojer,F.; Ferrer, J.; Richard, S.; Nagegowda, D.; Chye, M.; Bach, T.; Noel, J.

2006-01-01

408

Isolation of 4-coumarate Co-A ligase gene promoter from loblolly pine (Pinus taeda) and characterization of tissue-specific activity in transgenic tobacco.  

PubMed

We characterized promoter activity of a phenylpropanoid biosynthetic gene encoding 4-coumarate Co-A ligase (4CL), Pta4Clalpha, from Pinus taeda. Histochemical- and quantitative assays of GUS expression in the vascular tissue were performed using transgenic tobacco plants expressing promoter-GUS reporters. Deletion analysis of the Pta4Clalpha promoter showed that the region -524 to -252, which has two AC elements, controls the high expression levels in ray-parenchyma cells of older tobacco stems. High activity level of the promoter domain of Pta4CLalpha was also detected in the xylem cells under bending stress. DNA-protein complexes were detected in the reactions of the Pta4CLalpha promoter fragments with the nuclear proteins of xylem of P. taeda. The AC elements in the Pta4CLalpha promoter appeared to have individual roles during xylem development that are activated in a coordinated manner in response to stress in transgenic tobacco. PMID:19800807

Osakabe, Yuriko; Osakabe, Keishi; Chiang, Vincent L

2009-09-16

409

Cloning and characterization of a cDNA coding 3-hydroxy-3-methylglutary CoA reductase involved in glycyrrhizic acid biosynthesis in Glycyrrhiza uralensis.  

PubMed

The roots of Glycyrrhiza uralensis are widely used in Chinese medicine for their action of clearing heat, detoxicating, relieving cough, dispelling sputum and tonifying spleen and stomach. The reason why Glycyrrhiza uralensis has potent and significant actions is that it contains various active secondary metabolites, especially glycyrrhizic acid. In the present study, we cloned the cDNA coding 3-hydroxy-3-methylglutary CoA reductase (HMGR) involved in glycyrrhizic acid biosynthesis in Glycyrrhiza uralensis. The corresponding cDNA was expressed in Escherichia coli as fusion proteins. Recombinant HMGR exhibited catalysis activity in reduction of HMG-CoA to mevalonic acid (MVA) just as HMGR isolated from other species. Because HMGR gene is very important in the biosynthesis of glycyrrhizic acid in Glycyrrhiza uralensis, this work is significant for further studies concerned with strengthening the efficacy of Glycyrrhiza uralensis by means of increasing glycyrrhizic acid content and exploring the biosynthesis of glycyrrhizic acid in vitro. PMID:23888704

Liu, Ying; Xu, Qiao-Xian; Xi, Pei-Yu; Chen, Hong-Hao; Liu, Chun-Sheng

2013-05-01

410

Identification and characterization of the gene encoding the human phosphopantetheine adenylyltransferase and dephospho-CoA kinase bifunctional enzyme (CoA synthase).  

PubMed Central

The final two enzymes in the CoA biosynthetic pathway, phosphopantetheine adenylyltransferase (PPAT; EC 2.7.7.3) and dephospho-CoA kinase (DPCK; EC 2.7.1.24), are separate proteins in prokaryotes, but exist as a bifunctional enzyme in pig liver. In the present study we have obtained sequence information from purified pig-liver enzyme, and identified the corresponding cDNA in a number of species. The human gene localizes to chromosome 17q12-21 and contains regions with sequence similarity to the monofunctional Escherichia coli DPCK and PPAT. The recombinant 564-amino-acid human protein confirmed the associated transferase and kinase activities, and gave similar kinetic properties to the wild-type pig enzyme.

Aghajanian, Suren; Worrall, D Margaret

2002-01-01

411

Infrared and 13C MAS nuclear magnetic resonance spectroscopic study of acetylation of cotton.  

PubMed

The acetylation of commercial cotton samples with acetic anhydride without solvents in the presence of about 5% 4-dimethylaminopyridine (DMAP) catalyst was followed using Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy. This preliminary investigation was conducted in an effort to develop hydrophobic, biodegradable, cellulosic materials for subsequent application in oil spill cleanup. The FTIR results provide clear evidence for successful acetylation though the NMR results indicate that the level of acetylation is low. Nevertheless, the overall results indicate that cotton fibres are potential candidates suitable for further development via acetylation into hydrophobic sorbent materials for subsequent oil spill cleanup application. The results also indicate that de-acetylation, the reverse of the equilibrium acetylation reaction, occurred when the acetylation reaction was prolonged beyond 3 h. PMID:14670512

Adebajo, Moses O; Frost, Ray L

2004-01-01

412

Infrared and 13C MAS nuclear magnetic resonance spectroscopic study of acetylation of cotton  

NASA Astrophysics Data System (ADS)

The acetylation of commercial cotton samples with acetic anhydride without solvents in the presence of about 5% 4-dimethylaminopyridine (DMAP) catalyst was followed using Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy. This preliminary investigation was conducted in an effort to develop hydrophobic, biodegradable, cellulosic materials for subsequent application in oil spill cleanup. The FTIR results provide clear evidence for successful acetylation though the NMR results indicate that the level of acetylation is low. Nevertheless, the overall results indicate that cotton fibres are potential candidates suitable for further development via acetylation into hydrophobic sorbent materials for subsequent oil spill cleanup application. The results also indicate that de-acetylation, the reverse of the equilibrium acetylation reaction, occurred when the acetylation reaction was prolonged beyond 3 h.

Adebajo, Moses O.; Frost, Ray L.

2004-01-01

413

Lysine acetylation targets protein complexes and co-regulates major cellular functions.  

PubMed

Lysine acetylation is a reversible posttranslational modification of proteins and plays a key role in regulating gene expression. Technological limitations have so far prevented a global analysis of lysine acetylation's cellular roles. We used high-resolution mass spectrometry to identify 3600 lysine acetylation sites on 1750 proteins and quantified acetylation changes in response to the deacetylase inhibitors suberoylanilide hydroxamic acid and MS-275. Lysine acetylation preferentially targets large macromolecular complexes involved in diverse cellular processes, such as chromatin remodeling, cell cycle, splicing, nuclear transport, and actin nucleation. Acetylation impaired phosphorylation-dependent interactions of 14-3-3 and regulated the yeast cyclin-dependent kinase Cdc28. Our data demonstrate that the regulatory scope of lysine acetylation is broad and comparable with that of other major posttranslational modifications. PMID:19608861

Choudhary, Chunaram; Kumar, Chanchal; Gnad, Florian; Nielsen, Michael L; Rehman, Michael; Walther, Tobias C; Olsen, Jesper V; Mann, Matthias

2009-07-16

414

N-Terminal Acetylation Acts as an Avidity Enhancer Within an Interconnected Multiprotein Complex  

SciTech Connect

Although many eukaryotic proteins are amino (N)-terminally acetylated, structural mechanisms by which N-terminal acetylation mediates protein interactions are largely unknown. Here, we found that N-terminal acetylation of the E2 enzyme, Ubc12, dictates distinctive E3-dependent ligation of the ubiquitin-like protein Nedd8 to Cul1. Structural, biochemical, biophysical, and genetic analyses revealed how complete burial of Ubc12's N-acetyl-methionine in a hydrophobic pocket in the E3, Dcn1, promotes cullin neddylation. The results suggest that the N-terminal acetyl both directs Ubc12's interactions with Dcn1 and prevents repulsion of a charged N terminus. Our data provide a link between acetylation and ubiquitin-like protein conjugation and define a mechanism for N-terminal acetylation-dependent recognition.

Scott, Daniel C.; Monda, Julie K.; Bennett, Eric J.; Harper, J. Wade; Schulman, Brenda A. (Harvard-Med); (SJCH)

2012-10-25

415

An acetyl flavonol from Nervilia fordii (Hance) Schltr.  

PubMed

A new acetyl flavonol, named 3-O-acetyl-7-O-methyl kaemferol (1), together with the five known compounds rhamnocitrin (2), rhamnocitrin-3-O-beta-d-glucoside (3), rhamnocitrin-4'-beta-d-glucoside (4), rhamnazin (5), and p-hydroxyl benzoic acid (6) was isolated from Nervilia fordii (Hance) Schltr. The structures of the compounds were determined by spectroscopic analysis. All the compounds were evaluated against nitric oxide (NO) release, based on the production of NO in mice RAW264.7 stimulated by lipopolysaccharide (LPS). This new compound (1) showed potent inhibitory activity against the production of NO in RAW264.7 stimulated by LPS with the IC50 value of 16.79 microM. PMID:20183281

Zhou, Guang-Xiong; Lu, Chuan-Li; Wang, Heng-Shan; Yao, Xin-Sheng

2009-06-01

416

Acetylation of sulphanilamide in four marsupials and a monotreme.  

PubMed

1. The urinary metabolites of sulphanilamide (100 mg/kg, i.p.) have been studied in four marsupials (the Tasmanian devil, brushtail possum, pademelon and barred bandicoot), a monotreme (the echidna) and a eutherian (the rat). 2. All species excreted some unchanged sulphanilamide (20-30% of dose in 24 h). The major urinary metabolite in the devil, possum and pademelon was N4-acetylsulphanilamide (6-17%). This was less than that excreted by the rat (40%). These three marsupials and the rat also excreted small amounts of N1-acetyl and N1, N4-diacetylsulphanilamide. 3. The bandicoot and echidna were virtually unable to acetylate sulphanilamide, unlike the 16 other species of animals and birds in which this has been studied. The reason for this metabolic defect is unknown. PMID:6880241

McLean, S; Galloway, H; Butler, S; Whittle, D; Nicol, S C

1983-02-01

417

[Theoretical conformational analysis of methylamide N-acetyl-L-arginine].  

PubMed

The spatial structure of methylamide N-acetyl-L-argine was studied taking into account the non-valent and electrostati interactions, the torsion energy, and the distorsion of valency angles. Calculation of the favourable conformations of the molecule was carried out with the use of all the combinations of angles phi, psi, chi1 divided by chi4 as an intital approximation. These correspond to the low energy forms of the main chain and to the minima of the torsion potentials of the side chain. Conformational possibilities of arginine and lysine were compared. The calculated stable conformation of N-acetyl-L-arginine-methylamide are compared with the geometry of arginine residues in the proteins with known structure. PMID:1214809

Zhorov, B S; Popov, E M; Govyrin, V A

418

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

2013-03-07

419

Factors limiting the hydrolysis of casein by subtilisin DY.  

PubMed

It was shown that during the subtilisin DY-induced hydrolysis of casein relatively stable polypeptide structures are formed. In their interior these structures contain peptide bonds which are susceptible to the enzyme used. Heating (up to 100 degrees C) and/or application of ultrasound (25 kHz, 60 W) results in their unfolding. Data are provided, which show that under the enzyme-substrate complex formation does not lead to an enzyme conformation more susceptible to autolysis. Taking into account the described phenomena a higher degree of hydrolysis was attained in comparison to those obtained by standard enzymatic hydrolysis. PMID:3322321

Nedkov, P; Lilova, A; Tchorbanov, B

1987-10-01

420

Acid hydrolysis of pretreated lignocellulose from corn residue  

SciTech Connect

The lignocellulose derived from the hemicellulose hydrolysis of corn residue was steeped in 15 to 25% sulfuric acid at 40 to 103 degrees C, filtered to recover solids, and then dried in a fluidized bed dryer to concentrate the acid. Acid concentration, steeping temperature, drying time, and temperature effects are described by the current work. Hydrolysis of the pretreated lignocelloses gave 90% cellulose conversion with acid consumption corresponding to 1.50 g H/sub 2/SO/sub 4//g glucose and sugar concentrations in the hydrolyzate of up to 6.5 wt% in the best cases. Kinetic parameters are presented which describe the observed rates and extent of hydrolysis.

Bienkowski, P.R.; Ladisch, M.R.; Voloch, M.; Tsao, G.T.

1984-01-01

421

Acetylator Phenotype in Patients with p-Phenylenediamine Allergy  

Microsoft Academic Search

Objective:p-Phenylenediamine (PPD) has been widely distributed as hair dye ingredient and may be responsible for contact dermatitis. Since not all the subjects exposed to PPD react to the substance, we tested a possible predisposing factor of cutaneous drug metabolism. Methods: Eighty-five patients were selected on the basis of their patch test result for PPD. The acetylator status of patients was

Y. Kawakubo; M. Nakamori; E. Schöpf; M. Ohkido

1997-01-01

422

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

423

Acetylation of nuclear receptors in cellular growth and apoptosis  

Microsoft Academic Search

Post-translational modification of chromatin histones governs a key mechanism of transcriptional regulation. Histone acetylation, together with methylation, phosphorylation, ubiquitylation, sumoylation, glycosylation, and ADP ribosylation, modulate the activity of many genes by modifying both core histones and non-histone transcription factors. Epigenetic protein modification plays an important role in multiple cellular processes including DNA repair, protein stability, nuclear translocation, protein–protein interactions, and

Maofu Fu; Chenguang Wang; Xueping Zhang; Richard G Pestell

2004-01-01

424

Evidence against the existence of acetylated Sudan Black B  

Microsoft Academic Search

The nature of acetylated Sudan Black B (aSBB) has been investigated, and it has been found, by thin layer chromatography, that each fraction of aSBB has an Rf which is the same as that of a similar fraction of Sudan Black B (SBB). However, aSBB has been found to have fewer fractions, 9–12 than SBB, 14–16. The two major fractions

R. M. Lauder; A. D. Beynon

1989-01-01

425

Acetyl l Carnitine Treatment in Minimal Hepatic Encephalopathy  

Microsoft Academic Search

Minimal hepatic encephalopathy (MHE) is characterized by disturbance of mental state and neuromuscular function. To assess\\u000a the clinical efficacy of acetyl-l-carnitine (ALC) in the treatment of MHE, we performed a randomized, double-blind, placebo-controlled study administering\\u000a ALC in cirrhotic patients with this disease and evaluating their cognitive functions. One hundred and twenty-five cirrhotic\\u000a patients, of whom 21 were infected by hepatitis

Mariano Malaguarnera; Maria Pia Gargante; Erika Cristaldi; Marco Vacante; Corrado Risino; Lisa Cammalleri; Giovanni Pennisi; Liborio Rampello

2008-01-01

426

Acetylation of general transcription factors by histone acetyltransferases  

Microsoft Academic Search

The acetylation of histones increases the accessibility of nucleosomal DNA to transcription factors [1,2], relieving transcriptional repression [3] and correlating with the potential for transcriptional activity in vivo[4–7]. The characterization of several novel histone acetyltransferases –  including the human GCN5 homolog PCAF (p300\\/CBP-associated factor) [8], the transcription coactivator p300\\/CBP [9], and TAFII250 [10] –  has provided a potential explanation for

Axel Imhof; Xiang-Jiao Yang; Vasily V Ogryzko; Yoshihiro Nakatani; Alan P Wolffe; Hui Ge

1997-01-01

427

Two acetylated megastigmane glycosides from the leaves of Ilex paraguariensis.  

PubMed

Two acetylated megastigmane glycosides, matenosides A (1) and B (2), have been isolated from the MeOH extract of Ilex paraguariensis leaves, and their structures were elucidated on the basis of spectroscopic analysis. Compounds 1 and 2 exhibited human neutrophil elastase (HNE) inhibitory activity with IC(50) values of 50.4 muM and 11.1 microM, respectively. PMID:20361300

Xu, Guang-Hua; Kim, Young-Hee; Choo, Soo-Jin; Ryoo, In-Ja; Yoo, Jae-Kuk; Ahn, Jong-Seog; Yoo, Ick-Dong

2010-03-30

428

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

429

Human platelet stimulation by acetyl glyceryl ether phosphorylcholine.  

PubMed Central

Acetyl glyceryl ether phosphorylcholine (AGEPC) induced dose-dependent platelet aggregation and release of [3H]serotonin and platelet factor 4 in citrated human platelet-rich plasma. ADP scavengers or indomethacin prevented irreversible platelet aggregation responses induced by 0.2 microM AGEPC but had no effect upon platelet secretion; prostacyclin inhibited AGEPC-induced aggregation and secretion. EDTA or EGTA inhibited AGEPC-induced aggregation but had no effect on platelet secretion.

McManus, L M; Hanahan, D J; Pinckard, R N

1981-01-01

430

Enzymatic hydrolysis of polylactic acid fiber.  

PubMed

This study investigated the optimization of the enzymatic processing conditions for polylactic acid (PLA) fibers using enzymes consisting of lipases originating from different sources. The hydrolytic activity was evaluated taking into consideration the pH, temperature, enzyme concentration, and treatment time. The structural change of the PLA fibers was measured in the optimal treatment conditions. PLA fiber hydrolysis by lipases was maximized for lipase from Aspergillus niger at 40 °C for 60 min at pH 7.5 with 60% (owf) concentration, for lipase from Candida cylindracea at 40 °C for 120 min at pH 8.0 with 70% (owf) concentration, and for lipase from Candida rugosa at 45 °C for 120 min at pH 8.0 with 70% (owf) concentration. There was a change in protein absorbance of the treatment solution before and after all lipase treatments. The analyses of the chemical structure change and structural properties of the PLA due to lipase treatment was confirmed by tensile strength, differential scanning calorimetry, wide-angle X-ray scattering diffractometry, Fourier transform infrared spectroscopy, and scanning electron microscopy. PMID:21038086

Lee, So Hee; Song, Wha Soon

2010-10-31

431

Acetylation of alpha-chitin in ionic liquids.  

PubMed

Acetylation of alpha-chitin using acetic anhydride in an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), was performed. First, a mixture of chitin and AMIMBr (2% w/w) was heated at 100 degrees C for 24h for dissolution. Then, acetic anhydride (5-20 equiv) was added to the solution and the mixture was heated with stirring at desired temperatures for 24h. The product was precipitated by the addition of the reaction mixture into methanol. The IR spectrum of the product indicated the progress of acetylation. The degrees of substitution (DS), which were determined from the IR spectra, increased with increasing the amounts of acetic anhydride used for the reaction. The highest DS was 1.86, which was obtained by the reaction using 20 equiv of acetic anhydride at 100 degrees C. The product with this DS value was soluble in DMSO, and thus the structure of the product was further confirmed by (1)H NMR spectroscopy in DMSO-d(6). The DS value estimated by the integrated ratio of signals due to acetyl protons to a signal due to anomeric protons was in good agreement with that determined from the IR spectrum. PMID:19732868

Mine, Shozaburo; Izawa, Hironori; Kaneko, Yoshiro; Kadokawa, Jun-Ichi

2009-08-08

432

Structural and Functional Differentiation of Three Groups of Tyrosine Residues by Acetylation of N -Acetylimidazole in Manganese Stabilizing Protein †  

Microsoft Academic Search

To study its contribution to the assembly of the green plant manganese stabilizing protein (MSP) into photosystem II (PSII), tyrosine residues were specifically acetylated using N-acetylimidazole (NAI). In soluble MSP, three groups of Tyr residues could be differentiated by NAI acetylation: approximately 5 (actually 5.2) Tyr residues could be easily acetylated (superficial), 1 -2 Tyr residues could be acetylated when

Feng Zhang; Jinpeng Gao; Jun Weng; Cuiyan Tan; Kangchen Ruan; Chunhe Xu; Dean Jiang

2005-01-01

433

Identification of the Protein Acetyltransferase (Pat) Enzyme that Acetylates AcetylCoA Synthetase in Salmonella enterica  

Microsoft Academic Search

Post-translational modification of proteins is an efficient way cells use to control the activity of structural proteins, gene expression regulatory proteins, and enzymes. In eukaryotes, the Sir2-dependent system of protein acetylation\\/deacetylation controls a number of processes that affect cell longevity. Sir2 proteins have NAD+-dependent protein deacetylase activity and are found in all forms of life. Although the identity of the

Vincent J Starai; Jorge C Escalante-Semerena

2004-01-01

434

High Temperature Acid Hydrolysis of Cellulose for Alcohol Fuel Production.  

National Technical Information Service (NTIS)

In the past decade, a concerted effort has been made to develop a process for converting renewable lignocellulosic feedstocks into ethanol fuels. This can be accomplished by the hydrolysis of cellulose and hemicellulose to their component sugars and subse...

J. D. Wright

1983-01-01

435

Enantioselective Synthesis of (-)-Sclerophytin A by a Stereoconvergent Epoxide Hydrolysis  

PubMed Central

The cytotoxic natural product (-)-sclerophytin A was constructed in 13 steps from geranial. Highlights from the synthesis are a stereoselective Oshima-Utimoto reaction, a Shibata-Baba indium-promoted radical cyclization, and a novel stereoconvergent epoxide hydrolysis.

Wang, Bin; Ramirez, Armando P.; Slade, Justin J.; Morken, James P.

2010-01-01

436

INTERIM PROTOCOL FOR MEASURING HYDROLYSIS RATE CONSTANTS IN AQUEOUS SOLUTIONS  

EPA Science Inventory

A detailed protocol was developed to measure first- and second-order hydrolysis rate constants for organic chemicals for use in models for predicting persistence in aquatic systems. The protocol delineates theoretical considerations, laboratory experiments, and calculation proced...

437

Hydrolysis of Cellulose by Purified Cellulase Components: Synergistic Effects.  

National Technical Information Service (NTIS)

The hydrolysis of cellulose by purified cellulase components is reported. The adsorption of purified cellobiohydrolases (CBH I and II) and endoglucanases (EG I and II) from Trichoderma reesei strain L27 to microcrystalline cellulose (Avicel) has been stud...

J. Woodward N. E. Lee

1987-01-01

438

Production of Alcohol Fuels Via Acid-Hydrolysis Extrusion Technology.  

National Technical Information Service (NTIS)

Pilot plant data obtained using a modified single screw grain extruder to facilitate the conversion of raw cellulosic materials into fermentable monosaccharides via acid hydrolysis are analyzed. The following are discussed: cellulose availability and cost...

R. Noon T. Hochstetler

1981-01-01

439

Effect of Solvents on the Hydrolysis Reaction of Tetramethyl Orthosilicate.  

National Technical Information Service (NTIS)

High-pressure Raman spectroscopy is used to monitor the hydrolysis reaction of tetramethyl orthosilicate, TMOS, in solutions with methanol, acetonitrile, acetone, dioxane and formamide. The rate constants are experimentally determined for different temper...

T. W. Zerda G. Hoang

1990-01-01

440

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.

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

1971-01-01