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Query: EC:6.2.1.13 (acetyl-CoA synthetase)
 451 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purified alpha-thiophosphate diastereoisomers of adenosine 5'-(1-thio)-triphosphate were used to study the stereochemical course of the reaction catalyzed by yeast acetyl-CoA synthetase. Asymmetrically labeled adenosine 5'-thiophosphate was formed from the "B" diastereoisomer of adenosine 5'-(1-thio)-triphosphate and [18O]acetate. The label was found to be in the opposite orientation from the leaving pyrophosphate group showing that the acetate activation step occurred with inversion of configuration at the alpha-phosphorus.
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PMID:The stereochemical course of acetate activation by yeast acetyl-CoA synthetase. 2 94

Adenosine 5'-(thiophosphate) AMPS) contains a prochiral phosphorus center. Differentiation of the two diastereotopic oxygens would allow elucidation of the stereochemical course of biological adenylyl transfer reactions. A general method was developed to distinguish between the "pro-R" and "pro-S" oxygens. When we converted the AMPS to the isomer A of adenosine 5'-(1-thiotriphosphate) (ATPalphaS), which is known to have S configuration at Palpha, the pro-R oxygen is incorporated into the bridge position, whereas the pro-S oxygen is located at the nonbridge position. The 31P NMR spectra of the 17O-enriched compounds were used to distinguish between the bridge and nonbridge oxygens based on the decrease in the peak intensity of 31P NMR signals caused by the directly bound 17O isotope. The method was used to elucidate the stereochemical course of acetate activation catalyzed by yeast acetyl coenzyme A (CoA) synthetase. The results indicate that yeast acetyl-CoA synthetase is specific for the isomer B of ATPalphaS and that the nucleophilic displacement proceeds with net inversion of configuration at Palpha of ATPalphaS (B), supporting the "in-line" mechanism.
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PMID:Use of phosphorus-31 nuclear magnetic resonance to distinguish bridge and nonbridge oxygens of oxygen-17-enriched nucleoside triphosphates. Stereochemistry of acetate activation by acetyl coenzyme A synthetase. 3 27

Fast atom bombardment mass spectrometry (FAB-MS) has been used to measure positional isotope exchange rates in enzyme-catalyzed reactions. The technique has been applied to the reactions catalyzed by acetyl-CoA synthetase and argininosuccinate synthetase. The FAB technique is also able to quantitatively determine the oxygen-18 or oxygen-17 content of nucleotides on as little as 10 nmol of material with no prior derivatization. Acetyl-CoA synthetase has been shown by FAB-MS to catalyze the positional exchange of an oxygen-18 of ATP from the beta-nonbridge position to the alpha beta-bridge position in the presence of acetate. These results are consistent with acetyl adenylate as a reactive intermediate in this reaction. Argininosuccinate synthetase was shown not to catalyze a positional isotope exchange reaction designed to test for the formation of citrulline adenylate as a reactive intermediate. Argininosuccinate synthetase was also found not to catalyze the transfer of oxygen-18 from [ureido-18O]citrulline to the alpha-phosphorus of ATP in the absence of added aspartate. This experiment was designed to test for the transient formation of carbodiimide as a reactive intermediate. These results suggest that either argininosuccinate synthetase does not catalyze the formation of citrulline adenylate or the enzyme is able to completely suppress the rotation of the phosphoryl groups of PPi.
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PMID:Measurement of positional isotope exchange rates in enzyme-catalyzed reactions by fast atom bombardment mass spectrometry: application to argininosuccinate synthetase. 286 75

Data from laboratory-scale sequencing batch reactors operated in an anaerobic-aerobic cycle showed that a low influent phosphorus/chemical oxygen demand (COD) ratio feed favored a glycogen-accumulating metabolism (GAM)-dominated culture and that a high influent phosphorus/COD ratio feed favored a polyphosphate-accumulating metabolism (PAM)-dominated culture. The PAM-dominated culture anaerobically took up acetate approximately 7 times faster than the GAM-dominated culture. Adenosine triphosphate (ATP) balances were performed assuming eight different metabolic scenarios that included the Entner-Doudoroff or the Embden-Myerhof glycolytic pathway, acetyl-coenzyme A (CoA) synthase or the acetate kinase-phospho-transacetylase (AK-PTA) system for acetyl-CoA synthesis, and ATP synthesis or no ATP synthesis during fumarate reduction. The ATP available for transport of acetate into the cell (2) was calculated using these balances. The assumed quantity of ATP produced during fumarate reduction had a relatively small effect on alpha, particularly when PAM was dominant. When GAM was dominant, little or no ATP was available for acetate transport depending on the assumed scenario, and the Embden-Myerhof pathway was more feasible. The value of alpha increased with increasing PAM dominance for all eight metabolic pathways. The maximum calculated alpha value of 0.5 mol ATP/C-mol acetate uptake occurred at maximum PAM dominance and when the Embden-Myerhof pathway was active, when ATP was produced during fumarate reduction, and when the AK-PTA system was active. This value of alpha was higher than previously calculated values with the same metabolic assumptions. An acetate uptake mechanism was suggested that included acetyl-CoA synthetase and direct regeneration of the proton motive force by a proton-translocating pyrophosphatase. Polyphosphate-accumulating metabolism may have a competitive advantage over GAM through a higher anaerobic acetate uptake rate made possible by a greater use of energy for acetate uptake, by use of a different acetate uptake mechanism, or both.
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PMID:Enhanced biological phosphorus removal from wastewater by biomass with different phosphorus contents, Part II: Anaerobic adenosine triphosphate utilization and acetate uptake rates. 1470 9