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Query: EC:6.2.1.1 (ACS)
 78,556 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

A method is shown to be effective over a wide range of enzyme ratios for the simultaneous detection of the two isoenzymes of acetyl coenzyme A synthetase [acetate:coenzyme A ligase (AMP-forming); EC 6.2.1.1] in homogenates and cellular fractions of Saccharomyces cerevisiae. When this method was used, it was found that cells grown under anaerobic conditions contained only one variety of this enzyme, designated the nonaerobic synthetase, whereas cells grown with vigorous aeration contained principally the other, aerobic, synthetase. In cells grown as standing cultures (i.e., semi-aerobically), both enzymes were present and were found mainly in the extramitochondrial material of homogenates. When anaerobic cultures were aerated, the amount of aerobic enzyme increased steadily over a 24-h period, so that at the end of this time, aerated cells contained predominantly aerobic enzyme. During this same period, the amount of nonaerobic enzyme decreased. The percentage of aerobic enzyme that sedimented with the mitochondria increased steadily during this period of aeration, so that, at the end of 24 h of aeration, essentially all of the aerobic enzyme sedimented with the mitochondria. The nonaerobic enzyme was never found in this cellular compartment.
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PMID:Effects of aeration on formation and localization of the acetyl coenzyme A synthetases of Saccharomyces cerevisiae. 3 46

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

The present communication reports data on the lipid biosynthesis of Ehrlich ascites tumor cells grown in culture media supplemented with modified sera. Whereas the metabolisms of [14C]pyruvate and [14C]mevalonate are identical in all media tested, the incorporation of [14C] acetate is higher in medium with dialyzed serum than in medium with delipidized serum; it is suppressed in the absence of all lipids in culture medium. Cellular integrity is not impaired in modified media. The results indicate that acetyl-CoA synthetase of Ehrlich ascites tumor cells is not regulated by exogenous lipids as is known to be the case in nonmalignant cells.
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PMID:Unexpectedly low incorporation of isotopic acetate into lipids of Ehrlich ascites tumor cells cultured in lipid-poor medium. 3 70

A comparative study of the effects of varying levels of oxygen on some of the metabolic functions of the primitive eukaryote, Saccharomyces cerevisiae, has shown that these cells are responsive to very low levels of oxygen: the level of palmitoyl-Co A desaturase was greatly enhanced by only 0.03% (v/v) oxygen. Similarly, an acetyl-CoA synthetase associated predominantly with anaerobic growth, was stimulated by as little as 0.1% oxygen, while an isoenzyme correlated with aerobic growth, was maximally active at much higher oxygen levels (greater than 1%). Closely following this latter pattern were three mitochondrial enzymes that attained maximal activity only under atmospheric levels of oxygen.
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PMID:Oxygen as a factor in eukaryote evolution: some effects of low levels of oxygen on Saccharomyces cerevisiae. 4 Dec 5

Purple sulfur (Ectothiorhodospira shaposhnikovii, Chromatium minutissimum, Lamprobacter modestohalophilus, Thiocapsa roseopersicina) and nonsulfur (Rhodospirillum rubrum, Rhodopseudomonas palustris, Rhodopseudomonas spheroides) bacteria are capable of forming acetyl-CoA synthetase, phosphotransacetylase and acetokinase independent of the medium composition and growth conditions. In all of the purple sulfur bacteria with an exception of E. shaposhnikovii, the activity of acetokinase is much higher than in purple nonsulfur bacteria. Apart from being involved in the synthesis of acetyl-CoA, such enzymes as phosphotransacetylase, acetokinase and adenylate kinase may play an important role in energy processes of some purple bacteria in the dark.
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PMID:[Possible pathways for acetyl-CoA formation by purple bacteria]. 22 68

In light/dark synchronized cultures of Euglena gracilis Klebs Z the enzymes malate synthase, isocitrate lyase and acetate thiokinase were induced upon addition of acetate at all stages of the cell cycle. Cycloheximide and p-fluorophenylalanine inhibited the development of enzyme activity, showing that induction was dependent on protein synthesis. The maximum rate of induction for all three enzymes was constant for much of the cell cycle but doubles in a single step during the period of DNA replication. Although these data indicate that enzyme potential was regulated by gene dosage and that the structural gene for each enzyme was continuously available for transcription during the cell-cycle it was not possible by using inhibitors of RNA synthesis, to demonstrate concurrent transcription during enzyme induction.
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PMID:Induction potential for glyoxylate cycle enzymes during the cell cycle of Euglena gracilis. 24 Jul

The synthesis of a new coenzyme A analogue, N6-[N-(6-aminohexyl)carbamoylmethyl]-CoA, suitable for immobilisation through its terminal amino group to support matrices, is described. The synthetic route starts with bis(CoA) and involves the following steps: alkylation with iodoacetic acid and rearrangement yielding bis(N6-carboxymethyl-CoA), elongation of the carboxymethyl terminal with 1,6-diaminohexane using carbodiimide to yield bis(N6-[N-(6-aminohexyl)-carbamoylmethyl]-CoA) and finally the splitting of this bis[CoA analogue) through reduction with dithiothreitol to give the final product in approximately 10% overall yield. This CoA analogue showed 'coenzymic activity' with the enzymes acetyl-CoA synthetase, phosphotransacetylase and succinic thiokinase. Covalent binding of the CoA analogue to Sepharose 4B was normally carried out using its S-(5-thio-2-nitrobenzoic acid) derivative as this allows a convenient way for determining the amount of ligand coupled, based on the amount of 5-thio-2-nitrobenzoic acid liberated from the gel after reduction with dithiothreitol. After covalent binding of the CoA analogue to water-soluble activated dextran 70, the analogue was recycled while present in an ultrafiltration cell using the enzymes phosphotransacetylase and citrate synthase. The reaction was followed by measuring the citrate formed on addition of acetylphosphate and oxaloacetate. In affinity chromatographic studies it was shown that the CoA-Sepharose preparation could bind the CoA-dependent enzymes citrate synthase and succinic thiokinase and these could be biospecifically eluted using soluble CoA.
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PMID:N6-[N-(6-Aminohexyl)carbamoylmethyl]-coenzyme A. Synthesis and application in affinity chromatography and as an immobilized active coenzyme. 57 88

Thirteen chromosomal loci have been identified which affect acetate metabolism in Coprinus. Mutants at only two loci, acu-l and acu-7, are deficient in isocitrate lyase (ICL) (EC 4.1.3.1) activity. acu-1 mutants are unable to induce ICL because they lack acetyl-CoA synthetase which is required to convert acetate to the metabolic inducer of ICL. acu-7 is the structural gene for ICL. This was shown by selecting temperature sensitive acu+ revertants resulting from a second mutation within the acu-7 gene. One such revertant was shown to produce an ICL protein which was more thermolabile than the wild type enzyme. Other workers have postulated that ICL activity is important during asexual morphogenesis in fungi. No evidence was found for this in Coprinus. The morphological mutant oidial, which produces abundant asexual spores even in submerged culture, had the same low uninduced level of ICL activity as the wild type. Moreover, an acu-7 mutation had no effect on the expression of the oidial phenotype.
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PMID:Genetics and function of isocitrate lyase in Coprinus. 60 Feb 68

Methods are described for the direct optical assay of citrate, acetate, and acetoacetate production by isolated, incubated rat liver mitochondria. Each metabolite is converted into acetyl-CoA, using ATP: citrate lyase or acetyl-CoA synthetase or acetoacetyl-CoA synthetase and acetyl-CoA acetyltransferase, respectively. Arylamine acetyltransferase acts as auxiliary enzyme. It was shown that isolated rat liver mitochondria produce citrate, acetate and acetoacetate, and that production rates are stimulated by pyruvate and hexanoate. It was concluded that these three products might contribute to the transport of acetyl units across the mitochondrial membrane and thus serve as precursors in fatty acid synthesis. The rate of acetyl transfer does not seem to be rate-limiting with regard to the overall-process of fatty acid synthesis from carbohydrates.
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PMID:Transfer of C2-units across the mitochondrial membrane. Direct recording of citrate, acetate and acetoacetate production rates. 66 82


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