Gene/Protein Disease Symptom Drug Enzyme Compound
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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 three enzymes of ethanol metabolism alcohol dehydrogenase, aldehyde dehydrogenase and acetyl-CoA synthetase in the obligate aerobic yeast Rhodotorula gracilis are repressed by glucose and induced by C2 metabolic fuels with a regulatory pattern indicating a correlation in the control mechanisms. To try an identification of the molecular signals involved in the transmission of the inducing stimulus, experiments were carried out by blocking with 2 mM pyrazole the ethanol acetaldehyde metabolic step. Results indicate that ethanol is not specifically required as a molecular signal for induction.
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PMID:Regulation of enzymes of ethanol metabolism in yeast (Rhodotorula gracilis). 1 Jan 76

The physiology of Saccharomyces cerevisiae CBS 8066 was studied in glucose-limited chemostat cultures. Below a dilution rate of 0.30 h-1 glucose was completely respired, and biomass and CO2 were the only products formed. Above this dilution rate acetate and pyruvate appeared in the culture fluid, accompanied by disproportional increases in the rates of oxygen consumption and carbon dioxide production. This enhanced respiratory activity was accompanied by a drop in cell yield from 0.50 to 0.47 g (dry weight) g of glucose-1. At a dilution rate of 0.38 h-1 the culture reached its maximal oxidation capacity of 12 mmol of O2 g (dry weight)-1 h-1. A further increase in the dilution rate resulted in aerobic alcoholic fermentation in addition to respiration, accompanied by an additional decrease in cell yield from 0.47 to 0.16 g (dry weight) g of glucose-1. Since the high respiratory activity of the yeast at intermediary dilution rates would allow for full respiratory metabolism of glucose up to dilution rates close to mumax, we conclude that the occurrence of alcoholic fermentation is not primarily due to a limited respiratory capacity. Rather, organic acids produced by the organism may have an uncoupling effect on its respiration. As a result the respiratory activity is enhanced and reaches its maximum at a dilution rate of 0.38 h-1. An attempt was made to interpret the dilution rate-dependent formation of ethanol and acetate in glucose-limited chemostat cultures of S. cerevisiae CBS 8066 as an effect of overflow metabolism at the pyruvate level. Therefore, the activities of pyruvate decarboxylase, NAD+- and NADP+-dependent acetaldehyde dehydrogenases, acetyl coenzyme A (acetyl-CoA) synthetase, and alcohol dehydrogenase were determined in extracts of cells grown at various dilution rates. From the enzyme profiles, substrate affinities, and calculated intracellular pyruvate concentrations, the following conclusions were drawn with respect to product formation of cells growing under glucose limitation. (i) Pyruvate decarboxylase, the key enzyme of alcoholic fermentation, probably already is operative under conditions in which alcoholic fermentation is absent. The acetaldehyde produced by the enzyme is then oxidized via acetaldehyde dehydrogenases and acetyl-CoA synthetase. The acetyl-CoA thus formed is further oxidized in the mitochondria. (ii) Acetate formation results from insufficient activity of acetyl-CoA synthetase, required for the complete oxidation of acetate. Ethanol formation results from insufficient activity of acetaldehyde dehydrogenases.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Enzymic analysis of the crabtree effect in glucose-limited chemostat cultures of Saccharomyces cerevisiae. 256 99

The metabolism of acetaldehyde was studied in isolated dog, rat and guinea-pig kidney-cortex tubules. In contrast with previous observations of Cederbaum and Rubin in rat kidney mitochondria (Archs Biochem. Biophys. 179, 46-66 1977) acetaldehyde was found to be metabolized by the tubules at high rates and in a dose-dependent manner at concentrations up to 5-10 mM. At high acetaldehyde concentrations (1-10 mM) acetaldehyde removal was accompanied by a high rate of acetate accumulation which explained most of the acetaldehyde metabolized in dog and guinea-pig but not in rat kidney tubules. These species differences in acetaldehyde metabolism can be explained by the differences in activities of aldehyde dehydrogenase (EC 1.2.1.3) and acetyl-CoA synthetase (EC6.2.1.1), the enzymes involved in renal acetaldehyde metabolism which were measured in the renal cortex of the three species. The acetaldehyde carbon removed and not accounted for by acetate accumulation was completely oxidized to CO2 as demonstrated by the measurement of [U-14C]-acetaldehyde conversion into 14CO2. At "physiological" acetaldehyde concentrations (0.1 and 0.2 mM) acetaldehyde utilization was also concentration-dependent but no acetate accumulation was observed.
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PMID:Characteristics of acetaldehyde metabolism in isolated dog, rat and guinea-pig kidney tubules. 368 31

The physiology of Hanseniaspora uvarum K5 was studied in glucose-limited chemostat cultures and upon glucose pulse. Up to a dilution rate of 0.28 h-1, glucose was completely metabolized in biomass and CO2. Above this value, increase in the dilution rate was accompanied by sequential production of metabolites (glycerol, acetate and ethanol) and decrease in cell yield. Similar results were observed upon glucose pulse. From the enzyme activities (pyruvate dehydrogenase, pyruvate decarboxylase, NAD and NADP-dependent acetaldehyde dehydrogenases, acetyl coenzyme A synthetase and alcohol dehydrogenase) and substrate affinities, the following conclusions were drawn with respect to product formation of cells: (1) pyruvate was preferentially metabolized via pyruvate dehydrogenase, when biomass and CO2 were the only products formed; (2) acetaldehyde formed by pyruvate decarboxylase was preferentially oxidized in acetate by NADP-dependent aldehyde dehydrogenase; acetate accumulation results from insufficient activity of acetyl-CoA synthetase required for the complete oxidation of acetate; (3) acetaldehyde was oxidized in ethanol by alcohol dehydrogenase, in addition to acetate production.
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PMID:Glucose metabolism, enzymic analysis and product formation in chemostat culture of Hanseniaspora uvarum. 778 33

Single recessive mutations of the methylotrophic yeast Pichia methanolica acs1, acs2, acs3 and icl1 affecting acetyl-CoA synthetase and isocitrate lyase, and growth on ethanol as sole carbon and energy source, caused a defect in autophagic peroxisome degradation during exposure of methanol-grown cells to ethanol. As a control, a mutation in mdd1, which resulted in a defect of the 'malic' enzyme and also prevented ethanol utilization, did not prevent peroxisome degradation. Peroxisome degradation in glucose medium was unimpaired in all strains tested. Addition of ethanol to methanol-grown cells of acs1, acs2, acs3 and icl1 mutants led to an increase in average vacuole size. Thickening of peroxisomal membranes and tight contacts between groups of peroxisomes and vacuoles were rarely observed. These processes proceeded much more slowly than in wild-type or mdd1 mutant cells incubated under similar conditions. No peroxisomal remnants were observed inside vacuoles in the cells of acs1, acs2, acs3 and icl1 mutants after prolonged cultivation in ethanol medium. We hypothesize that the acs and icl mutants are defective in synthesis of the true effector--presumably glyoxylate--of peroxisome degradation in ethanol medium. Lack of the effector suspends peroxisome degradation at an early stage, namely signal transduction or peroxisome/vacuole recognition. Finally, these defects in peroxisome degradation resulted in mutant cells retaining high levels of alcohol oxidase which further led to increased levels of acetaldehyde accumulation upon incubation of mutant cells with ethanol.
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PMID:Impairment of peroxisome degradation in Pichia methanolica mutants defective in acetyl-CoA synthetase or isocitrate lyase. 929 Feb 8

Acetaldehyde is one of the intermediate products of ethanolic fermentation, which can be reduced to ethanol by alcohol dehydrogenase (ADH). Alternatively, acetaldehyde can be oxidized to acetate by aldehyde dehydrogenase (ALDH) and subsequently converted to acetyl-CoA by acetyl-CoA synthetase (ACS). To study the expression of ALDHs in plants we isolated and characterized a cDNA coding for a putative mitochondrial ALDH (TobAldh2A) in Nicotiana tabacum. TobALDH2A shows 54-60% identity at the amino acid level with other ALDHs and shows 76% identity with maize Rf2, a gene involved in restoration of male fertility in cms-T maize. TobAldh2A transcripts and protein were present at high levels in the male and female reproductive tissues. Expression in vegetative tissues was much lower and no induction by anaerobic incubation was observed. This suggests that TobALDH expression is not part of the anaerobic response, but may have another function. The use of specific inhibitors of ALDH and the pyruvate dehydrogenase (PDH) complex indicates that ALDH activity is important for pollen tube growth, and thus may have a function in biosynthesis or energy production.
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PMID:Aldehyde dehydrogenase in tobacco pollen. 934 59

The KlPDA1 gene, encoding the E1alpha subunit of the mitochondrial pyruvate-dehydrogenase (PDH) complex was isolated from a Kluyveromyces lactis genomic library by screening with a 1.1 kb internal fragment of the Saccharomyces cerevisiae PDA1 gene. The predicted amino acid sequence encoded by KlPDA1 showed 87% similarity and 79% identity to its S. cerevisiae counterpart. Disruption of KIPDA1 resulted in complete absence of PDH activity in cell extracts. The maximum specific growth rate on glucose of null mutants was 3.5-fold lower than that of the wild-type, whereas growth on ethanol was unaffected. Wild-type K. lactis CBS 2359 exhibits a Crabtree-negative phenotype, i.e. no ethanol was produced in aerobic batch cultures grown on glucose. In contrast, substantial amounts of ethanol and acetaldehyde were produced in aerobic cultures of an isogenic Klpda1 null mutant. A wild-type specific growth rate was restored after introduction of an intact KlPDA1 gene but not, as previously found for S. cerevisiae pda1 mutants, by cultivation in the presence of leucine. The occurrence of aerobic fermentation and slow growth of the Klpda1 null mutant indicate that, although present, the enzymes of the PDH bypass (pyruvate decarboxylase, acetaldehyde dehydrogenase and acetyl-CoA synthetase) could not efficiently replace the PDH complex during batch cultivation on glucose. Only at relatively low growth rates (D = 0.10 h(-1)) in aerobic, glucose-limited chemostat cultures, could the PDH bypass completely replace the PDH complex, thus allowing fully respiratory growth. This resulted in a lower biomass yield [g biomass (g glucose)-1] than in the wild-type due to a higher consumption of ATP in the PDH bypass compared to the formation of acetyl-CoA via the PDH complex.
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PMID:Inactivation of the Kluyveromyces lactis KlPDA1 gene leads to loss of pyruvate dehydrogenase activity, impairs growth on glucose and triggers aerobic alcoholic fermentation. 988 36

Rapid pollen tube growth requires a high rate of sugar metabolism to meet energetic and biosynthetic demands. Previous work on pollen sugar metabolism showed that tobacco pollen carry out efficient ethanolic fermentation concomitantly with a high rate of respiration (Bucher et al., 1995). Here we show that the products of fermentation, acetaldehyde and ethanol, are further metabolised in a pathway that bypasses mitochondrial PDH. The enzymes involved in this pathway are pyruvate decarboxylase, aldehyde dehydrogenase and acetyl-CoA synthetase. Radiolabelling experiments show that during tobacco pollen tube growth label of 14C-ethanol is incorporated into CO2 as well as into lipids and other higher molecular weight compounds. A role for the glyoxylate cycle appears unlikely since activity of malate synthase, a key enzyme of the glyoxylate cycle, could not be detected.
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PMID:The ethanolic fermentation pathway supports respiration and lipid biosynthesis in tobacco pollen. 1200 Jun 80

Activities of the key enzymes of ethanol metabolism were assayed in ethanol-grown cells of an Acinetobacter sp. mutant strain unable to synthesize exopolysaccharides (EPS). The original EPS-producing strain could not be used for enzyme analysis because its cells could not to be separated from the extremely viscous EPS with a high molecular weight. In Acinetobacter sp., ethanol oxidation to acetaldehyde proved to be catalyzed by the NAD(+)-dependent alcohol dehydrogenase (EC 1.1.1.1.). Both NAD+ and NADP+ could be electron accepters in the acetaldehyde dehydrogenase reaction. Acetate is implicated in the Acinetobacter sp. metabolism via the reaction catalyzed by acetyl-CoA-synthetase (EC 6.2.1.1.). Isocitrate lyase (EC 4.1.3.1.) activity was also detected, indicating that the glyoxylate cycle is the anaplerotic mechanism that replenishes the pool of C4-dicarboxylic acids in Acinetobacter sp. cells. In ethanol metabolism by Acinetobacter sp., the reactions involving acetate are the bottleneck, as evidenced by the inhibitory effect of sodium ions on both acetate oxidation in the intact cells and on acetyl-CoA-synthetase activity in the cell-free extracts, as well as by the limitation of the C2-metabolism by coenzyme A. The results obtained may be helpful in developing a new biotechnological procedure for obtaining ethanol-derived exopolysaccharide ethapolan.
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PMID:[Peculiarities of ethanol metabolism in an Acinetobacter sp. mutant strain defective in exopolysaccharide synthesis]. 1202 23

Ethanol metabolism in Acinetobacter sp. is limited by the rate of acetate assimilation in a reaction catalyzed by acetyl-CoA synthetase (EC 6.2.1.1). Effects of ions (sodium, potassium, and magnesium), byproducts of ethanol and acetaldehyde oxidation (NADH and NADPH), and pantothenic acid on this enzyme have been studied (sodium, NADH, and NADPH inhibit acetyl-CoA synthetase; pantothenic acid, potassium, and magnesium act as the enzyme activators). Conditions of culturing were developed, under which ethanol, acetaldehyde, and acetate in Acinetobacter cells were oxidized at the same rates, producing a threefold increase in the activity of acetyl-CoA synthetase in the cell-free extract. The results of studies of acetyl-CoA synthetase regulation in a mutant strain of Acinetobacter sp., which is incapable of forming exopolysaccharides, provide a basis for refining the technology of ethapolan production, involving the use of C2 substrates.
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PMID:[Regulation of acetate metabolism in a strain of Acinetobacter sp., growing on ethanol]. 1272 51


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