Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Bioluminescence provides a sensitive analytical approach for the measurement of low concentrations of ATP and can be used to monitor any reaction in which ATP is consumed or synthesized. We describe a quick, sensitive method involving bioluminescence for the quantitation of chloramphenicol in serum. Chloramphenicol acetyl transferase catalyzes the acetylation of chloramphenicol in the presence of acetyl coenzyme A. ATP is consumed when the acetylation reaction is coupled to the acetyl coenzyme A synthetase reaction. Residual ATP is then assayed with the firefly luciferin-luciferase reaction. The procedure can be completed in less than 1 h and requires as little as 20 microliter of serum. The response of the assay is linear with concentration through a range of 2 to 20 mg/L and shows good correlation with a gas-chromatographic method (r = 0.978) and a radioenzymic method (r = 0.985). No significant interference was found from five other antibiotics tested. The small sample requirement makes the assay especially applicable to infant and pediatric monitoring, where the effects of toxicity are greatest.
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PMID:A bioluminescence micromethod for measuring chloramphenicol in serum. 723 58

Cycloheximide, frequently used as an inhibitor of protein synthesis in vivo and in vitro, has been found to cause a significant reduction of the synthesis of digitonin-precipitable sterols from acetate, but not from mevalonate, at a concentration of 1 mM in the 10,000 x g supernatant fraction of rat liver homogenate preparations. The results of studies of the metabolism of labeled leucine under the same conditions indicated that the effect of cycloheximide on sterol synthesis from acetate was not related to an effect of cycloheximide on protein synthesis. Preincubation of the 10,000 x g supernatant fraction of rat liver homogenates with cycloheximide (1 mM) caused a significant reduction in the levels of acetate thiokinase and hydroxymethylglutaryl-CoA synthase activities but not of acetoacetyl-CoA thiolase activity. Preincubation of the 100,000 x g supernatant fraction of rat liver homogenates with cycloheximide (1 mM or 0.3 mM) also caused a significant reduction of the levels of hydroxymethylglutaryl-CoA synthase activity. When cycloheximide (1 mM) was preincubated with the 100,000 x g supernatant fraction, a reduction in the level of acetate thiokinase activity was observed. Preincubation of rat liver microsomes with cycloheximide (1 mM and 3 mM) had no effect on the level of hydroxymethylglutaryl-CoA reductase activity. These results suggest that biological effects observed upon exposure of cells or tissues to high concentrations of cycloheximide may not be exclusively due to effects of the cycloheximide on the synthesis of protein.
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PMID:Cycloheximide inhibits sterol biosynthesis in cell-free preparations of rat liver. 737 3

1. The lipogenic enzyme ATP citrate lyase (ATP:citrate oxaloacetate-lyase (pro-3S-CH2COO-acetyl-CoA; ATP-dephosphorylating), EC 4.1.3.8) is partially purified from human liver by ammonium sulfate fractionation and anionexchange chromatography. 2. Km values for the substrates are 1.1 x 10(-5) 1.3 x 10(-3), and 1.2 x 10(-4) M for CoASH, ATP and citrate, respectively. The hypolipidemic drug L(-)-hydroxycitrate is a competitive inhibitor with respect to citrate (Ki = 3 x 10(-4) M). 3. Specific activities measured in liver, adipose tissue and intestinal mucosa (autopsic and biopsic material) are in the range of 1 mU/mg protein suggesting that the citrate pathway does not significantly contribute to human lipogenesis. No stimulation is found after a 3-day carbohydrate-rich diet. 4. Specific activities of other key-enzymes of the acetyl-CoA production from carbohydrates (pyruvate dehydrogenase, cytosolic acetyl-CoA synthetase) are of the same low magnitude.
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PMID:Properties and organ distribution of ATP citrate (pro-3S)-lyase. 741 78

Mutants of Candida lipolytica that were unable to grow on acetate but able to utilize succinate or glycerol as a sole carbon source were isolated. Amongst the mutants isolated, one strain (Icl-) was specifically deficient in isocitrate lyase activity, whereas another strain (Acos-) was deficient in acetyl coenzyme A synthetase activity. Since the Icl- mutant could not grow either on n-alkane or its derivatives, such as fatty acid and long-chain dicarboxylic acid, any anaplerotic route other than the glyoxylate pathway was inconceivable as far as growth on these carbon sources was concerned. Acetyl coenzyme A is most likely a metabolic inducer of isocitrate lyase and malate synthase, because the Acos- mutant was characterized by the least susceptibility to induction of these enzymes by acetate. The structural gene for isocitrate lyase was most probably impaired in the Icl- mutant, since revertants (Icl-) produced thermolabile isocitrate lyase. The production of isocitrate from n-alkane by the revertants was enhanced in comparison with the parental strain.
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PMID:Role and control of isocitrate lyase in Candida lipolytica. 743 68

Highly purified rat liver fatty acid synthetase is completely inhibited when assayed in the presence of a coenzyme A-depleting system such as that catalyzed by phosphotransacetylase, acetyl-CoA synthetase, or ATP citrate lyase. The addition of free CoA causes a reversal of this inhibition. The requirement of free CoA is the same whether acetyl-CoA or butyryl-CoA serves as the primer for fatty acid synthetase. The CoA-depleted and thus inactive fatty acid synthetase system can be reactivated by the addition of a rat brain thioesterase or a rat mammary gland thioesterase II preparation. This reactivation appears to occur in the absence of free CoA. Long chain fatty acids (mainly palmitate) are formed by the thioesterase reactivated system. These results suggest that CoA is required for the termination of the fatty acid synthetase reaction. Possible mechanisms are discussed.
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PMID:Coenzyme A requirement for the termination reaction of rat liver fatty acid synthetase. 743 Jan 43

Previous studies of Arthrobacter pyridinolis indicated that during the first half of the growth cycle on D-fructose, the organism utilizes a respiration-coupled transport system and exhibits glyoxylate pathway activity; during the second half of the growth cycle, a phosphoenolypyruvate:D-fructose phosphotransferase system is used for transport and no glyoxylate pathway activity is found [Pelliccione et al. (1979) Eur. J. Biochem. 95, 69--75]. A citrate-synthase-deficient mutant had the following properties: (a) high constitutive levels of glyoxylate pathway enzymes on various substrates, while such levels were only found in the wild type when it was grown on acetate; (b) acetyl-CoA levels much higher than in the wild type grown on several different substrates, whereas other metabolite levels were similar in the two strains; and (c) under conditions for induction of the phosphotransferase system, the wild type exhibited at least twice as much phosphotransferase activity as the mutant strain. A mutant lacking acetyl-CoA synthetase exhibited no induction of the glyoxylate pathway in the presence of acetate, although acetate uptake was normal. The results indicate a role for acetyl-CoA as inducer of the glyoxylate pathway. They further suggest a possible role, perhaps indirect, in repression of the phosphotransferase system.
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PMID:A deficiency of citrate synthase results in constitutive expression of the glyoxylate pathway in Arthrobacter pyridinolis. 746 Sep 50

During batch growth of Alcaligenes eutrophus on benzoate-acetate mixtures, benzoate was the preferred substrate, with acetate consumption being delayed until the rate of benzoate consumption had diminished. This effect was attributed to a transcriptional control of the synthesis of acetyl coenzyme A (acetyl-CoA) synthetase, an enzyme necessary for the entry of acetate into the central metabolic pathways, rather than to a biochemical modulation of the activity of this enzyme. Analysis of a 2.4-kb mRNA transcript hybridizing with the A. eutrophus acoE gene confirmed this repression effect. In a benzoate-limited chemostat culture, derepression was observed, with no increase in the level of expression following an acetate pulse. Benzoate itself was not the signal triggering the repression of acetyl-CoA synthetase. This role was played by catechol, which transiently accumulated in the medium when high specific rates of benzoate consumption were reached. The lack of rapid inactivation of the functional acetyl-CoA synthetase after synthesis has been stopped enables A. eutrophus to retain the capacity to metabolize acetate for prolonged periods while conserving minimal protein expenditure.
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PMID:Acetate utilization is inhibited by benzoate in Alcaligenes eutrophus: evidence for transcriptional control of the expression of acoE coding for acetyl coenzyme A synthetase. 759 30

In Escherichia coli carrying the poly(3-hydroxyalkanoate) (PHA) biosynthesis pathway on a plasmid (pha+), the function of the ackA (acetate kinase) and pta (phosphotransacetylase) genes is necessary for efficient incorporation of 3-hydroxyvalerate (3-HV) into the copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)). Recombinant pha+ E. coli fadR atoC(Con) strains possessing mutations in ackA, pta, or both ackA and pta exhibited substantially reduced levels of 3-HV formation. Conversely, the same strains carrying the ackA gene on a multicopy plasmid exhibited an increase in 3-HV formation concomitant with a large increase in acetate kinase activity. However, if the strain possessing the multicopy ackA+ plasmid was mutant at the pta locus, it lost the ability to incorporate significant amounts of 3-HV into P(3HB-co-3HV). In addition to the ackA pta pathway, there is an inducible activity that can also mediate the incorporation of 3-HV into P(3HB-co-3HV). This pathway is repressed by glucose and is not normally operative in P(3HB-co-3HV) production in recombinant pha+ E. coli strains that are grown using glucose as the major carbon source. It appears likely that this activity is due to an inducible acetyl-CoA synthetase that converts propionate to propionyl-CoA.
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PMID:The function of ackA and pta genes is necessary for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) synthesis in recombinant pha+ Escherichia coli. 760 63

Two nuclear genes, RTG1 and RTG2, which sense the functional state of yeast mitochondria, have been described recently. Yeast strains with null alleles of either of these two genes (delta rtg1, delta rtg2) cannot grow on acetate as the sole carbon source and are auxotrophic for glutamate and aspartate. We report here a series of metabolic experiments and enzyme activity measurements that were made in an attempt to determine the reason for the acetate- phenotype and the glutamate/aspartate auxotrophy. Decreases in the activities (approximately 50%) in mitochondrial citrate synthase (CS1), acetyl-CoA synthetase, NAD isocitrate dehydrogenase, and pyruvate carboxylase were noted. When CS1 was overexpressed in the delta rtg1 and delta rtg2 mutants, these strains could grow on acetate but were still auxotrophic for glutamate/aspartate. We propose that, in the mutant strain, CS1 activity becomes limiting for efficient acetate utilization, but that other complex metabolic interactions are affected, limiting production of intermediates that would allow synthesis of glutamic and aspartic acids.
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PMID:Enzymatic and metabolic studies on retrograde regulation mutants of yeast. 772 18

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) synthetase activity. The facA gene, coding for the enzyme acetyl-CoA synthetase, was isolated from a P. chrysogenum genomic library using synthetic oligonucleotides derived from conserved regions from the corresponding genes of Aspergillus nidulans and Neurospora crassa. Vector pPC2-3, comprising a genomic 6.5 kb PstI fragment, was able to complement P. chrysogenum facA strains with frequencies up to 27 transformants.micrograms-1 DNA. Direct selection of transformants was accomplished using acetate and low amounts (0.001%) of glucose as carbon sources. About 50% of the transformants arose by integration of pPC2-3 DNA at the homologous facA locus and 50% by integration elsewhere in the genome. Determination of the nucleotide sequence of part of the cloned fragment showed the presence of an open reading frame of 2007 nucleotides, interrupted by five putative introns. Comparison of the nucleotide and the amino acid sequence of the facA gene of P. chrysogenum with the facA gene of A. nidulans reveals similarities of 80% and 89%, respectively. The putative introns present in the P. chrysogenum facA gene appear at identical positions as those in the A. nidulans facA gene, but show no significant sequence similarity.
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PMID: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. 776 89


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