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:2.3.3.1 (citrate synthase)
4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

meso-Tartrate inhibited the growth of non-meso-tartrate-utilizing strains of Salmonella typhimurium in peptone water media and mineral salts media with some, but not all, carbon sources. C-R intermediates of the tricarboxylic acid cycle or compounds readily converted to them and substrates metabolized independently of the C-6 part of the cycle spared bacteria from the inhibitory effects of meso-tartrate when added to cultures along with meso-tartrate. Experiments with cell-free extracts of non-meso-tartrate-utilizing strains from batch and continuous cultures showed that meso-tartrate was a competitive inhibitor of isocitrate dehydrogenase and isocitrate lyase activities and also inhibited citrate synthase and malate synthase activities. The synthesis of these enzymes was not inhibited by meso-tartrate. The isocitrate enzymes of meso-tartrate-utilizing strains of S. typhimurium were similarly inhibited by meso-tartrate, but inhibition of the growth of meso-tartrate-utilizing strains was demonstrable only in uninduced cultures in which the intracellular concentrations of meso-tartrate were high.
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PMID:Physiological basis for meso-tartrate sensitivity in some strains of Salmonella typhimurium. 699 76

The activity of enzymes of the citrate and glyoxylate cycles was comparatively assayed in the parent strain of Candida lipolytica producing citric and isocitric acids in a medium with hexadecane and in its two mutants one of which produced citrate and the other synthesized isocitrate. The enzyme activities were determined in the dynamics of the yeast growth: (a) in the exponential growth phase (no production of the acids); (b) in the lag phase (the beginning of the acid production); and (c) in the stationary phase (active production of the acids). All of the strains had a high activity of citrate synthase. The mutant producing citrate exhibited a high activity of isocitrate lyase and a low activity of aconitate hydratase, whereas the mutant producing isocitrate manifested a high activity of aconitate hydrase and a low activity of isocitrate dehydrogenase and isocitrate lyase. The data pertinent to a change in the enzyme activities due to the growth limitation with a nitrogen source and the production of the acids are considered for explaining the mechanism of overproduction of citric and isocitric acids from n-alkanes by yeast organisms.
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PMID:[Citrate and glyoxylate cycle enzyme activity in citric and isocitric acid synthesis by different strains of Candida lipolytica]. 707 Mar 6

The developmental and senescent patterns of a number of heart enzyme activities linked to energy metabolism have been studied in rats aged between 4 days and 21 months. A morphometric study of mitochondrial volume fractions and numbers has been also carried out. Developmental changes result in a rise of most mitochondrial enzymes (NADP+-isocitrate dehydrogenase, malic enzyme, succinate dehydrogenase, citrate synthase) and mitochondrial volume fractions. Exceptions are NAD+-isocitrate dehydrogenase, which declines from 4 days onwards, and NAD+-malate dehydrogenase, which declines and then rises over the same period. Senescent changes follow two different trends. While pyruvate kinase and those mitochondrial enzymes lying between citrate formation and isocitrate oxidation (citrate synthase, NADP+-and NAD+-isocitrate dehydrogenases) decline to some degree, mitochondrial succinate dehydrogenase and NAD+-malate dehydrogenase activities increase over the same period. This could point towards a partial impairment of Krebs cycle function, and a reduced energy-producing capacity in the aged rat heart.
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PMID:Comparison between developmental and senescent changes in enzyme activities linked to energy metabolism in rat heart. 726 74

Activities of citrate synthase, aconitase, NAD- and NADP-dependent isocitrate dehydrogenases were studied in mitochondria of heart and skeletal muscles of embryos and adult rabbits. Activity of these enzymes was some times lower in embryonal skeletal muscles as compared with the muscles of adult animals. Differences in activities of citrate synthase, aconitase and NADP-dependent isocitrate dehydrogenase were unsignificant in heart muscles of embryos and adult animals. Activity of NAD-dependent isocitrate dehydrogenase was distinctly higher in embryonal heart than in adult rabbits. The kinetic parameters enabled to conclude that in vitro regulation of NAD-dependent oxidation of isocitrate by substrate and activator ADP, characteristic for the enzyme from tissues of adult animals, was also found in embryos.
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PMID:[Enzymes of citrate and isocitrate conversion in the heart and skeletal muscle mitochondria of embryos and adult rabbits]. 742 88

Candida bombicola ATCC 22214 produces the glycolipid sophoroselipid when cultivated on a medium with glucose as the sole carbon source. Under phosphate-limiting conditions the product yield rises from 0.033 to 0.143 and the specific product formation rate rises from 0.004 h-1 to 0.007 h-1. Enhanced sophoroselipid synthesis is initiated by the decline of the specific activities of NAD- and NADP-dependent isocitrate dehydrogenase (EC 1.1.1.41 and 1.1.1.42) to 2% and 0% of the initial activities respectively. Constantly high specific activity of citrate synthase (EC 4.1.3.7) causes an accumulation of isocitrate and citrate in the mitochondria. Both acids are transported into the cytosol where citrate is cleaved by ATP: citrate lyase (EC 4.1.3.8) giving rise to acetyl-CoA, the precursor of fatty acid synthesis. The ATP: citrate lyase is unaffected by different energy charges; the apparent K(m) values for coenzyme A, ATP and citrate are 23 microM, 250 microM and 256 microM respectively. NADPH for fatty acid synthesis might be generated by further metabolism of oxaloacetate, the other product of the citrate-cleaving reaction, by oxidation of the isocitrate by the cytosolic NADP-dependent isocitrate dehydrogenase or via the hexose monophosphate shunt. A possible explanation for sophoroselipid formation during exponential growth is given.
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PMID:Initial steps of sophoroselipid biosynthesis by Candida bombicola ATCC 22214 grown on glucose. 898 37

Citrate synthase (citrate oxaloacetate-lyase, CoA-acetylating; EC 4.1.3.7, CS) was isolated and purified to homogeneity from a methylotrophic producer of polyhydroxybutyrate (PHB), Methylobacterium extorquens 15. The purification procedure includes streptomycin sulfate treatment of cell-free extract, ammonium sulfate fractionation, two steps of hydrophobic chromatography, and ion-exchange chromatography. The specific activity of the final enzyme preparation was 24 U/mg protein. The enzyme has apparent molecular weight 260 kD and consists of four 66-kD subunits. The enzyme shows a sigmoid saturation curve with CoASA (h = 1.3). Kinetic parameters are: K(m) = 84 microM for CoASA; K(m) = 12 microM for oxaloacetate; Vmax = 29.7 mumoles/min per mg protein. KCl at concentrations up to 80 mM activates the CS. ATP exerts a significant inhibitory effect on the enzyme activity, whereas NAD(P)H, isocitrate, alpha-ketoglutarate, ADP, acetoacetyl-CoA, glyoxylate, and glutamate have no influence. A possible role of the CS in coordinated control of CoASA transformation through the tricarboxylic acid cycle and PHB biosynthesis in this methylotroph is discussed.
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PMID:Purification and characterization of citrate synthase from Methylobacterium extorquens--a methylotrophic producer of polyhydroxybutyrate. 911 33

During a screen for respiration competent yeast mutants that were unable to grow with acetate as a carbon source, two idh2 cit1 double mutants were identified. These strains were defective in the catalytic subunit of the NAD(+)-dependent isocitrate dehydrogenase and citrate synthase of the tricarboxylic acid (TCA) cycle. The strains harboring the idh2 alleles from these strains had two unusual phenotypes. First, their growth on many nonfermentable carbon sources was much poorer than strains containing other idh2 mutations. Second, the poor growth phenotype could be suppressed by the presence of mutations in CIT1 and other genes encoding oxidative functions. Spontaneous suppressor mutants that restore fast growth on glycerol medium to strains harboring two idh2 alleles were isolated, and a large percentage of the suppressor mutations have been identified within the CIT1 gene and at several other loci. Elevated levels of several TCA cycle proteins were observed in these idh2 mutants that were not observed in the presence of suppressing cit1 mutations. Citrate and isocitrate concentrations were also elevated in the idh2 mutants, but probably not to toxic levels. Five idh2 alleles were sequenced to understand the defects of the two classes of mutations. Sequence analysis indicated that the poor growth phenotype was caused by the loss of Idh2p protein. Similarly, eight cit1 alleles were sequenced to understand their characteristics as glycerol suppressors of idh2. These and other studies indicate that any mutation within CIT1 was capable of suppressing the idh2 mutations. Several models to explain these interactions are discussed.
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PMID:Mutations in the IDH2 gene encoding the catalytic subunit of the yeast NAD+-dependent isocitrate dehydrogenase can be suppressed by mutations in the CIT1 gene encoding citrate synthase and other genes of oxidative metabolism. 924 91

Escherichia coli grew in a minimal medium on propionate as the sole carbon and energy source. Initially a lag phase of 4-7 days was observed. Cells adapted to propionate still required 1-2 days before growth commenced. Incorporation of (2-13C), (3-13C) or (2H3)propionate into alanine revealed by NMR that propionate was oxidized to pyruvate without randomisation of the carbon skeleton and excluded pathways in which the methyl group was transiently converted to a methylene group. Extracts of propionate-grown cells contained a specific enzyme that catalyses the condensation of propionyl-CoA with oxaloacetate, most probably to methylcitrate. The enzyme was purified and identified as the already-known citrate synthase II. By 2-D gel electrophoresis, the formation of a second propionate-specific enzyme with sequence similarities to isocitrate lyases was detected. The genes of both enzymes were located in a putative operon with high identities (at least 76% on the protein level) with the very recently discovered prp operon from Salmonella typhimurium. The results indicate that E. coli oxidises propionate to pyruvate via the methylcitrate cycle known from yeast. The 13C patterns of aspartate and glutamate are consistent with the further oxidation of pyruvate to acetyl-CoA. Oxaloacetate is predominantly generated via the glyoxylate cycle rather than by carboxylation of phosphoenolpyruvate.
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PMID:Propionate oxidation in Escherichia coli: evidence for operation of a methylcitrate cycle in bacteria. 932 32

A substrate cycle between citric acid cycle (CAC) intermediates isocitrate and 2-oxoglutarate, involving NAD+- and NADP+-linked isocitrate dehydrogenase (NAD-IDH and NADP-IDH, respectively) and mitochondrial transhydrogenase (H+-Thase), has recently been proposed. This cycle has been hypothesized to enhance mitochondrial respiratory control by increasing the sensitivity of NAD-IDH to its modulators and allowing for enhanced increases in flux through this step of the CAC during periods of increased ATP demand. The activities of the enzymes comprising the substrate cycle: NAD-IDH, forward and reverse NADP-IDH, and forward and reverse H+-Thase, along with the activity of a marker of mitochondrial content, citrate synthase (CS) were measured in mitochondria isolated from rabbit Type I and Type IIb muscles and in whole muscle homogenates, representing the various fiber types, from rats. In isolated rabbit muscle mitochondria, NAD-IDH had significantly higher (1.6 x ) activity in white muscle while forward NADP-IDH, forward and reverse H+-Thase, and CS all had significantly higher (1.2-1.6 x ) activities in red muscle. There was no difference in reverse NADP-IDH between fiber types. Similarly, in rat whole muscle enzyme activities normalized to CS, NAD-IDH had significantly higher activity in fast-twitch glycolytic (FG) fibers, while forward NADP-IDH and forward H+-Thase had significantly higher activities in slow-twitch oxidative (SO) fibers. These results suggest that differences in the activities of the substrate cycle enzymes between skeletal muscle fiber types could contribute to differences in respiratory control due to differential cycling rates and/or loci of control.
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PMID:Fiber-type-related differences in the enzymes of a proposed substrate cycle. 951 25

Key enzymes of the glyoxylate cycle, isocitrate lyase (ICL) and malate synthase (MS), have been detected in the liver of alloxan-treated rats. The activity of ICL in rat liver was 0.040 micromol/min/mg protein and the activity of MS was 0.022 micromol/min/mg protein. These enzymes were associated with the peroxisomal fraction. The activities of citrate synthase, malate synthase and malate dehydrogenase detected in the peroxisomal fraction were also increased by alloxan treatment. Isocitrate lyase was partially purified and displayed catalytic and regulatory properties similar to those of the enzyme isolated from the liver of starved rats (Popov, V.N. et al. (1996) FEBS Lett. 391, 87-90).
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PMID:Glyoxylate cycle enzymes are present in liver peroxisomes of alloxan-treated rats. 986 24


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