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)

The condensation of two propionyl-CoA units or a propionyl-CoA with acetyl-CoA is required for the synthesis of 2-methylvalerate or 2-methylbutyrate, respectively, two of the major fermentation products of Ascaris anaerobic muscle metabolism. An enzyme that preferentially catalyzes the condensation of propionyl-CoA rather than acetyl-CoA has been purified from the mitochondria of the parasitic intestinal nematode Ascaris lumbricoides var. suum. The purified enzyme is over 10 times more active with propionyl-CoA than with acetyl-CoA as substrate. It also catalyzes the coenzyme A-dependent hydrolysis of acetoacetyl-CoA at a rate four times higher than the propionyl-CoA condensation reaction. The purified Ascaris condensing enzyme preferentially forms the 2-methyl-branched-chain keto acids rather than the corresponding straight chain compounds. The native molecular weight of the purified enzyme was estimated to be 160,000 by gel filtration chromatography and 158,000 by high pressure liquid chromatography. The enzyme migrated as a single protein band with Mr 40,000 during sodium dodecyl sulfate-polyacrylamide electrophoresis, indicating that the enzyme is composed of four subunits of the same molecular weight. Chromatography on CM-sephadex resulted in the isolation of two separate peaks of activity, designated as A and B. Both A and B had the same molecular weight and subunit composition. However, they differed in their specific activities and isoelectric points. The pIs of condensing enzymes A and B were 7.6 and 8.4, respectively. Propionyl-CoA was the best substrate for the condensation reaction with both enzymes. However, the specific activity of enzyme B for both propionyl-CoA condensation (3.4 mumol/min/mg protein) and acetoacetyl-CoA thiolysis (13.8 mumol/min/mg protein) was 2.4 times higher than that obtained with enzyme A. Similarly, chromatography on phosphocellulose resolved the Ascaris condensing enzyme activity into one minor and two major peaks. All of these components had the same molecular weight and subunit composition, but differed in their specific activities. The two major phosphocellulose peaks cross-reacted immunologically when examined by the Ouchterlony double immunodiffusion technique. In addition, antiserum against the phosphocellulose most active form cross-reacted with forms A and B isolated by chromatography of the enzyme on CM-Sephadex, indicating that all forms were immunochemically related.
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PMID:Propionyl-CoA condensing enzyme from Ascaris muscle mitochondria. I. Isolation and characterization of multiple forms. 199 Sep 76

Citrate synthase which condenses acetyl-CoA and oxaloacetate to citrate was purified from Drosophila melanogaster. Some physicochemical as well as enzymatical properties were investigated. The optimum pH and temperature were pH 8.0-9.0 and 45 degrees C, respectively. The molecular weight of the enzyme was determined as 81,000 Da by gel filtration and the purified active enzyme consisted of two identical subunits which had a molecular mass of 48,700 on SDS-PAGE. Homogeneity of the purified enzyme was confirmed by SDS-PAGE and also by N-terminal amino acid sequence analysis. The Michaelis constants (K(m)) of the enzyme for acetyl-CoA and oxaloacetate were 6.7 microM and 3.1 microM, respectively. Kinetic studies showed that citrate synthase follows the concerted mechanism which forms a ternary complex. Propionyl-CoA, ATP, and intermediates of the TCA cycle, succinyl-CoA and alpha-ketoglutarate, behaved as inhibitors in vitro. Using pig and chicken heart enzymes for comparison, we found similarities at the N-terminal region. However, in the Ouchterlony immunodiffusion test, the polyclonal antibody raised against Drosophila citrate synthase did not show any crossreaction with pig, chicken or pigeon enzymes.
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PMID:Characterization of citrate synthase purified from Drosophila melanogaster. 938 45

Two separate citrate synthases from the extremely thermophilic bacterium Rhodothermus marinus have been identified and purified. One of the enzymes is a hexameric protein and is the first thermostable, hexameric citrate synthase to be isolated. The other is a dimeric enzyme, which is also thermostable but possesses both citrate synthase and 2-methyl citrate synthase activities. 2-Methyl citrate synthase uses propionyl-coenzyme A as one of its substrates and in Escherichia coli, for example, it has been implicated in the metabolism of propionate. However, no growth of R. marinus was observed using minimal medium with propionate as the sole carbon source, and both hexameric and dimeric enzymes were produced irrespective of whether propionate was included in the growth medium. The data are discussed with respect to the evolutionary relationships between the known hexameric and dimeric citrate synthases and 2-methyl citrate synthase.
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PMID:Rhodothermus marinus: a thermophilic bacterium producing dimeric and hexameric citrate synthase isoenzymes. 1187 62

Propionyl-CoA is an inhibitor of both primary and secondary metabolism in Aspergillus species and a functional methylcitrate cycle is essential for the efficient removal of this potentially toxic metabolite. Although the genomes of most sequenced fungal species appear to contain genes coding for enzymes of the methylcitrate cycle, experimental confirmation of pathway activity in filamentous fungi has only been provided for Aspergillus nidulans and Aspergillus fumigatus. In this study we demonstrate that pathogenic Fusarium species also possess a functional methylcitrate cycle. Fusarium solani appears highly adapted to saprophytic growth as it utilized propionate with high efficiency, whereas Fusarium verticillioides grew poorly on this carbon source. In order to elucidate the mechanisms of propionyl-CoA detoxification, we first identified the genes coding for methylcitrate synthase from both species. Despite sharing 96 % amino acid sequence identity, analysis of the two purified enzymes demonstrated that their biochemical properties differed in several respects. Both methylcitrate synthases exhibited low K(m) values for propionyl-CoA, but that of F. verticillioides displayed significantly higher citrate synthase activity and greater thermal stability. Activity determinations from cell-free extracts of F. solani revealed a strong methylcitrate synthase activity during growth on propionate and to a lesser extent on Casamino acids, whereas activity by F. verticillioides was highest on Casamino acids. Further phenotypic analysis confirmed that these biochemical differences were reflected in the different growth behaviour of the two species on propionyl-CoA-generating carbon sources.
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PMID:Methylcitrate cycle activation during adaptation of Fusarium solani and Fusarium verticillioides to propionyl-CoA-generating carbon sources. 1966 Nov 81

Citrate synthase is a central activity in carbon metabolism. It is required for the tricarboxylic acid (TCA) cycle, respiration, and the glyoxylate cycle. In Saccharomyces cerevisiae and Arabidopsis thaliana, there are mitochondrial and peroxisomal isoforms encoded by separate genes, while in Aspergillus nidulans, a single gene, citA, encodes a protein with predicted mitochondrial and peroxisomal targeting sequences (PTS). Deletion of citA results in poor growth on glucose but not on derepressing carbon sources, including those requiring the glyoxylate cycle. Growth on glucose is restored by a mutation in the creA carbon catabolite repressor gene. Methylcitrate synthase, required for propionyl-coenzyme A (CoA) metabolism, has previously been shown to have citrate synthase activity. We have been unable to construct the mcsADelta citADelta double mutant, and the expression of mcsA is subject to CreA-mediated carbon repression. Therefore, McsA can substitute for the loss of CitA activity. Deletion of citA does not affect conidiation or sexual development but results in delayed conidial germination as well as a complete loss of ascospores in fruiting bodies, which can be attributed to loss of meiosis. These defects are suppressed by the creA204 mutation, indicating that McsA activity can substitute for the loss of CitA. A mutation of the putative PTS1-encoding sequence in citA had no effect on carbon source utilization or development but did result in slower colony extension arising from single conidia or ascospores. CitA-green fluorescent protein (GFP) studies showed mitochondrial localization in conidia, ascospores, and hyphae. Peroxisomal localization was not detected. However, a very low and variable detection of punctate GFP fluorescence was sometimes observed in conidia germinated for 5 h when the mitochondrial targeting sequence was deleted.
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PMID:Metabolic and developmental effects resulting from deletion of the citA gene encoding citrate synthase in Aspergillus nidulans. 2017 36