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 activity of branched-chain aminotransferase in mitochondria isolated from rat tissues was examined, and the mitochondrial contribution to total tissue branched-chain aminotransferase activity was calculated using the mitochondrial marker enzyme citrate synthase. Mitochondrial aminotransferase activity was highest in heart followed by skeletal muscle, kidney and brain. In heart muscle all of the aminotransferase activity was accounted for by the mitochondrial fraction. Activity was found to be mitochondrial in skeletal muscle with high red fiber content and also in kidney cortex. Activity was predominantly cytosolic in brain and muscles with high white fiber composition. Thus, the distribution of branched-chain aminotransferase activity in skeletal muscle was dependent on fiber type. No branched-chain aminotransferase activity was detected in liver mitochondria, and in liver tissue activity was too low to be relevant at physiological concentrations of branched-chain amino acids. Within a tissue, regardless of the subcellular distribution of aminotransferase activity, the relative rates of transamination with subsaturating or "saturating" concentrations of KIV or isoleucine were similar. Finally, amino acid preference was also similar within a tissue, but not necessarily between or among different tissues.
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PMID:Subcellular distribution of branched-chain aminotransferase activity in rat tissues. 321 76

1. The effects of 2-oxo-4-methylpentanoate, 2-oxo-3-methylbutanoate and 2-oxo-3-methylpentanoate on the activity of pyruvate dehydrogenase (EC 1.2.4.1), citrate synthase (EC 4.1.3.7), acetyl-CoA carboxylase, (EC 6.4.1.2) and fatty acid synthetase derived from the brains of 14-day-old rats were investigated. 2. The pyruvate dehydrogenase enzyme activity was competitively inhibited by 2-oxo-3-methylbutanoate with respect to pyruvate with a K(i) of 2.04mm but was unaffected by 2-oxo-4-methylpentanoate or 2-oxo-3-methylpentanoate. 3. The citrate synthase activity was inhibited competitively (with respect to acetyl-CoA) by 2-oxo-4-methylpentanoate (K(i)~7.2mm) and 2-oxo-3-methylbutanoate (K(i)~14.9mm) but not by 2-oxo-3-methylpentanoate. 4. The acetyl-CoA carboxylase activity was not inhibited significantly by any of the 2-oxo acids investigated. 5. The fatty acid synthetase activity was competitively inhibited (with respect to acetyl-CoA) by 2-oxo-4-methylpentanoate (K(i)~930mum) and 2-oxo-3-methylpentanoate (K(i)~3.45mm) but not by 2-oxo-3-methylbutanoate. 6. Preliminary experiments indicate that 2-oxo-4-methylpentanoate and 2-oxo-3-phenylpropionate (phenylpyruvate) significantly inhibit the ability of intact brain mitochondria from 14-day-old rats to oxidize pyruvate. 7. The results are discussed with reference to phenylketonuria and maple-syrup-urine disease. A biochemical mechanism is proposed to explain the characteristics of these diseases.
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PMID:Differential effects of 2-oxo acids on pyruvate utilization and fatty acid synthesis in rat brain. 415 48

Oxidation rates of palmitate (total and antimycin-insensitive), pyruvate, leucine, 4-methyl-2-oxopentanoate and 3-methyl-2-oxobutanoate and activities of two mitochondrial marker enzymes (citrate synthase and cytochrome c oxidase) were assayed in liver and muscle homogenates of fed, clofibrate-treated and 18 hr-starved rats. Significant alterations in the clofibrate-treated and the starved rats were predominantly observed in the liver. Clofibrate feeding increased antimycin-insensitive (peroxisomal) and antimycin-sensitive (mitochondrial) palmitate oxidation and 4-methyl-2-oxopentanoate and pyruvate oxidation in liver. In muscle, only the activities of citrate synthase and cytochrome c oxidase were slightly decreased. Short starvation increased antimycin-sensitive palmitate and 4-methyl-2-oxopentanoate oxidation in liver. The rates of pyruvate and 3-methyl-2-oxobutanoate oxidation were decreased in muscle homogenates. Results suggest that myopathic phenomena observed after chronic clofibrate administration are not related to changes in the capacity of oxidative metabolism of muscle.
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PMID:Effect of clofibrate feeding on palmitate and branched-chain 2-oxo acid oxidation in rat liver and muscle. 631 Dec 21