Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.3.1 (citrate synthase)
 4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using the selective membrane-solubilizing properties of digitonin and a rapid centrifugation method to separate cytoplasmic and mitochondrial components, the metabolic state of mitochondrial glutathione was investigated in isolated rat hepatocytes. Two pools of GSH were released from hepatocytes incubated with increasing concentrations of digitonin. The largest pool (about 85% of cellular total) was released simultaneously with lactate dehydrogenase, the other pool with citrate synthase, indicating cytoplasmic and mitochondrial locations, respectively. The t1/2 of the mitochondrial pool was estimated by linear regression analysis to be 30 +/- 3 h, while the cytoplasmic pool turned over with a t1/2 of about 2 +/- 0.1 h. The rate of incorporation of [35S]methionine or cysteine into the cytoplasmic pool of GSH, when corrected for turnover, was 15 times greater than into the mitochondrial pool. Mitochondrial GSH was not depleted after 60 min with 185 microM diethyl maleate with or without 75 microM bis-1,3-(2-chloroethyl)-1-nitrosourea, a specific inhibitor of glutathione reductase, whereas cytoplasmic levels were reduced to 40% and 10% of control values, respectively. In vivo experiments, using L-(alpha S,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid to inactive gamma-glutamyl transpeptidase to limit cysteine formation from plasma GSH, demonstrated that in the absence of label reincorporation, liver glutathione exhibits a biphasic turnover. The rates of decay (half-lives) and percentages of total GSH under these conditions correlate well with the half-lives and pool distribution seen in the mitochondrial and cytoplasmic populations of GSH found in the isolated hepatocytes.
 ...
PMID:Status of the mitochondrial pool of glutathione in the isolated hepatocyte. 706 8

Cerulenin, an antifungal antibiotic produced by Cephalosporium caerulens, is a potent inhibitor of fatty acid synthase in various organisms, including Saccharomyces cerevisiae. The antibiotic inhibits the enzyme by binding covalently to the active center cysteine of the condensing enzyme domain. We isolated 12 cerulenin-resistant mutants of S. cerevisiae following treatment with ethyl methanesulfonate. The mechanism of cerulenin resistance in one of the mutants, KNCR-1, was studied. Growth of the mutant was over 20 times more resistant to cerulenin than that of the wild-type strain. Tetrad analysis suggested that all mutants mapped at the same locus, FAS2, the gene encoding the alpha subunit of the fatty acid synthase. The isolated fatty acid synthase, purified from the mutant KNCR-1, was highly resistant to cerulenin. The cerulenin concentration causing 50% inhibition (IC50) of the enzyme activity was measured to be 400 microM, whereas the IC50 value was 15 microM for the enzyme isolated from the wild-type strain, indicating a 30-fold increase in resistance to cerulenin. The FAS2 gene was cloned from the mutant. Sequence replacement experiments suggested that an 0.8 kb EcoRV-HindIII fragment closely correlated with cerulenin resistance. Sequence analysis of this region revealed that the GGT codon encoding Gly-1257 of the FAS2 gene was altered to AGT in the mutant, resulting in the codon for Ser. Furthermore, a recombinant FAS2 gene, in which the 0.8 Kb EcoRV-HindIII fragment of the wild-type FAS2 gene was replaced with the same region from the mutant, when introduced into FAS2-defective S. cerevisiae complemented the FAS2 phenotype and showed cerulenin resistance.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Cerulenin-resistant mutants of Saccharomyces cerevisiae with an altered fatty acid synthase gene. 804 67

The effect of endurance training on glutathione (GSH) status and antioxidant enzyme system was investigated in skeletal muscle, heart, and liver of female Sprague-Dawley rats pair fed an isocaloric diet. Ten weeks of treadmill training (25 m/min, 10% grade for 2 h/day, 5 days/wk) increased citrate synthase activity in the deep vastus lateralis (DVL) and soleus muscles by 79 and 39%, respectively (P < 0.01), but not in the heart or liver. In DVL, GSH content was increased 33% (P < 0.05) with training, accompanied by a 64% (P < 0.05) increase in glutamate content but no change in cysteine. Trained rats showed a 62 and 27% higher GSH peroxidase (GPX) and superoxide dismutase (SOD) activity, respectively (P < 0.05), in DVL compared with control rats. In contrast, GSH content and glutathione reductase (GR) activity in soleus declined with training (P < 0.05), whereas activities of GPX and SOD remained unchanged. Training did not alter GSH status in the liver or plasma but significantly decreased the GSH-to glutathione disulfide ratio in the heart. In addition, GR activity in the liver and GSH sulfur-transferase activity in the heart and DVL were significantly lower in the trained vs control rats DVL muscle had threefold higher gamma-glutamyl transpeptidase activity compared with other tissues; however no significant alteration was observed in the activity of gamma-glutamyltranspeptidase or gamma-glutamylcysteine synthetase in the liver, heart, or skeletal muscle. These data indicate that endurance training can cause tissue- and muscle fiber-specific adaptation of antioxidant systems and that GSH homeostasis in extrahepatic tissues may be determined by utilization and uptake of GSH via the gamma-glutamyl cycle.
 ...
PMID:Adaptations of glutathione antioxidant system to endurance training are tissue and muscle fiber specific. 903 30