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)

Maximal activities of rat skeletal muscle mitochondrial citrate synthase (CS), malate dehydrogenase (MDH), and alanine aminotransferase (ALT), as well as several other mitochondrial enzymes involved in various metabolic functions were significantly suppressed after a single bout of acute or exhaustive treadmill running. This enzymatic "down regulation" was maintained 24 and 48 h post exhaustion, especially in the untrained rats. Neither muscle cytosolic nor hepatic enzymes exhibited down regulation after exercise. Proteolysis was increased with exercise as assessed by the clearance of [3H]leucine previously incorporated into the proteins of the rats. Decreased CS, MDH, and ALT activities correlated with a significant loss of mitochondrial total protein sulfhydryl (r = 0.67, 0.68, 0.59, respectively, P less than 0.001) in untrained rats and both CS and MDH could be partially restored by incubation with dithiothreitol. Endurance-tested untrained and trained rats had significantly higher glutathione peroxidase (GPX) activity in both muscle mitochondria and cytosol which correlated significantly with endurance time (r = 0.70 and 0.74, respectively). It is concluded that enzymatic down regulation is not caused by proteolysis alone; i.e., peroxides and oxygen free radicals produced in prolonged exercise may alter the intramitochondrial redox state by oxidizing free thiols that may be required at active sites of these enzymes. Training may enhance the ability of the muscle to resist the toxic oxygen species by increasing GPX activity.
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PMID:Enzymatic down regulation with exercise in rat skeletal muscle. 336 59

The specific interaction of yeast citrate synthase with yeast mitochondrial inner membranes was characterized with respect to saturability of binding, pH optimum, effect of ionic strength, temperature response, and inhibition by oxalacetate. The binding ability of the inner membranes is inhibited by proteolysis and heat treatment, which implies that the membrane component(s) responsible for binding is a protein. A protein fraction from inner membranes when added to liposomes will bind citrate synthase. In addition, the binding of yeast fumarase, mitochondrial malate dehydrogenase, and cytosolic malate dehydrogenase to yeast inner membranes was examined. For these studies the yeast mitochondrial matrix enzymes, citrate synthase (from two types of yeast), malate dehydrogenase, and fumarase, as well as cytosolic malate dehydrogenase, were purified using rapid new techniques.
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PMID:The interaction of yeast citrate synthase with yeast mitochondrial inner membranes. 353 36

Activities of eight enzymes were measured in the sonic muscle of the gulf toadfish, Opsanus beta, to determine the metabolic poise of this unique tissue and to evaluate potential sex related differences in metabolism. In contrast to a prior study (Pennypacker et al., '85, J. Exp. Zool., 239: 259-264), we observed substantial activities of M4-lactate dehydrogenase, 333 to 482 units/g wet sonic muscle weight. This observation and the presence of high activities of other enzymes of glycolytic and anaerobic metabolism (pyruvate kinase and creatine phosphokinase) lead us to conclude that this tissue has high anaerobic capacity. Also in contrast to the observations of Pennypacker et al. ('85), we found that the activities of some enzymes indicative of aerobic metabolism are relatively low. For example, the activities of citrate synthase found in sonic muscle (1.5 to 2.7 units/g) are only slightly higher than values obtained for toadfish white skeletal muscle (1.2 units/g). The discrepancies between the results obtained by the two studies appear to be methodological ones. Lastly, significant differences in enzyme activities between males and females were observed for lactate dehydrogenase, malate dehydrogenase, and citrate synthase, and possible explanations for these differences are discussed.
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PMID:Reexamination of metabolic potential in the toadfish sonic muscle. 355 99

Formation of a bienzyme complex of pig heart mitochondrial malate dehydrogenase and citrate synthase in a buffered system is demonstrated by means of a covalently attached fluorescent probe to citrate synthase. Assuming 1:1 stoichiometry of the enzymes in the complex, an apparent dissociation constant of 10(-6) M was calculated from fluorescence anisotropy measurements. The effect of various metabolites on the interaction was tested. NAD+, oxalacetate, citrate, ATP, and L(-)- or D(+)-malate had no effect on the association of the two enzymes, whereas alpha-ketoglutarate increased and NADH decreased it. The interaction of mitochondrial citrate synthase with cytosolic malate dehydrogenase was found to be much weaker, whereas interaction of citrate synthase with another cytosolic enzyme, aldolase, could not be detected. In kinetic experiments, the activation of malate dehydrogenase by citrate synthase was observed. The effect of pyridine nucleotides and alpha-ketoglutarate is discussed in relation to the direction of the metabolic flow of oxalacetate.
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PMID:Quantitation of the interaction between citrate synthase and malate dehydrogenase. 357 Dec 48

An interest in both biochemical and clinical carnitine investigation has recently developed. A more complete and extensive study is obtained if acetyl-carnitine as well as carnitine are investigated. This research, using an improved and simplified method for carnitine and acetyl-carnitine determination in the same sample (1 ml) without radioisotopic tracer use, investigates if there are the same differences in their plasma levels at different times of the day. The sample was eluted in a chromatographic column (55 X 15 mm) containing Sephadex G-25M with phosphate buffer (25 mmol/l, pH 7.4). The fraction containing acetyl and free carnitine was divided and employed separately for two assays. The carnitine assay uses an enzymatic reaction catalyzed by carnitine acetyl-transferase (CAT) and measurements are carried out spectrophotometrically. The calibration curve shows r = 0.987 and sensitivity at 5 mumol/l (reference plasma values: 38 +/- 3 mumol/l in 9 subjects). The acetyl-carnitine assay is carried out concentrating the sample by lyophilization and then measuring the enzymatic coupled reactions catalyzed by CAT, malate dehydrogenase and citrate synthase fluorimetrically. The calibration curve gives r = 0.991 and sensitivity at 1.4 mumol/l (reference plasma values: 2.8 +/- 0.3 mumol/l in 9 subjects). Both assay methods are measured at the end point. The carnitine and acetyl-carnitine measured in the plasma of 6 normal subjects at different times of the day vary respectively from 28 to 37 mumol/l and from 1.1 to 5.2 mumol/l in agreement with plasma free fatty acid (FFA) variation from 230 to 779 microEq/l.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Plasma carnitine and acetyl-carnitine levels at different times of the day. 362 93

Studies by dynamic and total intensity light scattering, ultracentrifugation, electron microscopy, and chemical crosslinking on solutions of the pig heart mitochondrial enzymes, malate dehydrogenase and citrate synthase (separately and together) demonstrate that polyethylene glycol induces very large homoassociations of each enzyme, and still larger heteroenzyme complexes between these two enzymes in the solution phase. Specificity of this heteroassociation is indicated by the facts that heteroassociations with bovine serum albumin were not observed for either the mitochondrial dehydrogenase or the synthase or between cytosolic malate dehydrogenase and citrate synthase. The weight fraction of the enzymes in the mitochondrial dehydrogenase-synthase associated particles in the solution phase was less than 0.03% with the dilute conditions used in the dynamic light scattering measurements. Neither palmitoyl-CoA nor other solution conditions tested significantly increased this weight fraction of associated enzymes in the solution phase. Because of the extremely low solubility of the associated species, however, the majority of the enzymes can be precipitated as the heteroenzyme complex. This precipitation is a classical first-order transition in spite of the large particle sizes and broad size distribution. Ionic effects on the solubility of the heteroenzyme complex appear to be of general electrostatic nature. Polyethylene glycol was found to be more potent in precipitating this complex than dextrans, polyvinylpyrrolidones, ficoll, and beta-lactoglobulin.
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PMID:Polyethylene glycol-induced heteroassociation of malate dehydrogenase and citrate synthase. 366 37

DNA synthesis in nuclei and mitochondria purified from serum-supplemented rat glial cell cultures at different days after plating was studied. Furthermore in mitochondria, some enzymatic activities related to energy transduction (citrate synthase, malate dehydrogenase, total NADH-cytochrome c reductase, cytochrome oxidase and glutamate dehydrogenase) were measured. For DNA labeling [methyl-3H]thymidine was added to the culture medium at different days after plating. During the culture times studied the specific activity of total, nuclear, and mitochondrial DNA decreased from 8 days in vitro (DIV) to 21 DIV and increased at 30 DIV. The specific activity of nuclear DNA was always higher than that of mitochondrial DNA. The specific activity of the above mentioned mitochondrial enzymes increased from 8 DIV up to 21 DIV and decreased at 30 DIV, suggesting a relationship between the energy metabolism and the differentiation of glial cells in culture.
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PMID:Nuclear and mitochondrial DNA synthesis and energy metabolism in primary rat glial cell cultures. 373 66

In rat gastrocnemius muscle, the concentrations of glycolytic fuels, intermediates and end-products; Krebs cycle intermediates and related free amino acids; ammonia; energy store and mediators; and the energy charge potential were evaluated in normoxia or after repeated, alternate hypoxic and normoxic exposures (12 hr of hypoxia daily; for 5 days) with or without treatment with hopantenate (HOPA). Furthermore, in the crude extract and/or mitochondrial fraction the maximum rate (Vmax) of some muscular enzymes related to the anaerobic glycolytic pathway; the tricarboxylic acid cycle; and the electron transfer chain were evaluated. Hopantenate was administered daily at the dose of 250 mg.kg-1 i.p., for 5 days, 30 min before the beginning of the experimental normobaric hypoxia. The biochemical adaptation to intermittent normobaric hypoxic-normoxic exposures was characterized by the decrease of the muscular concentrations of citrate, alpha-ketoglutarate and glutamate, in absence of changes in the Vmax of the muscle enzymes related to energy transduction. In gastrocnemius muscle from hypoxic rats, by HOPA treatment, both citrate and alpha-ketoglutarate maintained normal values, aspartate decreased, while glutamate remained reduced to subnormal values. In the muscle from hypoxic animals, by hopantenate treatment the Vmax of the mitochondrial enzymes tested (citrate synthase, malate dehydrogenase, total NADH cytochrome c reductase, cytochrome oxidase) decreased in comparison with both hypoxic and normoxic untreated animals. This behaviour could be tentatively related to a mitochondrial sparing action concomitant with an intervention of the glutamate group of amino acids, even if the results do not allow a clear interpretation of the mechanism of HOPA action.
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PMID:Hopantenate interference on the adaptation of muscular energy metabolism to intermittent hypoxia. 375 4

3-Hydroxyacyl coenzyme A (CoA) dehydrogenase-binding protein was solubilized from inner mitochondrial membrane by using taurodeoxycholate at high ionic strength. The binding protein was isolated from the suspension using 3-hydroxyacyl-CoA dehydrogenase affinity chromatography. The protein eluted from the affinity column had a molecular weight of approximately 150,000, as determined by gel filtration. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the protein is a dimer consisting of 69,000 and 71,000 molecular weight subunits. The enzyme binding capacity of this protein was tested with a polyethylene glycol precipitation method: 0.5 mg of enzyme could be precipitated together with 1 mg of binding protein, showing that 1 mol of binding protein binds 1 mol of enzyme. This protein had no affinity toward malic dehydrogenase, citrate synthase, and fumarase. The approximately 2-fold increase in the 3-hydroxyacyl-CoA dehydrogenase activity when it was measured in the presence of the binding protein is additional evidence of enzyme-binding protein interaction. When incorporated into liposomes, the binding protein retained its ability to bind 3-hydroxyacyl-CoA dehydrogenase, but did not bind malic dehydrogenase, citrate synthase, and fumarase. These results suggest that the protein isolated by us has a specific function in anchoring a beta-oxidation enzyme to the matrix surface of the mitochondrial membrane.
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PMID:Isolation and characterization of 3-hydroxyacyl coenzyme A dehydrogenase-binding protein from pig heart inner mitochondrial membrane. 377 31

The maximal rate (Vmax) of some mitochondrial enzymatic activities related to the energy transduction (citrate synthase, malate dehydrogenase, NADH cytochrome c reductase as total, cytochrome oxidase) and amino acid metabolism (glutamate dehydrogenase) were evaluated in non-synaptic (free) and synaptic mitochondria from rat brain hippocampus. Three types of mitochondria were isolated from rats subjected to single i.m. treatment with L-acetylcarnitine (308 mg X kg-1) or to sub-chronic i.m. treatment with L-acetylcarnitine at three different dose levels (38; 154; 614 mg X kg-1, 5 days a week, for 4 weeks). With respect to the enzymatic pattern of three types of non-synaptic and synaptic mitochondria, in hippocampus a different maximal rate of both total NADH-cytochrome c reductase and cytochrome oxidase was observed, these activities being lower in "synaptic heavy" mitochondrial subfraction rather than that in both "free" and "synaptic light" ones. This confirms that in various types of brain mitochondria a different metabolic machinery exists. Acute treatment with L-acetylcarnitine decreased citrate synthase and glutamate dehydrogenase activities only in mitochondria obtained from synaptosomes. The sub-chronic treatment with L-acetylcarnitine decreased the activity of citrate synthase and total NADH-cytochrome c reductase activities only in the same type of mitochondria, i.e. synaptic mitochondria. Therefore in vivo administration of L-acetylcarnitine mainly affects some specific enzyme activities (suggesting a specific molecular trigger mode of action) of the intrasynaptic mitochondria (suggesting a specific subcellular trigger site of action).
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PMID:Action of L-acetylcarnitine on different cerebral mitochondrial populations from hippocampus. 396 36


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