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)

1. Percutaneous needle biopsies were obtained from six limb muscles in six horses before and during a training programme of 10 or 15 weeks designed to involve both aerobic and anaerobic work. In a subsequent detraining period, biopsies were also taken after 5 and 10 weeks. 2. Samples were analysed biochemically for enzyme activity of lactic dehydrogenase (LDH), creatine phosphokinase (CPK), aldolase (ALD), citrate synthase (CS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) and for glycogen content. Fibre typing was carried out histochemically before and 10 weeks after commencement of training. 3. There was a significant increase in the percentage of high myosin ATPase activity pH 9-4/high oxidative (FTH) fibres with a corresponding decrease in high myosin ATPase activity pH 9-4/low oxidative (FT) fibres and low myosin ATPase activity pH 9-4/high oxidative (ST) fibres after 10 weeks training. 4. During training, enzyme activities increased progressively but at different rates with an approximate twofold increase in all of the enzymes except CPK by the end of the training period. Changes in all the muscles studied were similar. Glycogen content increased by approximately 33% which was significant when all the muscles were considered together. 5. A decrease in enzyme activity occurred after 5 weeks detraining. However at 10 weeks a consistent but inexplicable increase in all enzyme levels, except CS again occurred. 6. It is concluded that training increased greatly the activity of enzymes involved in both aerobic and anaerobic metabolism.
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PMID:The effect of training and detraining on muscle composition in the horse. 14 28

Cell-free extracts of Rickettsia typhi were tested for activities of enzymes of the tricarboxylic acid cycle, of glutamate catabolism, and of glycolysis. The organisms were grown in the yolk sacs of chicken embryos, harvested shortly before the time of embryo death, purified by Renografin density gradient centrifugation, and ruptured in a French pressure cell. The following enzymatic activities were demonstrated: high levels of malate dehydrogenase (MDH), moderate levels of glutamate-oxaloacetate transaminase, glutamate, succinate, and isocitrate dehydrogenases, and citrate synthase, and low levels of glutamate-pyruvate transaminase. The specific activities of some of these enzymes were higher when the rickettsiae were harvested at a time of active proliferation, 3 to 4 days prior to embryo death. Rickettsial MDH was differentiated from host MDH by its migration pattern on polyacrylamide gel electrophoresis. The activities of MDH and two other dehydrogenases, demonstrable after the cells had been disrupted, were absent from purified, intact rickettsial preparations. No activity was detected for glucose-6-phosphate, 6-phosphogluconate, glyceraldehyde-3-phosphate, lactate dehydrogenases, phosphoglucose isomerase, fructoaldolase, or pyruvate kinase. Our results suggest that extracts of R. typhi that contain demonstrable enzymes involved in the catabolism of glutamate and tricarboxylic acid cycle intermediates, unlike Coxiella burnetti, lack detectable glycolytic activity.
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PMID:Enzymatic activities of cell-free extracts of Rickettsia typhi. 82 Jun 44

In recent years, evidence has been accumulating that metabolic pathways are organized in vivo as multienzyme clusters. Affinity electrophoresis proves to be an attractive in vitro method to further evidence specific associations between purified consecutive enzymes from the glycolytic pathway on the one hand, and from the citric acid cycle on the other hand. Our results support the hypothesis of cluster formation between the glycolytic enzymes aldolase, glyceraldehydephosphate dehydrogenase, and triosephosphate isomerase, and between the cycle enzymes fumarase, malate dehydrogenase, and citrate synthase. A model is presented to explain the possibility of regulation of the citric acid cycle by varying enzyme-enzyme associations between the latter three enzymes, in response to changing local intramitochondrial ATP/ADP ratios.
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PMID:Clustering of sequential enzymes in the glycolytic pathway and the citric acid cycle. 239 1

A method for a 50-60-fold purification of a cysteine proteinase from trophozoites of Entamoeba histolytica using 35-80% ammonium sulphate fractionation, gel chromatography on Sephadex G-75, and preparative isoelectric focusing is described. The enzyme was examined for its proteolytic potencies towards native enzyme substrates. The amebic proteinase directly inactivates aldolase and glyceraldehyde-3-phosphate dehydrogenase from rabbit muscle as well as glucose-6-phosphate dehydrogenase from yeast. The inactivation of citrate synthase from porcine heart proceeds rather slowly, whereas malate dehydrogenase from porcine heart is not affected by the amebic proteinase under the condition used. With the exception of aldolase all inactivated enzyme substrates have been cleaved by limited proteolyses yielding major cleavage products. The inactivation of aldolase probably functions by the release of a small segment from a terminus being essential for aldolase activity.
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PMID:Cysteine proteinase of Entamoeba histolytica. I. Partial purification and action on different enzymes. 287 Apr 30

To evaluate the participation of proteins derived from mitochondrial genes in the adaptive response of skeletal muscle to increased contractile activity, we administered chloramphenicol (CAP; 200-1,000 mg.kg-1.day-1), an inhibitor of translation from mitochondrial ribosomes, to adult rabbits undergoing electrical stimulation of the tibialis anterior muscle of one hind limb. In unmedicated animals, 10 days of electrical stimulation increased maximum velocity (Vmax) of cytochrome oxidase and citrate synthase by 214 +/- 17 and 201 +/- 16% (P less than 0.01). In a dose-dependent manner, CAP abolished activity-induced increases in cytochrome oxidase Vmax, suggesting that augmented mitochondrial protein synthesis is necessary for the adaptive response of enzymes that require protein subunits encoded by mitochondrial genes. However, CAP failed to inhibit activity-induced changes in Vmax of enzymes derived exclusively from nuclear genes (citrate synthase and aldolase). CAP also failed to inhibit activity-induced increases in mRNA transcribed from the nuclear genes encoding beta-F1 ATPase or myoglobin, or from the mitochondrial genes encoding 12S rRNA, 16S rRNA, or cytochrome b. These latter findings suggest that mitochondrial translation products do not participate in pretranslational regulation of these nuclear or mitochondrial genes in response to changes in contractile activity of skeletal muscle.
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PMID:Effects of inhibition of mitochondrial protein synthesis in skeletal muscle. 289 13

Eleven patients diagnosed and treated for congestive cardiomyopathy (COCM) of unknown aetiology, and another 10 patients, with congestive alcoholic heart muscle disease (ACOCM) were studied. Muscle biopsy samples were obtained from the vastus lateralis (VL) and the gastrocnemius (G) muscles. In part of the sample muscle the fibre pattern was classified by means of ATPase activity staining, a technique based on the pH lability of the fibres concerned. Fibre typing and area measurements were carried out by light microscope. The other part of the sample was used as muscle homogenate of which the Ca2+-activated ATPase activity as well as citrate synthetase (CS) and aldolase activities were measured. No significant difference was found in these enzyme activities between the two groups of patients. The proportion of the slow twitch (ST) fibres in the VL, mainly in the patients with ACOCM, was lower as compared to data for healthy subjects. A similar tendency was revealed for G. In both muscles tested, the area of ST fibres was smaller in the ACOCM group. The fast twitch (FT) fibre area proved to be slightly different in the two groups of subjects tested. Occurrence of degenerative signs in the histological tests was higher in the ACOCM than in the COCM group. It was concluded that differences in the skeletal muscles of patients with ACOCM and COCM may primarily account for the alcoholism. The disease of the heart muscle has little effect on the function of skeletal muscle. Even so, a low amount or lack of physical activity may have an unfavourable influence on the skeletal muscles of patients with heart muscle disease.
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PMID:Skeletal muscle biopsy studies of cardiac patients. 296 68

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

In three groups of healthy young subjects (n = 33; mean ages 6.4, 13.5, 17.1 years), muscle enzyme activities (creatine kinase, hexose phosphate isomerase, aldolase, pyruvate kinase, lactate dehydrogenase, citrate synthase, fumarase) of the vastus lateralis muscle were investigated to show age-dependent variations. A significant age-dependent increase in aldolase (P less than 0.05) and pyruvate kinase (P less than 0.01) activity and a decrease in fumarase activity (P less than 0.01) were computed. In relation to the age-dependent variation, maximum LDH activities could be measured at an age of 12-14 years; significantly decreased activities of the glycolytic enzymes could only be found in the youngest group.
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PMID:Skeletal muscle enzyme activities in healthy young subjects. 375 6

Crude extracts of both vegetative cells and glycerol-induced microcysts of Myxococcus xanthus contained the following enzyme activities: phosphofructokinase, phosphoglucoisomerase, fructose-1,6-diphosphatase, fructosediphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase, phosphopyruvate carboxylase, citrate synthase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, malate dehydrogenase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphoglucomutase, and uridine diphosphate glucose pyrophosphorylase. With the exception of isocitrate dehydrogenase, which was present at a fivefold higher concentration in microcysts, all activities in extracts from both types of cells were essentially equal. Hexokinase and pyruvate kinase could not be detected in extracts from either type of cell. Microcysts metabolized acetate at a lower rate than did vegetative cells. Most of this decrease was reflected in a substantial decrease in ability of microcysts to oxidize acetate to CO(2). In addition, microcysts and vegetative cells showed a different distribution of (14)C-label from incorporated acetate.
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PMID:Comparative intermediary metabolism of vegetative cells and microcysts of Myxococcus xanthus. 430 96

Cells of the aerotolerant anaerobe Giardia lamblia respire in the presence of oxygen. Endogenous respiration is stimulated by glucose but not by other carbohydrates and Krebs cycle intermediates. Endogenous and glucose-stimulated respiration are insensitive to cyanide, malonate, and 2,4-dinitrophenol, but are inhibited by atabrin and iodoacetamide. G. lamblia produces ethanol, acetate and CO2 both aerobically and anaerobically either from endogenous reserves or exogenous glucose. Molecular hydrogen is not produced. The following enzyme activities were detected in homogenates: hexokinase, fructose-biphosphate aldolase, pyruvate kinase, phosphoenolpyruvate carboxykinase, malate dehydrogenase, malate dehydrogenase (decarboxylating), pyruvate synthase, acetyl-CoA synthetase, alcohol dehydrogenase (NADP+), NADH dehydrogenase, NADPH dehydrogenase, NADPH oxidoreductase and superoxide dismutase. The enzymes of energy and carbohydrate metabolism are nonsedimentable (109 000 x g for 30 min). Activities of lactate dehydrogenase, hydrogenase, phosphate acetyltransferase, acetate kinase, citrate synthase, succinate dehydrogenase, fumarate hydratase and catalase were below the limits of detection. The results suggest the occurrence of glycolysis, energy production by substrate level phosphorylation and a flavin, iron-sulfur protein mediated electron transport system as well as the absence of cytochrome mediated oxidative phosphorylation and functional Krebs cycle.
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PMID:Energy metabolism of the anaerobic protozoon Giardia lamblia. 610 7


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