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. The activities of citrate synthase and NAD+-linked and NADP+-linked isocitrate dehydrogenases were measured in nervous tissue from different animals in an attempt to provide more information about the citric acid cycle in this tissue. In higher animals the activities of citrate synthase are greater than the sum of activities of the isocitrate dehydrogenases, whereas they are similar in nervous tissues from the lower animals. This suggests that in higher animals the isocitrate dehydrogenase reaction is far-removed from equilibrium. If it is assumed that isocitrate dehydrogenase activities provide an indication of the maximum flux through the citric acid cycle, the maximum glycolytic capacity in nervous tissue is considerably greater than that of the cycle. This suggest that glycolysis can provide energy in excess of the aerobic capacity of the tissue. 2. The activities of glutamate dehydrogenase are high in most nervous tissues and the activities of aspartate aminotransferase are high in all nervous tissue investigated. However, the activities of alanine aminotransferase are low in all tissues except the ganglia of the waterbug and cockroach. In these insect tissues, anaerobic glycolysis may result in the formation of alanine rather than lactate.
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PMID:Activities of citrate synthase, NAD+-linked and NADP+-linked isocitrate dehydrogenases, glutamate dehydrogenase, aspartate aminotransferase and alanine aminotransferase in nervous tissues from vertebrates and invertebrates. 0 Oct 3

Male 13-lined ground squirrels induced to emerge from hibernation resumed feeding and gained weight. The weight gain was supported by increases in the levels of glucose 6-phosphate dehydrogenase, L-alanine aminotransferase and carnitine acetyltransferase in the liver. Maturation of the testis occurred in a period of about 16 days spanning the time of induced arousal. The testes of hibernating males were characterized by higher levels of L-alanine aminotransferase, glucose 6-phosphate dehydrogenase and 3-hydroxyacyl-CoA dehydrogenase than the testes of aroused males. Hexokinase, carnitine acetyltransferase and citrate synthase levels were similar in the testes of hibernating and aroused males. 3-Hydroxyacyl-CoA dehydrogenase was more active and L-alanine aminotransferase less active in ground squirrel sperm than in rat sperm.
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PMID:Changes in enzyme levels in the testis and liver of the 13-lined ground squirrel (spermophilus tridecemlineatus) at the time of arousal from hibernation. 7 Oct 81

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

The maximal rate (Vmax) of some mitochondrial enzyme activities related to energy transduction (citrate synthase, alpha-ketoglutarate dehydrogenase, malate dehydrogenase, succinate dehydrogenase, NADH-cytochrome c reductase, cytochrome oxidase) and amino acid metabolism (glutamate dehydrogenase, glutamate-pyruvate transaminase and glutamate-oxaloacetate transaminase) are evaluated in non synaptic ("free") and intrasynaptic mitochondria from brain hippocampus. The different mitochondrial populations were isolated from rat subjected to single i.p. treatment with saline solution, almitrine (30 mg/kg) and delta-yohimbine (10 mg/kg). In control rats, the mitochondrial populations exhibit different enzymatic patterns. Acute treatment with almitrine decreases cytochrome oxidase activity in intra-synaptic mitochondria, while acute treatment with delta-yohimbine decreases succinate dehydrogenase activity in both types of free and intra-synaptic mitochondria. NADH-cytochrome c reductase activity is also decreased by acute treatment with almitrine ("free" and "synaptic" mitochondria) and delta-yohimbine (synaptic mitochondria only).
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PMID:Factors involved in drug interference on enzyme activities of three mitochondrial populations from rat hippocampus. 180 34

Viable toadfish hepatocytes were separated into distinct subpopulations by gradient centrifugation. Although 3-5 density subpopulations were obtained for each fish, only two metabolically and enzymatically different subpopulations could be discerned. In all cases, hepatocytes with the lowest density (less than 1.040 g ml-1) were more oxidative in scope, as judged by the activities of mitochondrial enzymes (citrate synthase, aspartate aminotransferase, glutamate dehydrogenase); activities of these enzymes (normalised to cell protein) were on average two- to threefold higher than in subpopulations with higher densities. Lower-density hepatocytes also contained higher levels of the urea cycle enzymes arginase and ornithine carbamoyltransferase. The higher-density subpopulations showed no significant differences from each other in enzymatic activities. Compared with lower-density cells, these hepatocytes had higher activities of two cytosolic enzymes, malate dehydrogenase and glutathione-S-transferase. There was no distinct distribution pattern for alanine aminotransferase and glutamine synthetase. Despite generally lower oxidative enzyme content, higher-density hepatocytes were metabolically more active, with 2.5- to fourfold higher rates of urea synthesis, gluconeogenesis and oxidation of lactate. We conclude that, although the toadfish liver shows distinct enzymatic and metabolic heterogeneity, this heterogeneity is dissimilar to the zonation pattern in the livers of mammals, in that separated toadfish hepatocyte types did not appear to possess exclusive metabolic functions. Notably, all cells were capable of metabolic functions that are strictly localised in mammalian liver. In nitrogen metabolism, glutamine synthetase displays a distribution pattern commensurate with its unique metabolic function in the liver of the ureogenic toadfish. Further, all subpopulations possessed detoxification capabilities as indicated by high levels of glutathione-S-transferase, a 'phase II' conjugation enzyme.
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PMID:Metabolic and enzymatic heterogeneity in the liver of the ureogenic teleost Opsanus beta. 205 Nov 31

The early stages of insulin-dependent diabetes mellitus are characterized by a selective inability to secrete insulin in response to glucose, coupled to a better response to nonnutrient secretagogues. The deficient glucose response may be a result of the autoimmune process directed toward the beta-cells. Interleukin-1 (IL-1) has been suggested to be one possible mediator of immunological damage of the beta-cells. In the present study we characterized the sensitivity of beta-cells to different secretagogues after human recombinant IL-1 beta (rIL-1 beta) exposure. Furthermore, experiments were performed to clarify the biochemical mechanisms behind the defective insulin response observed in these islets. Rat pancreatic islets were isolated and kept in tissue culture (medium RPMI-1640 plus 10% calf serum) for 5 days. The islets were subsequently exposed to 60 pM human recombinant IL-1 beta during 48 h in the same culture conditions as above and examined immediately after IL-1 exposure. The rIL-1 beta-treated islets showed a marked reduction of glucose-stimulated insulin release. Stimulation with arginine plus different glucose concentrations, and leucine plus glutamine partially counteracted the rIL-1 beta-induced reduction of insulin release. The activities of the glycolytic enzymes hexokinase, glucokinase, and glyceraldehyde 3-phosphate dehydrogenase, were similar in control and IL-1-exposed islets. Treatment with IL-1 also did not impair the activities of NADH+- and NADPH+-dependent glutamate dehydrogenase, glutamate-aspartate transaminase, glutamate-alanine transaminase, citrate synthase, and NAD+-linked isocitrate dehydrogenase. The oxidation of D-[6-14C]glucose and L-[U-14C]leucine were decreased by 50% in IL-1-treated islets. Furthermore, there was a significant decrease in the ratios of [2-14C]pyruvate oxidation/[1-14C]pyruvate decarboxylation and L-[U-14C]leucine oxidation/L-[1-14C]leucine decarboxylation, indicating that IL-1 decreases the proportion of generated acetyl-coenzyme-A residues undergoing oxidation. However, in the presence of IL-1 there was a significant increase in L-[U-14C]glutamate oxidation. These combined observations suggest that exposure to IL-1 induces a preferential decrease in glucose-mediated insulin release and mitochondrial glucose metabolism. This mitochondrial dysfunction seems to reflect an impairment in proximal steps of the Krebs cycle. It is conceivable that the IL-1-induced suppression and shift in islet metabolism can be an explanation for the beta-cell insensitivity to glucose observed in the early phases of human and experimental insulin-dependent diabetes mellitus.
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PMID:Differential sensitivity to beta-cell secretagogues in cultured rat pancreatic islets exposed to human interleukin-1 beta. 266 6

Nonselective and beta 1-selective adrenergic antagonists were tested for their effects on enzymatic adaptation to exercise training in rats as follows: trained + placebo (TC); trained + propranolol (TP); trained + atenolol (TA); and corresponding sedentary groups, SC and SP. Trained rats ran 1 h/d at 26.8 m/min, 15% grade, 5 d/wk, 10 wk. Both beta-antagonists were given at doses that decreased exercise heart rates by 25%. Training increased skeletal muscle citrate synthase, cytochrome c oxidase (Cyt-Ox), carnitine palmitoyltransferase (CPT), beta-hydroxyacyl coenzyme A dehydrogenase, mitochondrial malate dehydrogenase (MDH), and alanine aminotransferase (ALT) activities significantly in the TC group, but not in TP. These enzyme activities, except Cyt-Ox and CPT, were also significantly increased in TA. Hepatic phosphoenolpyruvate carboxykinase activity did not alter with training or beta-blockade. Fructose 1,6-bisphosphatase activity was lower in TC than in SC, but unchanged in TP or TA. Hepatic mitochondrial MDH and ALT activities increased with training only in TC. It is concluded that beta 2-adrenergic mechanisms play an essential role in the training-induced enzymatic adaptation in skeletal muscle.
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PMID:Enzymatic adaptation to physical training under beta-blockade in the rat. Evidence of a beta 2-adrenergic mechanism in skeletal muscle. 287 82

Single fibers of rabbit fast-twitch tibialis anterior (TA) muscles were analyzed after continuous low-frequency stimulation for up to 8 wk. After 2-5 wk, every fiber showed higher levels of citrate synthase, hexokinase, and 3-oxoacid CoA-transferase than any control fiber; in some cases these levels were 2-10 times higher (well above any found even in the control soleus, a slow-twitch muscle). Average levels of malate dehydrogenase and alanine transaminase also rose dramatically, but peak single fiber levels were not much above the highest in controls. These differential effects confirm at the single fiber level that chronic stimulation can alter mitochondrial composition. Lactate dehydrogenase, fructose-bisphosphatase, and adenylate kinase declined to levels far below those of any control TA fiber, and, in the case of fructose-bisphosphatase, to within the activity range of control soleus fibers. According to their staining reaction for myofibrillar ATPase, TA fibers were initially 23% type IIA, and 74% type IIB, but by 5 wk these had been converted to a mixture of type I, IIA, and IIC fibers. At 5 wk, levels of lactate dehydrogenase, adenylate kinase, and malate dehydrogenase were characteristic of their (new) ATPase type, but 3-oxoacid CoA transferase had increased to levels 6-15 times higher than in control fibers of the same type.
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PMID:Chronic stimulation of mammalian muscle: enzyme changes in individual fibers. 302 Sep 91

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


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