Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.1.1.41 (isocitrate dehydrogenase)
 3,101 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The isolation is described of pure cultures of three non-methane-utilizing methylotrophic bacteria which, together with the previously described Bacillus PM6, have a very limited range of growth substrates; these organisms are designated "restricted facultative' methylotrophs. Two of these isolates, W6A and W3A1, grow only on glucose out of 50 non-C1 compounds tested, whereas the third isolate S2A1 and Bacillus PM6 grow on betaine, glucose, gluconate, alanine, glutamate, citrate and nutrient agar, but not on any of a further 56 non-C1 compounds. Crude sonic extracts of trimethylamine-grown and glucose-grown W6A and W3A1 isolates, and of trimethylamine-grown C2A1 (an obligate methylotroph) contain (i) no detectable 2-oxogltarate dehydrogenase activity, (ii) very low or zero specific activities of succinate dehydrogenase and succinyl-CoA synthetase and (iii) NAD+-dependent isocitrate dehydrogenase activity. Extracts of trimethylamine-grown PM6 and S2A1 methylotrophs have (i) very low 2-oxoglutarate dehydrogenase specific activities, (ii) comparatively high specific activities of succinate dehydrogenase, malate dehydrogenase and succinyl-CoA synthetase and (iii) NADP+-dependent isocitrate dehydrogenase activity but no NAD+-dependent isocitrate dehydrogenase activity. The activities of most of these enzymes are increased during growth on glucose, alanine, glutamate or citrate, but only very low 2-oxoglutarate dehydrogenase activities are present under all growth conditions. The restricted facultative methylotrophs grow on certain non-C1 compounds in the absence of 2-oxoglutarate dehydrogenase and, in some cases, of other enzymes of the tricarboxylic acid cycle; these lesions cannot therefore be the sole cause of obligate methylotrophy.
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PMID:Tricarboxylic acid-cycle and related enzymes in restricted facultative methylotrophs. 0 Sep 91

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

The effect of a single interaperitoneal injection (6 mg/kg body weight) of aflatoxin B1 in propylene glycol on pyridine nucleotides and NDP linked dehydrogenases was studied 24 h after administration of the toxin. The liver showed a decrease in total proteins and pyridine nucleotides though levels of NADP and NADPH remained unchanged. Levels of NAD and NADH were decreased. The activities of hepatic of hwpRIX of hepatic malate dehydrogenase (MDH) and isocitrate dehydrogenase (ICDH) were not altered though ICDH showed an increase when expressed on protein basis. However, there was a significance decrease in the activity of combined HMP dehydrogenases. Adipose tissue showed increased activities of the HMP dehydrogenasess.
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PMID:Effect of aflatoxin B1 on pyridine nucleotides and NADP linked dehydrogenases. 0 75

Pig heart NAD-specific isocitrate dehydrogenase is inactivated by reaction with iodoacetate at pH 6.0. Loss of activity can be attributed to the formation of 1-2 mol of carboxymethyl-cysteine per peptide chain. The rate of inactivation is markedly decreased by the combined addition of Mn2+ and isocitrate, but not by alpha-ketoglutarate, the coenzyme NAD or the allosteric activator ADP. The substrate concentration dependence of the decreased rate of inactivation yields a dissociation constant of 1.6 mM for the enzyme-manganous-dibasic isocitrate complex, a value that is 50 times higher than the Km for this substrate. This result suggests that in protecting the enzyme against iodoacetate, isocitrate may bind to a region distinct from the catalytic site. Isocitrate and Mn2+ also prevent thermal denaturation, with an affinity for the enzyme close to that observed for the iodoacetate-sensitive site. The alkylatable cysteine residues may contribute to a manganous-isocitrate binding site which is responsible for stabilizing an active conformation of the enzyme.
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PMID:Alkylation of cysteinyl residues of pig heart NAD-specific isocitrate dehydrogenase by iodoacetate. 0 25

1. The activities of citrate synthase, NAD+-linked and NADP+-linked isocitrate dehydrogenase were measured in muscles from a large number of animals, in order to provide some indication of the importance of the citric acid cycle in these muscles. According to the differences in enzyme activities, the muscles can be divided into three classes. First, in a number of both vertebrate and invertebrate muscles, the activities of all three enzymes are very low. It is suggested that either the muscles use energy at a very low rate or they rely largely on anaerobic glycolysis for higher rates of energy formation. Second, most insect flight muscles contain high activities of citrate synthase and NAD+-linked isocitrate dehydrogenase, but the activities of the NADP+-linked enzyme are very low. The high activities indicate the dependence of insect flight on energy generated via the citric acid cycle. The flight muscles of the beetles investigated contain high activities of both isocitrate dehydrogenases. Third, other muscles of both vertebrates and invertebrates contain high activities of citrate synthase and NADP+-liniked isocitrate dehydrogenase. Many, if not all, of these muscles are capable of sustained periods of mechanical activity (e.g. heart muscle, pectoral muscles of some birds). Consequently, to support this activity fuel must be supplied continually to the muscle via the circulatory system which, in most animals, also transports oxygen so that energy can be generated by complete oxidation of the fuel. It is suggested that the low activities of NAD+-linked isocitrate dehydrogenase in these muscles may be involved in oxidation of isocitrate in the cycle when the muscles are at rest. 2. A comparison of the maximal activities of the enzymes with the maximal flux through the cycle suggests that, in insect flight muscle, NAD+-linked isocitrate dehydrogenase catalyses a non-equilibrium reaction and citrate synthease catalyses a near-equilibrium reaction. In other muscles, the enzyme-activity data suggest that both citrate synthase and the isocitrate dehydrogenase reactions are near-equilibrium.
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PMID:Activities of citrate synthase and NAD+-linked and NADP+-linked isocitrate dehydrogenase in muscle from vertebrates and invertebrates. 0 36

Mitochondrial preparations isolated from rat ventral prostate were capable of oxidizing isocitrate by way of NADP isocitrate dehydrogenase (NADP-IDH) and NAD-IDH. NAD-IDH activity required ADP for activation. The pH responses for NAD-IDH and NADP-IDH were quite different. The results indicated that two different enzymes were involved in the NAD- and NADP-IDH activities. Indirect evidence indicated that NADPH-NAD transhydrogenase activity might also be involved in the mitochondrial pathway for isocitrate oxidation. NADP-IDH activity was significantly greater than NAD-IDH activity. The oxidation of isocitrate through IDH activity was coupled to the cytochrome system by NADPH- and NADH-cytochrome c reductase activities. Citrate, via isocitrate, oxidation proceeded at a much slower rate suggesting that aconitase activity could be limiting in the oxidation of citrate. In comparison to other tissues, the prostate oxidative enzyme activities are considerably lower. The results suggest that the accumulation of high prostate citrate levels is not due to a limitation imposed by a lack of IDH activity in prostate mitochondria.
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PMID:Mitochondrial isocitrate dehydrogenase and isocitrate oxidation of rat ventral prostate. 1 37

Azotobacter beijerinckii was grown in ammonia-free glucose/mineral salts media in chemostat culture under oxygen or nitrogen limitation. Selected enzymes of the tricarboxylic acid cycle and poly-beta-hydroxybutyrate metabolism were monitored in relation to oxygen supply for both steady and transition states. Two dissolved oxygen concentrations were used for the nitrogen-limited steady state to investigate the possible effects of respiratory protection of nitrogenase on these enzymes. The levels of NADH oxidase, isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase increased markedly on relaxation of oxygen limitation while pyruvate dehydrogenase and citrate synthase were relatively unaffected. beta-Ketothiolase and acetoacetyl-CoA reductase levels decreased as oxygen limitation was relaxed. Respiratory activity, as measured by the QO2 value, increased with oxygen supply rate. Imposition of oxygen limitation on a nitrogen-limited culture caused an immediate increase in the NADH/NAD ratio but this rapidly readjusted to its previous steady-state value. These changes are discussed in relation to respiratory protection of nitrogenase and poly-beta-hydroxybutyrate metabolism in A. beijerinckii.
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PMID:Regulation of the tricarboxylic acid cycle and poly-beta-hydroxybutyrate metabolism in Azotobacter beijerinckii grown under nitrogen or oxygen limitation. 1 43

The effect of dietary DL-ethionine and/or DL-methionine on egg laying, and activities of some NAD linked-dehydrogenases and NADPH-producing enzymes in liver of Japanese quail, Coturnix coturnix japonica was investigated. A 0.30% DL-ethionine plus 0.30% DL-methionine supplemented diet reversed partially the egg laying inhibited by the diet with 0.30% DL-ethionine alone. No inhibitory effect on egg laying was observed for the diet supplemented with 0.30% DL-methionine alone. In marked contrast to the decreased activity of L-glycerol 3-phosphate dehydrogenase and malate dehydrogenase, significantly increased activity of lactate dehydrogenase was obtained for quail fed the DL-ethionine, and the DL-ethionine plus the DL-methionine supplemented diet, respectively. No marked changes in activities of these three dehydrogenases were obtained for quail fed the diet supplemented with DL-methionine alone. Although decreased activity was observed for all of the four NADPH-producing enzymes in quail fed the diet supplemented with DL-ethionine alone, the DL-ethionine plus DL-methionine, the smallest decrease was obtained for NADP-isocitrate dehydrogenase. The diet supplemented with DL-methionine alone induced markedly the respective activity of malic enzyme and glucose 6-phosphate dehydrogenase. These results indicate a relatively important function of NADP-isocitrate dehydrogenase for NADPH-production even under DL-ethionine toxicity and suggest complicated relationships between egg production and activities of enzymes associated with carbohydrate and lipid metabolism in quail liver.
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PMID:Effect of dietary DL-ethionine and/or DL-methionine on egg laying and activities of some cytoplasmic NAD linked-dehydrogenases and NADPH-producing enzymes in liver of Japanese quail, Coturnix coturnix japonica. 1

We have studied the isocitrate dehydrogenase of Tetrahymena pyriformis. This enzyme is able to utilize both NAD and NADP, but kinetic studies suggest that the enzymatic activity with NAD is not of physiological signifance. Some of the factors that might regualte the NADP-dependent isocitrate dehydrogenase were also studied. This enzyme has an absolute requirement for divalent cations; Mg,+ and Mn2+ will serve as cofactors but the latter is more effective than the former. It is known that this enzyme is subject to a concerted inhibition by oxaloacetate and glyoxylate. Either glyoxylate or oxaloacetate alone also are capable of inhibiting the enzyme although higher concentrations are required. We have found concerted inhibition also for the NAD-dependent isocitrate dehydrogenase from rat liver and yeast. The activity of the Tetrahymena pyriformis enzyme is inhibited by NADPH. This inhibition is competitive with NADP. The Ki and Km values are, respectively, 20 micrometers and 18 micrometers.
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PMID:Isocitrate dehydrogenase of Tetrahymena pyriformis. 2 34

The changes in the rates of citrate biosynthesis and utilization in rat brain, liver, kidney and heart, produced by hypoxia, action of 2,4-DNP and thyreotoxicosis, were compared with changes of some regulatory parameters under the same conditions. The comparison of citrate-synthase activities, citrate levels in tissues and 14C-incorporation from different precursors into citric acid permitted us to establish that the biosynthesis of citrate in brain was more intensive than in other tissues studied. The main source of acetyl-CoA for citrate-synthase reaction in brain is the oxidation of pyruvate. The ratio of adenine nucleotides plays an important role in the control of citrate-synthase activity in brain, where the oxaloacetate control is not as significant as in liver. NAD-specific isocitrate dehydrogenase reaction was found to be the dominant pathway for citrate oxidation in brain: more than 60 percent of brain citrate were oxidized by NAD-ICDH, while less than 10 percent of citric acid were utilized by this enzyme in other tissues studied. The existance of an adenine nucleotide control of NAD-ICDH activity in brain may be an additional mechanism for the regulation of the first steps of energy metabolism in brain.
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PMID:[Mechanisms regulating citric acid metabolism in the brain]. 2 9


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