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:1.1.1.41 (isocitrate dehydrogenase)
3,101 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A mathematical model is proposed to describe the behavior of the pyruvate metabolic reactions, Krebs cycle and oxidative phosphorylation over a wide range of changes in the pyruvate influx rate and the activities of ATPase and NADH-reoxidating dehydrogenase. The role of adenine and pyridine nucleotides in various allosteric regulations of the Krebs cycle enzymes is discussed. The accumulation of ATP and NADH has been shown to proceed in definite succession, which makes the allosteric regulation of the Krebs cycle enzymes successive too. First "works" the inhibition by ATP, then by NADH. It has been shown that the properties of the model are in qualitative agreement with the experimental data (Garber A., Hanson R. [1]) on pyruvate oxidation by mitochondria from guinea pig liver, when allosteric regulation of isocitrate dehydrogenase by adenine nucleotides is taken into account.
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PMID:[A mathematical model of the pyruvate oxidation in liver mitochondria. 1. Regulation of the Krebs cycle by adenine and pyridine nucleotides]. 19 85

After a brief exposition to glucose, Thiobacillus acidophilus was isolated from a culture of iron-grown T. ferrooxidans. Physicochemical analysis of its DNA showed a G+C content of 62.9-63.2%. The new isolate grows best at 25-30 degrees C and at pH 3.0. Growth is possible between pH 1.5 and 6.0. Thiobacillus acidophilus is apparently strictly aerobic. Ammonium salts are the only suitable source of nitrogen. The bacterium is a facultative autotroph. In addition to elemental sulfur, it obtains energy from organic compounds such as D-glucose, D-galactose, D-fructose, D-mannitol, D-xylose, D-ribose, D-arabinose, L-arabinose, sucrose, sodium citrate, malic acid,dl-aspartic acid, and dl-glutamic acid. Thiobacillus acidophilus possesses the key enzymes of the tricarboxylic acid (TCA) cycle including NAD-and NADP-linked isocitric dehydrogenase and alpha-ketoglutarate dehydrogenase, and the key enzymes of the hexose monophosphate pathway (glucose-6-phosphate and 6-phosphogluconate dehydrogenase, and fructose 1,6-diphosphate aldolase). NADH oxidase has been found in particulate fraction of extracts. Rhodanese and thiosulfate oxidase have also been detected.
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PMID:Thiobacillus acidophilus sp. nov.; isolation and some physiological characteristics. 23 84

The DPN-specific isocitrate dehydrogenase of pig heart is totally and irreversibly inactivated by 0.05 M potassium cyanate at pH 7.4 A plot of the rate constant versus cyanate concentration is not linear, but rather exhibits saturation kinetics, implying that cyanate may bind to the enzyme to give an enzyme-cyanate complex (K equal 0.125 M) prior to the covalent reaction. In the presence of manganous ion the addition of isocitrate protects the enzyme against cyanate inactivation, indicating that chemical modification occurs in the active site region of the enzyme. The dependence of the decrease of the rate constant for inactivation on the isocitrate concentration yields a dissociation constant for the enzyme-manganese-isocitrate complex which agrees with the Michaelis constant. The allosteric activator ADP, which lowers the Michaelis constant for isocitrate, does not itself significantly affect the cyanate reaction; however, it strikingly enhances the protection by isocitrate. The addition of the chelator EDTA essentially prevents protection by isocitrate and manganous ion, demonstrating the importance of the metal ion in this process. The substrate alpha-ketoglutarate and the coenzymes DPN and DPNH do not significantly affect the rate of modification of the enzymes by cyanate. Incubation of isocitrate dehydrogenase with 14C-labeled potassium cyanate leads to the incorporation of approximately 1 mol of radioactive cyanate per peptide chain concomitant with inactivation. Analysis of acid hydrolysates of the radioactive enzyme reveals that lysyl residues are the sole amino acids modified. These results suggest that cyanate, or isocyanic acid, may bind to the active site of this enzyme as an analogue of carbon dioxide and carbamylate a lysyl residue at the active site.
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PMID:Cyanate modification of essential lysyl residues of the diphosphopyridine nucleotide-specific isocitrate dehydrogenase of pig heart. 23 32

The 17 beta-hydroxysteroid dehydrogenase which was purified from porcine testicular microsomal fraction [Inano, H. and Tamaoki, B (1974) Eur. J. Biochem. 44, 13-23] catalyzed the reduction of androstenedione to testosterone with the accompanying oxidation of equimolar NADPH. For the oxido-reduction of the steroids, the 17 beta-hydroxysteroid dehydrogenase preferred NADP(H) to NAD(h). Transhydrogenation from NADPH to NAD+ or NADH to NADP+ through the cyclic oxido-reduction of the steroids by the purified 17 beta hydroxysteroid dehydrogenase preparation was not spectrophotometrically detectable, because of selective preference of the testicular 17 beta-hydroxysteroid dehydrogenase against NADP(H). To examine stereospecific transfer of the hydrogen from NADPH to androstenedione by the purified 17 beta-hydroxysteroid dehydrogenase, the following tritiated cofactors were synthesized: [4-3-H]NADP+ was prepared by catalytic replacement from non-radioactive NADP+ and 3H2O in the presence of potassium cyanide. Then, [4-pro-R3H]NADPH was enzymatically synthesized from the [4-3H]NADP+ by glucose 6-phosphate and its dehydrogenase. On the other hand, [4-pro-S-3H]NADPH was prepared from the [4-3H]NADP+ by isocitrate and isocitrate dehydrogenase. When androstenedione was incubated with the 17 beta-hydroxysteroid dehydrogenase in the presence of these stereospecifically 3H-labeled cofactors, only the tritium located at 4-pro-S position of the nicotinamide moiety of NADPH was transferred to testosterone. The location of the tritium in the testosterone molecule produced, 17alpha-position of the steroid, was assigned by the fact that the tritium of the testosterone remained in its molecule after acetylation, but was completely lost by oxidation.
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PMID:Relationship between steroids and pyridine nucleotides in the oxido-reduction catalyzed by the 17 beta-hydroxysteroid dehydrogenase purified from the porcine testicular microsomal fraction. 23 55

1. The contents of some intermediates of glycolysis, the citric acid cycle and adenine nucleotides have been measured in the freeze-clamped locust flight muscle at rest and after 10s and 3min flight. The contents of glucose 6-phosphate, pyruvate, alanine and especially fructose bisphosphate and triose phosphates increased markedly upon flight. The content of acetyl-CoA is decreased after 3min flight whereas that of acetylcarnitine is decreased markedly after 10s flight, but returns towards the resting value after 3min flight. The content of citrate is markedly decreased after both 10s and 3min flight, whereas that of isocitrate is changed very little after 10s and is increased by 50% after 3min. The content of oxaloacetate is very low in insect flight muscle and hence it was measured by a sensitive radiochemical assay. The content of oxaloacetate increased about 2-fold after 3min flight. A similar change was observed in the content of malate. The content of ATP decreased about 15%, whereas those of ADP and AMP increased about 2-fold after 3min flight. 2. Calculations based on O(2) uptake of the intact insect indicate that the rate of the citric acid cycle must be increased >100-fold during flight. Consequently, if citrate synthase catalyses a non-equilibrium reaction, the activity of the enzyme must increase >100-fold during flight. However, changes in the concentrations of possible regulators of citrate synthase, oxaloacetate, acetyl-CoA and citrate (which is an allosteric inhibitor), are not sufficient to account for this change in activity. It is concluded that there may be much larger changes in the free concentration of oxaloacetate than are indicated by the changes in the total content of this metabolite or that other unknown factors must play an additional role in the regulation of citrate synthase activity. 3. The increased content of oxaloacetate could be produced via pyruvate carboxylase, which may be stimulated during the early stages of flight by the increased concentration of pyruvate. 4. The decreases in the concentrations of citrate and alpha-oxoglutarate indicate that isocitrate dehydrogenase and oxoglutarate dehydrogenase may be stimulated by factors other than their pathway substrates during the early stages of flight. 5. Calculated mitochondrial and cytosolic NAD(+)/NADH ratios are both increased upon flight. The change in the mitochondrial ratio indicates the importance of the intramitochondrial ATP/ADP concentration ratio in the regulation of the rate of electron transfer in this muscle.
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PMID:Changes in the contents of adenine nucleotides and intermediates of glycolysis and the citric acid cycle in flight muscle of the locust upon flight and their relationship to the control of the cycle. 43 78

Mycotoxic porcine nephropathy was induced by p.o. administration of crystalline ochratoxin A for periods of 5 days, 3 months and 2 years. Enzyme activities of the renal tissue were studied histochemically. These were NADH-tetrazolium reductase, NADPH-tetrazolium reductase, lactate dehydrogenase, isocitrate dehydrogenase, succinate dehydrogenase, glucose-6-phosphate dehydrogenase, alpha-glycerophosphate dehydrogenase, unspecific acid phosphatase and unspecific alkaline phosphatase. The activity of NADH-tetrazolium reductase and succinate dehydrogenase was reduced in the proximal tubule of all nephrons after 5 days ochratoxin A exposure and remained reduced after 3 months and 2 years exposure. The effect of ochratoxin A on these enzymes would appear to cause the impairment of proximal tubular function and the morphological changes observed in the proximal tubule in ochratoxin A-induced mycotoxic porcine nephropathy. The localization of alterations in enzyme activity corresponds to the localization of ochratoxin A previously demonstrated in the kidney. The activities of NADPH-tetrazolium reductase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase and unspecific alkaline phosphatase were reduced focally corresponding to the areas with focal tubular atrophy and the degree of reduction was roughly parallel to the degree of atrophy.
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PMID:Ochratoxin A-induced mycotoxic porcine nephropathy: alterations in enzyme activity in tubular cells. 47 26

Intraacinar distribution of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), NADP-dependent isocitrate dehydrogenase (IDH), glutamate dehydrogenase (GluDH), lactate dehydrogenase (LDH) and NADH-tetrazolium dehydrogenase (TR) was studied in rat liver cryostat sections by multipositional microphotometric activity determinations. By statistical evaluation, activity of individual enzymes could be related to the acinar topography. Activity was evaluated with regard to distance of measuring position either from afferent (portal) or efferent (hepatic) vessels. Two independent distribution curves were obtained for each enzyme. Acinar distribution of all the enzymes studied followed sigmoid courses with maximal activity of SDH, MDH and LDH in zone 1 ("periportal") and GluDH, IDH, TR in zone 3 ("pericentral"). For all enzymes, maximum activity gradients were confined to zone 2 of the acinus. Data were also evaluated as ratios of activities in zone 1 and zone 3. The following ratios zone 1/zone 3 were obtained: SDH = 1.9, MDH = 1.7, IDH = 0.5, GluDH = 0.5, LDH = 1.3 and TR = 0.6.
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PMID:Microphotometric studies on intraacinar enzyme distribution in rat liver. 52 13

In this communication the results of applying various histochemical semipermeable membrane techniques to the localization of several enzymes in bovine and porcine heart are presented. The Purkinje fibers of the atrioventricular conducting system of the bovine heart differ from the myocardium proper in containing a greater activity of the glycolytic and gluconeogenetic enzymes--lactate dehydrogenase, glyceraldehyde-phosphate dehydrogenase, hexokinase, glucosephosphate isomerase and phosphoglucomutase, and less activity of the aerobic enzymes--NADH: nitroBT oxidoreductase and isocitrate dehydrogenase (NADP+). The metabolic reactions obtained with Purkinje fibers of the porcine heart are less pronounced. These histochemical findings are in accordance with the impression that Purkinje fibers, compared with the common myocardial fibers, have a higher rate of anaerobic metabolism and a lower rate of aerobic metabolism. The activity of the NADPH regenerating enzymes glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase (decarboxylating), and the activity of acid hydrolases such as non-specific esterase and acid phosphatase is higher in the Purkinje fibers of both the bovine and porcine heart.
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PMID:Enzyme histochemical studies on the Purkinje fibers of the atrioventricular system of the bovine and porcine hearts. 66 82

The activities of twelve enzymes were measured in crude extracts from cells of Escherichia coli K-10 grown aerobically or anaerobically in a defined medium in the presence or absence of nitrate. The activities of isocitrate dehydrogenase, aconitate hydratase, 2-oxoglutarate dehydrogenase, malate dehydrogenase, malic enzyme, and D-lactate dehydrogenase (NAD+-independent) were found to be higher in cells grown in nitrate respiration than in those in fermentation, but lower than in those in respiration. This finding may explain the incomplete oxidation in nitrate respiration and, on the other hand, suggests the operation of the tricarboxylic acid even under these conditions. The activities of succinate dehydrogenase and alcohol dehydrogenase in relation to the formation of fermentation product were as high in cells grown in fermentation as in those in respiration and were low in those in nitrate respiration. However, that ratio of the activities in the latter case to the activities in respiration was the same as the ratio for most enzymes in the tricarboxylic acid cycle. The level of lactate dehydrogenase (NAD+-dependent) was not affected by nitrate respiration but its activity in the extract was inhibited by nitrate and nitrite. The absence of lactate in the anaerobic culture with nitrate may be due to this inhibition as well as NADH oxidation by nitrate. Levels of glucose-6-phosphate dehydrogenase and glutamate dehydrogenase were not altered by the growth conditions and that of pyruvate dehydrogenase was low only in cells grown in fermentation.
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PMID:Effect of nitrate reduction on the enzyme levels in carbon metabolism in Escherichia coli. 77 52

1. Flight by insects is characterized by the most intense respiration known in biology and also the most controlled. Thus insect flight muscle may be the tissue of choice for the study of biochemical adaptation in the control of catabolism and biological oxidations, and many of the results obtained with insects have a significance and a relevance that transcend the boundaries between classes. In insects, such as the blowfly, flight is distinguished additionally by high wingbeat frequencies and an asynchronous type of excitation-contraction coupling. In spite of this intense muscular work, metabolic processes are not limited by the availability of oxygen. Also of importance is the morphological organization of the flight muscle and mitochondria, which have evolved ultrastructurally and biochemically into an effective catabolic machine. 2. In the fly, carbohydrate, principally glycogen, is the sole metabolic fuel; fats are not used in flight and enzymes concerned with fatty acid utilization are virtually lacking. Glycogenolysis does not lead to lactic acid; instead, the end products of glycolysis are pyruvate and alpha-glycerophosphate. The alpha-glycerophosphate cycle provides a mechanism not only for the reoxidation of glycolytically produced NADH but also for the stoicheiometric formation from each molecule of hexose equivalent of two molecules of pyruvate, which are then available for oxidation via the tricarboxylate cycle. The absence of dicarboxylate and tricarboxylate carriers from the mitochondria ensures that tricarboxylate-cycle intermediates do not exit from the mitochondrion but that pyruvate is oxidized to completion. On initiation of flight, mitochondrial oxidation of pyruvate is impeded by the lack of tricarboxylate-cycle intermediates for the generation of oxaloacetate. This is circumvented by the oxidation of proline. 3. The controls on metabolism in flight muscle, i.e. (1) glycogenolysis at phosphorylase and phosphorylase kinase, (2) glycolysis at phosphofructokinase, (3) alpha-glycerophosphate dehydrogenase, (4) proline dehydrogenase and (5) tricarboxylate cycle at isocitrate dehydrogenase, are effected by the phosphate potential and/or Ca2+. It is suggested that the metabolic changes, such as those seen in the rest-to-flight transition, are achieved by the concerted actions of these effectors at the different loci.
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PMID:Biochemical adaptations for flight in the insect. 78 15


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