Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.1.1.37 (malate dehydrogenase)
 4,591 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Little evidence has been available on the oxidative pathways of glutamine and glutamate, the major respiratory substrates of cancer cells. Glutamate formed from glutamine by phosphate-dependent glutaminase undergoes quantitative transamination by aerobic tumor mitochondria to yield aspartate. However, when malate is also added there is a pronounced decrease in aspartate production and a large formation of citrate and alanine, in both state 3 and 4 conditions. In contrast, addition of malate to normal rat heart, liver, or kidney mitochondria oxidizing glutamate causes a marked increase in aspartate production. Further analysis showed that extramitochondrial malate is oxidized almost quantitatively to pyruvate + CO2 by NAD(P)+-linked malic enzyme, present in the mitochondria of all tumors tested, but absent in heart, liver, and kidney mitochondria. On the other hand intramitochondrial malate generated from glutamate is oxidized quantitatively to oxalacetate by mitochondrial malate dehydrogenase of tumors. Acetyl-CoA derived from extramitochondrial malate via pyruvate and oxalacetate derived from glutamate via intramitochondrial malate are quantitatively converted into citrate, which is extruded. No evidence was found that malic enzyme of tumor mitochondria converts glutamate-derived malate into pyruvate as postulated in other reports. Possible mechanisms for the integration of mitochondrial malic enzyme and malate dehydrogenase activities in tumors are discussed.
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PMID:The pathways of glutamate and glutamine oxidation by tumor cell mitochondria. Role of mitochondrial NAD(P)+-dependent malic enzyme. 614 77

The significance of changes in lymph flow for the extracellular distribution and transport of cellular enzymes and for the level of enzyme activities in plasma was investigated. Specimens of thoracic duct lymph were obtained from an extracorporal lymph shunt in anaesthetized, conscious resting and treadmill exercising dogs (6 km X h-1 for 1 h) The activity of 10 enzymes and of protein content in lymph and plasma were studied, as well as lymph flow, lymphatic transport, and the lymph-plasma ratio of these compounds. Lactate, pH, and blood gases were monitored in venous blood. Lymph flow of 0.80 ml X min-1 in anaesthetized dogs more than doubled (to 1.86 ml X min-1) when the animals were conscious and resting. In anaesthetized dogs lymph enzyme activity was higher only for enzymes of predominately hepatic origin, such as choline esterase (CHE) and alanine aminoferase (ALAT), and was lower for aspartate aminotransferase (ASAT) and aldolase (ALD). In conscious dogs, due to activation of the skeletal muscle "tissue pump", lymphatic transport of enzymes with rather high activity in skeletal muscle, and of protein, is significantly enhanced. Enzyme activities in plasma, however, did not differ between the groups. Lymph-plasma activity ratios higher than one were found for lactate dehydrogenase (LDH), malate dehydrogenase (MDH), ASAT, creatine kinase (CK), ALD, and phosphohexose isomerase (PHI). Exercise stimulated lymph flow up to 4.9 ml X min-1, and increased the lymphatic activities of those enzymes with a lymph-plasma ratio higher than unity, these enzymes increasing in the plasma due to the highly increased lymphatic transport.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Enzyme activities in thoracic duct lymph and plasma of anaesthetized, conscious resting and exercising dogs. 642 59

Intact spinach (Spinacia oleracea L.) leaf peroxisomes converted glycerate to serine in the presence of NAD and alanine. The reaction proceeded optimally at pH9. Addition of oxaloacetate or alpha-ketoglutarate plus aspartate enhanced the conversion about three-fold. Alteration of the concentration of one of the reaction components, consisting of 2 mM glycerate, 0.2 mM NAD, 0.5 mM oxaloacetate, and 2 mM alanine, revealed half-saturation constants of 0.45 mM for glycerate, 0.06 mM for NAD, 0.02 mM for oxaloacetate, and 0.33 mM for alanine. The conversion proceeded with the formation of hydroxypyruvate followed by serine; hydroxypyruvate did not accumulate to a high amount in the presence or absence of alanine. The amino group donor could be alanine (half-saturation constant, 0.33 mM), glycine (0.45 mM), or asparagine (0.67 mM); the three amino acids produced roughly similar Vmax values. The results indicate that, in the conversion of glycerate to serine, the transamination is catalyzed by a hydroxypyruvate aminotransferase with characteristics unknown among all other studied leaf peroxisomal aminotransferases. The peroxisomal membrane is sparsely permeable to NAD/NADH, and the participation of the peroxisomal malate dehydrogenase in an electron shuttle system across the membrane in the regeneration of NAD/NADH is suggested.
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PMID:Conversion of glycerate to serine in intact spinach leaf peroxisomes. 643 26

Isolated rat hearts were, after a retrograde perfusion by the Langendorff procedure, rendered ischemic by lowering the aortic pressure to zero. The rate of proteolysis and temporal patterns of the changes in the concentrations of the metabolites of the tricarboxylic acid cycle, related amino acids, ammonia, and breakdown products of the adenine nucleotides were determined. The most significant change in the amino acid metabolism was a decrease of the proteolysis to one-tenth and a large accumulation of alanine, which was almost stoichiometric to the degradation of aspartate plus asparagine. The accumulation of malate and succinate was small compared with the metabolic net fluxes of aspartate and alanine. The metabolic balance sheet suggests that aspartate was converted to alanine. A prerequisite for this would be a feed in of carbon of aspartate to the tricarboxylic acid cycle as oxalacetate, reversal of the malate dehydrogenase, and production of pyruvate by the malic enzyme reaction. Alanine accumulating during ischemia is not glycolytic in origin but occurs through a concerted operation of anaplerotic reactions and tricarboxylic acid cycle metabolite disposal. The data also suggest that the potentially energy-yielding reduction of fumarate to succinate is not significant in the ischemic myocardium.
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PMID:Tricarboxylic acid cycle metabolites during ischemia in isolated perfused rat heart. 682 95

Chronic sumithion toxicity in experimental crabs was induced by exposing them for 15 and 30 days to 0.04 ppm sumithion solution. The enzymes concerned with glycogenolytic metabolism (phosphorylase), glycolytic metabolism (aldolase), aerobic metabolism [succinate dehydrogenase (SDH), malate dehydrogenase (MDH)], anaerobic metabolism, lactate dehydrogenase (LDH) and alanine amino transaminase (AIAT)], were assayed in the muscle of control and experimental crabs. Glycogen, pyruvic acid, lactic acid were also estimated in the muscle of both control and experimental crabs. The muscle tissue of chronic sumithion-exposed crab exhibited suppressed glycogenolysis and glycolysis with an onset of gluconeogenesis. In general, chronic sumithion exposure seems to result in an elevation of the synthetic phase of muscle carbohydrate metabolism.
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PMID:Chronic sumithion toxicity: effect on carbohydrate metabolism in crab muscle. 682 35

The maximal rate of some cerebral enzymatic activities related to energy transduction (hexokinase; phosphofructokinase; lactate dehydrogenase; citrate synthase; malate dehydrogenase; total NADH-cytochrome c reductase; cytochrome oxidase), amino acid metabolism (glutamate decarboxylase; glutamate dehydrogenase) and cholinergic metabolism (acetylcholine esterase) were tested in the cerebral cortex and in sub-cortical area of rats. The evaluations were performed both in the homogenate in toto and in the crude mitochondrial fraction, before and after a postdecapitative normothermic ischemia of 5, 10, 20, and 40 min duration. The results are discussed also with respect to the pharmacological pretreatment with two biological substances which may modulate amino acid (L-alanine) and phospholipid metabolism (CDP-choline). The analysis of the present data suggests the occurrence in brain tissue of a variety of interrelated factors implicated in the ischemia-induced changes of the maximal rate of the enzymatic activities related to the energy transduction. These include: (a) rearrangement of the enzymatic activities because of the changed metabolic and chemico-physical condition; (b) decrease in the activity of enzymes related to the electron transfer chain and glycolysis; (c) changes in enzymes related to mitochondrial membranes. The effects of in vivo administration of alanine or CDP-choline, even if significant, are not consistent throughout the time period studied.
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PMID:Changes induced by ischemia on some cerebral enzymatic activities related to energy transduction and amino acid metabolism. 685 30

A high dose of niridazole administered intraperitoneally (i.p.) to male rats over a period of 9 weeks induced alterations in the concentrations and activities of some important testicular constituents and enzymes, respectively. The concentrations of total and free cholesterol were higher than those of control animals but the concentration of esterified cholesterol was significantly lower than that of the control rats. Zinc concentration in the testis and prostate gland of niridazole-treated animals was significantly lower than in the control animals. Decreases in the activities of the following enzymes occurred in the testes of niridazole-treated rats: lactate and sorbitol dehydrogenases, aspartate and alanine aminotransferases and alkaline phosphatase. By contrast, there were increases in the activities of testicular malate dehydrogenase and prostate acid phosphatase of rats given niridazole.
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PMID:Niridazole-induced biochemical changes in the rat testis. 716 74

Exposure to simulated weightlessness (7-day water immersion and 7-day head-down tilt) caused a decrease in the activity of malate (MDH) and isocitrate dehydrogenase (ICDH), and creatine phosphokinase dehydrogenase (ICDH), and creatine phosphokinase (CPK) at the expense of its MM isoform whereas the activity of alanine (ALT) and aspartate aminotransferase (AST) and pattern of distribution of MDH isoforms remained unchanged. Exposure to acceleration of +3 Gz before and after simulated weightlessness revealed similar changes in the activity of MDH, ICDH, ALT, AST and MDH cytoplasmic fractions. However, the higher increase in the enzyme activity after simulated weightlessness may give evidence for a greater change in cell membrane permeability during acceleration effects that followed simulated weightlessness.
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PMID:[Energy-metabolism enzymes during combined exposure of the body to simulated weightlessness and gravitational overloads]. 728 61

Experiments were designed to investigate whether the metabolic responses of pregnant females are in keeping with the known state of gestational hyperinsulinemia. Groups of female rats fed a 32% protein diet were killed on days 13, 15, 17, 19 and 21 of pregnancy, during either daytime or during night-time. Liver pyruvate kinase and glucose-6-phosphate dehydrogenase activities were increased over nonpregnant values from day 13 onward in agreement with what can be expected as a result of the gestational hyperinsulinemia. Liver malate dehydrogenase (NADP) activity was increased to lesser extent and later. Pyruvate and lactate accumulated in maternal liver from day 13 onward. The fact that this accumulation could not be related to any further increase of food intake during this time and that it correlated at day 21 with litter size was taken as indication of a probable contribution of the conceptus to maternal pyruvate and lactate accumulation in late pregnancy. Liver alanine amino-transferase activity decreased as pregnancy progressed. No change in serine dehydratase activity was found. Cytosolic aspartate aminotransferase activity remained unchanged. Mitochondrial activity increased as pregnancy progressed.
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PMID:Possible metabolic implications of pyruvate and lactate accumulation in the liver of pregnant rats. 736 31

Changes in oxidative metabolism were studied in hepatopancreas, muscle, and hemolymph of the edible crab Scylla serrata, exposed to a sublethal concentration (2.5 ppm) of cadmium chloride. A significant decrease in glycogen, total carbohydrates, and pyruvate and an increase in lactate levels in hepatopancreas and muscle were observed. Hemolymph sugar levels were increased in experimental crabs. An increase in phosphorylase suggested increased glycogenolysis during cadmium toxicity. The decrease in lactate dehydrogenase activity and the increase in lactate content indicated reduced mobilization of pyruvate into the citric acid cycle. Krebs cycle enzymes such as succinate dehydrogenase and malate dehydrogenase were found to be decreased, suggesting impairment of mitochondrial oxidative metabolism as a consequence of cadmium toxicity. Glucose-6-phosphate dehydrogenase activity was increased, suggesting enhanced oxidation of glucose by the HMP pathway. Cytochrome-c oxidase and Mg2+ ATPase activity levels decreased, indicating impaired energy synthesis during cadmium stress. Acid and alkaline phosphatase activities increased, suggesting enhanced breakdown of phosphates to release energy in view of impaired ATPase system during cadmium exposure. A significant decrease in protein and free amino acid and an increase in ammonia, urea, and glutamine levels were observed in the tissues during exposure. An increase in protease, alanine aminotransaminase, and aspartate aminotransaminase suggested increased proteolysis and transamination of amino acids. The increase in glutamate dehydrogenase, AMP deaminase, and adenosine deaminase indicated increased ammonia production. The increased arginase and glutamine synthetase suggested the detoxification or mobilization of ammonia toward the production of urea and glutamine. These results suggest that cadmium affects oxidative metabolism and induces hyperammonemia, and crabs switch over their metabolic profiles toward compensatory mechanisms for the survivability in cadmium-polluted habitats.
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PMID:Changes in oxidative metabolism in selected tissues of the crab (Scylla serrata) in response to cadmium toxicity. 753 86


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