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:1.1.1.37 (malate dehydrogenase)
4,591 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mycelial growth front of the band strain of Neurospora grown on a solid surface exhibits a circadian rhythm of conidiation. Enzyme assays on extracts from that mycelium have shown that the activities of 6 of 13 enzymes (nicotinamide adenine dinucleotide nucleosidase, isocitrate lyase, citrate synthase, glyceraldehydephosphate dehydrogenase, phosphogluconate dehydrogenase, and glucose-6-phosphate dehydrogenase) and soluble-protein content oscillate with the visible morphological change. The rhythmic enzymes associated with the Krebs and glyoxylate cycles are more active during conidiogenesis, whereas the activities of the rhythmic enzymes of glycolysis and the hexose monophosphate shunt are reduced during that phase. The absence of enzyme oscillations in wild-type and fluffy strains which do not form conidia under the conditions employed suggests that the enzyme fluctuations are associated with conidiogenesis itself. Oscillations of enzyme activity as a function of time are restricted to the growth front. A permanent record of rhythmicity associated with conidial and nonconidial regions does, however, exist in the mycelial mat behind the growth front. The activities of three enzymes (nicotinamide adenine dinucleotide nucleosidase, glucose-6-phosphate dehydrogenase, and phosphogluconate dehydrogenase) are not directly influenced by CO(2) concentration, but are correlated with the prescence or absence of conidiation which is controlled by CO(2) concentration. In contrast, citrate synthase and malate dehydrogenase activities are correlated with changes in CO(2) concentration.
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PMID:Rhythms of enzyme activity associated with circadian conidiation in Neurospora crassa. 437 37

1. A method is described for extracting separately mitochondrial and extramitochondrial enzymes from fat-cells prepared by collagenase digestion from rat epididymal fat-pads. The following distribution of enzymes has been observed (with the total activities of the enzymes as units/mg of fat-cell DNA at 25 degrees C given in parenthesis). Exclusively mitochondrial enzymes: glutamate dehydrogenase (1.8), NAD-isocitrate dehydrogenase (0.5), citrate synthase (5.2), pyruvate carboxylase (3.0); exclusively extramitochondrial enzymes: glucose 6-phosphate dehydrogenase (5.8), 6-phosphogluconate dehydrogenase (5.2), NADP-malate dehydrogenase (11.0), ATP-citrate lyase (5.1); enzymes present in both mitochondrial and extramitochondrial compartments: NADP-isocitrate dehydrogenase (3.7), NAD-malate dehydrogenase (330), aconitate hydratase (1.1), carnitine acetyltransferase (0.4), acetyl-CoA synthetase (1.0), aspartate aminotransferase (1.7), alanine aminotransferase (6.1). The mean DNA content of eight preparations of fat-cells was 109mug/g dry weight of cells. 2. Mitochondria showing respiratory control ratios of 3-6 with pyruvate, about 3 with succinate and P/O ratios of approaching 3 and 2 respectively have been isolated from fat-cells. From studies of rates of oxygen uptake and of swelling in iso-osmotic solutions of ammonium salts, it is concluded that fat-cell mitochondria are permeable to the monocarboxylic acids, pyruvate and acetate; that in the presence of phosphate they are permeable to malate and succinate and to a lesser extent oxaloacetate but not fumarate; and that in the presence of both malate and phosphate they are permeable to citrate, isocitrate and 2-oxoglutarate. In addition, isolated fat-cell mitochondria have been found to oxidize acetyl l-carnitine and, slowly, l-glycerol 3-phosphate. 3. It is concluded that the major means of transport of acetyl units into the cytoplasm for fatty acid synthesis is as citrate. Extensive transport as glutamate, 2-oxoglutarate and isocitrate, as acetate and as acetyl l-carnitine appears to be ruled out by the low activities of mitochondrial aconitate hydratase, mitochondrial acetyl-CoA hydrolyase and carnitine acetyltransferase respectively. Pathways whereby oxaloacetate generated in the cytoplasm during fatty acid synthesis by ATP-citrate lyase may be returned to mitochondria for further citrate synthesis are discussed. 4. It is also concluded that fat-cells contain pathways that will allow the excess of reducing power formed in the cytoplasm when adipose tissue is incubated in glucose and insulin to be transferred to mitochondria as l-glycerol 3-phosphate or malate. When adipose tissue is incubated in pyruvate alone, reducing power for fatty acid, l-glycerol 3-phosphate and lactate formation may be transferred to the cytoplasm as citrate and malate.
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PMID:The intracellular localization of enzymes in white-adipose-tissue fat-cells and permeability properties of fat-cell mitochondria. Transfer of acetyl units and reducing power between mitochondria and cytoplasm. 439 82

(1) A ;cycling' method involving citrate synthase (EC 4.1.3.7) and malate dehydrogenase (EC 1.1.1.37) was modified by the inclusion of succinyl-CoA synthetase (EC 6.2.1.5) and hexokinase (EC 2.7.1.1) to permit the determination of very small amounts of succinyl-CoA in addition to CoA and acetyl-CoA. (2) Application of this technique to blowfly (Phormia regina) flight-muscle extracts reveals no change in acetyl-CoA concentration, a slight fall in CoA concentration and a rise in succinyl-CoA concentration during flight. (3) Extraction of isolated mitochondria during controlled (state 4) pyruvate oxidation reveals essentially only acetyl-CoA. Activation of respiration by ADP (state 3) or uncoupling agents leads to a fall in acetyl-CoA and a rise in CoA and succinyl-CoA content. (4) The presence of glycerol phosphate in addition to pyruvate results in a lower acetyl-CoA content in state 4. (5) It is contended that these results are consistent with a primary control of one of the reactions of the tricarboxylate cycle, rather than of pyruvate dehydrogenase, during the state 4 oxidation of pyruvate by isolated mitochondria, and that the modulation of citrate synthase activity by the ratio of acetyl-CoA/succinyl-CoA is unimportant under these conditions.
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PMID:The control of tricarboxylate-cycle of oxidations in blowfly flight muscle. The steady-state concentrations of coenzyme A, acetyl-coenzyme A and succinyl-coenzyme A in flight muscle and isolated mitochondria. 446 39

The isocitrate lyase from a thermophilic Bacillus is activated about threefold by a variety of salts. Such strong stimulation of activity is not seen with isocitrate lyase from the mesophiles, Bacillus licheniformis, Bacillus megaterium, Escherichia coli, and Aspergillus nidulans. The salt activation is markedly pH-dependent. At pH values above 8.6, salt (KCl) indeed inhibits the enzyme activity. Potassium chloride also causes a significant shift of the pH optimum of the enzyme towards the acid side. As the temperature of the enzyme reaction is raised, activation becomes progressively weaker. Potassium chloride also affords considerable protection against enzyme denaturation at 55 C. The activation and the stabilization, however, appear to be independent effects. Of six other enzymes in the thermophile that were examined, isocitrate dehydrogenase was equally strongly activated by KCl and malate synthase was less strongly, but significantly, activated; citrate synthase, malate dehydrogenase, glutamate dehydrogenase, and lactate dehydrogenase were unaffected or slightly inhibited by KCl. The property of being strongly activated by salt appears to be a peculiar characteristic of the thermophile isocitrate lyase and possibly evolved concomitantly with its thermostability.
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PMID:Isocitrate lyase from a thermophilic Bacillus: effect of salts on enzyme activity. 458

A technique was developed for the detection, on agar, of mutants of Bacillus subtilis that lacked a functional tricarboxylic acid cycle. Mutants devoid of detectable levels of aconitase, isocitric dehydrogenase, alpha-ketoglutarate dehydrogenase, succinic dehydrogenase, fumarase, and malate dehydrogenase have been isolated and characterized. Several mutants with conditionally expressible lesions, including a mutant with a heat-sensitive citrate synthase, have also been isolated. All of the mutants examined express all the biochemical markers normally absent in early-stage sporulation mutants except elastase, and some of these mutants sporulated nearly as well as the prototroph.
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PMID:Isolation and characterization of tricarboxylic acid cycle mutants of Bacillus subtilis. 499 41

The growth response of Listeria monocytogenes strains A4413 and 9037-7 to carbohydrates was determined in a defined medium. Neither pyruvate, acetate, citrate, isocitrate, alpha-ketoglutarate, succinate, fumarate, nor malate supported growth. Furthermore, inclusion of any of these carbohydrates in the growth medium with glucose did not increase the growth of Listeria over that observed on glucose alone. Resting cell suspensions of strain A4413 oxidized pyruvate but not acetate, citrate, isocitrate, alpha-ketoglutarate, succinate, fumarate, or malate. Cell-free extracts of strain A4413 contained active citrate synthase, aconitate hydratase, isocitrate dehydrogenase, malate dehydrogenase, fumarate hydratase, fumarate reductase, pyruvate dehydrogenase system, and oxidases for reduced nicotinamide adenine dinucleotide and reduced nicotinamide adenine dinucleotide phosphate. The alpha-ketoglutarate oxidation system, succinate dehydrogenase, isocitrate lyase, and malate synthase were not detected. Cytochromes were not detected. The data suggest that strain A4413, under these conditions, utilizes a split noncyclic citrate pathway which has an oxidative portion (citrate synthase, aconitate hydratase, and isocitrate dehydrogenase) and a reductive portion (malate dehydrogenase, fumarate hydratase, and fumarate reductase). This pathway is probably important in biosynthesis but not for a net gain in energy.
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PMID:Citrate cycle and related metabolism of Listeria monocytogenes. 499 14

1. In epididymal adipose tissue synthesizing fatty acids from fructose in vitro, addition of insulin led to a moderate increase in fructose uptake, to a considerable increase in the flow of fructose carbon atoms to fatty acid, to a decrease in the steady-state concentration of lactate and pyruvate in the medium, and to net uptake of lactate and pyruvate from the medium. It is concluded that insulin accelerates a step in the span pyruvate-->fatty acid. 2. Mitochondria prepared from fat-cells exposed to insulin put out more citrate than non-insulin-treated controls under conditions where the oxaloacetate moiety of citrate was formed from pyruvate by pyruvate carboxylase and under conditions where it was formed from malate. This suggested that insulin treatment of fat-cells led to persistent activation of pyruvate dehydrogenase. 3. Insulin treatment of epididymal fat-pads in vitro increased the activity of pyruvate dehydrogenase measured in extracts of the tissue even in the absence of added substrate; the activities of pyruvate carboxylase, citrate synthase, glutamate dehydrogenase, acetyl-CoA carboxylase, NADP-malate dehydrogenase and NAD-malate dehydrogenase were not changed by insulin. 4. The effect of insulin on pyruvate dehydrogenase activity was inhibited by adrenaline, adrenocorticotrophic hormone and dibutyryl cyclic AMP (6-N,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate). The effect of insulin was not reproduced by prostaglandin E(1), which like insulin may lower the tissue concentration of cyclic AMP (adenosine 3':5'-cyclic monophosphate) and inhibit lipolysis. 5. Adipose tissue pyruvate dehydrogenase in extracts of mitochondria is almost totally inactivated by incubation with ATP and can then be reactivated by incubation with 10mm-Mg(2+). In this respect its properties are similar to that of pyruvate dehydrogenase from heart and kidney where evidence has been given that inactivation and activation are catalysed by an ATP-dependent kinase and a Mg(2+)-dependent phosphatase. Evidence is given that insulin may act by increasing the proportion of active (dephosphorylated) pyruvate dehydrogenase. 6. Cyclic AMP could not be shown to influence the activity of pyruvate dehydrogenase in mitochondria under various conditions of incubation. 7. These results are discussed in relation to the control of fatty acid synthesis in adipose tissue and the role of cyclic AMP in mediating the effects of insulin on pyruvate dehydrogenase.
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PMID:Regulation of adipose tissue pyruvate dehydrogenase by insulin and other hormones. 515 98

The activities of the eight citric acid-cycle enzymes of rat bone-marrow cells were determined along with several other mitochondrial and non-mitochondrial enzymes. Four of the citric acid-cycle enzymes (aconitase, succinyl-CoA thiokinase, alpha-oxoglutarate dehydrogenase and succinate dehydrogenase) have closely similar low activities; two [isocitrate dehydrogenase (NAD) and citrate synthase] have intermediate activities; the remaining two (malate dehydrogenase and fumarase) have high activities. The other enzymes surveyed also exhibited a spread of three orders of magnitude, the mitochondrial enzymes showing no less variation than the others.
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PMID:The activities of the citric acid-cycle enzymes in rat bone-marrow cells. 566 55

Rats were trained by daily running exercises for 7 weeks. In addition, one group of rats was trained under the influence of propranolol, while another group received daily injections of propranolol only. None of the treatments used had influence on the activities of myocardial enzymes: 3-hydroxyacyl-CoA - dehydrogenase (HADH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), and citrate synthase (CS) which were assayed for estimating oxidative capacity, or lactate dehydrogenase (LDH) which was used as a measure of anaerobic capacity. Training without propranolol resulted in elevated activities of the oxidative enzymes in M. extensor digitorum and in M. soleus. The corresponding changes in the rat group trained with propranolol always were much smaller, despite an equal amount of training. Only the trend for lowered activity of LDH was observable in skeletal muscle of the rat groups trained both with and without propranolol. Long-term beta-blockade alone did not induce enzymatic changes. It is concluded that a functioning sympathetic nervous system is necessary for the adaptive responses of muscular metabolism to training. Blockade of the sympathetic influence during exercise periods also hampers the training-induced responses.
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PMID:Physical training under the influence of beta-blockade in rats. III. Effects on muscular metabolism. 610 47

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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