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

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.
 ...
PMID:Effect of aflatoxin B1 on pyridine nucleotides and NADP linked dehydrogenases. 0 75

Attempts were made to characterize mitochondrial malate dehydrogenase [L-malate: NAD+ oxidoreductase, EC 1.1.1.37] (M-MDH) purified from bovine cerebrum and to elucidate the mechanisms responsible for inhibition of the enzymic activity by Ag+. The molecular weights of the native enzyme and its subunits were 54,000-55,000 and 30,000-32,000, respectively. In general, the physiochemical and catalytic properties of bovine cerebral M-MDH was not very different from those of other corresponding mammalian enzymes. Incubation of the enzyme with Ag+ caused the loss of equivalent amounts of sulfhydryls with a parallel decrease of the enzymic activity. When the enzyme was exposed to 2-, 3.5-, and 5-fold molar excesses of Ag+, the enzymic activity showed an initial rapid fall and a subsequent slow restoration to a partially inactivated level (60-70, 45-50, and 15-20% of an untreated control, respectively), while the alpha-helical content of the enzyme fell exponentially with time. A 7-fold molar excess of Ag+ reduced both the enzymic activity and the alpha-helical content to a much greater degree and no restoration of the enzymic activity was observed. The Km values of Ag+-inactivated enzyme for NADH and oxaloacetate were the same as those of the native enzyme. The data suggest that Ag+ could inhibit enzymic activity both by reducing the structural regularity of the enzyme molecule and by attacking sulfhydryl groups necessary for the catalytic activity of bovine cerebral M-MDH.
 ...
PMID:Mitochondrial malate dehydrogenase of bovine cerebrum. Characterization and mechanisms of inhibition by silver ions. 0 92

The pH-dependent dissociation of porcine heart mitochondrial malate dehydrogenase (L-malate:NAD+ oxidoreductase, EC 1.1.1.37) has been further characterized using the technique of sedimentation velocity ultracentrifugation. The increased rate and specificity of the inactivation of mitochondrial malate dehydrogenase by the sulfhydryl reagent N-ethylmaleimide has been correlated with the pH-dependent dissociation of the enzyme. Data obtained using NAD+ and its component parts to reassociate the enzyme and also to protect the enzyme from inactivation by N-ethylmaleimide suggest that the sulfhydryl residues being modified by N-ethylmaleimide are inaccessible when the enzyme is in its dimeric form. A dissociation curve for the pH-dependent dissociation suggests that a limited number of residues are being protonated concomitant with dissociation of the enzyme. An apparent pKa of 5.3 has been determined for this phenomenon. Studies using enzyme modified by the sulfhydryl reagent N-ethylmaleimide indicate that selective modification of essential sulfhydryl residues alters the proper binding of NADH.
 ...
PMID:Investigation of the relation of the pH-dependent dissociation of malate dehydrogenase to modification of the enzyme by N-ethylmaleimide. 1 62

The effect of adrenalectomy on the activities of monoamine oxidase (MAO), NADH cytochrome c reductase (NCR), succinate dehydrogenase, malate dehydrogenase, fumarase, NAD+ nucleosidase and acid phosphatase in homogenates of rat hearts was examined. Besides MAO only the NCR activity increased. However, both the total and the rotenone-insensitive NCR activities increased, with that of the rotenone-insensitive being about half of the total, which indicated that the effect of adrenalectomy was exerted on components of this enzyme localized on both the inner and outer membranes of the mitochondrion. The lack of effect on the other enzymes suggests that adrenalectomy has a relatively selective action on MAO and NCR, and does not work by a generalized increase in protein synthesis or by an effect on the FAD cofactor. The MAO increase was seen with a variety of substrates, and was due to a rise in Vmax without change in Km. The response to adrenalectomy in the summer differed from that seen in the winter. The possible reasons for these effects of adrenalectomy are discussed.
 ...
PMID:The influence of adrenalectomy on monoamine oxidase and NADH cytochrome c reductase in the rat heart. 2 98

1. The pH-dependencies of the binding of NADH and reduced nicotinamide--benzimidazole dinucleotide to pig heart cytoplasmic malate dehydrogenase and lactate dehydrogenase are reported. 2. Two ionizing groups were observed in the binding of both reduced coenzymes to lactate dehydrogenase. One group, with pKa in the range 6.3--6.7, is the active-site histidine residue and its deprotonation weakens binding of reduced coenzyme 3-fold. Binding of both coenzymes is decreased to zero when a second group, of pKa 8.9, deprotonates. This group is not cysteine-165.3. Only one ionization is required to characterize the binding of the two reduced coenzymes to malate dehydrogenase. The group involved appears to be the active-site histidine residue, since its ethoxycarbonylation inhibits the enzyme and abolishes binding of reduced coenzyme. Binding of either reduced coenzyme increases the pKa of the group from 6.4 to 7.4, and deprotonation of the group is accompanied by a 10-fold weakening of coenzyme binding. 4. Two reactive histidine residues were detected per malate dehydrogenase dimer. 5. A mechanism which emphasizes the homology between the two enzymes is presented.
 ...
PMID:Malate dehydrogenase of the cytosol. Ionizations of the enzyme-reduced-coenzyme complex and a comparison with lactate dehydrogenase. 2 4

The stereospecificity of the chicken heart mitochondrial malate dehydrogenase as well as the ability of this enzyme to form various abortive complexes has been further investigated. The enzyme was found to be specific for the A-hydrogen of NADH. Complex formation of the enzyme with oxalacetate and oxidized coenzymes is pH-dependent and is promoted at alkaline pH values. The enol form of oxalacetate appears to be the species that participates in the formation of the complexes. The binding of L-malate, D-malate, or hydroxymalonate to the enzyme. NADH complex is also pH-dependent, and involves a group on the enzyme with a pK of 7.5. The binding of L-malate is promoted at alkaline pH values, whereas the binding of D-malate and hydroxymalonate is favored at acidic pH values. These results indicate that L-malate and enol-oxalacetate preferentially or exclusively bind to the nonprotonated form of the enzyme, whereas keto-oxalactate, hydroxymalonate, and D-malate only bind to the protonated form of the enzyme. Based on this conclusion, a detailed chemical mechanism for the malate dehydrogenase reaction has been postulated and a schematic illustration of the transition state of the enzyme is presented.
 ...
PMID:Studies on the mechanism of the malate dehydrogenase reaction. 3 61

A system of enzymes is required for the transport of reducing equivalents from reduced nicotinamide adenine dinucleotide (NADH) generated in the cytosol into the mitochondria by the substrate cycles. Also, the intestinal mitochondria must be capable of oxidizing the substrates of the cycles. Both substrate cycle enzymes and permeable mitochondria are necessary for the flow of pyruvate derived from glucose into the mitochondria for oxidative decarboxylation and for the efficient production of adenosine 5'-triphosphate (ATP) for the unique intestinal nutrient transport functions. Mitochondria from hamster intestinal mucosa were prepared exhibiting good respiratory control ratios. The isolated intestinal mitochondria would not oxidize NADH unless N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was added as a carrier of reducing equivalents. The rates of oxidation of the substrates of the L-glycerol 3-phosphate and the L-malate/1-aspartate substrate cycles were measured with the mitochondria isolated from the small intestinal mucosa. The key enzymes measured in the cytosol and mitochondria from the mucosa were NAD-L-glycerol 3-phosphate dehydrogenase, Fp-L-glycerol 3-phosphate dehydrogenase, L-malate dehydrogenase and L-glutamate-oxaloacetate transaminase. In addition, the substrate cyclase were simulated in vitro by following NADH oxidation by isolated mitochondria in the presence of added cytosolic constituents.
 ...
PMID:Flow of reducing equivalents into isolated intestinal mitochondria. 3 19

A NADH-linked oxygen-tolerant malate dehydrogenase was purified 270-fold from cell extracts of Methanospirillum hungatii. Inhibitors of the enzyme included ADP, alpha-ketoglutarate, and excess NADH. Inhibition patterns for ADP were competitive with respect to NADH and non-competitive with respect to oxalacetate. Inhibition by alpha-ketoglutarate was non-competitive with oxalacetate as variable substrate and uncompetitive with respect to NADH. alpha-Ketoglutarate is surmised to function as an end-product inhibitor of the enzyme in reactions converting oxalacetate to alpha-ketoglutarate. No enzyme activity was detected in the direction of malate conversion to oxalacetate, in keeping with a strictly biosynthetic function of the enzyme. An analysis of variance of intial rate data fit to sequential and ping-pong equations showed that a sequential mechanism was perferred. The malate dehydrogenase of M. hungatii resembles those of many other bacteria and eucaryotic cells respect to molecular weight (61,700) and reaction mechanism, but may be regulated differently.
 ...
PMID:Properties of malate dehydrogenase isolated from Methanospirillum hungatii. 3 74

Two allozymes (MDHf and MDHs) of cytoplasmic malate dehydrogenase of Drosophila virilis were partially purified and their biochemical properties were compared. MDHf has a pH optimum of 9.75 and MDHs one of 9.25 for malate oxidation. Optimal pH for oxaloacetate reduction is 6.75 and 8.0 for MDHf and MDHs, respectively. The Km value for oxaloacetate of MDHs is approximately twice as that of MDHf. No differences were found with respect to thermostability and Km's for malate, NAD+, or NADH. These results are discussed in terms of the physiological role of cytoplasmic malate dehydrogenase of D. virilis.
 ...
PMID:Biochemical differences between cytoplasmic malate dehydrogenase allozymes of Drosophila virilis. 4 84

1. A biochemical comparison was made among cytoplasmic malate dehydrogenase allozymic variants from Drosophila melanogaster. Experiments were carried out on enzyme extracted from six different genotypes: three homozygotes and their respective heterozygotes. 2. The allozyme forms (MDH A, MDH B, MDH C) were indistinguishable in terms of NAD and L-malate optima, while they are distinguishable in terms of NADH and OAA saturation conditions. Activities were inhibited at concentrations greater than 0.36 and 0.40 mM NADH for BB and AA, CC, respectively, while in relation to OAA inhibition was observed at concentrations higher than 3 or 6 mM for the AA, CC and BB, respectively. 3. differences among genotypes were also observed in thermal stability: Km values for OAA, L-malate, NADH and NAD: and pG optima. 4. A simple method is presented for the separation of the cytoplasmic from the mitochondrial malate dehydrogenase.
 ...
PMID:Biochemical studies of supernatant malate dehydrogenase allozymes in Drosophila melanogaster. 4 55


1 2 3 4 5 6 7 8 9 10 Next >>