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)

A thioredoxin has been highly purified from rabbit bone marrow. This thioredoxin is heat-stable, has a molecular weight of approximately 13,000, and contains 4 half-cystines. It is a substrate for the NADPH-dependent thioredoxin reductase of rabbit bone marrow, catalyzes the reduction of insulin disulfides by dithiothreitol, and is a hydrogen donor for methionine sulfoxide reductase of yeast. Although active as a hydrogen donor for ribonucleotide reductase of Lactobacillus leichmannii, this activity could not be demonstrated when the bone marrow thioredoxin was tested with the ribonucleotide reductases of rabbit bone marrow and Corynebacterium nephridii. A regulatory role for the bone marrow thioredoxin was investigated by determining its ability to activate two of the enzymes of spinach chloroplasts known to require thioredoxin for their activation. The bone marrow thioredoxin effectively activates spinach NADP-malate dehydrogenase but not spinach fructose 1,6-diphosphatase. These observations suggest that instead of serving as a hydrogen donor for ribonucleotide reduction in bone marrow, this thioredoxin may be involved in the regulation of the activity of bone marrow enzyme(s).
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PMID:Properties of a thioredoxin purified from rabbit bone marrow which fails to serve as a hydrogen donor for the homologous ribonucleotide reductase. 635 4

Chromatium vinosum, an anaerobic photosynthetic purple sulfur bacterium, resembles aerobic bacterial cells in that it has an NADP-thioredoxin system composed of a single thioredoxin which is reduced by NADPH via NADP-thioredoxin reductase. Both protein components were purified to homogeneity, and some of their properties were determined. Chromatium vinosum thioredoxin was slightly larger than other bacterial thioredoxins (13 versus 12 kilodaltons) but was similar in its specificity (ability to activate chloroplast NADP-malate dehydrogenase more effectively than chloroplast fructose-1,6-bisphosphatase) and immunological properties. As in other bacteria, Chromatium vinosum NADP-thioredoxin reductase was an arsenite-sensitive flavoprotein composed of two 33.5-kilodalton subunits, that required thioredoxin for the NADPH-linked reduction of 5,5'-dithiobis(2-nitrobenzoic acid). Chromatium vinosum NADP-thioredoxin reductase very effectively reduced several different bacterial-type thioredoxins (Escherichia coli, Chlorobium thiosulfatophilum (this name has not been approved by the International Committee of Systematic Bacteriology), Rhizobium meliloti) but not others (Clostridium pasteurianum, spinach chloroplast thioredoxin m). The results show that Chromatium vinosum contains an NADP-thioredoxin system typical of evolutionarily more advanced microorganisms.
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PMID:Thioredoxin system of the photosynthetic anaerobe Chromatium vinosum. 637 36

NADP-linked isocitrate dehydrogenase and malic enzyme [malate dehydrogenase (decarboxylating) (NADP)] activities were characterized in the cytosol of pancreatic islet cells. D-Glucose and L-leucine augmented the cytosolic NADPH/NADP+ ratio, as judged from the isocitrate/2-oxoglutarate and malate/pyruvate islet contents. The flow rate through the malic enzyme was judged from the output of labelled pyruvate by islets exposed to either L-[U-14C]glutamine or L-[U-14C]leucine. The cytosolic generation of NADPH, e.g. at the level of the malic enzyme, may play a role in the coupling of metabolic to secretory events in the process of nutrient-stimulated insulin release.
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PMID:The coupling of metabolic to secretory events in pancreatic islets. The cytosolic redox state. 637 86

Histochemical analysis for NADP-dependent dehydrogenases, succinate dehydrogenase, NADH and NADPH- tetrazoleum reductases and esterase was conducted on primary cultures of adipose tissue stromal-vascular cells. Enzyme activities were restricted to clusters of lipid laden cells (adipocytes). The number of enzyme reactive adipocytes increased with length of culture. Coverslips were partially coated with collagen to allow comparisons of cell differentiation on coated (C-glass) and uncoated glass (U-glass) surface. There were no reactions for NADH- and NADPH- tetrazoleum reductases (TR) in cells on C-glass whereas adipocytes and stromal cells on U-glass were reactive. Glucose-6-phosphate (G6PDH) and 6-phosphogluconate (6PGDH) dehydrogenase activities were markedly demonstrated in both stromal cells and adipocytes on U-glass. Malate (MDH) and isocitrate (ICDH) dehydrogenase activities were higher in adipocytes than in stromal cells on the U-glass. Stromal cells on C-glass were either devoid of these enzymes (G6PDH, MDH, 6PGDH, ICDH) or activity was restricted to a small area of the cytoplasm. There were two levels of staining intensity in (MDH, ICDH, G6PDH, 6PGDH) adipocyte clusters on C-glass. Elimination of phenazine methosulphate from the NADP-dependent dehydrogenase medias and SDH media, caused a reduction in enzyme reactive adipocytes on the C-glass. This manipulation did not reduce the number of enzyme reactive cells on U-glass. Cells on C-glass and U-glass were distinctly different in esterase stained coverslips. These studies demonstrated enzyme histochemical reactions of adipocytes and stromal cells in primary culture that were dependent on the type of extracellular matrix. Furthermore, enzyme histochemistry was shown to be useful for delineating adipocytes from stromal cells in primary cultures.
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PMID:The histochemistry of developing adipocytes in primary stromal-vascular cultures of rat adipose tissue. 642 89

The oxidative and phosphorylative properties of mitochondria isolated from Neurospora crassa were investigated as a function of growth stage. The rates of oxidation of exogenous NADH and NADPH varied independently of each other, thus ruling out the existence of only one unspecific dehydrogenase. Two different pathways were involved in the oxidation of NAD-linked substrates, as indicated by changes in the rate of oxygen uptake, the sensitivity to rotenone, and the efficiency of phosphorylation. One pathway was sensitive to rotenone and involved three energy-coupling sites, whereas the other was resistant to rotenone and bypassed complex I. Our results indicated that the activity of complex I of the respiratory chain increased markedly in the late exponential phase of growth, remained high in the stationary phase, and then decreased when conidiae were formed. In contrast, the activity of the rotenone-resistant bypass was maximal in the early exponential phase. With malate (plus glutamate) as a substrate, the sensitivity to rotenone and the ADP/O ratios were always lower than those observed with other NAD-linked substrates, suggesting a possible cooperation between malate dehydrogenase and the rotenone-resistant pathway. The rate of oxygen uptake measured in the presence of rotenone was significantly increased by the addition of exogenous NAD+, suggesting that added NAD+ could interact with the rotenone-resistant bypass.
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PMID:Properties of mitochondria as a function of the growth stages of Neurospora crassa. 646 22

BCNU has been reported to cause a rapid, irreversible inhibition of human erythrocyte glutathione reductase (GR) at chemotherapeutic dosage, without affecting metabolic enzymes. This inhibition may mediate some of the therapeutic and toxic effects of BCNU. Thiol containing agents such as reduced glutathione can protect cells against BCNU and a change in glutathione concentrations could modify BCNU effectiveness. At doses of 50 mg/kg (LD-50) and 100 mg/kg, i.p., BCNU decreased the activity of GR in mouse kidney, liver, brain, and heart with a greater loss in those animals which died from drug administration. GR activity tended to recover but still remained below control at 96 hours. Erythrocyte GR activity was reduced only at the higher BCNU dose. CCNU (100 mg/kg, i.p.) did not affect GR activity. BCNU also decreased creatine kinase, malate dehydrogenase, and lactate dehydrogenase activities. The inhibition of GR in vitro occurred only after biochemical reduction of the enzyme with NADPH. The oxidation state of GR may determine its sensitivity to BCNU in the human erythrocyte but we were unable to demonstrate an unusually high sensitivity or a specific effect of BCNU on GR in mouse tissues.
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PMID:The effects of BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) and CCNU (1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea) on glutathione reductase and other enzymes in mouse tissue. 662 14

It is shown that ageing induces in rats intensification of a GSH-dependent antioxidant effect of the liver cytozole, growth of glutathione-S-transferase activity of cytozole, microsomes and mitochondria, a decrease of the NADPH generation rate in cytozole with malate and glucose-6-phosphate oxidation (the rate remaining at high level with isocytrate oxidation). It is supposed that under definite physiological conditions a lowered rate of NADPH generation in the malate dehydrogenase and glucose-6-phosphate dehydrogenase reactions in old animals may limit the efficiency of the NADPH-GSH-dependent antioxidant system of the liver cells. The peroxidase activity of cytochrome P-450 of microsomes and the glutathione reductase activity (EC 1.6.4.2) of cytozole rise in the liver of rats up to their 12 months and fall considerably with ageing. Cytochrome P-450 in the membranes of endoplasmic reticulum plays the role of an antioxidant.
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PMID:[Enzymes of the antioxidant system of rat liver during aging]. 663 13

NADP-malate dehydrogenase was purified from leaves of Zea mays in the absence of thiol-reducing agents by (NH4)2SO4, polyethylene glycol, and pH fractionation followed by dye-ligand affinity chromatography and gel filtration. The purified enzyme is completely inactive (no activity detected between pH 6 and 9) but can be reactivated by thiol-reducing agents including dithiothreitol and thioredoxin. The active enzyme shows distinctly alkaline pH optima when assayed in either direction; Km values at pH 8.5 are oxaloacetate, 18 microM; malate, 24 mM; NADPH, 50 microM; and NADP, 45 microM. The reduction of oxaloacetate is inhibited by NADP (competitive with respect to NADPH, Ki = 50 microM). The molecular weight of the native inactive or active enzyme is 150,000 with subunits of Mr 38,000. Active enzyme is much more sensitive (greater than 50-fold) to heat denaturation than is the inactive enzyme and is irreversibly inactivated by N-ethylmaleimide whereas the inactive enzyme is insensitive to this reagent. The active and inactive forms of NADP-malate dehydrogenase are assumed to correspond to dithiol and disulfide forms of the enzyme, respectively. The relative coenzyme-binding affinities of inactive NADP-malate dehydrogenase differ by a factor of 10(2) from the binding affinities for active NADP-malate dehydrogenase and 10(4) for non-thiol-regulated NAD-specific malate dehydrogenase. It is proposed that the 100-fold change in differential binding of NADP and NADPH upon conversion of NADP-malate dehydrogenase to the disulfide form may sufficiently alter the equilibrium of the central enzyme-substrate complexes, and hence the catalytic efficiency of the enzyme, to explain the associated loss of activity.
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PMID:Regulation of C4 photosynthesis: physical and kinetic properties of active (dithiol) and inactive (disulfide) NADP-malate dehydrogenase from Zea mays. 666 24

Inactive NADP-malate dehydrogenase (disulfide form) from chloroplasts of Zea mays is activated by reduced thioredoxin while the active enzyme (dithiol form) is inactivated by incubation with oxidized thioredoxin. This reductive activation of NADP-malate dehydrogenase is inhibited by over 95% in the presence of NADP and the Kd for this interaction of NADP with the inactive enzyme is about 3 microM. Other substrates of the enzyme (malate, oxaloacetate, or NADPH) do not effect the rate of enzyme activation but NADPH can reverse the inhibitory effect of NADP. It appears that NADPH (Kd = 250 microM) and NADP (Kd = 3 microM) compete for the same site, presumably the coenzyme-binding site at the active centre. Apparently the enzyme . NADP binary complex cannot be reduced by thioredoxin whereas the enzyme . NADPH complex is reduced at the same rate as is the free enzyme. Similarly the oxidative inactivation of reduced NADP-malate dehydrogenase is inhibited by up to 85% by NADP and NADPH completely reverses this inhibition. The Kd values of the active-reduced enzyme for NADP and NADPH were both estimated to be 30 microM. From these data a model was constructed which predicts how changing NADPH/NADP levels in the chloroplast might change the steady-state level of NADP-malate dehydrogenase activity. The model indicates that at any fixed ratio of reduced to oxidized thioredoxin high proportions of active NADP-malate dehydrogenase and, hence, high rates of oxaloacetate reduction, can only occur with very high NADPH/NADP ratios.
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PMID:Regulation of C4 photosynthesis: regulation of activation and inactivation of NADP-malate dehydrogenase by NADP and NADPH. 666 25

Thioredoxin systems composed of several thioredoxin isoproteins and a NADPH: thioredoxin reductase are contained in the albumin-globulin fraction of wheat and soy-bean seed proteins. Two wheat thioredoxins I and II were separated on CM-cellulose whereas soy-bean extracts could be resolved into three thioredoxins I, II, and III on DEAE-cellulose. These proteins were purified to apparent homogeneity and were shown by sodium dodecylsulfate/polyacrylamide gel electrophoresis to possess the molecular weight Mr identical to 12000 typical of the single bacterial and animal thioredoxin. In contrast, gel filtration runs may yield erroneous estimates of thioredoxin molecular weights. The seed thioredoxins can serve as ribonucleotide reductase (Escherichia coli) substrates. They stimulate spinach NADP: malate dehydrogenase but are inactive towards chloroplast fructose-bisphosphatase. These results demonstrate that the number of thioredoxins in nongreen plant tissues approaches that of leaves; additional explanations must therefore be sought for the multiple thioredoxin profiles of plants besides diversification for light-dependent and light-independent functions.
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PMID:Plant seeds contain several thioredoxins of regular size. 668 37


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