Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The X-ray structure analyses of four glutathione reductase complexes and derivatives have been extended to 2 A resolution and refined. The results are discussed in conjunction with the structure of the oxidized native enzyme known at 1.54 A resolution. While the residual co-ordinate errors are around 0.2 A, some significant shifts even in this range could be established. Points of particular interest are the 3.2 A approach of C4N of nicotinamide to N5F of flavin in hydride transfer geometry, the hydrogen bond geometries of the 2'-phosphate of NADPH as compared to inferior geometries for an inorganic phosphate binding together with NADH, the differential mobilities of parts of the substrates as derived from refined atomic temperature factors, and the stabilization of the thiolate of the proximal Cys63 by conformational changes of neighboring residues as well as by flavin. In addition, catalytically competent His467' is seen to interact more optimally with the sulfur of glutathione-I than with the distal sulfur of Cys58. The observed participation of water molecules for both NADPH and glutathione binding is so extensive that a prediction of the binding mode merely from the polypeptide structure would be very difficult. The accurately known geometries allowed us to draw some conclusions on the enzyme mechanism and suggest a possible scenario of the catalysis.
J Mol Biol 1989 Nov 05
PMID:Substrate binding and catalysis by glutathione reductase as derived from refined enzyme: substrate crystal structures at 2 A resolution. 258 16

Initial Polytron treatment with subsequent exposure to the bacterial proteinase Nagarse has been shown to result in the isolation of two distinct populations of cardiac mitochondria, subsarcolemmal and interfibrillar mitochondria, respectively. Although these populations have been shown to possess distinct biochemical properties, few studies have been reported which document the potential differences in their response to pathological insult. We therefore examined the effect of acute hypoxia with or without reoxygenation as well as treatment with phosphate on oxidative phosphorylation on both groups of mitochondria. Freshly-isolated interfibrillar mitochondria (IFM) exhibited significantly higher respiratory values, with the exception of the ADP:O ratios, than subsarcolemmal mitochondria (SLM). With pyruvate-malate as respiratory substrate, 40 minutes hypoxia alone produced no effect on SLM whereas a stimulation in respiration was seen in IFM. A 40-minute reoxygenation period depressed the oxidative phosphorylation rate in SLM whereas it was stimulated in IFM. These treatments did not produce any effect in either population when succinate was the substrate of choice. Because of the latter observation, the possibility that increased lability of complex I of the electron transport chain accounted for the differences associated with NAD-linked substrates was studied by assessing NADH oxidation of sonicated mitochondria following the treatments. SLM exhibited enhanced permeability to exogenous NADH as well as increased sensitivity to sonication following either hypoxia or hypoxia/reoxygenation compared to IFM. Compared to hypoxia/reoxygenation, increasing concentrations of phosphate (5-15 mM) produced a marked depression in oxidative phosphorylation of SLM whereas IFM were relatively resistant. The toxic effects of phosphate were much more evident with pyruvate-malate as substrates; with succinate, oxidative phosphorylation of IFM was not depressed by phosphate whereas only a slight depression was observed with SLM. The latter population similarly exhibited reduced NADH oxidation following phosphate treatment whereas IFM were unaffected. Our studies show a differential sensitivity of two mitochondrial populations to hypoxia/reoxygenation, and, more markedly to phosphate. Since these effects were much less pronounced with succinate-linked respiration and since they were associated with defective NADH oxidation in SLM, it is suggested that the differences between the two populations may be accounted for by the increased lability of complex I of SLM due to hypoxia/reoxygenation or phosphate.
Mol Cell Biochem 1989 Oct 05
PMID:Acute effects of hypoxia and phosphate on two populations of heart mitochondria. 260 32

A new sampling method of cross-sectioning the canine heart in situ was developed. A mechanical device, driven by spring power, enabled cross-sectioning of a short-axis plane of the beating canine heart (4 mm thick) with high speed rotating blades, at a pre-determined phase of the cardiac cycle, and instantaneous freeze-clamping (2.4 mm thick) with pre-cooled aluminum blocks, all within 120 ms. By this method, the anatomical structures of the sample were well preserved. Transmural metabolism and flow distribution were instantaneously fixed and high resolution of the two-dimensional redox state was obtained by application of NADH fluorescence photography. Micro-samplings from the desired portion of the cross-sectional slice were possible at -190 degrees C. NADH fluorescence of the samples did not increase from the surface to 1.2 mm in depth, confirming that there was no ischemic artifact. With the present technique, a heart sample in which transmural metabolism, and the redox state, are fixed and visualized is attainable, thus providing a new tool for the study of myocardial ischemia.
J Mol Cell Cardiol 1989 Feb
PMID:A rapid cross-sectioning and freeze-clamping device for the beating canine heart. 266 89

Phosphorylation in isolated Ascaris suum mitochondria was much greater in the presence of malate than succinate, but, in the absence of added adenine nucleotides, incubations in succinate resulted in substantial elevations in intramitochondrial ATP levels. Succinate-dependent phosphorylation was stimulated aerobically and this stimulation was due almost entirely to a site I, rotenone-sensitive, phosphorylation. Increased substrate level phosphorylation, coupled to propionate formation, or additional sites of electron-transport associated ATP synthesis were not significant. Under aerobic conditions, 14CO2 evolution from 1,4-[14C]succinate was stimulated and NADH/NAD+ ratios were elevated, but the formation of [14C]propionate was unchanged. It appears that succinate was metabolized to pyruvate and acetate, and NADH, generated from the decarboxylations of malate and pyruvate, was the primary source of reducing power fueling electron-transport. The terminal oxidase and final electron-acceptor are still not clearly defined. However, ferricyanide, H2O2, and 100% oxygen all stimulated succinate-dependent phosphorylation. A possible role for cytochrome c peroxidase in A. suum mitochondrial metabolism is discussed.
Mol Biochem Parasitol 1989 Feb
PMID:Succinate-dependent energy generation in Ascaris suum mitochondria. 271 Jan 62

Recently, an exogenous NADH-oxidase has been shown to be a source of oxygen derived toxic species in heart mitochondria. This enzyme uses NADH and oxygen to form superoxide radicals and hydrogen peroxide. Growing evidence suggests that oxygen radicals and hydrogen peroxide may contribute to cardiac damage during ischemia or hypoxia. The activity of the enzyme NADH-oxidase could play an important role in the damage caused by oxygen derived toxic species, especially since cellular defense mechanisms against free radicals are depleted under ischemic conditions. In this study, a cytochemical method was used to visualize hydrogen peroxide, the reaction product of NADH-oxidase activity, in normal and ischemic dog myocardium. The NADH-oxidase reaction product was present in weak amounts in mitochondria from normoxic myocardium. In viable ischemic areas a high degree of activity was observed in the mitochondria. In infarcted tissue mitochondria contained few or no reaction product at all. The results support the hypothesis that hydrogen peroxide and oxygen radicals produced in the mitochondria by a high NADH-oxidase activity may contribute to the mitochondrial damage observed during ischemia when NADH is no longer oxidized by the respiratory chain and cellular defense mechanisms are impaired.
J Mol Cell Cardiol 1989 Apr
PMID:Mitochondrial hydrogen peroxide generation by NADH-oxidase activity following regional myocardial ischemia in the dog. 274 59

17 beta-Hydroxysteroid oxidoreductase, the enzyme that catalyses the interconversion of oestradiol and oestrone, is known to be present in human breast tissue. However, it is not known whether one or more forms of the enzyme is present. Homogenates of breast adipose tissue and breast glandular tissue were fractionated and fractions assayed in the oxidative direction with NAD+ and NADP+ as coenzymes, and in the reductive direction with NADH and NADPH as coenzymes. Ultracentrifugation of homogenates showed that there was membrane-bound activity and soluble activity. The soluble activity was due to a number of forms of the enzyme with different molecular weights, three in breast adipose tissue and two in breast glandular tissue, as shown by fractionation with (NH4)2SO4 followed by chromatography on Sephadex G-200. The forms of the enzyme isolated differed in their affinities for substrates and coenzymes and in the relative rates at which they catalysed the oxidative and reductive reactions. Preliminary experiments with breast tumours showed that they also contained membrane-bound activity and more than one soluble form of the enzyme.
J Mol Endocrinol 1989 Jan
PMID:Multiple forms of 17 beta-hydroxysteroid oxidoreductase in human breast tissue. 276 15

p-Chloromercuribenzoate alters various reactions of rat liver glucose (hexose phosphate) dehydrogenase differently. The reagent has little effect on the glucose: NAD or the glucose: NADP oxidoreductases, doubles the rates of oxidations of galactose-6-phosphate and glucose-6-phosphate by NADP and greatly stimulates the oxidations of glucose-6-phosphate and galactose-6-phosphate by NAD. The reagent appears to react with a sulfhydryl group of the enzyme since activation is reversed and prevented by mercaptoethanol. The direct reaction of the reagent with the enzyme is indicated by its lower thermal stability in the presence of the p-chloromercuribenzoate. The size of the enzyme appears to be the same when determined by sucrose gradient centrifugation in the presence or absence of p-chloromercuribenzoate. In microsomes, the oxidation of NADH or NADPH hampers measurements of glucose dehydrogenase. Since p-chloromercuribenzoate inhibits microsomal oxidation of reduced nicontinamide nucleotides, it is possible to assay for glucose dehydrogenase accurately in the presence of the mercurial in microsomes and microsomal extracts and thus measure the effectiveness of a detergent in extracting the enzyme from microsomes.
Mol Cell Biochem 1989 Apr 11
PMID:The activation of glucose dehydrogenase by p-chloromercuribenzoate. 277 Jul 7

Regulation of beta-oxidation under various metabolic conditions and energy loads was studied by employing a newly developed method for assaying 3-hydroxyacyl-CoA and 2-trans-enoyl-CoA intermediates of fatty acid oxidation. A 66% inhibition of oleate oxidation with a concomitant 68% inhibition of oxygen consumption resulted in a 81% decrease in the carnitine/acyl-carnitine ratio, but the concentrations of 2-trans-enoyl-CoA and 3-hydroxyacyl-CoA esters did not change significantly and the acid-insoluble acyl-CoA content did not change. The acetyl-CoA concentration increased three-fold, however, and there was a simultaneous tendency for the NADH/NAD+ ratio to shift towards oxidation. The results suggest that the main regulatory site of fatty acid oxidation resides at an early step in the pathway. Since the concentrations of the acyl-CoA derivatives identified did not undergo major changes even though the acyl-carnitine concentration changed some rate limitation must already occur at the steps of acyl transport into the mitochondria or the carnitine acyltransferase II.
J Mol Cell Cardiol 1989 Aug
PMID:Energy-linked regulation of mitochondrial fatty acid oxidation in the isolated perfused rat heart. 277 13

A series of mouse lines with increased resistance to respiratory inhibitors which block electron transport through the protonmotive cytochrome b of complex III have been isolated in this laboratory. We describe here the isolation of a mutant with increased resistance to HQNO (2-n-heptyl-4-hydroxyquinoline-N-oxide) whose phenotype is due to a nuclear mutation. At the cellular level, there is a severe reduction in respiration with the residual oxygen consumption being resistant to inhibitors of both ubiquinol-cytochrome c oxidoreductase and cytochrome oxidase. At the mitochondrial level, there was a severe derangement in NADH oxidase activity. Electron transport through the succinate oxidase span of the respiratory chain and its coupling to oxidative phosphorylation are also reduced in this nuclear mutant but not to the same extent. It is concluded that the primary defect in the mutant lies within a nuclear gene encoding a component of complex I (NADH-ubiquinol oxidoreductase). In addition, further biochemical characterization of the mitochondrially inherited inhibitor-resistant mutants has demonstrated that they also show significant reductions in the efficiency of energy transduction and in the rate of cytochrome b electron transport.
Somat Cell Mol Genet 1987 Sep
PMID:Characterization of mouse nuclear and mitochondrial mutants with increased resistance to cytochrome b inhibitors. 282 32

Mitochondrial membranes from Trypanosoma brucei procyclic trypomastigotes generated superoxide anion and hydrogen peroxide in a 2:1 ratio when supplemented with NADH. Fumarate inhibited hydrogen peroxide formation (Ki = 16 microM) with the same affinity as it stimulated NADH-fumarate reductase activity. Superoxide anion production was also 65% inhibited by fumarate (Ki = 20 microM). The KM for NADH of the NADH-fumarate reductase (60 microM) was also similar to that for hydrogen peroxide generation in the absence of fumarate (30 microM). These results suggest that the NADH-fumarate reductase is involved as a source for free radical generation in T. brucei mitochondria.
Mol Biochem Parasitol 1987 Aug
PMID:Possible role of the NADH-fumarate reductase in superoxide anion and hydrogen peroxide production in Trypanosoma brucei. 282 35


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