Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A weak NADH oxidase activity of lipoamide dehydrogenase at neutral pH is increased as much as 15-fold by the addition of KI or (NH4)2SO4. The addition of NAD+ shifts the optimum pH for the KI-induced oxidase activity from 6.3 to 5.5 without changing the maximum activity. The optimum pH is similarly shifted to 5.6 when sulfhyldryl groups of the enzyme are oxidized in the presence of small amount of cupric ion. The NADH: lipoamide and NADH: p-benzoquinone reductase activities are strongly inhibited by KI but both are increased by the presence of (NH4)2SO4. The known intermediate having a charge-transfer band at 530 nm can be seen upon an addition of NADH to the enzyme in the presence of (NH4)2SO4 but not in the presence of KI. The enzyme flavin is reductase by a stoichiometric amount of NADH when KI is present.
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PMID:Salts- induced oxidase activity of lipoamide dehydrogenase from pig heart. 3 86

An acetate-requiring leaky mutant was induced from Bacillus subtilis 168, and activities of its three alpha-keto acid dehydrogenases were compared with the respectives activities of the parent strain. Both pyruvate and alpha-ketoisovalerate dehydrogenase activities in the mutant were consideralby lower, being only 10-17% of those of the parent, but alpha-ketoglutarate dehydrogenase activity was unchanged. These dehydrogenases are complexed composed of three enzymes: a carboxylase, a lipoic reductase-transacylase, and a dihydrolipoyl dehydrogenase. The carboxylase activity of the affected complexes was no different. Total dihydrolipoyl dehydrogenase activity was only one-third. Thus dihydrolipoyl dehydrogenase is the defective enzyme in the two dehydrogenase complexes; the activity remaining in the mutant is accounted for by the activity of the intact alpha-ketoglutarate dehydrogenase.
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PMID:Activities of alpha-ketoisovalerate, pyruvate, and alpha-ketoglutarate dehydrogenases in a mutant of Bacillus subtilis. 81 42

Cell-free preparations of the purple sulphur bacterium Thiocapsa roseopersicina grown in the light under anaerobic conditions and in the dark under aerobic conditions contain thiosulphate reductase and rhodanase. Dihydrolipoate is an electron donor in the cleavage of thiosulphate catalysed by thiosulphate reductase. Lipoate dehydrogenase (NADH: lipoate oxidoreductase) found in extracts of the cells of T. roseopersicina catalyses the reduction of lipoate. The activity of the enzymes involved in thiosulphate metabolism increases in the cells of T. roseopersicina growing under aerobic conditions in the dark on a mineral medium containing thiosulphate.
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PMID:[Enzymes involved in thiosulfate metabolism in Thiocapsa roseopersicina under various conditions of growth]. 101 54

The pyruvate dehydrogenase complex from Axotobacter vinelandii was isolated in a five-step procedure. The minimum molecular weight of the pure complex is 600,000, as based on an FAD content of 1.6 nmol-mg protein-1. The molecular weight is 1.0-1.2 X 10(6), indicating 1 mole of lipoamide dehydrogenase dimer per complex molecule. Sodium dodecylsulphate gel electrophoretical patterns show that apart from pyruvate dehydrogenase (Mr89,000) and lipoamide dehydrogenase (Mrmonomer 56,000) two active transacetylase isoenzymes are present with molecular weight on the gel 82,000 and 59,000 but probably actually lower. The pure complex has a specific activity of the pyruvate-NAD+ reductase (overall) reaction of 10 units-mg protein-1 at 25 degrees C. The partial reactions have the following specific activities in units-mg protein-1 at 25 degrees C under standard conditions: pyruvate-K3Fe(CN)6 reductase 0.14, transacetylase 3.6 and lipoamide dehydrogenase 2.9. The properties of this complex are compared with those from other sources. NADPH reduced the FAD of lipoamide dehydrogenase as well in the complex as in the free form. NADP+ cannot be used as electron acceptor. Under aerobic conditios pyruvate oxidase reaction, dependent on Mg2+ and thiamine pyrophosphate, converts pyruvate into CO2 and acetate; V is 0.2 mumol 02-min-1-mg-1, Km(pyruvate)0.3 mM. The kinetics of this reaction shows a linear 1/velocity-1/[pyruvate] plot. K3Fe(CN)6 competes with the oxidase reaction. The oxidase activity is stimulated by AMP and sulphate and is inhibited by acetyl-CoA. The partially purified enzyme contains considerable phosphotransacetylase activity. The pure complex does not contain this activity. The physiological significance of this activity is discussed.
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PMID:The pyruvate-dehydrogenase complex from Azotobacter vinelandii. 120 21

Environmental and clinical isolates of mercury-resistant (resistant to inorganic mercury salts and organomercurials) bacteria have genes for the enzymes mercuric ion reductase and organomercurial lyase. These genes are often plasmid-encoded, although chromosomally encoded resistance determinants have been occasionally identified. Organomercurial lyase cleaves the C-Hg bond and releases Hg(II) in addition to the appropriate organic compound. Mercuric reductase reduces Hg(II) to Hg(O), which is nontoxic and volatilizes from the medium. Mercuric reductase is a FAD-containing oxidoreductase and requires NAD(P)H and thiol for in vitro activity. The crystal structure of mercuric ion reductase has been partially solved. The primary sequence and the three-dimensional structure of the mercuric reductase are significantly homologous to those of other flavin-containing oxidoreductases, e.g., glutathione reductase and lipoamide dehydrogenase. The active site sequences are the most conserved region among these flavin-containing enzymes. Genes encoding other functions have been identified on all mercury ion resistance determinants studied thus far. All mercury resistance genes are clustered into an operon. Hg(II) is transported into the cell by the products of one to three genes encoded on the resistance determinants. The expression of the operon is regulated and is inducible by Hg(II). In some systems, the operon is inducible by both Hg(II) and some organomercurials. In gram-negative bacteria, two regulatory genes (merR and merD) were identified. The (merR) regulatory gene is transcribed divergently from the other genes in gram-negative bacteria. The product of merR represses operon expression in the absence of the inducers and activates transcription in the presence of the inducers. The product of merD coregulates (modulates) the expression of the operon. Both merR and merD gene products bind to the same operator DNA. The primary sequence of the promoter for the polycistronic mer operon is not ideal for efficient transcription by the RNA polymerase. The -10 and -35 sequences are separated by 19 (gram-negative systems) or 20 (gram-positive systems) nucleotides, 2 or 3 nucleotides longer than the 17-nucleotide optimum distance for binding and efficient transcription by the Escherichia coli sigma 70-containing RNA polymerase. The binding site of MerR is not altered by the presence of Hg(II) (inducer). Experimental data suggest that the MerR-Hg(II) complex alters the local structure of the promoter region, facilitating initiation of transcription of the mer operon by the RNA polymerase. In gram-positive bacteria MerR also positively regulates expression of the mer operon in the presence of Hg(II).
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PMID:Bacterial resistances to inorganic mercury salts and organomercurials. 131 Nov 13

ESR spectroscopic evidence is presented for the formation of vanadium(IV) in the reduction of vanadium(V) by three typical, NADPH-dependent, flavoenzymes: glutathione reductase, lipoyl dehydrogenase, and ferredoxin-NADP+ oxidoreductase. The vanadium(V)-reduction mechanism appears to be an enzymatic one-electron reduction process. Addition of superoxide dismutase (SOD) showed that the generation of vanadium(IV) does not involve the superoxide (O2-) radical significantly. Measurements under anaerobic atmosphere showed, however, that the enzymes-vanadium-NADPH mixture can cause the reduction of molecular oxygen to generate H2O2. The H2O2 and vanadium(IV) thus formed react to generate hydroxyl (.OH) radical. The .OH formation is inhibited strongly by catalase and to a lesser degree by SOD, but it is enhanced by exogenous H2O2, suggesting the occurrence of a Fenton-like reaction. The inhibition of vanadium(IV) formation by N-ethylmaleimide indicates that the SH group on the flavoenzyme's cystine residue plays an important role in the enzyme's vanadium(V) reductase function. These results thus reveal a new property of the above-mentioned, NADPH-dependent flavoenzymes--their function as vanadium(V) reductases, as well as that as generators of .OH radical in the vanadium(V) reduction mechanism.
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PMID:Flavoenzymes reduce vanadium(V) and molecular oxygen and generate hydroxyl radical. 165 58

The DNA sequence of the Salmonella typhimurium ahp locus was determined. The locus was found to contain two genes that encode the two proteins (C22 and F52a) that comprise the S. typhimurium alkyl hydroperoxide reductase activity. The predicted sequence of the F52a protein component of the alkyl hydroperoxide reductase was found to be highly homologous to the Escherichia coli thioredoxin reductase protein (34% identity with many conservative substitutions). The homology was found to be particularly striking in the region containing the redox-active cysteines of the thioredoxin reductase molecule, and among the identities were the redox-active cysteines themselves. Aside from the strong similarity to thioredoxin reductase, overall homology between the F52a protein and other flavoprotein disulfide oxidoreductases such as glutathione reductase, dihydrolipoamide dehydrogenase, and mercuric reductase was found to be rather limited, and the conserved active site segment common to the three proteins was not observed within the F52a protein. However, three short segments that have been implicated in FAD and NAD binding were found to be conserved between the F52a protein and the other disulfide reductases. These results suggest that the alkyl hydroperoxide reductase is the second known member of a class of disulfide oxidoreductases which was represented previously by thioredoxin reductase alone; they also allow the putative assignment of several functional domains.
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PMID:Alkyl hydroperoxide reductase from Salmonella typhimurium. Sequence and homology to thioredoxin reductase and other flavoprotein disulfide oxidoreductases. 219 51

An NADPH-specific disulfide reductase that is active with bis-gamma-glutamylcystine has been purified 1,900-fold from Halobacterium halobium to yield a homogeneous preparation of the enzyme. Purification of this novel reductase, designated bis-gamma-glutamylcystine reductase (GCR), and purification of halobacterial dihydrolipoamide dehydrogenase (DLD) were accomplished with the aid of immobilized-metal-ion affinity chromatography in high-salt buffers. Chromatography of GCR on immobilized Cu2+ resin in buffer containing 1.23 M (NH4)2SO4 and on immobilized Ni2+ resin in buffer containing 4.0 M NaCl together effected a 120-fold increase in purity. Native GCR was found to be a dimeric flavoprotein of Mr 122,000 and to be more stable to heat when in buffer of very high ionic strength. DLD was chromatographed on columns of immobilized Cu2+ resin in buffer containing NaCl and in buffer containing (NH4)2SO4, the elution of DLD differing markedly in the two buffers. Purified DLD was found to be a heat-stable, dimeric flavoprotein of Mr 120,000 and to be very specific for NAD. The utility of immobilized-metal-ion affinity chromatography for the purification of halobacterial enzymes and the likely cellular function of GCR are discussed.
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PMID:The novel disulfide reductase bis-gamma-glutamylcystine reductase and dihydrolipoamide dehydrogenase from Halobacterium halobium: purification by immobilized-metal-ion affinity chromatography and properties of the enzymes. 313 40

Lipoamide dehydrogenase (EC 1.6.4.3) from the ketoglutarate dehydrogenase complex of adrenals catalyzes the oxidation of NADH by lipoamide and quinone compounds according to the "ping-pong" scheme. The catalytic constants of these reactions are equal to 220 and 24 s-1, respectively (pH 7.0). The maximal quinone reductase activity is observed at pH 5.6, whereas the lipoamide reductase activity changes insignificantly at pH 7.5-5.5. The maximal dihydrolipoamide-NAD+ reductase activity is observed at pH 7.8. The oxidative constants of quinone electron acceptors vary from 6 X 10(6) to 4 X 10(2) M-1 s-1 and increase with their redox potential. The patterns of NAD+ inhibition in the quinone reductase reaction differ from that of lipoamide reductase reaction. The quinones are reduced by lipoamide dehydrogenase in the one-electron mechanism.
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PMID:[Characteristics of the interaction of adrenal lipoamide dehydrogenase with physiological and quinone electron acceptors]. 357 23

The mechanism of the enhancing effect of methyl viologen (MV) and flavin-adenine dinucleotide (FAD) on sulfoxide reduction which is mediated by a combination of aldehyde oxidase (AO) from guinea pig liver and one-electron reducing flavoenzymes, such as milk xanthine oxidase (XO), was examined. The activity of anaerobic reduction of diphenyl sulfoxide (DPSO) to diphenyl sulfide (DPS) was less than 1 nmol/min/mg protein of AO preparation in a system consisting of hypoxanthine, XO and AO. However, the sulfoxide reduction by this system was enhanced about 6- and 100-fold by the additions of FAD and MV, respectively. In the system containing MV or FAD, other one-electron reducing flavoenzymes such as nicotinamide adenine dinucleotide (reduced form) (NADH) dehydrogenase, lipoamide dehydrogenase and glutathione reductase with an appropriate electron donor, could replace XO. The ability of supplemented flavoenzymes to facilitate DPSO reduction correlated with their abilities to reduce MV and FAD. When AO was omitted from the combined system, no sulfoxide reduction was observed. Stoichiometric study revealed that MV semiquinone and FADH2 were oxidized at ratios of 2 and 1 mol, respectively, per mol of DPS formed. These results indicate that either MV or FAD serves as an electron carrier from the supplemented flavoenzymes to AO, a terminal reductase of sulfoxide.
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PMID:Sulfoxide reduction catalyzed by guinea pig liver aldehyde oxidase in combination with one-electron reducing flavoenzymes. 383 63


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