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 protein fraction from Escherichia Coli soluble extracts contain a NAD(P)H:hydrogen peroxide oxidoreductase activity. This activity is compared to and found to be distinct from well-known E. Coli enzymes involved in the protection from peroxides: hydroperoxidase I (HPI) and its o-dianisidine peroxidase component and the alkyl hydroperoxide reductase.
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PMID:NAD(P)H oxidation by hydrogen peroxide in Escherichia coli. 206 79

Assimilatory ferredoxin-nitrite reductase (EC 1.7.7.1, ammonia: ferredoxin oxidoreductase) has been purified 5300-fold with a specific activity of 625 units/mg protein from the filamentous non-heterocystous cyanobacterium Phormidium laminosum. The enzyme was soluble and consisted of a single polypeptidic chain of 54 kDa. It catalyzed the reduction of nitrite to ammonia using ferredoxin or flavodoxin as electron donor. Methyl and benzyl viologens were also effective as electron donors but neither flavins nor NAD(P)H were. The apparent Michaelis constants for nitrite, ferredoxin and methyl viologen were 40, 22 and 215 microM, respectively. Nitrite reductase activity was inhibited effectively by cyanide and thiol reagents. The enzyme exhibited absorption maxima at 281, 391 (Soret), 570 (alpha) and 695 nm, with epsilon 391 of 4.3 x 10(4) M-1 cm-1, and an absorbance ratio A281/A391 of 1.95, suggesting the presence of siroheme as prosthetic group. These results show that this enzyme is similar to those of eukaryotic organisms.
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PMID:Purification and some properties of the nitrite reductase from the cyanobacterium Phormidium laminosum. 211 28

The effects of butylated hydroxyanisole (BHA), a commonly used food antioxidant, on oxygen consumption, ATPase activity, and the redox state of some electron carriers of rat liver mitochondria have been studied. It was observed that BHA slightly stimulated state 4 respiration but strongly inhibited ADP- and uncoupler-stimulated respiration on NAD(+)- and FAD-linked substrates. ATPase activity and vectorial H+ ejection were affected only slightly by BHA, suggesting that BHA predominantly inhibits mitochondrial electron flow. Experiments to determine its site of action showed that BHA did not noticeably affect electron flow through cytochrome oxidase; in contrast, NADH:duroquinone reductase activity and electron flow through ubiquinone-cytochrome b-cytochrome c complex were inhibited strongly because the oxidation of duroquinol was affected markedly. The BHA block of electron transport was bypassed by both N,N,N',N'-tetramethyl-p-phenylenediamine and 2,6-dichlorophenolindophenol. Also, the presence of BHA changed the redox state of cytochrome b and c1 to a more oxidized level. These observations suggest that electron transport is inhibited by BHA at the NADH-ubiquinone and at the ubiquinone-cytochrome b levels. From Hill plots, it is clear that more than one binding site is involved in complete inhibition; in addition, available evidence suggests that there may be two sites at the substrate side of ubiquinone and another two sites at the oxygen side of ubiquinone. Consequently, mitochondrial ATP synthesis would be interrupted. This event could be related to the toxicity of BHA.
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PMID:Effect of butylated hydroxyanisole on electron transport in rat liver mitochondria. 214 54

The oxidation of camphor by cytochrome P-450cam requires the participation of a flavoprotein, putidaredoxin reductase, and an iron-sulfur protein, putidaredoxin, to mediate the transfer of electrons from NADH to P-450 for oxygen activation. A 2.2-kilobase pair BamHI-StuI fragment from whole cell DNA of camphor-grown Pseudomonas putida has been cloned and sequenced. Translation of the sequence revealed two open reading frames that could code for putidaredoxin reductase and putidaredoxin. In the case of putidaredoxin, the translated sequence matched the published sequence (Tanaka, M., Haniu, M., Yasunobu, K. T., Dus, K., and Gunsalus, I. C. (1974) J. Biol. Chem. 249, 3689-3701) with the exception of one amino acid. Codon usage in these proteins, like the proteins of other Pseudomonads, is strongly biased to G + C in the third nucleotide. A potential transcription termination site was found 3' to the putidaredoxin coding region. The "FAD-binding" amino acid consensus sequence, present in other flavoproteins, was found in putidaredoxin reductase beginning at residue 11 and a second occurrence of this sequence was found beginning with amino acid 156. The second sequence could represent the NAD-binding site. The regions encoding putidaredoxin reductase and putidaredoxin were subcloned and independently expressed in Escherichia coli at the level of 0.4 and 4.8 mg of enzymatically active protein/g wet weight of cells, respectively. Site-directed mutagenesis was used to change the rare start codon, GTG, of putidaredoxin reductase to ATG which resulted in an 18-fold increase in the level of expression of this protein to 7.4 mg/g wet weight of cells. The construction of these two clones, which express these important proteins, will facilitate studies of their interaction with each other and with P-450cam.
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PMID:Putidaredoxin reductase and putidaredoxin. Cloning, sequence determination, and heterologous expression of the proteins. 218 Sep 40

Several NAD(P)H-dependent ferri-reductase activities were detected in sub-cellular extracts of the yeast Saccharomyces cerevisiae. Some were induced in cells grown under iron-deficient conditions. At least two cytosolic iron-reducing enzymes having different substrate specificities could contribute to iron assimilation in vivo. One enzyme was purified to homogeneity: it is a flavoprotein (FAD) of 40 kDa that uses NADPH as electron donor and Fe(III)-EDTA as artificial electron acceptor. Isolated mitochondria reduced a variety of ferric chelates, probably via an 'external' NADH dehydrogenase, but not the siderophore ferrioxamine B. A plasma membrane-bound ferri-reductase system functioning with NADPH as electron donor and FMN as prosthetic group was purified 100-fold from isolated plasma membranes. This system may be involved in the reductive uptake of iron in vivo.
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PMID:Iron-reductases in the yeast Saccharomyces cerevisiae. 218 97

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

Selected aspects of the metabolism of Plasmodium falciparum are reviewed, but conclusions based on the study of other species of plasmodia are intentionally not included since these may not be applicable. The parasites increase glucose consumption 50-100 fold as compared to uninfected red cells; most of the glucose is metabolized to lactic acid. The parasite contains a complete set of glycolytic enzymes. Some enzymes such a hexokinase, enolase and pyruvate kinase are vastly increased over corresponding levels in uninfected red cells. However, the pathway for synthesizing 2,3-diphosphoglycerate (2,3-DPG) is absent. Parasitized red cells show a decline in the concentration of 2,3-DPG which may function as an inhibitor for certain essential enzyme pathways. Pentose shunt activity is increased in absolute terms, but as a percent of total glucose consumption, there is a decrease during parasite infection of the red cell. The parasite contains a gene for G6PD and can produce a small quantity of parasite-encoded enzyme. It is not clear if the production of this enzyme can be up-regulated in G6PG deficient host red cells. The NADPH normally produced by the pentose shunt can be obtained from other parasite pathways (such as glutamate dehydrogenase). NADPH may subserve additional needs in the infected red cell such as driving diribonucleotide reductase activity--a rate limiting enzyme in DNA synthesis. The role of NADPH in protecting the parasite-red cell system against oxidative stress (via glutathione reduction) remains controversial. Parasitized red cells contain about 10 times more NAD(H) than uninfected red cells, but the NADP(H) content is unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Plasmodium falciparum carbohydrate metabolism: a connection between host cell and parasite. 225 22

Hack and Helmy's method for the histochemical identification of NAD(P)H nitroblue tetrazolium reductase activity was employed to pinpoint reductase activity in certain cells in the mouse. High activity was observed in the following: lower airway epithelium, liver (centrilobular zone), eyelid (meibomian and sebaceous glands), vulval gland and parotid gland (striated cells of intralobular ducts). All of these cells had previously been identified as sites of binding of the reactive metabolites formed from the enzymic reduction of misonidazole (MISO) (Cobb et al., 1989). It had previously been thought that MISO binding would only take place in significant amounts in hypoxic tissues (tumour and possibly liver) since in normoxic tissues oxygen should reverse the initial one electron enzymic reduction, thus preventing progressive reduction to reactive species. We suggest that the very high levels of reductase in the above listed, probably normoxic, tissues contribute significantly to the accumulation of bound reactive MISO metabolite(s).
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PMID:NAD(P)H nitroblue tetrazolium reductase levels in apparently normoxic tissues: a histochemical study correlating enzyme activity with binding of radiolabelled misonidazole. 233 39

Administration of phenylhydrazine to rats converted molecular form 1 of the liver biliverdin reductase into its disulfide bridged dimer (molecular form 3). This oxidative dimerization was shown not to be mediated by the NAD(+)-dependent dehydrogenase [(1984) Biochem. Biophys. Res. Commun. 121, 249-254]. Administration of diamide produced the same conversion. Although hepatic levels of GSH also decreased, no mixed disulfides of the reductase and GSH could be detected. Administration of the antioxidants allopurinol and alpha-tocopherol together with the diamide did not affect this conversion of molecular forms produced by the latter. The diamide also oxidized molecular form 1 of biliverdin reductase in vitro and molecular form 3 was formed. The chemical oxidation took place at a high rate and was partially inhibited by GSH but not by cysteine.
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PMID:The in vivo and in vitro oxidation of molecular form 1 of biliverdin reductase to molecular form 3 by diamide. 233 51

The tetrazolium salt procedure of van Gelder (1965) for the demonstration of GABA transaminase (GABAT; the most important GABA degrading enzyme) was adapted for microphotometric measurements of GABAT activities in brain sections using the hippocampus of rats as selected brain region. The final incubation medium consisted of 50 mM GABA, 5 mM alpha-ketoglutarate, 7 mM NAD, 10 mM sodium azide, 6 mM nitroblue tetrazolium chloride, 20 mM malonate and 15% polyvinyl alcohol in 0.05 M Hepes buffer; the final pH was 8.0. There was a linear relationship between GABAT activity and section thickness up to 14 microns and between GABAT activity and reaction time at least up to 20 min (kinetic and end-point measurements). Phenazine methosulfate as an exogenous electron carrier and pyridoxal-5-phosphate as coenzyme of GABAT did not enhance the demonstrable GABAT activities, whereas sodium azide as a blocker of the respiratory chain resulted in an increase of demonstrable enzyme activities. A coreaction of succinate dehydrogenase was excluded by the use of malonate (competitive inhibitor). Using the incubation medium described GABAT activities were demonstrated via the endogenous enzymes succinic semialdehyde dehydrogenase and NADH tetrazolium reductase which were shown to be not rate limiting and seems to be similarly localized as GABAT.
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PMID:Microphotometric determination of enzymes in brain sections. II. GABA transaminase. 233 51


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