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)

Microsomal superoxide anion (O2-) production was detected using the chemiluminigenic probe, bis-N-Methylacridinium nitrate (lucigenin). Superoxide dismutase (SOD) inhibited 55% of the light emission but in the presence of a detergent (Triton X100) SOD inhibited the light emission by 94%. Lucigenin chemiluminescence from rat liver microsomes supplemented with NADPH was found to be selective and sensitive in detecting the O2- production. Treatment of rats with poly IC and LPS resulted in a decrease of the hepatic microsomal cytochrome P450 content by 44% and 37% respectively. The decrease in the cytochrome P450 contents was accompanied by a decrease in LgCl from the hepatic microsomal fractions by 61% for the poly IC and by 51% for the LPS treated rats. This is the first report to demonstrate that decreased P450 in the presence of normal amounts of cytochrome P450(c) reductase produce correspondingly less O2- from the microsomes.
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PMID:Effect of interferon inducers on superoxide anion generation from rat liver microsomes detected by lucigenin chemiluminescence. 254 91

Electron paramagnetic resonance spectra obtained during turnover of the Mo center of NADH:nitrate reductase at pH 8 were comprised of two Mo(V) species, signal A (g1 = 1.996, g2 = 1.969, g3 = 1.967, A1H = 1.25 mT, A2H = 1.18 mT, and A3H = 1.63 mT) and signal B (g1 = 1.996, g2 = 1.969, and g3 = 1.967), the former exhibiting superhyperfine interaction due to strong coupling with a single, exchangeable proton. Binding of halides and nitrite to the Mo center increased the proportion of signal A whereas phosphate had no effect on the EPR line shape. Halides decreased and phosphate increased the rates of enzyme activities involving the Mo center (NADH:nitrate reductase and reduced methyl viologen:nitrate reductase), but neither had any effect on activities involving FAD (NADH:ferricyanide reductase) or heme (NADH:cytochrome c reductase), indicating specific binding of halides to the Mo center. Halides were found to be weak, mixed competitive-noncompetitive inhibitors (Cl- KI = 39 mM, mu = 0.2 M, pH 8) of nitrate reductase forming a catalytically inactive ternary halide-nitrate-enzyme complex. Inhibition patterns changed from nearly noncompetitive (F-) to nearly competitive (I-). The weakening of nitrate binding due to halide binding correlated with increased halide electronegativity rather than ionic radius. In contrast, phosphate (Kd = 7.4 mM, mu = 0.2 M, pH 8) and arsenate were determined to be nonessential activators, characterized by a constant value of (Vmax/Km)app, increasing nitrate reductase activity by weakening nitrate binding without affecting the stability of the transition state. Phosphate had no effect on product inhibition by nitrite (KI = 0.33 mM) or the oxidation-reduction midpoint potentials of the Mo center.
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PMID:EPR and kinetic analysis of the interaction of halides and phosphate with nitrate reductase. 255 63

Among nitrogen oxides, NO and NO2 are free radicals and show a variety of biological effects. NO2 is a strongly oxidizing toxicant, although NO, not oxidizing as NO2, is toxic in that it interacts with hemoglobin to form nitrosyl- and methemoglobin. Nitrosylhemoglobin shows a characteristic electron spin resonance (ESR) signal due to an odd electron localized on the nitrogen atom of NO and reacts with oxygen to yield nitrate and methemoglobin, which is rapidly reduced by methemoglobin reductase in red cells. NO was found to inhibit the reductase activity. Part of NO inhaled in the body is oxidized by oxygen to NO2, which easily dissolves in water and converts to nitrite and nitrate. The nitrite oxidizes oxyhemoglobin autocatalytically after a lag. The mechanism of the oxidation, particularly the involvement of superoxide, was controversial. The stoichiometry of the reaction has now been established using nitrate ion electrode and a methemoglobin free radical was detected by ESR during the oxidation. Complete inhibition of the autocatalysis by aniline or aminopyrine suggests that the radical catalyzes conversion of nitrite to NO2, which oxidizes oxyhemoglobin. Recently NO was shown to be one of endothelium-derived relaxing factors and the relaxation induced by the factor was inhibited by hemoglobin and potentiated by superoxide dismutase.
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PMID:The interaction between nitrogen oxides and hemoglobin and endothelium-derived relaxing factor. 255 83

Addition of sodium nitrate to growing cultures of Aspergillus parasiticus (ATCC 36537) induces the synthesis of enzymes involved in nitrate assimilation (NO3- reductase), of enzymes in the pentose pathway (glucose-6-phosphate dehydrogenase), and of enzymes in the mannitol cycle (mannitol- and mannitol-1-phosphate dehydrogenases). Addition of NO3- also causes a dose-dependent suppression of synthesis of the polyketide secondary metabolite, versicolorin A. We suggest that in the presence of NO3- plus peptone, the cytoplasmic NADPH/NADP ratio may be elevated, resulting in increased conversion of malonyl coenzyme A to fatty acid rather than to polyketide.
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PMID:Nitrate induces enzymes of the mannitol cycle and suppresses versicolorin synthesis in Aspergillus parasiticus. 261 92

Propionibacterium acnes P13 was isolated from human feces. The bacterium produced a particulate nitrate reductase and a soluble nitrite reductase when grown with nitrate or nitrite. Reduced viologen dyes were the preferred electron donors for both enzymes. Nitrous oxide reductase was never detected. Specific growth rates were increased by nitrate during growth in batch culture. Culture pH strongly influenced the products of dissimilatory nitrate reduction. Nitrate was principally converted to nitrite at alkaline pH, whereas nitrous oxide was the major product of nitrate reduction when the bacteria were grown at pH 6.0. Growth yields were increased by nitrate in electron acceptor-limited chemostats, where nitrate was reduced to nitrite, showing that dissimilatory nitrate reduction was an energetically favorable process in P. acnes. Nitrate had little effect on the amounts of fermentation products formed, but molar ratios of acetate to propionate were higher in the nitrate chemostats. Low concentrations of nitrite (ca. 0.2 mM) inhibited growth of P. acnes in batch culture. The nitrite was slowly reduced to nitrous oxide, enabling growth to occur, suggesting that denitrification functions as a detoxification mechanism.
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PMID:Dissimilatory nitrate reduction by Propionibacterium acnes. 262 64

Mutants of Salmonella typhimurium that lack the biosynthetic sulfite reductase (cysI and cysJ mutants) retain the ability to reduce sulfite for growth under anaerobic conditions (E. L. Barrett and G. W. Chang, J. Gen. Microbiol., 115:513-516, 1979). Here we report studies of sulfite reduction by a cysI mutant of S. typhimurium and purification of the associated anaerobic sulfite reductase. Sulfite reduction for anaerobic growth did not require a reducing atmosphere but was prevented by an argon atmosphere contaminated with air (less than 0.33%). It was also prevented by the presence of 0.1 mM nitrate, which argues against a strictly biosynthetic role for anaerobic sulfite reduction. Anaerobic growth in liquid minimal medium, but not on agar, was found to require additions of trace amounts (10(-7)M) of cysteine. Spontaneous mutants that grew under the argon contaminated with air also lost the requirement for 10(-7)M cysteine for anaerobic growth in liquid. A role for sulfite reduction in anaerobic energy generation was contraindicated by the findings that sulfite reduction did not improve cell yields, and anaerobic sulfite reductase activity was greatest during the stationary phase of growth. Sulfite reductase was purified from the cytoplasmic fraction of the anaerobically grown cysI mutant and was purified 190-fold. The most effective donor in crude extracts was NADH. NADPH and methyl viologen were, respectively, 40 and 30% as effective as NADH. Oxygen reversibly inhibited the enzyme. Two high-molecular-weight proteins separated by gel filtration (Mr 360,000 and 490,000, respectively) were required for maximal activity with NADH. Indirect evidence, including in vitro complementation experiments with a cysG mutant extract, suggested that the 360,000-Mr component contains siroheme and is the terminal reductase. This component was further purified to near homogeneity and was found to consist of a single subunit of molecular weight 67,500. The anaerobic sulfite reductase showed some resemblance to the biosynthetic sulfite reductase, but apparently it has a unique, as yet unidentified function.
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PMID:Characterization of anaerobic sulfite reduction by Salmonella typhimurium and purification of the anaerobically induced sulfite reductase. 265 37

The nucleotide sequence of the narGHJI operon that encodes the nitrate reductase of Escherichia coli was completed. It encodes four polypeptides NarG, NarH, NarJ and NarI of molecular weight 138.7, 57.7, 26.5 and 25.5 kDa, respectively. The analysis of deduced amino acid sequence failed to reveal any structure capable of binding iron within the NarG polypeptide. In contrast, cysteine arrangements typical of iron-sulfur centers were found in the NarH polypeptide. This suggested that the latter is an electron transfer unit of the nitrate reductase complex. Such a view is opposite to the current description of the nitrate reductase. The findings allowed us to propose a model for the electron transfer steps that occur during nitrate reduction. The NarG polypeptide was found to display a high degree of homology with numerous E. coli molybdoproteins. Moreover, the same genetic and functional organizations as well as the presence of highly conserved stretches of amino acids were noted between both NarG/NarH and DmsA/DmsB (encoding the dimethyl sulfoxide reductase) pairs.
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PMID:Nitrate reductase of Escherichia coli: completion of the nucleotide sequence of the nar operon and reassessment of the role of the alpha and beta subunits in iron binding and electron transfer. 267 54

Nitric oxide reductase of Paracoccus denitrificans was purified, with the use of 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO) detergent, as membrane vesicles of apparent Mr = 2-3 x 10(6). Fifty percent of the protein was a peptide of Mr = 34,000. Further fractionation with sodium dodecyl sulfate (SDS) resulted in vesicles in which the peptide constituted 90-95% of the protein. This peptide, which is rich in Ala, Gly, Ser, Asx, and Glx, is considered to be the peptide of nitric oxide reductase. The CHAPSO- and SDS-fractionated preparations lost activity at 4 degrees C, pH 7.4, with half-times, respectively, of about 6 days and 4 h. Specific activities at 32 degrees C, pH 7.4, of about 0.33 mumol of NO x min-1 x mg-1 were realized after fractionation with CHAPSO in a phenazine methosulfate/ascorbate-based assay. The Km(NO) was less than or equal to 17 microM at pH 7.4. Rates decreased substantially below pH 5 and above pH 7.6. The preparations were free or almost free of cytochromes, exhibited otherwise no absorption bands in the visible region, contained no redox metals except for very small amounts of iron, were not inhibited by EDTA or some other common inhibitors of redox-metal enzymes, and were not observed to catalyze the reduction of nitrate, nitrite, or N2O. An absorption band at 274 nm in both the CHAPSO- and SDS-fractionated preparations was attributed to the presence of a solvent-soluble chromophore. N-Bromosuccinimide (NBS) inactivated the enzyme and bleached the chromophore both in the enzyme preparation and, after its purification, in 95% ethanol. NBS-inactivated enzyme could be reconstituted with purified chromophore, which alone seemed to have no nitric oxide reductase activity, but not with purified chromophore that had been reacted with NBS. Spectral changes interpretable as due to changes in redox state were not observed when enzyme was exposed to NO or certain reducing agents.
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PMID:Purification and some characteristics of nitric oxide reductase-containing vesicles from Paracoccus denitrificans. 270 79

Nitrite production by nodules and roots of pea plants (Pisum sativum L., cultivar Alaska) inoculated with Rhizobium leguminosarum strain 3855 has been studied. Nitrate reductase (NR) activity and nitrite reductase (NiR) activity of the bacteroidal and cytosolic fractions of the nodules were also determined, as well as the nitrite content of the nodules cytosol. Nitrite production by nodules and roots from plants treated with 5 mM KNO3 was higher than that of nodules and roots from plants not treated with nitrate, and regardless of the nitrate treatment, nitrite production increased with the incubation period. The presence of nitrate, propanol or both compounds in the incubation mixtures significantly increased the nitrite production by nodules and roots. Nitrite reductase activity was detected in fresh by isolated bacteroids of R. leguminosarum strain 3855, although the presence of nitrate reductase activity could not be detected both in bacteroids of nodules isolated from plants treated or not with 5 mM KNO3. After isolation, when bacteroids were incubated in a mixture with nitrate, nitrate reductase activity developed after incubation for 12 h. Consequently, there was an increase in nitrite reductase activity, which resulted in the disappearance of the nitrite previously accumulated in the incubation medium. Nitrate utilization by bacteroids was not detected until 5 h from the beginning of the incubation period. Since the presence of chloramphenicol or rifampicin in the incubation medium prevented the development of the nitrate reductase activity, such activity was induced in bacteroids. Nitrite content and nitrate reductase and nitrite reductase activities of the cytosol from nodules of pea plants treated or not with 5 mM KNO3 varied with the buffer used for nodules homogenization. However, no nitrite was found when nodules were homogenized with ethanol, what indicates that nitrite accumulation in the cytosol occurs during the homogenization process of the nodules.
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PMID:[Utilization of nitrate by bacteroids and cytosol of nodules formed by Rhizobium leguminosarum]. 280 36

The dimethyl sulfoxide (DMSO) reductase operon coding for a membrane-bound iron-sulfur, molybdoenzyme, which functions as a terminal reductase in Escherichia coli, has been isolated and cloned from an E. coli gene bank. Two clones, MV12(pLC19-36) and MV12(pLC43-43), overexpressed both DMSO and trimethylamine N-oxide (TMAO) reductase activities 13- to 15-fold compared with wild-type cells. Amplification was highest in cells grown anaerobically on fumarate, while cells grown on DMSO or TMAO displayed reduced levels of enzyme amplification. Growth on nitrate or aerobic growth repressed expression of the enzyme. A 6.5-kilobase-pair DNA restriction endonuclease fragment was subcloned from pLC19-36 into the vector pBR322, yielding a recombinant DMSO reductase plasmid, pDMS159. Two polypeptides were amplified and identified on sodium dodecyl sulfate-polyacrylamide gels of proteins from E. coli HB101 harboring pDMS159: a membrane-bound protein with molecular weight 82,600 and a soluble polypeptide with molecular weight 23,600. Three plasmid-encoded polypeptides with molecular weights of 87,500, 23,300, and 22,600 were detected by in vivo transcription/translation studies. The smallest subunit was poorly defined and not detectable by Coomassie blue staining. The DMSO reductase operon was localized to the 20.0-min position on the E. coli linkage map.
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PMID:Molecular cloning and expression of the Escherichia coli dimethyl sulfoxide reductase operon. 283 66


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