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:1.7.1.4 (nitrite reductase)
1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutants with defective respiratory nitrite utilization (Nir- phenotype) were obtained by transposon Tn5 insertion into genomic DNA of the ZoBell strain of Pseudomonas stutzeri. Three representative mutants were characterized with respect to their activities of nitrite and nitric oxide reduction, cytochrome cd1 content, and pattern of soluble c-type cytochromes. Mutant strain MK201 overproduced cytochrome c552 about fourfold by comparison with the wild type, but possessed an in vitro functional cytochrome cd1. Mutant strain MK202 lacked cytochrome cd1 and, simultaneously, had low amounts of cytochrome c552 and the split alpha-peak c-type cytochrome. Strain MK203 synthesized nitrite reductase defective in the heme d1 prosthetic group. Irrespective of these biochemically distinct Nir- phenotypes, all mutants preserved the nitric oxide-reducing capability of the wild type. The mutant characteristics demonstrate that cytochrome cd1 is essential for nitrite respiration of P. stutzeri and establish the presence of a nitric oxide-reducing system distinct from cytochrome cd1. They also indicate the functional or regulatory interdependence of c-type cytochromes.
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PMID:Defects in cytochrome cd1-dependent nitrite respiration of transposon Tn5-induced mutants from Pseudomonas stutzeri. 283 27

1. A Clark-type electrode that responds to nitric oxide has been used to show that cytoplasmic membrane vesicles of Paracoccus denitrificans have a nitric-oxide reductase activity. Nitrous oxide is the reaction product. NADH, succinate or isoascorbate plus 2,3,5,6-tetramethyl-1,4-phenylene diamine can act as reductants. The NADH-dependent activity is resistant to freezing of the vesicles and thus the NADH:nitric-oxide oxidoreductase activity of stored frozen vesicles provides a method for calibrating the electrode by titration of dissolved nitric oxide with NADH. The periplasmic nitrite reductase and nitrous-oxide reductase enzymes are absent from the vesicles which indicates that nitric-oxide reductase is a discrete enzyme associated with the denitrification process. This conclusion was supported by the finding that nitric-oxide reductase activity was absent from both membranes prepared from aerobically grown P. denitrificans and bovine heart submitochondrial particles. 2. The NADH: nitric-oxide oxidoreductase activity was inhibited by concentrations of antimycin or myxothiazol that were just sufficient to inhibit the cytochrome bc1 complex of the ubiquinol--cytochrome-c oxidoreductase. The activity was deduced to be proton translocating by the observations of: (a) up to 3.5-fold stimulation upon addition of an uncoupler; and (b) ATP synthesis with a P:2e ratio of 0.75. 3. Nitrite reductase of cytochrome cd1 type was highly purified from P. denitrificans in a new, high-yield, rapid two- or three-step procedure. This enzyme catalysed stoichiometric synthesis of nitric oxide. This observation, taken together with the finding that the maximum rate of NADH:nitric-oxide oxidoreductase activity catalysed by the vesicles was comparable with that of NADH:nitrate-oxidoreductase, is consistent with a role for nitric-oxide reductase in the physiological conversion of nitrate or nitrite to dinitrogen gas. 4. Intact cells of P. denitrificans also reduced nitric oxide in an antimycin- or myxothiazol-sensitive manner. However, nitric oxide was not detected by the electrode during the reduction of nitrate. Nitric-oxide synthesis from nitrate could be detected with cells in the presence of very low concentrations of Triton X-100 which selectively inhibits nitric-oxide reductase activity. 5. Nitric oxide was detected as an intermediate in denitrification by including haemoglobin with an anaerobic suspension of cells that was reducing nitrate. The characteristic spectrum of the nitric oxide derivative of haemoglobin was observed.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The energy-conserving nitric-oxide-reductase system in Paracoccus denitrificans. Distinction from the nitrite reductase that catalyses synthesis of nitric oxide and evidence from trapping experiments for nitric oxide as a free intermediate during denitrification. 292 Jul 32

Anaerobic cytochrome c552 was purified to electrophoretic homogeneity by ion-exchange chromatography and gel filtration from a mutant of Escherichia coli K 12 that synthesizes an increased amount of this pigment. Several molecular and enzymatic properties of the cytochrome were investigated. Its relative molecular mass was determined to be 69 000 by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. It was found to be an acidic protein that existed in the monomeric form in the native state. From its heme and iron contents, it was concluded to be a hexaheme protein containing six moles of heme c/mole protein. The amino-acid composition and other properties of the purified cytochrome c552 indicated its similarity to Desulfovibrio desulfuricans hexaheme cytochrome. The cytochrome c552 showed nitrite and hydroxylamine reductase activities with benzyl viologen as an artificial electron donor. It catalyzed the reduction of nitrite to ammonia in a six-electron transfer. FMN and FAD also served as electron donors for the nitrite reduction. The apparent Michaelis constants for nitrite and hydroxylamine were 110 microM and 18 mM, respectively. The nitrite reductase activity of the cytochrome c552 was inhibited effectively by cupric ion and cyanide.
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PMID:Purification of a hexaheme cytochrome c552 from Escherichia coli K 12 and its properties as a nitrite reductase. 300 98

Mutants have been isolated which lack NADH-dependent nitrite reductase activity but retain NADPH-dependent sulphite reductase and formate hydrogenlyase activities. These NirB- strains synthesize cytochrome c552 and grow normally on anaerobic glycerol-fumarate plates. The defects map in a gene, nirB, which is extremely close to cysG, the gene order being crp, nirB, cysG, aroB. Complementation studies established that nirB+ and cysG+ can be expressed independently. The data strongly suggest that nirB is the structural gene for the 88 kDal NADH-dependent nitrite oxidoreductase apoprotein (EC 1.6.6.4). The nirB gene is apparently defective in the previously described nirD mutant, LCB82. The nirH mutant, LCB197, was unable to use formate as electron donor for nitrite reduction, but NADH-dependent nitrite reductase was extremely active in this strain and a normal content of cytochrome c552 was detected. Strains carrying a nirE, nirF or nirG mutation gave normal rates of nitrite reduction by glucose, formate or NADH.
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PMID:Isolation, characterization and complementation analysis of nirB mutants of Escherichia coli deficient only in NADH-dependent nitrite reductase activity. 390 30

The composition of the membrane-bound electron transport system of Haemophilus parainfluenzae underwent modification in response to the terminal electron acceptor in the growth medium. H. parainfluenzae was able to grow with O(2), nitrate, fumarate, pyruvate, and substrate amounts of nicotinamide adenine dinucleotide (NAD) as electron acceptors. When O(2) served as the electron acceptor and its concentration was lowered below 20 mum, the bacteria formed more cytochromes b, c, a(1), a(2), and o than were present in the cells grown at 150 to 200 mum O(2). Nitrate and nitrite reductase activities also appeared during growth at the low O(2) concentrations in the absence of added nitrate. Cytochrome levels in cells grown anaerobically with fumarate, pyruvate, or NAD as terminal acceptors were similar to those formed in cells grown at low O(2) concentrations. Cells grown with nitrate had higher levels of cytochromes c, b, and o, and of nitrate and nitrite reductases, than did cells grown with the other acceptors. The formation of cytochrome oxidase a(2) was repressed by the presence of nitrate in the growth medium. The critical O(2) concentration (the O(2) concentration at which the rate of O(2) uptake becomes demonstrably dependent on the O(2) concentration) was about 100 mum in cells grown with nitrate and about 15 mum in cells grown with the other acceptors. A mutant of H. parainfluenzae was found to make about 10% as much cytochrome c as the wild type, and its formation of cytochrome a(2) was not repressed by nitrate. The critical O(2) concentration of the mutant was high when it was grown with nitrate, suggesting that the high levels of cytochrome c and the absence of cytochrome a(2) from the wild type are not responsible for the high critical O(2) concentration. The modifications of the respiratory system induced by changing the terminal electron acceptor were inhibited by the presence of chloramphenicol, which suggests that protein synthesis is involved.
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PMID:Effect of nitrate, fumarate, and oxygen on the formation of the membrane-bound electron transport system of Haemophilus parainfluenzae. 431 51

Freezing and thawing of Nitrosomonas, followed by centrifugation of the homogenate at 3,000 x g, resulted in a fraction which appeared to consist of an intact membrane-envelope complex and contained approximately 50% of the cell protein and more than 90% of the ubiquinone and cytochrome A-type mammalian cytochrome c oxidase activity. The supernatant fraction, resulting from subsequent centrifugation of the extract at 100,000 x g, contained approximately 50% of the cell protein and more than 80% of the B- and C-type cytochrome and P-463 and the enzymes glutamate dehydrogenase; hydroxylamine dehydrogenase; nitrite synthetase; nitrite reductase; and 2,6-dichlorophenolindophenol-, p-phenylenediamine-, pyrogallol-, and hydroquinone-oxidase. Data on the concentration of electron transport components in Nitrosomonas are presented.
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PMID:Electron transport systems of Nitrosomonas: isolation of a membrane-envelope fraction. 433 11

A dissimilatory nitrite reductase from the facultatively phototrophic bacterium, Rhodopseudomonas palustris strain 1a1 was studied. A basic level of the enzyme (10-50 mU/mg protein) was measured in dark, aerated and anaerobic, photosynthetic cultures. A marked derepression of enzyme synthesis occurred under conditions of oxygen limitation (200-300 mU/mg protein). The addition of nitrite (or nitrate) to the culture medium had only a slight effect on the maximal nitrite reductase titer of cells. The enzyme was purified from photosynthetically grown cells by precipitation with ammonium sulfate, gel filtration through Sepharose 6B and repeated chromatography on DE 52-cellulose. As estimated by gel filtration, the nitrite reductase had a molecular weight of about 120 000 +/- 12 000 and yielded only one band (mol. wt. of about 68 000 +/- 7000) in SDS-gel electrophoresis. The isoelectric point of the enzyme was at pH 5.1. Nitric oxide (NO) was identified as the reaction product of nitrite reduction. The enzyme also exhibited cytochrome c-oxidase activity and was active with chemically reduced viologen dyes, FMN and cytochrome c as electron donors. Highly purified nitrite reductase preparations contained 10 mol% of a c-type cytochrome. Trace metal analyses indicated the presence of Cu in the enzyme. Consistent with the detection of Cu was the finding that the Cu-chelator, diethyldithiocarbamate, strongly inhibited the nitrite reductase.
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PMID:Purification and characterization of a dissimilatory nitrite reductase from the phototrophic bacterium Rhodopseudomonas palustris. 667 Mar 57

Paracoccus halodenitrificans produced a membrane-associated nitrite reductase. Spectrophotometric analysis showed it to be associated with a cd-cytochrome and located on the inner side of the cytoplasmic membrane. When supplied with nitrite, membrane preparations produced nitrous oxide and nitric oxide in different ratios depending on the electron donor employed. The nitrite reductase was maximally active at relatively low concentrations of sodium chloride and remained attached to the membranes at 100 mM sodium chloride.
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PMID:A dissimilatory nitrite reductase in Paracoccus halodenitrificans. 671 19

Two gentamicin-resistant mutants of Pseudomonas aeruginosa PAO 503 were selected after ethyl methane sulfonate mutagenesis. Mutant PAO 2403 had significantly increased resistance to aminoglycoside but not to other antibiotics. Mutant PAO 2402 showed a similar spectrum of resistance but of lower magnitude. Both mutants showed no detectable cytochrome d and had a high frequency of reversion to a fully wild-type phenotype. PAO 2403 had a marked decrease and PAO 2402 had a moderate decrease in nitrite reductase activity. Both mutants had reduced uptake of gentamicin and dihydrostreptomycin. Mutant PAO 2403 showed a general decrease in transport rate of cationic compounds, whereas mutant PAO 2402 had only deficient glucose transport. Both mutants showed enhanced rates of glutamine transport and no change in glutamic acid transport. Other components of electron transport and oxidative phosphorylation were normal. These mutants involve ferrocytochrome C551 oxidoreductase formed only on anaerobic growth but illustrate transport defects in aerobically grown cells.
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PMID:Aminoglycoside-resistant mutants of Pseudomonas aeruginosa deficient in cytochrome d, nitrite reductase, and aerobic transport. 679 88

Significant nitrate reductase activity was detected in mutants of Salmonella typhimurium which mapped at or near chlC and which were incapable of growth with nitrate as electron acceptor. The same mutants were sensitive to chlorate and performed sufficient nitrate reduction to permit anaerobic growth with nitrate as the sole nitrogen source in media containing glucose. The mutant nitrate-reducing protein did not migrate with the wild-type nitrate reductase in polyacrylamide electrophoretic gels. Studies of the electrophoretic mobility in gels of different polyacrylamide concentration revealed that the wild-type and mutant nitrate reductases differed significantly in both size and charge. The second enzyme also differed from the wild-type major enzyme in its response to repression by low pH and its lack of response to repression by glucose. The same mutants were found to be derepressed for nitrite reductase and for a cytochrome with a maximal reduced absorbance at 555 nm at 25 degrees C. This cytochrome was not detected in preparations of the wild type grown under the same conditions. Extracts of these mutants contained normal amounts of the b-type cytochromes which, in the wild type, were associated with nitrate reductase and formate dehydrogenase, respectively, although they could not mediate the oxidation of these cytochromes with nitrate. They were capable of oxidizing the derepressed 555-nm peak cytochrome with nitrate. It is suggested that these mutants synthesize a nitrate-reducing enzyme which is distinct from the chlC gene product and which is repressed in the wild type during anaerobic growth with nitrate.
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PMID:Evidence of a second nitrate reductase activity that is distinct from the respiratory enzyme in Salmonella typhimurium. 704 Mar 38


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