Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.7.1.4 (nitrite reductase)
 1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
 ...
PMID:Effect of nitrate, fumarate, and oxygen on the formation of the membrane-bound electron transport system of Haemophilus parainfluenzae. 431 51

1. In Aspergillus nidulans nitrate and nitrite induce nitrate reductase, nitrite reductase and hydroxylamine reductase, and ammonium represses the three enzymes. 2. Nitrate reductase can donate electrons to a wide variety of acceptors in addition to nitrate. These artificial acceptors include benzyl viologen, 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride, cytochrome c and potassium ferricyanide. Similarly nitrite reductase and hydroxylamine reductase (which are possibly a single enzyme in A. nidulans) can donate electrons to these same artificial acceptors in addition to the substrates nitrite and hydroxylamine. 3. Nitrate reductase can accept electrons from reduced benzyl viologen in place of the natural donor NADPH. The NADPH-nitrate-reductase activity is about twice that of reduced benzyl viologen-nitrate reductase under comparable conditions. 4. Mutants at six gene loci are known that cannot utilize nitrate and lack nitrate-reductase activity. Most mutants in these loci are constitutive for nitrite reductase, hydroxylamine reductase and all the nitrate-induced NADPH-diaphorase activities. It is argued that mutants that lack nitrate-reductase activity are constitutive for the enzymes of the nitrate-reduction pathway because the functional nitrate-reductase molecule is a component of the regulatory system of the pathway. 5. Mutants are known at two gene loci, niiA and niiB, that cannot utilize nitrite and lack nitrite-reductase and hydroxylamine-reductase activities. 6. Mutants at the niiA locus possess inducible nitrate reductase and lack nitrite-reductase and hydroxylamine-reductase activities. It is suggested that a single enzyme protein is responsible for the reduction of nitrite to ammonium in A. nidulans and that the niiA locus is the structural gene for this enzyme. 7. Mutants at the niiB locus lack nitrate-reductase, nitrite-reductase and hydroxylamine-reductase activities. It is argued that the niiB gene is a regulator gene whose product is necessary for the induction of the nitrate-utilization pathway. The niiB mutants either lack or produce an incorrect product and consequently cannot be induced. 8. Mutants at the niiribo locus cannot utilize nitrate or nitrite unless provided with a flavine supplement. When grown in the absence of a flavine supplement the activities of some of the nitrate-induced enzymes are subnormal. 9. The growth and enzyme characteristics of a total of 123 mutants involving nine different genes indicate that nitrate is reduced to ammonium. Only two possible structural genes for enzymes concerned with nitrate utilization are known. This suggests that only two enzymes, one for the reduction of nitrate to nitrite, the other for the reduction of nitrite to ammonium, are involved in this pathway.
 ...
PMID:Genetic and biochemical studies of nitrate reduction in Aspergillus nidulans. 438 27

1. In rice seedlings synthesis of methyl viologen-nitrite reductase was stimulated by light, as was that of NADH-nitrate oxidoreductase (EC 1.6.6.1). A small residual effect of light on the synthesis of the enzymes persisted in the dark for a short time. 2. In etiolated seedlings exposed to light and nitrate, a lag period of 3h was necessary before enzyme synthesis commenced, whereas in green seedlings kept in the dark for 36h, synthesis of both the enzymes started as soon as light and nitrate were provided. 3. Experiments with cycloheximide suggested that fresh protein synthesis in light was necessary for formation of active enzymes. Mere activation by light of inactive enzymes or their precursors, was not involved. 4. In green seedlings synthesis of nitrite reductase was more sensitive to chloramphenicol than that of nitrate reductase. In chloramphenicol-treated etiolated seedlings, however, synthesis of both the enzymes was inhibited to the same extent on subsequent light-treatment. 5. A close correlation was observed between inhibition of the Hill reaction by 3-(3,4-dichlorophenyl)-1,1-dimethylurea and simazin [2-chloro-4,6-bis(ethylamino)-s-triazine] (at high concentration) and the inhibition of enzyme synthesis. At lower concentrations, however, simazin stimulated nitrate reductase. 6. In a single leaf synthesis of enzymes was observed only in portions exposed to light, whereas little activity was present in the dark covered part. 7. CO(2) deprivation severely inhibited the synthesis of enzymes in the light. Sucrose could not reverse this effect. 8. In excised embryos cultured in synthetic media containing sucrose, light was also essential for enzyme formation. 9. It is suggested that redox changes taking place in the green tissues as a result of the Hill reaction create conditions favourable for the induced synthesis of nitrate reductase and nitrite reductase.
 ...
PMID:Role of light in the synthesis of nitrate reductase and nitrite reductase in rice seedlings. 466 75

A denitrifying mutant of Bacillus stearothermophilus NCA 2184, strain 2184-D, was used to explore the development of nitrate respiration in relation to oxygen respiration. Aerobically grown wild-type cultures could acquire the ability to use nitrate as a result of selection of nitrate-respiring mutants by the presence of nitrate and a reduced oxygen tension. Fluctuation analysis has revealed that the frequency of occurrence of the nitrate-respiring mutant is about 7.5 x 10(-8) per bacterium per generation. Nitrate reductase and nitrite reductase appeared to be induced sequentially in strain 2184-D by the addition of nitrate. The formation of both of these enzymes was repressed by oxygen so that cells grown aerobically with nitrate possessed a low basal level of nitrate reducatase and exhibited no denitrification. The rate of synthesis of nitrate reductase increased quickly after addition of nitrate and removal of oxygen. It then declined to a lower steady-state level. Cells grown anaerobically with nitrate retained approximately 30 to 40% of the respiratory activity of aerobically grown cells. Aeration of anaerobically grown cells in the presence of amino acids increased the respiratory activity to normal aerobic levels. This aeration promoted rapid degradation of the existing nitrate reductase with or without the added amino acids.
 ...
PMID:Influence of oxygen on development of nitrate respiration in Bacillus stearothermophilus. 578 97

In L. minor grown in sterile culture, the primary enzymes of nitrate assimilation, nitrate reductase (NR), nitrite reductase (NiR) and glutamate dehydrogenase (GDH) change in response to nitrogen source. NR and NiR levels are low when grown on amino acids (hydrolyzed casein) or ammonia; both enzymes are rapidly induced on addition of nitrate, while addition of nitrite induces NiR only. Ammonia represses the nitrate induced synthesis of both NR and NiR.NADH dependent GDH activity is low when grown on amino acids and high when grown on nitrate or ammonia, but the activities of NADPH dependent GDH and Alanine dehydro-genase (AIDH) are much less affected by nitrogen source. NADH-GDH and AIDH are induced by ammonia, and it is suggested that these enzymes are involved in primary nitrogen assimilation.
 ...
PMID:Nitrogen metabolis of Lemna minor. II. Enzymes of nitrate assimilation and some aspects of their regulation. 579 47

The metabolism of inorganic nitrogen compounds was studied in extracts of Penicillium atrovenetum which had been grown under conditions in which beta-nitropropionic acid (BNP) synthesis varied from 0 to 12.5 mumoles per ml. None of the extracts was able to oxidize ammonium ion or nitrite. An enzyme was detected which catalyzed the oxidation of hydroxylamine with cytochrome c as the electron acceptor. The activity of this enzyme was not related to the ability of the organism to produce BNP. Nitrate and nitrite reductase activities were detected only in P. atrovenetum cultures grown on nitrate as a nitrogen source. These results indicated that BNP synthesis is probably not directly associated with the metabolism of inorganic nitrogen compounds and that an organic pathway for the formation of the nitro group is more likely. The activities of certain enzymes related to the metabolism of aspartic acid were investigated. Aspartate ammonia-lyase activity could not be detected in P. atrovenetum extracts. Aspartate aminotransferase and glutamate dehydrogenase activities were found in the extracts but were highest in the cultures which did not produce BNP. beta-Nitroacrylic acid reductase activity was highest in extracts of cultures which were actively synthesizing BNP.
 ...
PMID:Role of ammonium ion in the biosynthesis of beta-nitropropionic acid. 580 74

In Neurospora crassa, synthesis of the enzymes of nitrate assimilation, nitrate reductase and nitrite reductase, was repressed by the presence of ammonium, glutamate, or glutamine. This phenomenon was a manifestation of the regulatory process termed nitrogen metabolite repression whereby alternative pathways of nitrogen acquisition are not expressed in cells enjoying nitrogen sufficiency. However, the glutamine synthetase mutant gln-1b had derepressed levels of the nitrate assimilation enzymes. The inability of glutamine to achieve nitrogen metabolite repression in this mutant militated against its potential role as the direct effector of this regulation.
 ...
PMID:Effect of the gln-1b mutation on nitrogen metabolite repression in Neurospora crassa. 610 13

D-Erythrose, which has been shown to enhance nitrogenase activity (acetylene reduction) by isolated heterocysts, was studied for its effects on nitrogenase activity and nitrite uptake by whole filaments of Anabaena sp. strain 7120. D-Erythrose had little effect on acetylene reduction in the light; however, at a concentration of 10 mM, it could restore 3'-(3,4-dichlorophenyl)-1',1'-dimethyl urea-inhibited or dark-limited levels to light-supported levels. Sucrose, glucose, or fructose did not exhibit similar effects. D-Erythrose had little effect on nitrite uptake, an indirect measure of nitrite reductase activity by nitrate-grown whole filaments. It was concluded that erythrose effects were mediated by heterocysts and were therefore specific for nitrogenase.
 ...
PMID:Effects of D-erythrose on nitrogenase activity in whole filaments of Anabaena sp. strain 7120. 623 47

Campylobacter sputorum subspecies bubulus contains a membrane-bound nitrite reductase which catalyses the six-electron reduction of nitrite to ammonia. Formate and L-lactate are used as hydrogen donors. Cells of C. sputorum grown with nitrate or nitrite contain cytochromes of the b- and c-type and a carbon monoxide-binding cytochrome c. In addition, a special membrane-bound carbon monoxide-binding pigment is found. Nitrite reduction with formate or L-lactate as a hydrogen donor is strongly inhibited by 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO). Nitrite reduction by bacterial suspensions with lactate as a hydrogen donor is strongly inhibited by carbonylcyanide-m-chlorophenylhydrazone (CCCP) whereas nitrite reduction with formate as a hydrogen donor is not inhibited at all. Leads to H+/O values and leads to H+/NO-2 values were measured with ascorbate + N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), formate (in the absence and presence of carbonic anhydrase) and L-lactate as a hydrogen donor. The results are summarized in a scheme for electron transport from formate or lactate to oxygen or nitrite which shows a periplasmic orientation of formate dehydrogenase and nitrite reductase and a cytoplasmic orientation of lactate dehydrogenase and oxygen reduction, and which shows proton translocation with a leads to H+/2e value of 2.0. The leads to H+/O and leads to H+/NO-2 values predicted by this scheme are in good agreement with the experimental values.
 ...
PMID:Electron transport-linked proton translocation at nitrite reduction in Campylobacter sputorum subspecies bubulus. 628 Jun 34

Under anaerobic conditions, Klebsiella pneumoniae reduced nitrite (NO2-), yielding nitrous oxide (N2O) and ammonium ions (NH4+) as products. Nitrous oxide formation accounted for about 5% of the total NO2- reduced, and NH4+ production accounted for the remainder. Glucose and pyruvate were the electron donors for NO2- reduction to N2O by whole cells, whereas glucose, NADH, and NADPH were found to be the electron donors when cell extracts were used. On the one hand, formate failed to serve as an electron donor for NO2- reduction to N2O and NH4+, whereas on the other hand, formate was the best electron donor for nitrate reduction in either whole cells or cell extracts. Mutants that are defective in the reduction of NO2- to NH4+ were isolated, and these strains were found to produce N2O at rates comparable to that of the parent strain. These results suggest that the nitrite reductase producing N2O is distinct from that producing NH4+. Nitrous oxide production from nitric oxide (NO) occurred in all mutants tested, at rates comparable to that of the parent strain. This result suggests that NO reduction to N2O, which also uses NADH as the electron donor, is independent of the protein(s) catalyzing the reduction of NO2- to N2O.
 ...
PMID:Production of nitrous oxide from nitrite in Klebsiella pneumoniae: mutants altered in nitrogen metabolism. 634 20


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>