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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Staphylococcus aureus has membrane-associated sn-glycerol-3-phosphate dehydrogenase activity that is strongly activated by detergents. The enzyme can be measured spectrophotometrically in intact cells in assay systems containing lauryldimethylamine oxide (Ammonyx LO). The dehydrogenase activity was located exclusively in the membrane fraction of cells grown with glycerol under aerobic conditions or under anaerobic conditions with the addition of nitrate; there was no evidence of multiple forms. Development of sn-glycerol-3-phosphate dehydrogenase activity was studied with suspensions of cells grown previously under semianaerobic conditions with glucose and nitrate. The wild-type strain rapidly formed the enzyme when incubated with glycerol under aerobic conditions or under semianaerobic conditions in the presence of nitrate. Under similar conditions, suspensions of hem mutant H-14 required the addition of hemin. Induction of the enzyme was strongly repressed by glucose with both organisms. A procedure was established to obtain cells of mutant H-14 with sn-glycerol-3-phosphate dehydrogenase and nitrate reductase activities, but which could not link the systems unless supplemented with hemin. The coupled activity could also be reconstructed in vitro by the addition of hemin to the depleted membranes.
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PMID:sn-Glycerol-3-phosphate dehydrogenase and its interaction with nitrate reductase in wild-type and hem mutant strains of Staphylococcus aureus. 63 13

Seventeen strains of the new species Bacillus azotoformans were isolated by enrichment culture in peptone broth inoculated with pasteurized soil and then incubated under N2O at 32 degrees C. The bacterium is a Gram-negative rod, motile with peritrichous flagella, which produces oval spores without exosporia in swollen sporangia. However, the cells have thick walls, mesosomes, and persistent septa characteristic of Gram-positive bacteria. The bacterium lacks fermentative activity, does not attack carbohydrates, has complex growth requirements, and will grow anaerobically only if one of the following electron acceptors is present: NO3-, NO2-, N2O, S4O6--, or fumarate. Nitrate, nitrite, and nitrous oxide are denitrified with the production of N2. The microorganism is mesophilic, gives a positive oxidase reaction, synthesizes a type c cytochrome, and does not hydrolyse gelatin, starch, or "Tween 80." Poly-beta-hydroxybutyric acid is snythesized when the bacterium is grown in a medium containing DL-3-hydroxybutyrate. The following enzymes are present: nitrate reductase A, respiratory nitrite reductase, tetrathionate and fumarate reductases, and L-glutamate dehydrogenase. The following enzymes are absent: thiosulfate reductase, urease, lecithinase, arginine dihydrolase, phenylalanine deaminase, and catalase. For the 17 strains, the mean value of the G = C percent of the DNA is 39.8 +/- 1.2. All the strains are highly similar.
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PMID:[Morphological, physiological and taxonomic studies of Bacillus azotoformans]. 65 12

Chlorate resistant spontaneous mutants of Azospirillum spp. (syn. Spirillum lipoferum) were selected in oxygen limited, deep agar tubes with chlorate. Among 20 mutants from A. brasilense and 13 from A. lipoferum all retained their functional nitrogenase and 11 from each species were nitrate reductase negative (nr-). Most of the mutants were also nitrite reductase negative (nir-), only 3 remaining nir+. Two mutants from nr+ nir+ parent strains lost only nir and became like the nr+ nir- parent strain of A. brasilense. No parent strain or nr+ mutant showed any nitrogenase activity with 10 mM NO3-. In all nr- mutants, nitrogenase was unaffected by 10 mM NO3-. Nitrite inhibited nitrogenase activity of all parent strains and mutants including those which were nir-. It seems therefore, that inhibition of nitrogenase by nitrate is dependent on nitrate reduction. Under aerobic conditions, where nitrogenase activity is inhibited by oxygen, nitrate could be used as sole nitrogen source for growth of the parent strains and one mutant (nr- nir-) and nitritite of the parent strains and 10 mutants (all types). This indicates the loss of both assimilatory and dissimilatory nitrate reduction but only dissimilatory nitrite reduction in the mutants selected with chlorate.
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PMID:Nitrate and nitrite reductase negative mutants of N2-fixing Azospirillum spp. 69 99

1. The dye-linked methanol dehydrogenase from Paracoccus denitrificans grown aerobically on methanol has been purified and its properties compared with similar enzymes from other bacteria. It was shown to be specific and to have high affinity for primary alcohols and formaldehyde as substrate, ammonia was the best activator and the enzyme could be linked to reduction of phenazine methosulphate. 2. Paracoccus denitrificans could be grown anaerobically on methanol, using nitrate or nitrite as electron acceptor. The methanol dehydrogenase synthesized under these conditions could not be differentiated from the aerobically-synthesized enzyme. 3. Activities of methanol dehydrogenase, formaldehyde dehydrogenase, formate dehydrogenase, nitrate reductase and nitrite reductase were measured under aerobic and anaerobic growth conditions. 4. Difference spectra of reduced and oxidized cytochromes in membrane and supernatant fractions of methanol-grown P. denitrificans were measured. 5. From the results of the spectral and enzymatic analyses it has been suggested that anaerobic growth on methanol/nitrate is made possible by reduction of nitrate to nitrite using electrons derived from the pyridine nucleotide-linked dehydrogenations of formaldehyde and formate, the nitrite so produced then functioning as electron acceptor for methanol dehydrogenase via cytochrome c and nitrite reductase.
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PMID:Aerobic and anaerobic growth of Paracoccus denitrificans on methanol. 71 72

The denitrifying capacity of 15 strains of Bacillus licheniformis was evaluated. In general, N2 production by the cultures on complex media containing NO3- is irregular and quite slow and three of the strains never produce gas. Bacillus licheniformis grows rapidly in anaerobiosis on peptone medium containing NO3- which is reduced to NO2-. None of the strains grow in peptone medium with NO2- or N2O as the respiratory substrate, nor do they grow under an atmosphere of 10% NO-90% N2. Denitrification was studied in cell suspensions using gas chromatography. N2O production from NO3- or NO2- is always weak at best; nitric oxide is reduced to N2O at an appreciable rate. All the strains synthesize nitrate reductase A in anaerobiosis when NO3- is present. In cell extracts, nitrite reductase activity is always negligible or nil with tetramethyl-p-phenylenediamine as an electron donor.
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PMID:[Denitrification by Bacillus licheniformis]. 75 76

Nitrate reductase from Escherichia coli is induced by nitrate and derepressed by oxygen removal after a lag phase. Elimination of inducer, shift to aerobic conditions and addition of actinomycin D causes the decline in the rate of its synthesis, which eventually may stop. Kinetic analysis of the sensitivity of the biosynthetic process to oxygen, chloramphenicol, actinomycin D and rifampicin gave results which we interprete as evidence that oxygen (and possibly nitrate) affect simultaneously both the transcriptional and translational processes.
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PMID:Regulation of nitrate reductase at the transcriptional and translational levels in Escherichia coli. 76 27

Membrane-bound nitrate reductase of Escherichia coli consists of three subunits designated as A, B, and C, with subunit C being the apoprotein of cytochrome b, A hemA mutant that cannot synthesize delta-aminolevulinic acid (ALA) produces a normal, stable, membrane-bound enzyme when grown with ALA. When grown without ALA, this mutant makes a reduced amount of membrane-bound enzyme that is unstable and contains no C subunit. Under the same growth conditions, this mutant accumulates a large amount of a soluble form of the enzyme in the cytoplasm. Accumulation of this cytoplasmic form begins immediately upon induction of the enzyme with nitrate. The cytoplasmic form is very similar to the soluble form of the enzyme obtained by alkaline heat extraction. It is a high-molecular-weight complex with a Strokes radius of 8.0 nm and consists of intact A and B subunits. When ALA is added to a culture growing without ALA, the cytoplasmic form of the enzyme is incorporated into the membrane in a stable form, coincident with the formation of functional cytochrome b. Reconstitution experiments indicate that subunit C is present in cultures grown without ALA but is reduced in amount or unstable. These results indicate that membrane-bound nitrate reductase is synthesized via a soluble precursor containing subunits A and B, which then binds to the membrane upon interaction with the third subunit, cytochrome b.
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PMID:Biosynthesis of membrane-bound nitrate reductase in Escherichia coli: evidence for a soluble precursor. 77 Apr 17

When Escherichia coli was grown on medium containing 10 mM tungstate the formation of active formate dehydrogenase, nitrate reductase, and the complete formate-nitrate electron transport pathway was inhibited. Incubation of the tungstate-grown cells with 1 mM molybdate in the presence of chloramphenicol led to the rapid activation of both formate dehydrogenase and nitrate reductase, and, after a considerable lag, the complete electron transport pathway. Protein bands which corresponded to formate dehydrogenase and nitrate reductase were identified on polyacrylamide gels containing Triton X-100 after the activities were released from the membrane fraction and partially purified Cytochrome b1 was associated with the protein band corresponding to formate dehydrogenase but was not found elsewhere on the gels. When a similar fraction was prepared from cells grown on 10 mM tungstate, an inactive band corresponding to formate dehydrogenase was not observed on polyacrylamide gels; rather, a new faster migrating band was present. Cytochrome b1 was not associated with this band nor was it found anywhere else on the gels. This new band disappeared when the tungstate-grown cells were incubated with molybdate in the presence of chloramphenicol. The formate dehydrogenase activity which was formed, as well as a corresponding protein band, appeared at the original position on the gels. Cytochrome b1 was again associated with this band. The protein band which corresponded to nitrate reductase also was severely depressed in the tungstate-grown cells and a new faster migrating band appeared on the polyacrylamide gels. Upon activation of the nitrate reductase by incubation of the cells with molybdate, the new band diminished and protein reappeared at the original position. Most of the nitrate reductase activity which was formed appeared at the original position of nitrate reductase on gels although some was present at the position of the inactive band formed by tungstate-grown cells. Apparently, inactive forms of both formate dehydrogenase and nitrate reductase accumulate during growth on tungstate which are electrophoretically distinct from the active enzymes. Activation by molybdate results in molecular changes which include the reassociation of cytochrome b1 with formate dehydrogenase and restoration of both enzymes to their original electrophoretic mobilities.
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PMID:Formation of the formate-nitrate electron transport pathway from inactive components in Escherichia coli. 77 Apr 33

Mutation in at least ten genes can result in chlorate reistance in Aspergillus nidulans. Mutation in seven of these genes also results in the inability to use nitrate as nitrogen source. The various classes of resistant mutant obtained occur in different proportions, depending on whether or not a mutagenic treatment is employed, and also on which nitrogen source is used for selection. The prinicipal effect of mutagen arises because mutations in the niaD gene, the nitrate reductase structural gene, are relatively much commoner when no mutagen is used than after treatment with N-methyl-N'-nitro-N-nitrosoguanidine. This may be connected with the finding that deletions involving the niaD gene are relatively more common among samples of spontaneous niaD mutants. Some of these deletions extend to the neighbouring niiA gene, the structural gene for nitrite reductase. The selection procedures used were designed to avoid bias in favour of any particular chlorate resistant phenotype. Even if biases existed however, these could not account for the variation found from nitrogren source to nitrogen source in the proportions of certain resistant classes having apparently identical chlorate resistance phenotypes.
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PMID:Cholorate toxicity in Aspergillus nidulans: the selection and characterisation of chlorate resistant mutants. 77 8

1. Nitrate reductase was purified 134-fold from Escherichia coli K12. The purification procedure involves the release by Triton X-100 of the enzyme from the cell envelope. i. The purified enzyme exists in aqueous solution either as a monomer (mol. wt. about 220 000) or as an associated form (probably a tetramer; mol.wt. about 880 000). 3. The purified enzyme has three subunits with apparent mol.wts. of 150 000, 67000 and 65000. An additional subunit of apparent mol.wt. 20000 is present in a haem-containing fraction that is also produced by the preparative procedure described. 4. None of the enzyme subunits is present in the cell envelope of cells grown in the absence of nitrate. 5. Reversible changes in the activity of nitrate reductase in vitro with FMNH2 as reductant can be induced under circumstances which are without effect on the reduced Benzyl Viologen-NO3-activity.
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PMID:Purification and some properties of nitrate reductase (EC 1.7.99.4) from Escherichia coli K12. 78 44


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