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

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

Cowpea seeds variety Fettriat were planted in Nile silt soil and inoculated with 5 strains of cowpea rhizobia. After 50 and 80 days, the plants were uprooted, analysed for dry weight, total nitrogen, fresh weight of nodules, nitrate reductase activity in the leaves, and nitrate reductase and dehydrogenase activities in the nodule homogenate in the presence or absence of succinate, citrate, and ethyl alcohol. The data were analysed to establish the correlation coefficients between total nitrogen and other characteristics. A significant positive correlation existed between total nitrogen and fresh weight of nodules in both cuts (after 50 and 80 days). The correlation was significant between total nitrogen and dry weight of the plants in the first cut, but was non-significant in the second one. Nitrate reductase activity in leaves and nodule homogenates in the presence of different hydrogen donors were positively correlated in the first cut and negatively correlated in the second one. Nitrate reductase activity in the leaves was much less than that in the nodule homogenates. A negative correlation was noticed between phenol content of the nodules and total nitrogen. In the first cut, while the correlation between total nitrogen and dehydrogenase activity in the presence of citrate or absence of any hydrogen donors was positive, it was negative with ethanol and succinate. In the second cut, however, all the dehydrogenase activities were negatively correlated with total nitrogen.
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PMID:The correlation between the efficiency of rhizobia and nitrate reductase and dehydrogenase activities of cowpea nodules. 72 13

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

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

Two commercially available micromethod multitest systems (API, Analytab Products, Inc., Minitek-Bioquest) were compared with conventional tests suggested by the Center for Disease Control for the identification of anaerobes. Anaerobiosis for the microsystems was achieved using GasPak system (BBL), A total of 175 anaerobes, including 158 clinical isolates and 17 reference strains, were used. Gram morphology, gas-liquid chromatography data, and biochemical reactions from the Center for Disease Control and Virginia Polytechnic Institute anaerobic manuals were used to identify the organisms. The Minitek system included a new anaerobe inoculum broth and two new disks, dextrose without nitrate and nitrate reductase disks. The percentage of correlation of 12 biochemicals using Minitek and 11 biochemicals using the API were compared with the Center for Disease Control reactions. The percentage of correlation of both positive and negative reactions with the API anaerobic strip ranged from 70.8 to 99.4% and with the Minitek from 97.1 to 100%. The microsystems were also evaluated as to the ease of use, adaptabilty to a clinical laboratory, time, and cost.
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PMID:Comparison of API and Minitek to Center for Disease Control methods for the biochemical characterization of anaerobes. 78 9

Nitrate reductase was investigated in extracts from cells of a chlorate-resistant mutant strain of E. coli which grew anaerobically on nitrate as the sole source of nitrogen. The nitrate reductase was of particulate nature and reduced chlorate like the nitrate reductase from the wild strain, but in contrast was inhibited only weakly by azide or cyanide. Nitrate reductase activity was found in extracts from the mutant cells grown on nitrate as the sole source of nitrogen, but not in extracts from cells grown in complex nutrient medium. Addition of ammonia also caused a decrease in activity. Accordingly, the nitrate reductase in the chlorate-resistant mutant is of the assimilatory type.
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PMID:Assimilatory nitrate reductase in a chlorate-resistant mutant of Escherichia coli. 79 Jul 86

Active transport of amino acids by membrane vesicles from Escherichia coli, grown anaerobically on glucose in the presence of nitrate, can be energized under anaerobic conditions by electron transfer in the nitrate respiration system with formate as electron donor and nitrate as acceptor. A high rate of amino acid transport is also obtained under anaerobic conditions by electron transfer from formate to the nitrate analogue chlorate or to the membrane-impermeable electron acceptor ferricyanide. Electron transfer from formate to nitrate results in the generation of an electrical potential as is indicated by the uptake of the lipophilic cation triphenylmethylphosphonium. Ferricyanide accpets electrons from at least two sites of the nitrate respiration system. One of these sites appears to be nitrate reductase, because cytochrome b, reduced by formate, is completely reoxidized by ferricyanide and glutamate transport energized by formate plus ferricyanide and formate plus nitrate are affected by the same electron transfer inhibitors. A second site of electron transfer to ferricyanide appears to be located prior to nitrate reductase in the nitrate respiration system, since formate is oxidized at a higher rate in the presence of ferricyanide than with nitrate while formate/ferricyanide energizes transport of amino acids at a lower rate than formate/nitrate. Moreover, electron transfer inhibitors block electron transfer from formate to nitrate to a significantly higher extent than from formate to ferricyanide. The effects of irradiation of the membrane vesicles with near ultra-violet light suggest that quinones play an essential role in the electron transfer from formate to nitrate or ferricyanide. Irradiation blocks completely formate-dependent nitrate and ferricyanide reduction and active transport driven by formate/nitrate and formate/ferricyanide, but has hardly any effect on the activity of formate dehydrogenase and on ascorbate/phenazine methosulphate/oxygen-driven transport. Similar effects of ferricyanide have been observed in membrane vesicles from E. coli, grown anaerobically in the presence of fumarate. In these membrane vesicles a high rate of lactose and triphenylmethylphosphonium uptake under anaerobic conditions is obtained by electron transfer from glycerol 1-phosphate to fumarate and also to ferricyanide and evidence has been presented for the involvement of cytochromes in these electron transfers.
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PMID:Active transport by membrane vesicles from anaerobically grown Escherichia coli energized by electron transfer to ferricyanide and chlorate. 79 48


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