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)

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

Mutants of A. nidulans at several loci lack detectable NADPH-nitrate reductase activity. These loci include niaD, the structural gene for the nitrate reductase polypeptide, and five other loci termed cnxABC, E, F, G and H which are presumed to be involved in the formation of a molybdenum-containing component (MCC) necessary for nitrate reductase activity. When forzen mycelia from A. nidulans deletion mutant niaD26 were homogenized in a Ten Broeck homogenizer together with frozen mycelia from either cnxA6, cnxE29, cnsF12, cnxG4 or cnxH3 strains grown on urea + nitrate as the nitrogen source, nitrate reductase activity was detectable in the extract. Similar results were obtained by co-homogenizind niaD mycelia with Neurospora crassa nit-1 mycelia induced on nitrate. Thus, all A. nidulans cnx mutants are similar to the N. crassa nit-1 strain in their capacity to yield NADPH-nitrate reductase in the presence of the presumed MCC. As judged by the amounts of nitrate reductase formed, niaD26 mycelia grown on urea +/- nitrate contained much more available MCC than ammonium-grown mycelia. No NADPH-nitrate reductase activity was found in extracts prepared by co-homogenizing mycelia from all five A. nidulans cnx strains. Wild-type A. nidulans NADPH-nitrate reductase acid dissociated by adjustment to pH 2.0-2.5 AND RE-ADJUSTED TO PH 7 could itself re-assemble to form active nitrate reductase and thus was not a useful source of MCC for these experiments. These results are consistent with the conclusion that the active nitrate reductase complex is composed of polypeptide components which are the niaD gene product, plus the MCC which is formed through the combined action of the cnx gene products. Further, the production of MCC may be regulated in response to the nitrogen nutrition available to the organism.
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PMID:Formation of NADPH-nitrate reductase activity in vitro from Aspergillus nidulans niaD and cnx mutants. 79 78

Three genotypically different chlorate resistant mutants, chl I, chl II and chl III, appeared to lack completely nitrate reductase A, chlorate reductase C and tetrathionate reductase activity. Fumarate reductase is only partially affected in chl I and chl III and unaffected in chl II. Formate dehydrogenase is only partially diminished in chl II, hydrogenase is diminished in chl I and chl II and completely absent in chl III. Subunits of nitrate reductase A, chlorate reductase C and tetrathionate reductase have been identified in protein profiles of purified cytoplasmic membranes from the wild type and the three mutant strains, grown under various conditions. Only the presence and absence of the largest subunits of these enzymes appeared to be correlated with their repression and derepression in the wild type membranes. On the cytoplasmic membranes of the chl I and chl III mutants these subunits lack for the greater part. In the chl II mutant, however, these subunits are inserted in the membrane all together after anaerobic growth with or without nitrate. A model for the repression/derepression mechanism for the reductases has been proposed. It includes repression by cytochrome b components, whereas the redox-state of the nitrate reductase A molecule itself is also involved in its derepression under anaerobic conditions.
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PMID:The correlation between the protein composition of cytoplasmic membranes and the formation of nitrate reductase A, chlorate reductase C and tetrathionate reductase in Proteus mirabilis wild type and some cholate resistant mutants. 79 38

Nitrate reductase (Nar) activity, and its regulation, have been studied in B. subtilis and Spo0 mutants derived from it. The mutants are blocked at the stage zero of sporulation. The only Nar detected was the membrane-bound Nar A, which has been solubilized and purified. The enzyme itself, and its regulation, seem to be the same in Spo+ and Spo0 strains. Under all conditions tested, however, the mutants were hyperproducers of Nar A. Whether produced by a Spo+ or a Spo0 strain, the purified enzyme has the same Km on nitrate, and the same heat inactivation kinetics. In situ in membrane vesicles of a Spo+ strain, it displays the same Km and its thermoinactivation is exponential. In mutant vesicles, however, two Km's are observed, one normal and one five times higher, and thermoinactivation follows an initial period of activation. The higher Km disappears after heat activation. The Spo0 mutation studied seems to result in a modification of the membrane, such that insertion of Nar A in the modified membrane confers to the enzyme new allotopic properties. Additional and abnormal enzyme-binding sites may be created as a result of the mutation and these may be normalized during heat activation.
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PMID:Increased nitrate reductase A activity as a sign of membrane alteration in early blocked asporogenous mutants of Bacillus subtilis. 82 43

Forty-eight mutants unable to reduce nitrate were isolated from "cowpea" Rhizobium sp. strain 32Hl and examined for nitrogenase activity in culture. All but two of the mutants had nitrogenase activity comparable with the parental sttain and two nitrogenase-defective strains showed alterations in their symbiotic properties. One strain was unable to nodulate either Macroptilium atropurpureum or Vigna uguiculata and, with the other, nodules appeared promptly, but effective nitrogen fixation was delayed. These results, and the relatively low proportion of nitrate reductase mutants with impaired nitrogenase activity, do not support the proposed commanality between nitrogenase and nitrate reductase in cowpea rhizobia. Inhibition studies of the effect of nitrate and its reduction products on the nitrogenase activity in cultured strains 32Hl and the nitrate reductase-deficient, Nif+ strains, indicated that nitrogenase activity was sensitive to nitrite rather than to nitrate.
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PMID:Nitrogen fixation in nitrate reductase-deficient mutants of cultured rhizobia. 83 84

A soluble nitrate reductase from the bacterium Acinetobacter calcoaceticus grown on nitrate has been characterized. The reduction of nitrate to nitrite is mediated by an enzyme of 96000 molecular weight that can use as electron donors either viologen dyes chemically reduced with dithionite or enzymatically reduced with NAD(P)H, through specific diaphorases which utilize viologens as electron acceptors. Nitrate reductase activity is molybdenumdependent as shown by tungstate antagonistic experiments and is sensitive to--SH reagents and metal chelators such as KCN. The enzyme synthesis is repressed by ammonia. Moreover, nitrate reductase activity undergoes a quick inactivation either by dithionite and temperature or by dithionite in the presence of small amounts of nitrate. Cyanate prevents this inactivating process and can restore the activity once the inactivation had occurred, thus suggesting that an interconversion mechanism may participate in the regulation of Acinetobacter nitrate reductase.
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PMID:Assimilatory nitrate reductase from Acinetobacter calcoaceticus. 84 99

Nitrate and nitrite reduction under aerobic, microaerophillic, and anaerobic conditions was demonstrated in Spirillum lipoferum (ATCC 29145). Nitrite did not accumulated during assimilatory nitrate reduction in air. The nitrite produced during dissimilatory nitrate reduction accumulated in the medium but not in the cells. On exposure of the bacteria to nitrate and anaerobiosis, a low initial rate (lag) was followed by accelerated rates of nitrite accumulation. A 3-h anaerobic pretreatment, in the absence of nitrate, did not a void the lag phase. No nitrate reductase activity (NRA) developed in the presence of chloramphenicol. The data suggest that induction of anaerobic NRA in S. lipoferum required nitrate and protein synthesis. Anaerobic N2-ase by S. lipoferum was greatly stimulated in the presence of nitrate. The time course of nitrate reduction was coincidental with the pattern of nitrate-stimulated N2-ase activity inidcating that a relationship exists between these two processes.
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PMID:Nitrate reduction nitrogenase activity in Spirillum lipoferum1. 85 23

The strains were isolated from soil by enrichment in a liquid minimal medium containing ethanol, acetate, succinate, L-malate or tartrate, under an N2O atmosphere at 32 degrees C. All fourteen strains can use the following 25 sources of carbon and energy under aerobic conditions: glycerate, ethanol, propanol, acetate, butyrate, malonate, succinate, glutarate, sebacate, glycollate, L-lactate, D-lactate, L-malate, DL-3-hydroxybutyrate, pyruvate, fumarate, itaconate, mesaconate, crotonate, L-alpha-alanine, D-alpha-alanine, L-leucine, asparagine, L-tyrosine, and L-proline. They hydrolyze Tween 80 but not gelatin. Nitrate is used as nitrogen source. Nitrate reductase A and respiratory nitrite reductase are present. Four of the strains are clearly and easily distinguishable from the others on the basis of six characters: special morphology of colonies; in ability to use isovalerate and DL-valine, inability to use glucose, absence of exocellular amylase, and high level of metapyrocatechase. Their G + C content is 66-67%. One of the strains is distinct from the others by the yellow pigmentation of its colonies, its ability to use D-glucuronate, trehalose, D-sorbitol and citraconate, ability to grow at 4 degrees but not at 40 degrees, and a lower G + C content: 63%. One strain accumulates poly-beta-hydroxybutyrate. This work confirms the well-known, wide variability of the bacteria belonging to the P. stutzeri group. Denitrification by two of the strains was quantitatively studied using cell suspensions. Cells from NO-3-containing anaerobic cultures reduce NO-3, NO-2 and NO to N2O and N2; they reduce slowly N2O to N2. Cells grown in anaerobic cultures under N2O also reduce NO-3, NO-2 and NO to N2O and N2 but they reduce N2O rapidly to N2.
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PMID:[Study of 14 denitrifying soil bacteria of the "pseudomonas stutzeri" group isolated by enrichment culture in the presence of nitrous oxide (author's transl)]. 86 7


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