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)

A nitrate reductase (EC 1.6.6.1)-inactivating factor has been isolated from 8-day-old wheat leaves. The purification schedule involved ammonium sulfate precipitation, Sephadex G-100 filtration, DEAE-cellulose chromatography, and Sephadex G-150 filtration. No accurate assessment could be made as to the degree of purification relative to crude extract as the inactivating factor could not be detected in crude extract. However a 2,446-fold purification was achieved from the ammonium sulfate fraction to the pooled enzyme from the Sephadex G-150 step.The inactivating factor was heat-labile and had a molecular weight of 37,500. The inactivating factor was particularly sensitive to the divalent metal chelators, 1,10-phenanthroline and bathophenanthroline. Evidence indicated that Fe(2+) may be the functional metal. The trypsin inhibitors N-alpha-p-tosyl-l-lysine chloromethyl ketone and alpha-N-benzoyl-l-arginine were inhibitory. However, phenylmethyl sulfonyl fluoride, an inhibitor of serine peptide hydrolases, was not inhibitory. Neither casein nor hemoglobin nor a range of artificial substrates were hydrolyzed by the inactivating factor. Highly purified wheat leaf nitrite reductase (EC 1.7.99.3) and ribulose 1,5-bisphosphate carboxylase:oxygenase (EC 4.1.1.39) were not affected by the nitrate reductase-inactivating factor.The inactivating factor was more active toward the NADH-nitrate reductase compared to either of the component enzymic activities flavin adenine mononucleotide-nitrate reductase and methyl viologen-nitrate reductase. The NADH-ferricyanide reductase (diaphorase) component was the least sensitive.
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PMID:In Vitro Stability of Nitrate Reductase from Wheat Leaves: III. Isolation and Partial Characterization of a Nitrate Reductase-inactivating Factor. 1666 Oct 24

The nitrite-reducing activity of the normal susceptible biotype of lambsquarters (Chenopodium album L.) was strongly inhibited by atrazine in the assay medium, both in the case of the in vivo assays of leaf discs in light, and in vitro photoreduction assays of crude extracts. In vitro assays of crude extracts with methylviologen or ferredoxin supplying the reducing potential were not inhibited by atrazine. In the resistant biotype, inhibition of nitrite reduction did not occur with any of the above assays. Thus, it appears that atrazine does not inhibit nitrite reductase itself, but rather the availability of photosynthetically supplied electrons for the reduction. Atrazine had no effect when added to the media for either in vivo or in vitro assays of nitrate reduction by either the susceptible or resistant biotype.Young lambsquarters plants were treated with atrazine by spraying the leaves at a rate which was lethal for susceptible plants after 5 or 6 days, but had little effect on the resistant biotype. Nitrite did not accumulate in either biotype, but remained present at the level of about 0.1 microgram nitrite N per gram fresh weight. The nitrate content of susceptible-type leaves did increase to two or three times the initial level, during the first four days after spraying. Usually the only visible effect on the plants during this time was a decreased growth rate. Twenty-four hours after spraying the following activities had fallen to 25% or less of the activities of solvent-sprayed control plants: in vivo nitrite reductase, in vivo nitrate reductase, in vitro NADH-nitrate reductase, in vitro reduced flavin mononucleotidenitrate reductase, and in vitro NADH-diaphorase. In these atrazine-treated plants, in vitro nitrite reductase activity with reducing potential supplied by methylviologen was not affected, nor were any of the above activities in leaves of atrazine-treated resistant plants. The abrupt fall in nitrate reductase represents an effect of atrazine not directly related to inhibition of photosynthesis.
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PMID:Reduction of Nitrate and Nitrite in Lambsquarters (Chenopodium album) Biotypes Resistant and Susceptible to Atrazine Toxicity. 1666 20

The effect of tungsten on the development of endogenous and nitrate-induced NADH- and FMNH(2)-linked nitrate reductase activities in primary leaves of 10-day-old soybean (Glycine max [L.] Merr.) seedlings was studied. The seedlings were grown with or without exogenous nitrate. High levels of endogenous nitrate reductase activities developed in leaves of seedlings grown without nitrate. However, no endogenous nitrite reductase activity was detected in such seedlings. The FMNH(2)-linked nitrate reductase activity was about 40% of NADH-linked activity. Tungsten had little or no effect on the development of endogenous NADH- and FMNH(2)-linked nitrate reductase activities, respectively. By contrast, in nitrate-grown seedlings, tungsten only inhibited the nitrate-induced portion of NADH-linked nitrate reductase activity, whereas the FMNH(2)-linked activity was inhibited completely. Tungsten had no effect on the development of nitrate-induced nitrite reductase activity. The complete inhibition of FMNH(2)-linked nitrate reductase activity by tungsten in nitrate-grown plants was apparently an artifact caused by the reduction of nitrite by nitrite reductase in the assay system. The results suggest that in soybean leaves either the endogenous nitrate reductase does not require molybdenum or the molybdenum present in the seed is preferentially utilized by the enzyme complex as compared to nitrate-induced nitrate reductase.
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PMID:Differential effect of tungsten on the development of endogenous and nitrate-induced nitrate reductase activities in soybean leaves. 1666 75

Chenopodium rubrum cells were grown in suspension as a photoautotrophic culture with a 16 hour day. Cell growth had three phases: a 3-day lag, a 3-week logarithmic phase, and a 10-day stationary phase. Chlorophyll content increased steadily during log phase and reached a level of 0.5 to 0.6 mg Chl g(-1) fresh weight. Soluble protein of the cells increased more rapidly from day 4 to day 12 than during midlog phase. Initially, ammonium was taken up in preference to nitrate. However, during the second two weeks of growth, ammonium and nitrate were taken up simultaneously; this period of growth was the time of highest rates of N uptake by the cultured cells. Glutamine synthetase had a high specific activity (17 mumol.hour(-1) mg(-1) protein) in day 1 cells, and this level was sustained until midlog phase when it increased by 20%. Methyl viologen-dependent glutamate synthase specific activity increased rapidly in lag phase cells (day 4 = 10 mumol.hour(-1) mg(-1) protein), but decreased by day 9 to about 50% of the peak and remained constant. NADH:nitrate reductase specific activity increased rapidly in lag phase cells and reached a plateau that lasted from day 4 to 14 (1 mumol.hour(-1) mg(-1) protein). Methyl viologen-dependent nitrite reductase specific activity was high when assayed on day 5 and increased to a maximum on day 15 to 16 (12 mumol.hour(-1) mg(-1) protein). NADPH- and NADH-dependent glutamate dehydrogenase specific activities remained rather constant throughout the growth cycle. The cells appeared to have developed photosynthetic competence and to have leaf-like activities of nitrogen assimilation enzymes.
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PMID:Development of Nitrogen Assimilation Enzymes during Photoautotrophic Growth of Chenopodium rubrum Suspension Cultures. 1666 39

A non-heme iron containing protein which bears an antigenic similarity to ferredoxin from spinach leaves (Spinacia oleracea L.) has been identified in extracts prepared from young roots of maize (Zea mays L., hybrid W64A x W182E). The ferredoxin-like root electron carrier could substitute for ferredoxin in a cytochrome c reduction system in which pyridine nucleotide (NADPH) reduces the root electron carrier in a reaction catalyzed by ferredoxin-NADP(+) reductase (EC 1.6.7.1) from spinach leaves. However, the root electron carrier did not mediate the photoreduction of NADP(+) in an illuminated reconstituted chloroplast system.A pyridine nucleotide reductase which shares identical immunological determinants with the ferredoxin-NADP(+) reductase from spinach leaves has also been characterized from maize roots. Root pyridine nucleotide reductase mediated the transfer of electrons from either NADPH or NADH to cytochrome c via ferredoxin or the root electron carrier. Under chemical reducing conditions with sodium dithionite and bicarbonate, the ferredoxin-like root electron carrier served as an electron carrier for the ferredoxin-requiring glutamate synthase (EC 1.4.7.1) and nitrite reductase (EC 1.7.7.1) obtained from maize roots or leaves. In the presence of root pyridine nucleotide reductase and root electron carrier, either NADPH or NADH served as the primary electron donor for glutamate synthesis in extracts from maize roots or leaves. The electron transport system originating with NADH or NADPH, was, however, not able to mediate the reduction of NO(2) (-) to NH(3).
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PMID:An electron transport system in maize roots for reactions of glutamate synthase and nitrite reductase : physiological and immunochemical properties of the electron carrier and pyridine nucleotide reductase. 1666 48

The specific activities of nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase were determined in intact protoplasts and intact chloroplasts from Chlamydomonas reinhardtii. After correction for contamination, the data were used to calculate the portion of each enzyme in the algal chloroplast. The chloroplast of C. reinhardtii contained all enzyme activities for nitrogen assimilation, except nitrate reductase, which could not be detected in this organelle. Glutamate synthase (NADH- and ferredoxin-dependent) and glutamate dehydrogenase were located exclusively in the chloroplast, while for nitrite reductase and glutamine synthetase an extraplastidic activity of about 20 and 60%, respectively, was measured. Cells grown on ammonium, instead of nitrate as nitrogen source, had a higher total cellular activity of the NADH-dependent glutamate synthase (+95%) and glutamate dehydrogenase (+33%) but less activity of glutamine synthetase (-10%). No activity of nitrate reductase could be detected in ammonium-grown cells. The distribution of nitrogen-assimilating enzymes among the chloroplast and the rest of the cell did not differ significantly between nitrate-grown and ammonium-grown cells. Only the plastidic portion of the glutamine synthetase increased to about 80% in cells grown on ammonium (compared to about 40% in cells grown on nitrate).
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PMID:Localization of Nitrogen-Assimilating Enzymes in the Chloroplast of Chlamydomonas reinhardtii. 1666 9

A nas gene region from Rhodobacter capsulatus E1F1 containing the putative nasB gene for nitrite reductase was previously cloned. The recombinant His(6)-NasB protein overproduced in E. coli showed nitrite reductase activity in vitro with both reduced methyl viologen and NADH as electron donors. The apparent K ( m ) values for nitrite and NADH were 0.5 mM and 20 microM, respectively, at the pH and temperature optima (pH 9 and 30 degrees C). The optical spectrum showed features that indicate the presence of FAD, iron-sulfur cluster and siroheme as prosthetic groups, and nitrite reductase activity was inhibited by sulfide and iron reagents. These results indicate that the phototrophic bacterium R. capsulatus E1F1 possesses an assimilatory NADH-nitrite reductase similar to that described in non-phototrophic organisms.
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PMID:Expression and characterization of the assimilatory NADH-nitrite reductase from the phototrophic bacterium Rhodobacter capsulatus E1F1. 1689 35

We investigated the role of glutamine synthetases (cytosolic GS1 and chloroplast GS2) and glutamate synthases (ferredoxin-GOGAT and NADH-GOGAT) in the inorganic nitrogen assimilation and reassimilation into amino acids between bundle sheath cells and mesophyll cells for the remobilization of amino acids during the early phase of grain filling in Zea mays L. The plants responded to a light/dark cycle at the level of nitrate, ammonium and amino acids in the second leaf, upward from the primary ear, which acted as the source organ. The assimilation of ammonium issued from distinct pathways and amino acid synthesis were evaluated from the diurnal rhythms of the transcripts and the encoded enzyme activities of nitrate reductase, nitrite reductase, GS1, GS2, ferredoxin-GOGAT, NADH-GOGAT, NADH-glutamate dehydrogenase and asparagine synthetase. We discerned the specific role of the isoproteins of ferredoxin and ferredoxin:NADP(+) oxidoreductase in providing ferredoxin-GOGAT with photoreduced or enzymatically reduced ferredoxin as the electron donor. The spatial distribution of ferredoxin-GOGAT supported its role in the nitrogen (re)assimilation and reallocation in bundle sheath cells and mesophyll cells of the source leaf. The diurnal nitrogen recycling within the plants took place via the specific amino acids in the phloem and xylem exudates. Taken together, we conclude that the GS1/ferredoxin-GOGAT cycle is the main pathway of inorganic nitrogen assimilation and recycling into glutamine and glutamate, and preconditions amino acid interconversion and remobilization.
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PMID:Implication of the glutamine synthetase/glutamate synthase pathway in conditioning the amino acid metabolism in bundle sheath and mesophyll cells of maize leaves. 1847 60

The nitrite oxidizing Alphaproteobacterium, Nitrobacter winogradskyi, primarily conserves energy from the oxidation of nitrite (NO(2)(-))to nitrate (NO(3)(-)) through aerobic respiration. Almost 20 years ago, NO-dependent NADH formation was reported to occur in both aerobic and anaerobic cell suspensions of N. winogradskyi strain 'agilis', suggesting that NO oxidation might contribute to energy conservation by Nitrobacter. Recently, the N. winogradskyi Nb-255 genome was found to contain a gene (Nwin_2648) that encodes a putative copper-containing nitrite reductase (NirK), which may reduce NO(2)(-) to NO. In this study, the putative nirK was found to be maximally transcribed under low O(2) (between zero and 4% O(2)) in the presence of NO(2)(-). Transcription of nirK was not detected under anaerobic conditions in the absence of NO(2)(-) or in the presence of NO(3)(-) and pyruvate. Although net production of NO could not be detected from either aerobically grown or anaerobically incubated cells, exogenous NO was consumed by viable cells and concomitantly inhibited NO(2)(-)-dependent O(2) uptake in a reversible, concentration dependent manner. Both NO(2(-)-dependent O(2) uptake and NO consumption were inhibited by 1 mM cyanide suggesting involvement of cytochrome oxidase with NO consumption. Abiotic consumption of NO was measured, yet, both the rates and kinetics of NO transformation in buffer alone, or by heat killed, or cyanide-treated cells differed from those of viable cells. In light of this new information, a modified model is proposed to explain how NirK and NO manage electron flux in Nitrobacter.
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PMID:Expression of a putative nitrite reductase and the reversible inhibition of nitrite-dependent respiration by nitric oxide in Nitrobacter winogradskyi Nb-255. 1897 23

The influences of 50 and 100muM Ni on growth, tissue Ni accumulation, concentrations of nitrate, ammonium, glutamate, and proline as well as the activities of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), alanine aminotransferase (AlaAT), and aspartate aminotransferase (AspAT) were examined in the shoots of wheat seedlings cv. Zyta. Exposure of the seedlings to Ni resulted in a rapid accumulation of this metal in the shoots, which was accompanied by significant reduction in fresh weight of these organs. Tissue nitrate content decreased in response to Ni stress, while ammonium concentration increased substantially. Glutamate concentration was slightly lowered up to the 4th day of the metal exposure. In contrast, proline content increased significantly, starting from the first day after Ni treatment. NR activity showed a decline of up to 40% below the control level after Ni application; however, its activation state remained unaltered. Heavy metal treatment also resulted in a marked decrease in NiR activity, which after 7d of exposure to 100muM Ni was almost 80% lower than in the control. GS activity in wheat shoots was not influenced by Ni application. Contrary to Fd-GOGAT exhibiting reduced activity in the shoots of Ni-treated wheat seedlings, NADH-GOGAT activity was considerably enhanced, exceeding the control value even by 165%. After 7d of exposure to Ni, both NADH-GDH and NAD-GDH activities in wheat shoots were markedly induced; however, NAD-GDH activity showed a significant decrease at the early stage of the experiment. Both AlaAT and AspAT glutamate-producing activities were considerably stimulated by Ni treatment. Our results suggest that induction of NADH-GOGAT, NADH-GDH, AlaAT, and AspAT activities may compensate for the reduced Fd-GOGAT activity and serve as an alternative means of glutamate synthesis in wheat shoots under Ni stress.
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PMID:Nickel-induced changes in nitrogen metabolism in wheat shoots. 1918 88


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