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)

This report describes the isolation and characterization of a Neurospora crassa mutant with an impaired regulation of nitrate reductase. Glutamine, which prevents the induction of nitrate reductase in N. crassa, did so relatively ineffectively in this mutant. The mutation did not affect the regulation of all enzymes regulated by "nitrogen metabolite regulation"; it did affect the regulation of nitrate reductase, nitrite reductase, histidase, and acetamidase, as well as that of thiourea sensitivity. The mutation was not allelic with nit-2, the gene controlling a general positive effector of nitrogen metabolite-regulated enzyme formation.
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PMID:Physiological characterization of a Neurospora crassa mutant with impaired regulation of nitrate reductase. 610 86

This work reports the isolation and preliminary characterization of Nicotiana plumbaginifolia mutants resistant to methylammonium. Nicotiana plumbaginifolia plants cannot grow on low levels of nitrate in the presence of methylammonium. Methylammonium is not used as a nitrogen source, although it can be efficiently taken up by Nicotiana plumbaginifolia cells and converted into methylglutamine, an analog of glutamine. Glutamine is known to repress the expression of the enzymes that mediate the first two steps in the nitrate assimilatory pathway, nitrate reductase (NR) and nitrite reductase (NiR). Methylammonium has therefore been used, in combination with low concentrations of nitrate, as a selective agent in order to screen for mutants in which the nitrate pathway is de-repressed. Eleven semi-dominant mutants, all belonging to the same complementation group, were identified. The mutant showing the highest resistance to methylammonium was not affected either in the utilization of ammonium, accumulation of methylammonium or in glutamine synthase activity. A series of experiments showed that utilization of nitrite by the wild-type and the mutant was comparable, in the presence or the absence of methylammonium, thus suggesting that the mutation specifically affected nitrate transport or reduction. Although NR mRNA levels were less repressed by methylammonium treatment of the wild-type than the mutant, NR activities of the mutant remained comparable with or without methylammonium, leading to the hypothesis that modified expression of NR is probably not responsible for resistance to methylammonium. Methylammonium inhibited nitrate uptake in the wild-type but had only a limited effect in the mutant. The implications of these results are discussed.
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PMID:Methylammonium-resistant mutants of Nicotiana plumbaginifolia are affected in nitrate transport. 860 51

A mutant (M45) of the cyanobacterium Synechococcus sp. strain PCC 7942, which is defective in active transport of nitrate, was used for the studies of the nitrogen regulation of the genes involved in nitrate and CO2 assimilation. In a medium containing 30 mM nitrate as the nitrogen source, M45 grew under constant stress of nitrogen deficiency and accumulated a five-times-larger amount of the transcript of nirA, the gene for nitrite reductase, compared with nitrate-grown wild-type cells. By contrast, the level of the transcript of rbcL, the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, was 40% of the wild-type level. Addition of ammonium to the culture of M45 abolished the accumulation of the nirA transcript and stimulated the accumulation of the rbcL transcript, showing that ammonium repressed and activated the transcription of nirA and rbcL, respectively. Glutamine, the initial product of ammonium fixation, also showed negative and positive effects on nirA and rbcL, respectively. One of the metabolites of glutamine, carbamoylphosphate, and its decomposition product, cyanate, were found to repress nirA and also to markedly activate rbcL. Cyanate negatively regulated another ammonium-repressible gene, glnA, but had no effect on the psbAI and rps1 genes. The effects of cyanate were not ascribable to the ammonium and CO, resulting from its decomposition. These findings suggested that cyanate may act as a regulator of the ammonium-responsive genes involved in carbon and nitrogen assimilation in the cyanobacterium.
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PMID:Regulation by cyanate of the genes involved in carbon and nitrogen assimilation in the cyanobacterium Synechococcus sp. strain PCC 7942. 862 39

Activities of nitrate reductase (NR; EC 1.6.6.1), nitrite reductase (NiR; EC 1.7.7.1), glutamine synthetase (GS; EC 6.3.1.2) and glutamate dehydrogenase (GDH; EC 1.4.1.3) were measured in cotyledons of sunflower (Helianthus annuus L. cv Peredovic) seedlings during germination and early growth under various external nitrogen sources. The presence of NO 3 (-) in the medium promoted a gradual increase in the levels of NR and NiR activities during the first 7 d of germination. Neither NR nor NiR activities were increased in a nitrogen-free medium or in media with either NH 4 (+) or urea as nitrogen sources. Moreover, the presence of NH 4 (+) did not abolish the NO 3 (-) -dependent appearance of NR and NiR activities. The increase of NR activity was impaired both by cycloheximide and chloramphenicol, which indicates that both cytoplasmic 80S and plastidic 70S ribosomes are involved in the synthesis of the NR molecule. By contrast, the appearance of NiR activity was only inhibited by cycloheximide, indicating that NiR seems to be exclusively synthesized on the cytoplasmic 80S ribosomes. Glutamine-synthetase activity was also strongly increased by external NO 3 (-) but not by NH 4 (+) or urea. The appearance of GS activity was more efficiently suppressed by cycloheximide than chloramphenicol. This indicates that GS is mostly synthesized in the cytoplasm. The cotyledons of the dry seed contain high levels of GDH activity which decline during germination independently of the presence or absence of a nitrogen source. Cycloheximide, but not chloramphenicol, greatly prevented the decrease of GDH activity.
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PMID:Development of nitrogen-assimilating enzymes in sunflower cotyledons during germination as affected by the exogenous nitrogen source. 2422 79

Nitrate and nitrite reductases were both induced by adding three concentrations of nitrate to the nutrient supply of nitrate-starved barley seedlings. Enzyme induction was not proportional to the amount of nitrate introduced. Glutamine synthetase also increased above a high endogenous activity but the increase did not differ significantly between any of the three nitrate treatments. Nitrate accumulated rapidly in leaves of plants given 4.0 mM or 0.5 mM nitrate but not with 0.1 mM nitrate. In all treatments, amino acids in leaves increased for 2 d, chiefly attributable to glutamine, then declined. Transferring plants from the three nitrate treatments to nitrate-free nutrient produced an immediate decline in nitrate reductase but nitrite reductase continued to increase for 2 d, before declining. Glutamine-synthetase activity was not affected by withdrawal of nitrate, nor did nitrate withdrawal retard plant growth during the 9-d period of the experiment. The disparity between accumulated nitrate and nitrate-reducing capacity and the rapid decrease in leaf nitrate when nutrient nitrate supply was removed, indicated the presence of a nitrate-storage pool that could be called upon to maintain amino-acid production in times of nitrogen starvation.
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PMID:Some effects of nitrate abundance and starvation on metabolism and accumulation of nitrogen in barley (Hordeum vulgare L. cv Sonja). 2425 30

The nirk gene encoding the copper-containing nitrite reductase (CuNiR), a key catalytic enzyme in the environmental denitrification process that helps to produce nitric oxide from nitrite. The molecular mechanism of denitrification process is definitely complex and in this case a theoretical investigation has been conducted to know the sequence information and amino acid composition of the active site of CuNiR enzyme using various Bioinformatics tools. 10 Fasta formatted sequences were retrieved from the NCBI database and the domain and disordered regions identification and phylogenetic analyses were done on these sequences. The comparative modeling of protein was performed through Modeller 9v14 program and visualized by PyMOL tools. Validated protein models were deposited in the Protein Model Database (PMDB) (PMDB id: PM0080150 to PM0080159). Active sites of nirk encoding CuNiR enzyme were identified by Castp server. The PROCHECK showed significant scores for four protein models in the most favored regions of the Ramachandran plot. Active sites and cavities prediction exhibited that the amino acid, namely Glycine, Alanine, Histidine, Aspartic acid, Glutamic acid, Threonine, and Glutamine were common in four predicted protein models. The present in silico study anticipates that active site analyses result will pave the way for further research on the complex denitrification mechanism of the selected species in the experimental laboratory.
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PMID:Comparative analysis of amino acid composition in the active site of nirk gene encoding copper-containing nitrite reductase (CuNiR) in bacterial spp. 2806 15