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)

Whereas in freely suspended cell cultures growing photoautotrophically under non-limiting carbon conditions nitrite and nitrate were simultaneously consumed after ammonium consumption was complete, in alginate-entrapped cell cultures a sequential consumption of nitrite (first) and nitrate was observed after ammonium had almost been fully removed. In this paper results are reported that show inhibition of nitrate consumption by nitrite in immobilized cells. However no inhibition of nitrate active transport was observed. The sequential consumption of ammonium, nitrite and nitrate by Ca-alginate immobilized cells is explained on the basis of local ammonium accumulation due to its photoproduction by photorespiration, that could be caused by the increase of the O2/CO2 ratio around the entrapped cells. Measurements of light-dependent oxygen production (LDOP) and activity levels of nitrogen assimilation enzymes, including nitrite reductase (NiR) and glutamine synthetase (GS) in immobilized cells, determined under photorespiration stimulating conditions, are shown that support this explanation.
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PMID:Inhibition of nitrate consumption by nitrite in entrapped Chlamydomonas reinhardtii cells. 1180 Apr 87

An important biochemical feature of autotrophs, land plants and algae, is their incorporation of inorganic nitrogen, nitrate and ammonium, into the carbon skeleton. Nitrate and ammonium are converted into glutamine and glutamate to produce organic nitrogen compounds, for example proteins and nucleic acids. Ammonium is not only a preferred nitrogen source but also a key metabolite, situated at the junction between carbon metabolism and nitrogen assimilation, because nitrogen compounds can choose an alternative pathway according to the stages of their growth and environmental conditions. The enzymes involved in the reactions are nitrate reductase (EC 1.6.6.1-2), nitrite reductase (EC 1.7.7.1), glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 1.4.1.13-14, 1.4.7.1), glutamate dehydrogenase (EC 1.4.1.2-4), aspartate aminotransferase (EC 2.6.1.1), asparagine synthase (EC 6.3.5.4), and phosphoenolpyruvate carboxylase (EC 4.1.1.31). Many of these enzymes exist in multiple forms in different subcellular compartments within different organs and tissues, and play sometimes overlapping and sometimes distinctive roles. Here, we summarize the biochemical characteristics and the physiological roles of these enzymes. We also analyse the molecular evolution of glutamine synthetase, glutamate synthase and glutamate dehydrogenase, and discuss the evolutionary relationships of these three enzymes.
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PMID:Nitrogen-assimilating enzymes in land plants and algae: phylogenic and physiological perspectives. 1220 56

To define further the early, or primary, events that occur in maize (Zea mays) seedlings exposed to NO3-, accumulation of chloroplast glutamine synthetase (GS2; EC 6.3.1.2) and ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC 1.4.7.1), transcripts were examined in roots and leaves. In roots, NO3- treatment caused a rapid (within 30 min), transient, and cycloheximide-independent accumulation of GS2 and Fd-GOGAT transcripts. In addition, 10 [mu]M external NO3- was sufficient to cause transcript accumulation. The induction was NO3- specific, since NH4Cl treatment did not affect mRNA levels. GS2 and Fd-GOGAT mRNA accumulation in roots was similar to that observed for nitrate reductase (NR) mRNA. Therefore, the four genes involved in NO3- assimilation (NR, nitrite reductase, GS2, and Fd-GOGAT) are expressed in the root primary response to NO3-, suggesting that all four genes can respond to the same signal transduction system. In contrast, relatively high levels of GS2 and Fd-GOGAT mRNAs were present in untreated leaf tissue, and NO3- treatment had little or no influence on transcript accumulation. Rapid, transient, and cycloheximide-independent NR mRNA expression was seen in the NO3--treated leaves, demonstrating that NO3- was not limiting. The NO3--independent constitutive expression of GS2 and Fd-GOGAT is likely due to the requirement for reassimilation of photorespiratory NH4+ in these young leaves.
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PMID:Glutamine Synthetase and Ferredoxin-Dependent Glutamate Synthase Expression in the Maize (Zea mays) Root Primary Response to Nitrate (Evidence for an Organ-Specific Response). 1223 79

Physiological alterations and regulation of heterocyst and nitrogenase formation have been studied in Het(-) Fix(-) mutant strain of diazotrophic cyanobacterium Anabaena variabilis. Het(-) Fix(-) mutant strain of A. variabilis has been isolated by N-methyl-N'-nitro-N"-nitrosoguanidine (NTG) mutagenesis and was screened with the penicillin enrichment (500 microg ml(-1)). Growth, heterocyst differentiation, nitrogenase and glutamine synthetase (biosynthetic and transferase), (14)CO(2)-fixation, nitrate reductase (NR), nitrite reductase (NiR), glucose-6-phosphate dehydrogenase (G6PDH), and isocitrate dehydrogenase (IDH) activities, and NO(3)(-), NO(2)(-), and NH(4)(+) uptake and whole cell protein profile in different metabolic conditions were studied in the Het(-) Fix(-) mutant strain taking wild-type A. variabilis as reference. Het(-) Fix(-) mutant strain was incapable of assimilating elemental nitrogen (N(2)) due to its inability to form heterocysts and nitrogenase and this was the reason for its inability to grow in BG-11(0) medium (free from combined nitrogen). In contrast, wild-type strain grew reasonably well in the absence of combined nitrogen sources and also showed heterocyst differentiation (8.5%) and nitrogenase activity (10.8 etamol C(2)H(4) formed microg(-1) Chl a h(-1)) in N(2)-medium. Wild-type strain also exhibited higher NR, NiR, and GS activities compared to its Het(-) Fix(-) mutant strain, which may presumably be due to acquisition of high uptake of NO(3)(-), NO(2)(-), and NH(2)(+). Wild-type strain in contrast to its Het(-) Fix(-) mutant strain also exhibited high level of G6PDH, IDH, and (14)CO(2) fixation activities. Low levels of G6PDH and IDH activities in Het(-) Fix(-) mutant strain further confirmed the lack of heterocyst differentiation and nitrogenase activity in the Het(-) Fix(-) mutant strain.NR, NiR, and GS activities in both the strains were energy-dependent and the energy required is mainly derived from photophosphorylation. Furthermore, it was found that de novo protein synthesis is necessarily required for the activities of NR, NiR, and GS in both wild-type and its Het(-) Fix(-) mutant strain.
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PMID:Physiological alterations and regulation of heterocyst and nitrogenase formation in Het(-) Fix(-) mutant strain of Anabaena variabilis. 1223 60

Nia30(145) transformants with very low nitrate reductase activity provide an in vivo screen to identify processes that are regulated by nitrate. Nia30(145) resembles nitrate-limited wild-type plants with respect to growth rate and protein and amino acid content but accumulates large amounts of nitrate when it is grown on high nitrate. The transcripts for nitrate reductase (NR), nitrite reductase, cytosolic glutamine synthetase, and glutamate synthase increased; NR and nitrite reductase activity increased in leaves and roots; and glutamine synthetase activity increased in roots. The transcripts for phosphoenolpyruvate carboxylase, cytosolic pyruvate kinase, citrate synthase, and NADP-isocitrate dehydrogenase increased; phosphoenolpyruvate carboxylase activity increased; and malate, citrate, isocitrate, and [alpha]-oxoglutarate accumulated in leaves and roots. There was a decrease of the ADP-glucose pyrophosphorylase transcript and activity, and starch decreased in the leaves and roots. After adding 12 mM nitrate to nitrate-limited Nia30(145), the transcripts for NR and phosphoenolpyruvate carboxylase increased, and the transcripts for ADP-glucose pyrophosphorylase decreased within 2 and 4 hr, respectively. Starch was remobilized at almost the same rate as in wild-type plants, even though growth was not stimulated in Nia30(145). It is proposed that nitrate acts as a signal to initiate coordinated changes in carbon and nitrogen metabolism.
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PMID:Nitrate Acts as a Signal to Induce Organic Acid Metabolism and Repress Starch Metabolism in Tobacco. 1223 66

P(II) proteins signal the cellular nitrogen status in numerous bacteria, and in cyanobacteria P(II) is subjected to serine phosphorylation when the cells experience a high C to N balance. In the unicellular cyanobacterium Synechococcus sp. PCC 7942, the P(II) protein (glnB gene product) is known to mediate the ammonium-dependent inhibition of nitrate and nitrite uptake. The analysis of gene expression through RNA/DNA hybridization indicated that a P(II)-null mutant was also impaired in the induction of NtcA-dependent, nitrogen assimilation genes amt1 (ammonium permease), glnA (glutamine synthetase) and nir (nitrite reductase), as well as of the N-control gene ntcA, mainly under nitrogen deprivation. This gene expression phenotype of the glnB mutant could be complemented by wild-type P(II) protein or by modified P(II) proteins that cannot be phosphorylated and mimic either the phosphorylated (GlnB(S49D) and GlnB(S49E)) or unphosphorylated (GlnB(S49A)) form of P(II). However, strains carrying the GlnB(S49D) and GlnB(S49E) mutant proteins exhibited higher levels of expression of nitrogen-regulated genes than the strains carrying the wild-type P(II) or the GlnB(S49A) protein.
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PMID:Transcriptional effects of the signal transduction protein P(II) (glnB gene product) on NtcA-dependent genes in Synechococcus sp. PCC 7942. 1275 2

In order to better understand the effects of heavy metals on the growth of plants, we decided to perform recovering experiments by following both chemical and physiological parameters in cadmium pre-stressed tomato seedlings after cadmium had been removed from the nutrient solution. The work shows that cadmium suppression results in resumption of growth activity. The biomass of leaves and stems rose steadily. The increase in root biomass exceeded those of leaves and stems. At the same time, nitrate content was increased to reach the level obtained with unstressed controls. In all the organs studied, the activities of the enzymes involved in the anabolic nitrogen primary assimilation pathways (nitrate reductase (NR), nitrite reductase (NiR) and glutamine synthetase (GS) soared after that cadmium had been removed. While NAD(+)-dependent glutamate dehydrogenase (GDH-NAD+) activity also rose progressively during the recovering time, the cognate NADH-dependent glutamate dehydrogenase (GDH-NADH) activity decreased. This result allows us to propose that the ammonia produced by the stress-induced protein catabolism is detoxified and re-assimilated by the GDH-NADH isoenzyme. On the basis of these results, we will discuss the ability of the plant to dilute the effects of pollutants during the recovering period. An important outcome of this work is that a transient contamination of the culture medium by pollutants is not necessarily followed by a significant depreciation in product yield or quality.
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PMID:[Reversibility of the effects of cadmium on the growth and nitrogen metabolism in the tomato(Lycopersicon esculentum)]. 1289 45

The genes encoding the structural components of the nitrate/nitrite assimilation system of the oceanic cyanobacterium Synechococcus sp. strain WH 8103 were cloned and characterized. The genes encoding nitrate reductase (narB) and nitrite reductase (nirA) are clustered on the chromosome but are organized in separate transcriptional units. Upstream of narB is a homologue of nrtP that encodes a nitrate/nitrite-bispecific permease rather than the components of an ABC-type nitrate transporter found in freshwater cyanobacteria. Unusually, neither nirA nor ntcA (encoding a positive transcription factor of genes subject to nitrogen control) were found to be tightly regulated by ammonium. Furthermore, transcription of glnA (encoding glutamine synthetase) is up-regulated in ammonium-grown cells, highlighting significant differences in nitrogen control in this cyanobacterium. Nitrogen depletion led to the transient up-regulation of ntcA, nirA, nrtP, narB, and glnA in what appears to be an NtcA-dependent manner. The NtcA-like promoters found upstream of nirA, nrtP, and narB all differ in sequence from the canonical NtcA promoter established for other cyanobacteria, and in the case of nirA, the NtcA-like promoter was functional only in cells deprived of combined nitrogen. The ecological implications of these findings are discussed in the context of the oligotrophic nature of oceanic surface waters in which Synechococcus spp. thrive.
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PMID:Nitrate/nitrite assimilation system of the marine picoplanktonic cyanobacterium Synechococcus sp. strain WH 8103: effect of nitrogen source and availability on gene expression. 1466 Mar 43

Different responses of spinach and kidney bean plants to various concentrations of NO(2) in the light and in the dark were shown. Spinach is more resistant than NO(2) than kidney bean. It is not only due to its greater tolerance to NO(2)(-) accumulated in leaves, but also to its stronger ability to metabolize NO(2)(-). The injury of spinach induced by the exposure to high concentration NO(2) in the light was not caused by the accumulation of NO(2)(-), but concerned the large amount of accumulated NH(3). The primary causes of NH(3) accumulation were that the activity of nitrite reductase was not affected by the fumigation on the one hand, and the activities of glutamine synthetase and glutamate synthase were inhibited on the other.
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PMID:Response of spinach and kidney bean plants to nitrogen dioxide. 1509 11

Tomato (Lycopersicon esculentum) seedlings were grown in the presence of cadmium. After 1 week of Cd treatment, a sharp decline in biomass accumulation in the leaves and roots was observed, together with a decrease in the rate of photosynthetic activity due to both Rubisco and chlorophyll degradation and stomata closure. Cadmium induced a significant decrease in nitrate content and inhibition of the activities of nitrate reductase, nitrite reductase, glutamine synthetase (GS) and ferredoxin-glutamate synthase. An increase in NADH-glutamate synthase and NADH-glutamate dehydrogenase activity was observed in parallel. The accumulation of ammonium into the tissues of treated plants was accompanied by a loss of total protein and the accumulation of amino acids. Gln represented the major amino acid transported through xylem sap of Cd-treated and control plants. Cadmium treatment increased the total amino acid content in the phloem, maintaining Gln/Glu ratios. Western and Northern blot analysis of Cd-treated plants showed a decrease in chloroplastic GS protein and mRNA and an increase in cytosolic GS and glutamate dehydrogenase transcripts and proteins. An increase in asparagine synthetase mRNA was observed in roots, in parallel with a strong increase in asparagine. Taken together, these results suggest that the plant response to Cd stress involved newly induced enzymes dedicated to coordinated leaf nitrogen remobilization and root nitrogen storage.
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PMID:Cadmium toxicity induced changes in nitrogen management in Lycopersicon esculentum leading to a metabolic safeguard through an amino acid storage strategy. 1557 44


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