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)

Understanding of the influences of root-zone CO2 concentration on nitrogen (N) metabolism is limited. The influences of root-zone CO2 concentration on growth, N uptake, N metabolism and the partitioning of root assimilated 14C were determined in tomato (Lycopersicon esculentum). Root, but not leaf, nitrate reductase activity was increased in plants supplied with increased root-zone CO2. Root phosphoenolpyruvate carboxylase activity was lower with NO3(-)- than with NH4(+)-nutrition, and in the latter, was also suppressed by increased root-zone CO2. Increased growth rate in NO3(-)-fed plants with elevated root-zone CO2 concentrations was associated with transfer of root-derived organic acids to the shoot and conversion to carbohydrates. With NH4(+)-fed plants, growth and total N were not altered by elevated root-zone CO2 concentrations, although 14C partitioning to amino acid synthesis was increased. Effects of root-zone CO2 concentration on N uptake and metabolism over longer periods (> 1 d) were probably limited by feedback inhibition. Root-derived organic acids contributed to the carbon budget of the leaves through decarboxylation of the organic acids and photosynthetic refixation of released CO2.
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PMID:The influence of root assimilated inorganic carbon on nitrogen acquisition/assimilation and carbon partitioning. 1572 Jun 30

It has been demonstrated that the NO* produced by nitric oxide synthase or by the reduction of nitrite by nitrate reductase plays an important role in plants' defense against microbial pathogens. The detection of nitrosyl Lb in nodules strongly suggests that NO* is also formed in functional nodules. Moreover, NO* may react with superoxide (which has been shown to be produced in nodules by various processes), leading to the formation of peroxynitrite. We have determined the second-order rate constants of the reactions of soybean oxyleghemoglobin with nitrogen monoxide and peroxynitrite. At pH 7.3 and 20 degrees C, the values are on the order of 10(8) and 10(4) M-1 s-1, respectively. In the presence of physiological amounts of CO2 (1.2 mM), the second-order rate constant of the reaction of oxyleghemoglobin peroxynitrite is even larger (10(5) M-1 s-1). The results presented here clearly show that oxyleghemoglobin is able to scavenge any NO* and peroxynitrite formed in functional nodules. This may help to stop NO* triggering a plant defense reaction.
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PMID:Oxyleghemoglobin scavenges nitrogen monoxide and peroxynitrite: a possible role in functioning nodules? 1626 61

Microbial N2O release during the course of thawing of soil was investigated in model experiment focusing on denitrification, since freeze-thaw has been shown to cause significant physical and biological changes in soil, including a surge of N2O and CO2. The origin of these is still controversially discussed. The increase in denitrification after thawing may be attributed to the diffusion of organic substrates newly available to denitrifiers from disrupted soil aggregates, leading to an increase in microbial activity. Laboratory experiments with upper soil layer of a grassland were conducted in microcosms for real-time gas measurements during the entire phase of freeze and thaw. Shifts in microbial communities were evident on resolution of 16S and 18S rRNA genes and transcripts by denaturing gradient gel electrophoresis (DGGE). Microbial expression profiles were compared by RNA-arbitrarily primed PCR technique and subsequent resolution of amplified products on acrylamide gels. Differences in expression levels of periplasmic nitrate reductase gene (napA) and cytochrome cd1 nitrite reductase (nirS) were observed by most-probable-number-reverse transcription-PCR, with higher levels of expression occurring just after thawing began, followed by a decrease. napA and nirS DGGE profiles showed no change in banding patterns with fingerprints derived from DNA, whereas those derived from cDNA showed a clear succession of denitrifying bacteria, with the most complex pattern being observed at the end of the N2O surge. This study provides insight into the structural community changes and expression dynamics of denitrifiers as a result of freeze-thaw stress. Also, the results presented here support the belief that the gas fluxes observed during thawing is a result of freezing initiated high microbial activity.
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PMID:Influence of freeze-thaw stress on the structure and function of microbial communities and denitrifying populations in soil. 1651 65

This work is concerned with the metabolism of Caldithrix abyssi-an anaerobic, moderately thermophilic bacterium isolated from deep-sea hydrothermal vents of the Mid-Atlantic Ridge and representing a new, deeply deviated branch within the domain Bacteria. Cells of C. abyssi grown on acetate and nitrate, which was reduced to ammonium, possessed nitrate reductase activity and contained cytochromes of the b and c types. Utilization of acetate occurred as a result of the operation of the TCA and glyoxylate cycles. During growth of C. abyssi on yeast extract, fermentation with the formation of acetate, propionate, hydrogen, and CO2 occurred. In extracts of cells grown on yeast extract, acetate was produced from pyruvate with the involvement of the following enzymes: pyruvate:ferredoxin oxidoreductase (2.6 micromol/(min mg protein)), phosphate acetyltransferase (0.46 micromol/(min mg protein)), and acetate kinase (0.3 micromol/(min mg protein)). The activity of fumarate reductase (0.14 micromol/(min mg protein)), malate dehydrogenase (0.17 micromol/(min mg protein)), and fumarate hydratase (1.2 micromol/(min mg protein)), as well as the presence of cytochrome b, points to the formation of propionate via the methyl-malonyl-CoA pathway. The activity of antioxidant enzymes (catalase and superoxide dismutase) was detected. Thus, enzymatic mechanisms have been elucidated that allow C. abyssi to switch from fermentation to anaerobic respiration and to exist in the gradient of redox conditions characteristic of deep-sea hydrothermal vents.
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PMID:[Investigation of the catabolism of acetate and peptides in the new anaerobic thermophilic bacterium Caldithrix abyssi]. 1675 61

Tetraselmis gracilis, a Prasinophycean alga found in estuaries and in the open ocean, was cultivated under different conditions of aeration, which resulted in variations of inorganic carbon in the medium. Relative growth rates, nitrate reductase and carbonic anhydrase activities were daily determined and correlated to the concentration of nitrate, nitrite, phosphate, inorganic and organic carbon in the media. Nitrate reductase catalyzes the reversible carbon dioxide hydration reaction. The activity profiles of both enzymes during 10 days of cultivation under aeration with air showed an inverse relationship: the maximum in the activity of nitrate reductase coincided with the minimum of carbonic anhydrase activity. An ionizable organic carbon species with pKa in the range of metabolites of the photorespiratory path was found parallel with the increase of carbonic anhydrase activity and the decrease of nitrate reductase activity. The onset of photorespiration is probably one of the factors involved in the simultaneous regulation of these enzymatic processes. Cultures aerated with air containing 5% CO2 showed different profiles for nitrate reductase activity and nitrate uptake.
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PMID:The profiles of nitrate reductase and carbonic anhydrase activity in batch cultivation of the marine microalgae Tetraselmis gracilis growing under different aeration conditions. 1681 46

Thiobacillus denitrificans is one of the few known obligate chemolithoautotrophic bacteria capable of energetically coupling thiosulfate oxidation to denitrification as well as aerobic respiration. As very little is known about the differential expression of genes associated with key chemolithoautotrophic functions (such as sulfur compound oxidation and CO2 fixation) under aerobic versus denitrifying conditions, we conducted whole-genome, cDNA microarray studies to explore this topic systematically. The microarrays identified 277 genes (approximately 10% of the genome) as differentially expressed using RMA (robust multiarray average) statistical analysis and a twofold cutoff. Genes upregulated (ca. 6- to 150-fold) under aerobic conditions included a cluster of genes associated with iron acquisition (e.g., siderophore-related genes), a cluster of cytochrome cbb3 oxidase genes, cbbL and cbbS (encoding the large and small subunits of form I ribulose 1,5-bisphosphate carboxylase/oxygenase, or RubisCO), and multiple molecular chaperone genes. Genes upregulated (ca. 4- to 95-fold) under denitrifying conditions included nar, nir, and nor genes (associated, respectively, with nitrate reductase, nitrite reductase, and nitric oxide reductase, which catalyze successive steps of denitrification), cbbM (encoding form II RubisCO), and genes involved with sulfur compound oxidation (including two physically separated but highly similar copies of sulfide:quinone oxidoreductase and of dsrC, associated with dissimilatory sulfite reductase). Among genes associated with denitrification, relative expression levels (i.e., degree of upregulation with nitrate) tended to decrease in the order nar > nir > nor > nos. Reverse transcription-quantitative PCR analysis was used to validate these trends.
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PMID:Whole-genome transcriptional analysis of chemolithoautotrophic thiosulfate oxidation by Thiobacillus denitrificans under aerobic versus denitrifying conditions. 1698 May 3

With the target CO2 concentration of FACE plots being 200 micromol x mol(-1) above that in ambient air, this paper studied the effect of free-air CO2 enrichment (FACE) on leaf nitrate reductase activity (NRA) of Oryza sativa L. cultivar Wuxianjing 14. The results showed that FACE obviously increased the NRA of functional leaves at all growth stages, with an average increment of 50%, 20%, 60%, 80% and 30% at the stages of jointing, booting, heading, 10 after heading, and 20 days after heading, respectively, showing a pronounced effect at jointing, heading and 10 days after heading. Nitrogen application rate also had an obvious effect on the absolute value of NRA in functional leaves under FACE condition. The magnitude of NRA in three nitrogen treatments was in the order of normal nitrogen (NN) > low nitrogen (LN) > high nitrogen (HN) at jointing stage, HN > NN > LN at both booting and heading stages, and NN > HN > LN at both 10 days and 20 days after heading, respectively. The interactive effect of FACE and N supply on NAR varied with the growth stage of Wuxianjing 14, being very significant or significant at the stages of jointing and 20 and 10 days after heading, but not significant at booting and heading stages.
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PMID:[Effect of free-air CO2 enrichment (FACE) on leaf nitrate reductase activity of Oryza sativa L. cultivar Wuxianjing 14]. 1726 50

Ralstonia eutropha is a strictly respiratory facultative lithoautotrophic beta-proteobacterium. In the absence of organic substrates, H2 and CO2 are used as sole sources of energy and carbon. In the absence of oxygen, the organism can respire by denitrification. The recent determination of the complete genome sequence of strain H16 provides the opportunity to reconcile the results of previous physiological and biochemical studies in light of the coding capacity. These analyses revealed genes for several isoenzymes, permit assignment of well-known physiological functions to previously unidentified genes, and suggest the presence of unknown components of energy metabolism. The respiratory chain is fueled by two NADH dehydrogenases, two uptake hydrogenases and at least three formate dehydrogenases. The presence of genes for five quinol oxidases and three cytochrome oxidases indicates that the aerobic respiration chain adapts to varying concentrations of dioxygen. Several additional components may act in balancing or dissipation of redox energy. Paralogous sets of nitrate reductase and nitric oxide reductase genes result in enzymatic redundancy for denitrification.
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PMID:Genomic view of energy metabolism in Ralstonia eutropha H16. 1895 61

Contamination of soil and water by chromium (Cr) is increasing enormously due to anthropogenic activities. The potential of plants to accumulate or stabilize Cr compounds forthe purpose of remediation of Cr contamination has been recognized in recent years. We conducted pot experiments to study photosynthesis and associated attributes in cv Pusa Jai Kisan of Indian mustard under natural as well as Cr-loaded environmental conditions. High doses of Cr caused toxic effects in plants, as evident by a reduction in photosynthetic rate (24.3 to 8.7 micromol CO2 m(-2)s(-1) at 80 DAS), nitrate reductase activity (3.76 to 1.30 micromol nitrite g(-1) f. wt. h(-1) at 80 DAS) and the contents of chlorophyll (1.49 to 0.86 mg g(-1) f. wt. at 80 DAS) and soluble protein (2.96 to 1.93 mg g(-1) f. wt. at 80 DAS). Since plants lack a specific Cr-transport system, mineral nutrient contents also changed due to Cr toxicity. Cr accumulation in different plant parts was affected by both duration and dose of Cr treatments, with a maximal localization of Cr in roots (up to 0.77 mg g(-1) d. wt) at initial stages (40 DAS) and in stem (up to 4.19 mg g(-1) d. wt) at the later stage (80 DAS) of plant growth. Thus, Indian mustard was able to withstand Cr stress and protect itself from Cr toxicity by altering various metabolic processes. Owing to its ability to accumulate large amounts of Cr, it may be useful in the process of land reclamation.
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PMID:Chromium-induced alterations in photosynthesis and associated attributes in Indian mustard. 2303 87

Regulation of nitrate reductase (NR) by reversible phosphorylation at a conserved motif is well established in higher plants, and enables regulation of NR in response to rapid fluctuations in light intensity. This regulation is not conserved in algae NR, and we wished to test the evolutionary origin of the regulatory mechanism by physiological examination of ancient land plants. Especially a member of the lycophytes is of interest since their NR is candidate for regulation by reversible phosphorylation based on sequence analysis. We compared Selaginella kraussiana, a member of the lycophytes and earliest vascular plants, with the angiosperm Arabidopsis thaliana, and also tested the moss Physcomitrella patens. Interestingly, optimization of assay conditions revealed that S. kraussiana NR used NADH as an electron donor like A. thaliana, whereas P. patens NR activity depended on NADPH. Examination of light/darkness effects showed that S. kraussiana NR was rapidly regulated similar to A. thaliana NR when a differential (Mg(2+) contra EDTA) assay was used to reveal activity state of NR. This implies that already existing NR enzyme was post-translationally activated by light in both species. Light had a positive effect also on de novo synthesis of NR in S. kraussiana, which could be shown after the plants had been exposed to a prolonged dark period (7 days). Daily variations in NR activity were mainly caused by post-translational modifications. As for angiosperms, the post-translational light activation of NR in S. kraussiana was inhibited by 3-(3,4-dichlorophenyl)-1*1-dimethylurea (DCMU), an inhibitor of photosynthesis and stomata opening. Evolutionary, a post-translational control mechanism for NR have occurred before or in parallel with development of vascular tissue in land plants, and appears to be part of a complex mechanisms for coordination of CO2 and nitrogen metabolism in these plants.
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PMID:Post-translational control of nitrate reductase activity responding to light and photosynthesis evolved already in the early vascular plants. 2339 36


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