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)

Nitrite and nitrate (NO2 and NO3), the oxidative products of nitric oxide (NO), were elevated in the plasma of rabbits on the third day following ligation of a coronary artery. This elevation coincided with increased activity of the inducible form of nitric oxide synthase (iNOS) in infarcted heart muscle. Data are reported which relate the elevated plasma concentrations of NO2+NO3 (NO(x)) to the increased induction of iNOS in an infarcted heart. NO2 and NO3 in plasma were measured by chemiluminescence. Nitrate was converted to nitrite by nitrate reductase. Plasma from the ear vein, right and left ventricle, and coronary sinus were analyzed for NO(x), and iNOS activity was enzymatically determined in infarcted, risk, and normal areas of the heart. The production equivalent of NO(x) by the heart and lung was also calculated. In addition, the effect of a specific inhibitor of iNOS, S-methylisothiourea sulfate (SMT) on plasma concentration and myocardial production of NO(x) was determined. It was concluded that the elevation of plasma NO(x) following onset of myocardial ischemia was directly related to increased induction of iNOS in the heart. This conclusion was based on a proportional and simultaneous increase in NO(x) plasma concentration with myocardial iNOS activation. The inhibitory effect of SMT furnished additional confirmation of the relationship between myocardial iNOS activation and NO(x) plasma levels in experimental myocardial infarction.
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PMID:Oxidation products of nitric oxide, NO2 and NO3, in plasma after experimental myocardial infarction. 904 16

Nitrite and nitrate determinations in biological fluids are increasingly being used as markers of nitric oxide production. We have modified a nitrate reductase and Griess reaction method for the measurement of serum nitrate and nitrite in ultrafiltrated samples using a microtitre plate. The recoveries of nitrate and nitrite were 95% (range = 86-113%) and 100% (range = 92-109%), respectively. The intra and inter assay coefficients of variation for nitrate plus nitrite in the concentration range 40-50 microM were 9.1% and 7.8%, and in the concentration range of 2.5-10 microM 23.4% and 25.5%, respectively. At its lower limit the assay is able to detect 125 pmoles of nitrate plus nitrite in 50 microL of sample (2.5 mumol/L). A mean serum nitrate plus nitrite level of 32.8 mumol/L (SD 12.3) was measured in 24 healthy adult volunteers (12 men and 12 women), no age or sex differences were noted.
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PMID:Adaptation of the nitrate reductase and Griess reaction methods for the measurement of serum nitrate plus nitrite levels. 946 59

Nitrate is a significant nitrogen source for plants and microorganisms. Recent molecular genetic analyses of representative bacterial species have revealed structural and regulatory genes responsible for the nitrate-assimilation phenotype. Together with results from physiological and biochemical studies, this information has unveiled fundamental aspects of bacterial nitrate assimilation and provides the foundation for further investigations. Well-studied genera are: the cyanobacteria, including the unicellular Synechococcus and the filamentous Anabaena; the gamma-proteobacteria Klebsiella and Azotobacter; and a Gram-positive bacterium, Bacillus. Nitrate uptake in most of these groups seems to involve a periplasmic binding protein-dependent system that presumably is energized by ATP hydrolysis (ATP-binding cassette transporters). However, Bacillus may, like fungi and plants, utilize electrogenic uptake through a representative of the major facilitator superfamily of transport proteins. Nitrate reductase contains both molybdenum cofactor and an iron-sulfur cluster. Electron donors for the enzymes from cyanobacteria and Azotobacter are ferredoxin and flavodoxin, respectively, whereas the Klebsiella and Bacillus enzymes apparently accept electrons from a specific NAD(P)H-reducing subunit. These subunits share sequence similarity with the reductase components of bacterial aromatic ring-hydroxylating dehydrogenases such as toluene dioxygenase. Nitrite reductase contains sirohaem and an iron-sulfur cluster. The enzymes from cyanobacteria and plants use ferredoxin as the electron donor, whereas the larger enzymes from other bacteria and fungi contain FAD and NAD(P)H binding sites. Nevertheless, the two forms of nitrite reductase share recognizable sequence and structural similarity. Synthesis of nitrate assimilation enzymes and uptake systems is controlled by nitrogen limitation in all bacteria examined, but the relevant regulatory proteins exhibit considerable structural and mechanistic diversity in different bacterial groups. A second level of control, pathway-specific induction by nitrate and nitrite in Klebsiella, involves transcription antitermination. Several issues await further experimentation, including the mechanism and energetics of nitrate uptake, the pathway(s) for nitrite uptake, the nature of electron flow during nitrate reduction, and the action of transcriptional regulatory circuits. Fundamental knowledge of nitrate assimilation physiology should also enhance the study of nitrate metabolism in soil, water and other natural environments, a challenging topic of considerable interest and importance.
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PMID:Nitrate assimilation by bacteria. 932 45

Nitrite and nitrate represent the products of the final pathway of nitric oxide metabolism. These two ions were analyzed by capillary electrophoresis (CE) in serum, cerebrospinal fluid, urine and tissue homogenates by mixing the sample with acetonitrile containing NaBr as an internal standard, followed by centrifugation. The supernatant was injected hydrodynamically on a capillary 50 cm x 75 microns (I.D.) and electrophoresed at 6 kV (reversed polarity) in 1.4% sodium chloride in phosphate buffer for 13 min with detection at 214 nm. In addition to removal of the proteins, acetonitrile caused sample stacking. Urinary nitrate analysis by CE was compared to that by the enzymatic Aspergillus nitrate reductase method, with a correlation coefficient of 0.96.
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PMID:Analysis of nitrate in biological fluids by capillary electrophoresis. 936 97

In aerobically grown Azorhizobium caulinodans strain IRBG 46, in vivo expression of nitrate reductase (NR) and nitrite reductase (NiR) requires the presence of either nitrate or nitrite. On the contrary mere microaerobic conditions are sufficient for the expression of NR and NiR, however, addition of nitrate to the growth medium enhanced the activities of the enzymes. Optimum concentration of nitrate for maximum expression of NR and NiR activities was different in aerobic and microaerobic conditions. Nitrite was released into the medium both in aerobic and microaerobic conditions beyond a particular concentration of nitrate in the medium. Dissimilatory nitrate reduction was affected to a lesser extent by ammonium compared to assimilatory nitrate reduction.
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PMID:Effect of combined nitrogen on the expression of nitrate reductase and nitrite reductase in Azorhizobium caulinodans. 947 63

The role of arbuscular mycorrhizal (AM) fungi in assisting their host plant in nitrate assimilation was studied. With polymerase chain reaction technology, part of the gene coding for the nitrate reductase (NR) apoprotein from either the AM fungus Glomus intraradices or from maize was specifically amplified and subsequently cloned and sequenced. Northern (RNA) blot analysis with these probes indicated that the mRNA level of the maize gene was lower in roots and shoots of mycorrhizal plants than in noncolonized controls, whereas the fungal gene was transcribed in roots of AM plants. The specific NR activity of leaves was significantly lower in AM-colonized maize than in the controls. Nitrite formation catalyzed by NR was mainly NADPH-dependent in roots of AM-colonized plants but not in those of the controls, which is consistent with the fact that NRs of fungi preferentially utilize NADPH as reductant. The fungal NR mRNA was detected in arbuscules but not in vesicles by in situ RNA hybridization experiments. This appears to be the first demonstration of differential formation of transcripts of a gene coding for the same function in both symbiotic partners.
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PMID:Expression of maize and fungal nitrate reductase genes in arbuscular mycorrhiza. 961 42

Nitrite (NO2-), an end product of nitrogen radical metabolism, has recently been shown to increase tyrosine nitration by activated leukocytes indicating that nitrite modulates the immune response. We investigated the hypothesis that nitrite may increase nitration of molecular targets within activated cells leading to altered cell cycle progression. Intracellular nitrite was increased by transfection of murine macrophage-like RAW 264.7 cells with the nitrate reductase gene obtained from barley. Nitrate reductase facilitates the conversion of nitrate to nitrite; thus when extracellular nitrate is present, intracellular nitrite will be increased. Results show that addition of KNO3 increases NO2- production and intracellular nitrotyrosine accumulation in the transfectant but not the parent. Inhibition of nitric oxide synthesis with L-NAME during activation with IFN-gamma + LPS reduced NO2- production to the same extent in both cell lines; however, cellular accumulation of nitrotyrosine was reduced by only 25% in the transfectant (P = 0.21) and 49% in the parent cell line (P = 0.007), suggesting that intracellular nitrite increased nitrotyrosine accumulation through a pathway not requiring NO synthesis, i.e., myeloperoxidase system. Approximately 15% of the transfected cells had 4n DNA content 24 h postactivation compared to < 1% of the parent cells. Increased DNA copy number was correlated to nitrotyrosine accumulation. These findings show that intracellular nitrite can increase accumulation of nitrotyrosine and that nitration is linked to cell cycle perturbation.
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PMID:Nitrate reductase alters 3-nitrotyrosine accumulation and cell cycle progression in LPS + IFN-gamma-stimulated RAW 264.7 cells. 1010 Apr 92

The combined action of ammonia monooxygenase, AMO, (NH(3)+2e(-)+O(2)-->NH(2)OH) and hydroxylamine oxidoreductase, HAO, (NH(2)OH+H(2)O-->HNO(2)+4e(-)+4H(+)) accounts for ammonia oxidation in Nitrosomonas europaea. Pathways for electrons from HAO to O(2), nitrite, NO, H(2)O(2) or AMO are reviewed and some recent advances described. The membrane cytochrome c(M)552 is proposed to participate in the path between HAO and ubiquinone. A bc(1) complex is shown to mediate between ubiquinol and the terminal oxidase and is shown to be downstream of HAO. A novel, red, low-potential, periplasmic copper protein, nitrosocyanin, is introduced. Possible mechanisms for the inhibition of ammonia oxidation in cells by protonophores are summarized. Genes for nitrite- and NO-reductase but not N(2)O or nitrate reductase are present in the genome of Nitrosomonas. Nitrite reductase is not repressed by growth on O(2); the flux of nitrite reduction is controlled at the substrate level.
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PMID:Electron transfer during the oxidation of ammonia by the chemolithotrophic bacterium Nitrosomonas europaea. 1100 50

Measurement of nitrite and nitrate, the stable oxidation products of nitric oxide (NO), provides a useful tool to study NO synthesis in vivo and in cell cultures. A simple and rapid fluorometric HPLC method was developed for determination of nitrite through its derivatization with 2,3-diaminonaphthalene (DAN). Nitrite, in standard solution, cell culture medium, or biological samples, readily reacted with DAN under acidic conditions to yield the highly fluorescent 2,3-naphthotriazole (NAT). For analysis of nitrate, it was converted to nitrite by nitrate reductase, followed by the derivatization of nitrite with DAN to form NAT. NAT was separated on a 5-microm reversed-phase C18 column (150X4.6 mm, I.D.) guarded by a 40-microm reversed-phase C18 column (50x4.6 mm, I.D.), and eluted with 15 mM sodium phosphate buffer (pH 7.5) containing 50% methanol (flow-rate, 1.3 ml/min). Fluorescence was monitored with excitation at 375 nm and emission at 415 nm. Mean retention time for NAT was 4.4 min. The fluorescence intensity of NAT was linear with nitrite or nitrate concentrations ranging from 12.5 to 2,000 nM in water, cell culture media, plasma and urine. The detection limit for nitrite and nitrate was 10 pmol/ml. Because NAT is well separated from DAN and other fluorescent components present in biological samples, our HPLC method offers the advantages of high sensitivity and specificity as well as easy automation for quantifying picomole levels of nitrite and nitrate in cell culture medium and biological samples.
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PMID:Rapid determination of nitrite by reversed-phase high-performance liquid chromatography with fluorescence detection. 1107 72

To quantitatively characterise the nitrate reductase activity in the human oral cavity, a new assay based on holding 20 ml of 10 mg nitrate-N/L solution in the mouth was developed. The mouth assay appeared to relate primarily to the oral cavity surface rather than to the saliva. Nitrite formation in the assay was 50-100 times higher compared to in vitro incubation. In the proposed assay, the nitrite formation linearly increased over a period of 3 min. The average nitrate reductase activity in the oral cavity of 20 subjects was 2.39+/-1.52 microg nitrite-N formed/person x min. The nitrate reductase activity measured for two subjects at different hours varied about 15% for the same subject. The average nitrate reductase activity measured in June for 10 subjects (3.43+/-1.75 microg-N/person x min) was significantly higher than that measured in November for 10 other subjects (1.54+/-0.46 microg-N/person x min). Therefore, the nitrate reductase activity in the oral cavity appears to be influenced by the seasonal conditions. Although the amounts of nitrite formed in the mouth assay increased with increasing levels of nitrate, the rate of nitrate to nitrite reduction decreased with increasing levels of nitrate. The nitrite formation was also affected by the pH, with an optimal pH about 8. The nitrite formation was not influenced by uptake in the mouth of glucose, L-ascorbic acid and L-arginine.
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PMID:Quantitative measurement of the nitrate reductase activity in the human oral cavity. 1129 86


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