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)

The inhibition of seedling growth and nitrate reductase activity in 5 d old Vigna radiata (L.) Wilczek cv. Pusa Baisakhi in the presence of 1.0 mM lead acetate increased drastically, if NaCl (6 and 12 EC) was also present in the nutrient media along with the metal salt. Correspondingly higher endogenous Na+ levels were accumulated in the roots and leaves of seedlings in presence of the two stresses. On the other hand, the levels of endogenous lead get reduced in presence of NaCl in both the roots and leaves. Roots accumulated more Pb2+ and Na+ than the leaves. The two stresses affect more drastically in the additive or even synergistic manner during the early growth phase of the seedlings.
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PMID:Effect of lead on growth and nitrate assimilation of Vigna radiata (L.) Wilczek seedlings in a salt affected environment. 1282 Oct 5

The present study shows that when freezing nitrite containing biological samples in the presence of sodium and phosphate, a process of tyrosine nitration and S-nitrosocysteine formation is observed. The underlying mechanism is obviously based on the already described pH decrease in sodium phosphate buffered solutions during the freezing process and probably involves nitrous acid as an intermediate. However, in pure potassium phosphate buffer freeze-artefacts were absent. The yield of 3-nitrotyrosine from albumin-bound or free tyrosine depends not only on the concentration of nitrite, tyrosine or protein, and sodium phosphate but also on the velocity of the freezing process. Nitrite and nitrate were quantified by the Griess/nitrate reductase assay. 3-nitrotyrosine formation was quantitatively measured by HPLC analysis with optical and electrochemical detection as well as qualitatively investigated by immunohistochemistry and slot blot analysis using 3-nitrotyrosine specific antibodies. The formation of S-nitrosocysteine was detected by S-nitrosothiol specific antibodies and quantified by a fluorometric assay. Irrespective of the mechanism and although the here presented results cannot be generalized, the data warrant caution for the analysis of nitration or nitros(yl)ation products following freezing of nitrite containing biological material.
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PMID:A new pitfall in detecting biological end products of nitric oxide-nitration, nitros(yl)ation and nitrite/nitrate artefacts during freezing. 1556 66

Enterobacter cloacae SLD1a-1 is capable of reducing selenium oxyanions to elemental selenium under both aerobic and anaerobic conditions. In this study the enzyme that catalyses the initial reduction of selenate (SeO4(2-)) to selenite (SeO3(2-)) has been localised to isolated cytoplasmic membrane fractions. Experiments with intact cells have shown that the putative selenate reductase can accept electrons more readily from membrane-impermeable methyl viologen than membrane-permeable benzyl viologen, suggesting that the location of the catalytic site is towards the periplasmic side of the cytoplasmic membrane. Enzyme activity was enhanced by growing cells in the presence of 1 mM sodium molybdate and significantly reduced in cells grown in the presence of 1 mM sodium tungstate. Non-denaturing polyacrylamide gel electrophoresis (PAGE) gels stained for selenate and nitrate reductase activity have revealed that two distinct membrane-bound enzymes catalyse the reduction of selenate and nitrate. The role of this membrane-bound molybdenum-dependent reductase in relation to selenate detoxification and energy conservation is discussed.
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PMID:Selenate reduction by Enterobacter cloacae SLD1a-1 is catalysed by a molybdenum-dependent membrane-bound enzyme that is distinct from the membrane-bound nitrate reductase. 1463 34

Dietary and endogenous nitrates are excreted in urine, and during infection with nitrate-reducing bacteria they are reduced to nitrite. At a low pH nitrite is converted to a variety of nitrogen oxides that are toxic to bacteria. We hypothesized that acidification of nitrite-rich infected urine would result in the killing of the nitrate-reducing bacteria. An Escherichia coli control strain and a mutant lacking nitrate reductase activity were preincubated in urine supplemented with sodium nitrate (0 to 10 mM) at pH 7.0. Then, the nitrite-containing bacterial culture was transferred (and diluted 1/10) to slightly acidic urine (pH 5 and 5.5) containing ascorbic acid (10 mM) and growth was monitored. The control strain produced nitrite in amounts related to the amount of nitrate added. This strain was killed when the culture was transferred to acidic urine. In contrast, the mutant that did not produce nitrite retained full viability. When control bacteria were grown in acidic urine with nitrate and ascorbic acid present from the start of the experiment, no inhibition of growth was noted. The MICs and minimal bactericidal concentrations of sodium nitrite-ascorbic acid in acidic urine were comparable to those of conventional antibiotics. Preincubation of nitrate-reducing E. coli in nitrate-rich urine leads to the accumulation of nitrite. Subsequent acidification of the urine results in generation of nitrogen oxides that are bactericidal. Killing, however, requires a sequential procedure in which the bacteria are first allowed to grow in a nitrate-rich neutral environment, later followed by acidification. We speculate that ingestion of nitrate followed some hours later by acidification of urine could be a new therapeutic strategy for the treatment of urinary tract infections.
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PMID:In vitro evaluation of a new treatment for urinary tract infections caused by nitrate-reducing bacteria. 1463 71

Previous reports have shown that some bacteria, including Salmonella, use a dissimilatory nitrate reductase enzyme pathway (NREP) in anaerobic environments. This enzyme reduces nitrate to nitrite and has been shown to cometabolize chlorate to cytotoxic chlorite. The present investigations were performed to evaluate the susceptibility of a competitive exclusion culture (CE) to the experimental chlorate product (ECP). A commercially available CE product was evaluated for its nitrate reductase activity and therefore its chlorate sensitivity. Individual isolates (in triplicate) were cultured in 10 mL of Viande Levure broth containing 5 mM sodium nitrate or 10 mM sodium chlorate. Bacterial growth (optical density at 625 nm) was measured and 1-mL aliquots were removed concurrently for colorimetric determination of nitrate content at 0, 3, 6, and 24 h. Of the 15 different facultative strains, 11 had slight NREP utilization, 3 had moderate NREP utilization, and the remainder were NREP negative (with slight and moderate NREP utilization: >0.1 to <1.0 mM and >1.0 mM nitrate used within 6 h, respectively). Of the obligate anaerobes evaluated, 3 had slight NREP utilization and the remainder were NREP negative. In vivo studies utilizing both products (CE and ECP) in a horizontal transmission challenge model (seeders + contacts) showed significant reductions in Salmonella from 5.37 to 1.76 log10 cfu/g and 3.94 to 0.07 log10 cfu/g, respectively. The combined effect of the CE culture and an ECP are effective in killing these food-borne pathogens.
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PMID:Utilization of the nitrate reductase enzymatic pathway to reduce enteric pathogens in chickens. 1555 62

This study deals with the effects of the agents that dissipate the individual components of the proton motive force (short-chain fatty acids, nigericin, and valinomycin) upon the methyl viologen-coupled nitrate reductase activity in intact cells. Substitution of butyrate or acetate for chloride in Tris-buffered assay media resulted in a marked inhibition at pH 7. In a Tris--chloride buffer of neutral pH, the reaction was almost fully inhibitable by nigericin. Alkalinisation increased the IC(50) value for nigericin and decreased the maximal inhibition attained. Both types of inhibitions could be reversed by the permeabilisation of cells or by the addition of nitrite, and that caused by nigericin disappeared at high extracellular concentrations of potassium. These data indicate that nitrate transport step relies heavily on the pH gradient at neutral pH. Since the affinity of cells for nitrate was strongly diminished by imposing an inside-positive potassium (or lithium) diffusion potential at alkaline external pH, a potential dependent step may be of significance in the transporter cycle under these conditions. Experiments with sodium-depleted media provided no hints for Na(+) as a possible H(+) substitute.
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PMID:Energy coupling to nitrate uptake into the denitrifying cells of Paracoccus denitrificans. 1611 75

The results showed that when Thellungiella halophila was treated with NaCl, the fresh and dry weight, the water content, the succulency of whole plant and the root/shoot ratio were decreased (Figs. 2-4, 7); the organic matter content in roots was increased and the inorganic matter content in roots was decreased, while those in shoots changed in the opposite direction (Fig. 6); osmotic adjustment ability, the Na+ content, the root activity were increased (Figs. 5, 7, 8); the nitrate reductase activity increased significantly; the O(-)(2*) content decreased at about NaCl 50 mmol/L but increased at about NaCl 100-400 mmol/L (Fig. 10). The micrographs of T. halophila leaf surface by scanning electron microscope (SEM) indicate that there is no salt gland or bladder on the surface of T. halophila (Fig. 1), so it is not a salt-secreting halophyte. The determination of growth parameters, the Na(+) content and Na(+) X-ray (Table 1) microanalysis of T. halophila indicate that T. halophila is not a salt-exclusing halophyte but it probability is a salt-dilution halophyte.
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PMID:[Effects of salt stress on the growth and the nitrate reductase activity in Thellungiella halophila]. 1622 88

Xanthomonas maltophilia ATCC 17666 is an obligate aerobe that accumulates nitrite when grown on nitrate. Spectra of membranes from nitrate-grown cells exhibited b-type cytochrome peaks and A(615-630) indicative of d-type cytochrome but no absorption peaks corresponding to c-type cytochromes. The nitrate reductase (NR) activity was located in the membrane fraction. Triton X-100-extracted reduced methyl viologen-NRs were purified on DE-52, hydroxylapatite, and Sephacryl S-300 columns to specific activities of 52 to 67 mumol of nitrite formed per min per mg of protein. The cytochrome-containing NR(I) separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis into a 135-kDa alpha-subunit, a 64-kDa beta-subunit, and a 23-kDa gamma-subunit with relative band intensities indicative of a 1:1:1 alpha/beta/gamma subunit ratio and a M(r) of 222,000. The electronic spectrum of dithionite-reduced purified NR displayed peaks at 425, 528, and 558 nm, indicative of the presence of a cytochrome b, an interpretation consistent with the pyridine hemochrome spectrum formed. The cytochrome b of the NR was reduced under anaerobic conditions by menadiol and oxidized by nitrate with the production of nitrite. This NR contained 0.96 Mo, 12.5 nonheme iron, and 1 heme per 222 kDa: molybdopterin was detected with the Neurospora crassa nit-1 assay. A smaller reduced methyl viologen-NR (169 kDa), present in various concentrations in the Triton X-100 preparations, lacked a cytochrome spectrum and did not oxidize menadiol. The characteristics of the NRs and the absence of c-type cytochromes provide insights into why X. maltophilia accumulates nitrite.
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PMID:Purification of Two Nitrate Reductases from Xanthomonas maltophilia Grown in Aerobic Cultures. 1634 5

Anabaena cylindrica grown with nitrate required higher levels of sodium (0.4 meq/l NaCl) to prevent chlorosis than when grown without combined nitrogen (0.004 meq/l NaCl). Nitrite accumulated in sodium-deficient cultures containing nitrate. Amounts of nitrite similar to those found in deficient cultures when added to normal cultures resulted in a chlorosis of the cells. Thus loss of chlorophyll was caused by nitrite toxicity.A deficiency of sodium resulted in an increased incorporation of (15)NO(3), (15)NO(2), (15)NH(3) or (14)C glutamate into protein compared with normal cells. The enzyme nitrate reductase was markedly increased in cells grown without sodium.Evidence from chloramphenicol treatment of the cells suggests that sodium may exert its control of nitrate reductase through a protein factor(s).By contrast, N(2) fixation was reduced in sodium deficient cells. Since the incorporation of ammonia or glutamate into protein was increased under these conditions, it is likely that the element is required for the conversion of N(2) gas into ammonia. Various nitrogenous compounds including ammonium chloride, amides and amino acids at low concentrations (0.1 mm) greatly reduced the nitrite accumulation in sodium-deficient cultures.
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PMID:Some Effects of Sodium on Nitrate Assimilation and N(2) Fixation in Anabaena cylindrica. 1665 97

Five-or six-day old seedlings of corn (Zea mays L.) were exposed to 0.25 mm Ca(NO(3))(2), 1.0 mm sodium 2-[N-morpholino]-ethanesulfonate, 5 mug Mo per liter and 50 mug of chloramphenicol per ml at pH 6. Nitrate uptake was determined from depletion of the ambient solution. The pattern of nitrate uptake was characterized, after the first 20 minutes, by a low rate which increased steadily to a maximal rate by 3 to 4 hours. Transfer of nitrate to the xylem did not totally account for the increase. Development of the maximal accelerated rate did not occur at 3 C with excised roots nor with seedlings whose endosperm had been removed. Use of CaCl(2) rather than Ca(NO(3))(2) resulted in a linear rate of chloride uptake during the first 4 hours, and chloride uptake was not as restricted by endosperm removal as was nitrate uptake.Nitrite pretreatments or the addition of cycloheximide (2 mug ml(-1)), puromycin (400 mug ml(-1)) and 6-methylpurine (0.5 mm) restricted maximal development of the accelerated nitrate uptake rate. Actinomycin D (20 mug ml(-1)) inhibited the rate only after about three hours exposure. The RNA and protein synthesis inhibitors also restricted nitrate reductase induction in the apical segments of the root tissue. The data suggest that development of the maximal accelerated rate of nitrate uptake depended upon continuous protein synthesis, and the hypothesis that synthesis of a specific nitrate transport protein must occur is advanced. But the alternative hypothesis, i.e., that induction of nitrate reductase (and/or a consequence of the act of nitrate reduction) provided the required stimulus, remains tenable.
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PMID:Nitrate Uptake by Dark-grown Corn Seedlings: Some Characteristics of Apparent Induction. 1665 72


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