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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)

A method has been developed to study the synthesis and decay of the messenger RNA for nitrate reductase in Neurospora crassa. Glutamine prevents the synthesis of the mRNA which appears to have a half-life of approximately 8.5 min.
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PMID:Stability of messenger RNA for nitrate reductase in Neurospora crassa. 14 59

The effects of cytokinin and nitrate on the activity of nitrate reductase (NR) in isolated embryos of Agrostemma githago L. were studied. It was shown that the effects of cytokinin and NO-3 on the induction of NR is additive during 8, 12 and 18 hrs of embryos incubation in the solutions of the two inducers. Anticytokinin decreased the cytokinin induced NR by 35--39% and had no effect on the NR induction by nitrate. The substrate and hormonal induction of NR differed in the duration of the lag period. This difference dependent on the physiological state of the embryos at the beginning of incubation. The data obtained are indicative of the independence of cytokinin and NO-3 effects on the NR synthesis in isolated embryos of Agrostemma githago L. Abscisic acid supressed cytokinin- and nitrate-induced NR and had practically no effect on total incorporation of the label into the protein. It is assumed that the induced synthesis of the protein is more sensitive to the action of abscisic acid that the total protein synthesis.
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PMID:[Effect of nitrate and cytokinin on nitrate reductase activity in isolated corncockle embryos]. 15 76

The effect of different nitrogen compounds on the induction of reduced nicotinamide adenine dinucleotide phosphate-nitrate reductase was examined in Neurospora crassa. Whereas in the wild-type strain several amino acids and ammonia inhibit the formation of nitrate reductase, only glutamine, cysteine, and histidine are shown to inhibit the synthesis of nitrate reductase in a glutamine-requiring auxotroph. None of the amino acids inhibited nitrate reductase activity in vitro. The effects of cysteine and histidine are nonspecific, these amino acids being inhibitory of the growth of the organism. The effect of glutamine on the induction of nitrate reductase is not due to an inhibition of the uptake of the inducer nitrate. By the use of histidine-, pyrimidine-, and arginine-requiring auxotrophs, it was shown that glutamine appears to act per se and does not seem to be converted to another product in order to be effective in repression. The repression of nitrate reductase by ammonia appears, from the results described herein, to be indirect; ammonia has to be converted first to glutamine in order to be effective in repression.
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PMID:Nitrogen metabolite repression of nitrate reductase in Neurospora crassa. 15 87

The assimilatory nitrate reductase of the phototrophic bacterium Rhodopseudomonas capsulata strain AD2 was purified to homogeneity by a combination of ammonium sulfate fractionation, chromatography on DEAE-cellulose and isoelectric focusing (isoelectric point of 4.8). The purified enzyme was active only with reduced viologen dyes or reduced flavin as electron donors. Contrary to other bacterial assimilatory nitrate reductases, the enzyme was not inhibited by chlorate, but rather accepted this substance as an alternate substrate. The molecular weight of the enzyme was 185,000 dalton as determined by gelfiltration. Subunit analysis by sodium dodecyl sulfate (SDS) gel electrophoresis yielded a single protein band with a molecular weight of 85,000 dalton,, suggesting that the enzyme was composed of two identical subunits. The nitrate reductase contained 0.8 g-atoms molybdenum per 1.85 x 10(5) g protein and exhibited absorption maxima at 418, 523 and 552 nm in the reduced state (dithionite as reductant). The nitrate reductase of Rps. capsulata AD2 is the first prokaryotic enzyme of the assimilatory type that has been shown to contain heme.
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PMID:Assimilatory nitrate reductase of Rhodopseudomonas capsulata AD2: a molybdo-hemeprotein. 15 48

The plastoquinone antagonist 2,5-dibromothymoquinone was found to inhibit NO-3 reduction from NADH by the nitrate reductase complex from wheat. It accepts electrons from NADH through the NADH dehydrogenase activity of the nitrate reductase. However, it does not inhibit the reduction of 2,6-dichlorophenol-indophenol by the enzyme. This suggests that the two compounds may be accepting electrons at different places from the enzyme. Further it was observed that reduced DCIP could be oxidized by DBMIB in the absence of NADH indicating that the electron flow in the nitrate reductase complex may take place in a unidirectional way.
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PMID:Inhibition of the nitrate reductase complex by dibromothymoquinone. 15 94

Membrane vesicles of Veillonella alcalescens, grown in the presence of L-lactate and KNO-3, actively transport amino acids under anaerobic conditions in the presence of several electron donors and the electron acceptor nitrate. The highest initial rates of uptake are obtained with L-lactate, followed by reduced nicotinamide adenine dinucleotide, glycerol-1-phosphate, formate, and L-malate.. The membrane vesicles contain the dehydrogenases for these electron donors, and these enzymes are coupled with nitrate reductase. In membrane vesicles from cells, grown in the presence of nitrate, the dehydrogenases are not coupled with fumarate reducatase, and anaerobic transport of amino acids does not occur with fumarate as electron acceptor. Under aerobic conditions none of the physiological electron donors can energize transport. However, a high rate of uptake is observed with the electron donor system ascorbate-phenazine metho-sulfate. This electron donor system also effectively energizes transport under anaerobicconditions in the presence of the electron acceptor nitrate.
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PMID:Amino acid transport in membrane vesicles of obligately anaerobic Veillonella alcalescens. 16 33

NADH:nitrate reductase (EC 1.6.6.1) from Chlorella vulgaris has been purified 640-fold with an over-all yield of 26% by a combination of protamine sulfate fractionation, ammonium sulfate fractionation, gel chromatography, density gradient centrifugation, and DEAE-chromatography. The purified enzyme is stable for more than 2 months when stored at minus 20 degrees in phosphate buffer (pH 6.9) containing 40% (v/v) glycerol. After the initial steps of the purification, a constant ratio of NADH:nitrate reductase activity to NADH:cytochrome c reductase and reduced methyl viologen:nitrate reductase activities was observed. One band of protein was detected after polyacrylamide gel electrophoresis of the purified enzyme. This band also gave a positive stain for heme, NADH dehydrogenase, and reduced methyl viologen:nitrate reductase. One band, corresponding to a molecular weight of 100, 000, was detected after sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme contains FAD, heme, and molybdenum in a 1:1:0.8 ratio. One "cyanide binding site" per molybdenum was found. No non-heme-iron or labile sulfide was detected. From a dry weight determination of the purified enzyme, a minimal molecular weight of 152, 000 per molecule of heme or FAD was calculated. An s20, w of 9.7 S for nitrate reductase was found by the use of sucrose density gradient centrifugation and a Stokes radius of 89 A was estimated by gel filtration techniques. From these values, and the assumption that the partial specific volume is 0.725 cc/g, a molecular weight of 356, 000 was estimated for the native enzyme. These data suggest that the native enzyme contains a minimum of 2 molecules each of FAD, heme, and molybdenum and is composed of at least three subunits.
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PMID:Reduced nicotinamide adenine dinucleotide-nitrate reductase of Chlorella vulgaris. Purification, prosthetic groups, and molecular properties. 16 92

The synthesis of nitrate reductase and its incorporation into the cytoplasmic membrane of Escherichia coli strain A1004a (5-aminolaevulinic acid auxotroph) does not require synthesis of cytochrome b. The synthesis of the apoprotein(s) of the cytochrome b of the respiratory pathway from NADH to nitrate appears to be inhibited by the absence of haem. No member of the respiratory pathway from NADH to oxygen is capable of reducing nitrate reductase directly. The site on nitrate reductase that oxidizes FMNH2 is located on the cytoplasmic aspect of the cytoplasmic membrane.
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PMID:Synthesis and sideedness of membrane-bound respiratory nitrate reductase (EC1.7.99.4) in Escherichia coli lacking cytochromes. 16 87

1. In respiratory nitrate reductase I of Klebsiella aerogenes, 0.24 atom of molybdenum, eight iron-sulfur groups and four tightly bound, non-heme iron atoms per molecule of enzyme (Mr 260 000) are found. 2. EPR spectra at 83 degrees K of oxidized and reduced nitrate reductase I show complex lines at g = 2.02 and g = 1.98, which are more intense in the reduced than in the oxidized enzyme. The resonances, the shape and intensity of which are rather temperature insensitive, are attributed to two species of paramagnetic molybdenum. In dithionite-reduced enzyme all these lines are saturated at the same microwave power of 15 mW. This is not the case in oxidized enzyme, where the resonance at g = 2.02 is hard to saturate. Addition of nitrate to dithionite-reduced reductase I decreases the intensity of the EPR lines to about that of oxidized enzyme. The participation of molybdenum in the electron transfer process has been discussed. 3. At 18 degrees K the oxidized enzyme exhibits an axial-symmetrical signal with g parallel = 2.10 and g = 2.03, and a signal with unknown symmetry at g = 2.015. Upon reduction by dithionite, a ferredoxin type of signal is observed with g values at 2.05, 1.95 and 1.88, while the g = 2.015 signal disappears. Reoxidation by nitrate causes a concomitant disappearance of the ferredoxin type of signal and reappearance of the g = 2.015 signal; hence iron-sulfur centres participate in the transfer of electrons to nitrate. 4. Nitrate reductase II, containing only two (Mr 117 000 and 57 000) of the three subunits found in nitrate reductase I and lacking the tightly bound iron, does not exhibit the axial-symmetrical signal (g = 2.10 and 2.03). Thus, it suggested that this signal in nitrate reductase I stems from an iron centre in the low-molecular weight subunit (Mr 52 000). 5. Inhibition studies confirm the participation of metals in the transfer of electrons from reduced benzylviologen to nitrate and show that the binding sites for these substrates are different.
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PMID:Characterization of the respiratory nitrate reductase of Klebsiella aerogenes as a molybdenum-containing iron-sulfur enzyme. 17 Sep 83

Millimolar concentrations of tervalent manganese pyrophosphate can partially activate nitrate reductase which has been inactivated with NADH and HCN. The tervalent manganese complex is nevertheless not reduced by NADH in the presence of the enzyme, that is, it is not a substrate for the diaphorase moiety of the nitrate reductase. Ferric o-phenanthroline, on the other hand, is a good diaphorase substrate, but fails to activate the inactive enzyme.
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PMID:Nitrate reductase from Chlorella vulgaris. Reaction with manganese (III) pyrophosphate and with ferric o-phenanthroline. 18 Dec 48


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