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)

Membrane fractions with L-lactate dehydrogenase, sn-glycerol-3-phosphate (G3P) dehydrogenase, and nitrate reductase activities were prepared from Staphylococcus aureus wild-type and hem mutant strains. These preparations reduced ferric to ferrous iron with L-lactate or G3P as the source of reductant, using ferrozine to trap the ferrous iron. Reduction of ferric iron was insensitive to 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO) with either L-lactate or G3P as reductant, but oxalate and dicumarol inhibited reduction with L-lactate as substrate. The membranes had L-lactate- and G3P-nitrate reductase activities, which were inhibited by azide and by HQNO. Reduction of ferric iron under anaerobic conditions was inhibited by nitrate with preparations from the wild-type strain. This effect of nitrate was abolished by blocking electron transport to the nitrate reductase system with azide or HQNO. Nitrate did not inhibit reduction of ferric iron in heme-depleted membranes from the hem mutant unless hemin was added to restore L-lactate- and G3P-nitrate reductase activity. We conclude that reduced components of the electron transport chain that precede cytochrome b serve as the source of reductant for ferric iron and that these components are oxidized preferentially by a functional nitrate reductase system.
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PMID:Reduction of ferric iron by L-lactate and DL-glycerol-3-phosphate in membrane preparations from Staphylococcus aureus and interactions with the nitrate reductase system. 20 71

A ferredoxin was purified from Clostridium perfringens by DEAE-cellulose chromatography and Sephadex G-50 gel filtration. It had absorption maxima at 390 and 280 nm. The molecular weight was estimated to be 6,000 by Sephadex gel filtration and from the results of amino acid analysis. The isoelectric point was 3.0. It contained four atoms of iron, four atoms of labile sulfur, and six cysteine residues. This ferredoxin as well as ferredoxin from C. pasteurianum acted as an electron donor for nitrate reductase from C. perfringens. The ferredoxin could also act as an electron donor for the hydrogenase from C. pasteurianum in hydrogen evolution.
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PMID:Studies on nitrate reductase of Clostridium perfringens. II. Purification and some properties of ferredoxin. 21 25

1. The respiratory nitrate reductase of Klebsiella aerogenes was solubilized from the bacterial membranes by deoxycholate and purified further by means of gel chromatography in the presence of deoxycholate, and anion-exchange chromatography. 2. Dependent on the isolation procedure two different homogeneous forms of the enzyme, having different subunit compositions, can be obtained. These forms are designated nitrate reductase I and nitrate reductase II. Both enzyme preparations are isolated as tetramers having sedimentation constants (s20,w) of 22.1 S and 21.7 S for nitrate reductase I and II, respectively. The nitrate reductase I tetramer has a molecular weight of about 106. 3. In the presence of deoxycholate both enzyme preparations dissociate reversibly into their respective monomeric forms. The monomeric form of nitrate reductase I has a molecular weight of about 260 000 and a sedimentation constant of 9.8 S. For nitrate reductase II these values are 180 000 and 8.5 S, respectively. 4. Nitrate reductase I consists of three different subunits, having molecular weights of 117 000; 57 000 and 52 000, which are present in a 1:1:2 molar ratio, respectively. Nitrate reductase II contains only the subunits with a molecular weight of 117 000 and 57 000 in a equimolar ratio. 5. Treatment at pH 9.5 in the presence of deoxycholate and 0.05 M NaCl or ageing removes the 52 000 Mr subunit from nitrate reductase I. This smallest subunit, in contrast to the other subunits, is a basic protein. 6. The 52 000 Mr subunit has no catalytic function in the intramolecular electron transfer from reduced benzylviologen to nitrate. However, it appears to have a structural function since nitrate reductase II, which lacks this subunit, is much more labile than nitrate reductase I. Inactivation of nitrate reductase II can be prevented by the presence of deoxycholate. 7. The spectrum of the enzyme resembles that of iron-sulfur proteins. No cytochromes or contaminating enzyme activities are present in the purified enzyme. Only reduced benzylviologen was found to be capable of acting as an electron donor. 8. p-Chlormercuribenzoate enhances the enzymatic activity at concentrations of 0.1 mM and lower. At higher p-chlormercuribenzoate concentrations the enzymatic activity is inhibited non-competitively with either nitrate or benzylviologen as a substrate. The inhibition is not counteracted by cysteine.
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PMID:Purification, structure and properties of the respiratory nitrate reductase of Klebsiella aerogenes. 23 57

The potentials of the couples Mo(IV)--(Mo(V) and Mo(V)--Mo(VI) in nitrate reductase from Escherichia coli K12 were measured as + 180 mV and + 220 mV respectively at pH 7.14. The potentials associated with two other e.p.r. signals, believed to be due to iron--sulphur centres, were measured as + 50 mV and + 80 mV.
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PMID:Oxidation--reduction potentials of molybdenum and iron--sulphur centres in nitrate reductase from Escherichia coli. 37 49

The membrane-bound formate dehydrogenase of Escherichia coli grown anaerobically in the presence of nitrate was solubilized with deoxycholate and purified to near homogeneity. The purification procedure included ammonium sulfate fractionation and chromatography on Bio-Gel A-1.5m and DEAE Bio-Gel A in the presence of the nonionic detergent, Triton X-100. This detergent caused a significant decrease in the molecular weight of the soluble formate dehydrogenase complex and allowed the enzyme then to be resolved from other membrane components. Anaerobic conditions were required throughout due to the sensitivity of the enzyme to oxygen inactivation. Formate dehydrogenase was judged to be at least 93 to 99% pure by the following procedures: polyacrylamide gel electrophoresis in the presence of Triton X-100 and sodium dodecyl sulfate, gel filtration, and sedimentation velocity studies. The purified enzyme exists as a detergent-protein complex (0.20 +/- 0.03 g of Triton X-100/g of protein) which has an S20,w of 18.1 S and a Stokes radius of 76 A. This corresponds to a molecular weight of 590,000 +/- 59,000. The enzyme had an absorbance spectrum of a b-type cytochrome which could be completely reduced by formate. The heme content corresponds to an equivalent weight of 154,000 which suggests a tetrameric structure for the enzyme. Formate dehydrogenase was found to contain (in relative molar amounts): 1.0 heme, 0.95 molybdenum, 0.96 selenium, 14 non-heme iron, and 13 acid-labile sulfide. Neither FAD nor FMN could be detected. The enzyme contains three polypeptides, designated alpha, beta, and gamma, whose molecular weights were estimated by gel electrophoresis in the presence of sodium dodecyl sulfate to be 110,000, 32,000, and 20,000, respectively. After separation of the polypeptides by gel filtration in the presence of sodium dodecyl sulfate alpha, beta, and gamma were found in 1:1.2:0.55 molar ratios. A study of the enzyme obtained from cells grown with [75Se]selenite showed that only the alpha polypeptide contained significant amounts of selenium. The enzyme will catalyze the formate-dependent reduction of phenazine methosulfate, dichlorophenolindophenol, methylene blue, nitroblue tetrazolium, benzyl viologen, methyl viologen, ferricyanide, and coenzyme Q6. Cyanide, azide, p-hydroxymercuribenzoate, iodoacetamide, and oxygen inhibit the enzyme. The procedure which was designed for the purification of formate dehydrogenase also yields a highly purified preparation of nitrate reductase. This nitrate reductase has been shown to contain significant amounts of heme (Enoch, H. G., and Lester, R. L. (1974) Biochem. Biophys. Res Commun. 61,1234-1241). The enzyme contains three polypeptides with molecular weights of 155,000, 63,000, and 19,000. When measured in the presence of Trition X-100 the Stokes radius of nitrate reductase is 75 A and the S20,w is 16 S which corresponds to a molecular weight of 498,000.
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PMID:The purification and properties of formate dehydrogenase and nitrate reductase from Escherichia coli. 109 93

The roles of molybdenum and iron in the enzymes of the assimilatory nitrate-reducing system from Azotobacter chroococcum have been investigated. 1. By adding 99 Mo-molybdate to a cell culture of A. chrocococcum with nitrate as the nitrogen source, it has been possible to incroporate the radioactive metal into a purified preparation of the enzyme nitrate reductase. 2. When 185 W-tungstate was supplied to a culture medium lacking added molybdate, a 185 W-labelled nitrate reductase preparation with negligible activity could be obtained. This in vivo incorporation of tungsten was competitively hindered by molybdenum. 3. The cellular level of nitrite reductase activity gradually increased in response to the addition of increasing amounts of iron to the culture medium. Under the same conditions, of the level of nitrate reductase activity was not affected.
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PMID:Molybdenum and iron as functional consitituents of the enzymes of the nitrate-reducing system of Azotobacter chroococcum. 111 63

The redox properties of the iron-sulfur centers of the two nitrate reductases from Escherichia coli have been investigated by EPR spectroscopy. A detailed study of nitrate reductase A performed in the range +200 mV to -500 mV shows that the four iron-sulfur centers of the enzyme belong to two classes with markedly different redox potentials. The high-potential group comprises a [3Fe-4S] and a [4Fe-4S] cluster whose midpoint potentials are +60 mV and +80 mV, respectively. Although these centers are magnetically isolated, they are coupled by a significant anticooperative redox interaction of about 50 mV. The [4Fe-4S]1+ center occurs in two different conformations as shown by its composite EPR spectrum. The low-potential group contains two [4Fe-4S] clusters with more typical redox potentials (-200 mV and -400 mV). In the fully reduced state, the three [4Fe-4S]1+ centers are magnetically coupled, leading to a broad featureless spectrum. The redox behaviour of the high-pH EPR signal given by the molybdenum cofactor was also studied. The iron-sulfur centers of the second nitrate reductase of E. coli, nitrate reductase Z, exhibit essentially the same characteristics than those of nitrate reductase A, except that the midpoint potentials of the high-potential centers appear negatively shifted by about 100 mV. From the comparison between the redox centers of nitrate reductase and of dimethylsulfoxide reductase, a correspondence between the high-potential iron-sulfur clusters of the two enzymes can be proposed.
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PMID:EPR and redox characterization of iron-sulfur centers in nitrate reductases A and Z from Escherichia coli. Evidence for a high-potential and a low-potential class and their relevance in the electron-transfer mechanism. 132 Oct 49

Two membrane-bound nitrate reductases, NRA and NRZ, exist in Escherichia coli. Both isoenzymes are composed of three structural subunits, alpha, beta, and gamma encoded by narG/narZ, narH/narY and narI/narV, respectively. The genes are in transcription units which also contain a fourth gene encoding a polypeptide, delta, which is not part of the final enzyme. A strain which is devoid of, or does not express, the nar genes, was used to investigate the role of the delta and gamma polypeptides in the formation and/or processing of the nitrate reductase. When only the alpha and beta polypeptides are produced, an (alpha beta) complex exists which is inactive and soluble. When the alpha, beta and delta polypeptides are produced, the (alpha beta) complex is active with artificial donors such as benzyl viologen but is soluble. When the alpha, beta and gamma polypeptides are produced, the (alpha beta) complex is inactive but partially binds the membrane. It was concluded that the gamma polypeptide is involved in the binding of the (alpha beta) complex to the membrane while the delta polypeptide is indispensable for the (alpha beta) nitrate reductase activity. The activation by the delta polypeptide does not seem to involve the insertion of the redox centres of the enzyme since the purified inactive (alpha beta) complex was shown to contain the four iron-sulphur centres and the molybdenum cofactor, which are normally present in the native purified enzyme. The extreme sensitivity of this inactive complex to thermal denaturation or tryptic treatment favours the idea that the delta polypeptide promotes the correct assembly of the alpha and beta subunits. Although this corresponds to the definition of a chaperone protein this possibility has been rejected. In this study we have also demonstrated that the delta or gamma polypeptide encoded by one nar operon can be substituted successfully for by its respective counterpart from the other nar operon to give an active membrane bound heterologous nitrate reductase enzyme.
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PMID:Involvement of the narJ or narW gene product in the formation of active nitrate reductase in Escherichia coli. 154 6

The inhibitory effects of nitrate (NO3-) and nitrite (NO2-) on dissimilatory iron (FE3+) reduction were examined in a series of electron acceptor competition experiments using Shewanella putrefaciens 200 as a model iron-reducing microorganism. S. putrefaciens 200 was found to express low-rate nitrate reductase, nitrite reductase, and ferrireductase activity after growth under highly aerobic conditions and greatly elevated rates of each reductase activity after growth under microaerobic conditions. The effects of NO3- and NO2- on the Fe3+ reduction activity of both aerobically and microaerobically grown cells appeared to follow a consistent pattern; in the presence of Fe3+ and either NO3- or NO2-, dissimilatory Fe3+ and nitrogen oxide reduction occurred simultaneously. Nitrogen oxide reduction was not affected by the presence of Fe3+, suggesting that S. putrefaciens 200 expressed a set of at least three physiologically distinct terminal reductases that served as electron donors to NO3-, NO2-, and Fe3+. However, Fe3+ reduction was partially inhibited by the presence of either NO3- or NO2-. An in situ ferrozine assay was used to distinguish the biological and chemical components of the observed inhibitory effects. Rate data indicated that neither NO3- nor NO2- acted as a chemical oxidant of bacterially produced Fe2+. In addition, the decrease in Fe3+ reduction activity observed in the presence of both NO3- and NO2- was identical to the decrease observed in the presence of NO2- alone. These results suggest that bacterially produced NO2- is responsible for inhibiting electron transport to Fe3+.
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PMID:Effects of nitrate and nitrite on dissimilatory iron reduction by Shewanella putrefaciens 200. 154 35

Evidence is presented on the effects of low and high concentrations of iron on growth, nutrient uptake (NH+4 and NO3-), photosynthesis (CO2-fixation and O2-evolution) and nitrate reductase (NR) activity of A. doliolum and C. vulgaris under monochromatic irradiation. Control cultures (not treated with FeCl3) showed maximum growth under fluorescent followed by red, yellow, blue and green lights (fluorescent greater than yellow greater than red greater than blue greater than green). The inhibition was of synergistic type under yellow and red lights at all the iron concentrations tested. However, under blue and green lights the interaction was less than additive type. All the processes studied responded in a similar manner to a particular color of light. Under fluorescent light at low Fe concentrations, stimulation of NR, 14CO2-fixation and O2-evolution was noticed in both the test organisms. However, even the lowest concentration of iron tested was inhibitory to these processes under yellow and red lights. Under blue light at 20 micrograms.ml-1 Fe, NR activity was inhibited by 98%. This study clearly demonstrates that metal toxicity to phytoplankton will be greatly affected by spectral quality, hence it will have great significance in limnological research.
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PMID:Impact of spectral quality on toxicity of iron in Anabaena doliolum and Chlorella vulgaris. 158 69


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