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

---

Query: EC:1.7.1.2 (nitrate reductase)
3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reduced nicotinamide adenine dinucleotide phosphate (NADPH):nitrate oxidoreductase (EC 1.6.6.2) from Aspergillus nidulans wild-type bi-1 was purified by means of salt fractionation, gel filtration, affinity chromatography, and polyacrylamide gel electrophoresis. Enzyme which was adsorbed on Cibacron blue agarose could be eluted with 2 mM NADPH or 2 mM oxidized NADP (NADP(+)), the former being about three times more effective than the latter. About half the total NADPH:nitrate reductase activity adsorbed on agarose required elution with 1 M NaCl. This salt-elutable form remained active with NADPH and was not converted to the NADPH-elutable form after readsorption on Cibacron blue agarose. The NADPH-eluted enzyme exhibited a markedly different electrophoretic mobility than the enzyme eluted with NADP(+) or NaCl. After electrophoresis on polyacrylamide gels, the NADPH-eluted NADPH:nitrate reductase was separated into four proteins, two of which contained nonheme iron and exhibited reduced methyl viologen-nitrate reductase activity. None of these proteins, singly or in combination, reduced nitrate with NADPH as substrate. Difference spectra analyses and specific heme iron stains revealed the presence of cytochrome b(557) in the largest of the proteins. The molecular weights of the four proteins, which were determined from the relationship of their mobilities on varied concentrations of acrylamide gel, were 360,000, 300,000, 240,000, and 118,000. The subunit molecular weights of these, which are determined via sodium dodecyl sulfate slab gel electrophoresis, were 49,000, 50,000, and 75,000. The key role of NADPH in maintenance of the active form of the heteromultimer is further substantiated.
...
PMID:Further characterization of the reduced nicotinamide adenine dinucleotide phosphate: nitrate oxidoreductase in Aspergillus nidulans. 3 44

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.
...
PMID:Assimilatory nitrate reductase of Rhodopseudomonas capsulata AD2: a molybdo-hemeprotein. 15 48

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.
...
PMID:Reduced nicotinamide adenine dinucleotide-nitrate reductase of Chlorella vulgaris. Purification, prosthetic groups, and molecular properties. 16 92

The laboratory and clinical evaluation of a potassium nitrate-saturated disk for the rapid detection of nitrate reductase production in anaerobes was investigated. The optimal disk concentration and incubation time were determined by utilizing triplicate sets of quadrant plates prepared with supplemented brucella (Difco) blood agar and swabbed with a 24-h broth (BBL; 135 C thioglycolate) suspension of the test organism. Each set of plates received one control disk and three disks of varying concentrations of potassium nitrate (1 to 8 mg) with 0.1% sodium molybdate. All sets were incubated in GasPak jars for 24, 48, or 72 h, and subsequently sulfanilic acid and 1,6-Cleve's acid were added to each disk. A pink or red color change was indicative of nitrate reductase production. Eighty-eight stock isolates, 23 American Type Culture Collection strains, and 214 fresh clinical isolates were evaluated and compared with results obtained with tubes of preduced indole-nitrite medium (BBL) incubated for 7 to 10 days. The 6-mg disk incubated for 48 h yielded an overall agreement of 89% with the conventional tube technique, and fresh clinical isolates demonstrated better disk-tube agreement (93%) than previously frozen stock strains. The simplicity and ease of this disk test suggest its value as a preliminary screening procedure for nitrate reductase production. There were no false positives. Negative results by disk should be rechecked by tube.
...
PMID:Simple disk technique for detection of nitrate reduction by anaerobic bacteria. 32 77

The cytoplasmic nitrate reductase in heme mutant H-14 of Staphylococcus aureus was partially purified by steps which included ammonium sulfate fractionation and chromatography on Bio-Gel A 1.5m and ion-exchange columns. The active fractions from the ion-exchange columns showed two forms of the enzyme upon electrophoresis in nondenaturing gels of polyacrylamide; these corresponded to proteins of R(f) 0.16 and 0.28. Each form contained a predominant polypeptide of molecular weight 140,000, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The R(f) 0.16 form contained another major polypeptide of molecular weight 57,000, but the R(f) 0.28 form contained several other polypeptides. The sedimentation properties of the enzyme were examined after partial purification on Bio-Gel A 1.5m. In sucrose gradients containing Triton X-100 the enzyme sedimented as a homogeneous peak with an estimated molecular weight of 225,000; without detergent a heterogeneous profile was observed of molecular weight greater than 250,000. Treatment of the enzyme with trypsin increased the specific activity, and the enzyme sedimented as a homogeneous peak in sucrose gradients without Triton X-100, with an estimated molecular weight of 202,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that trypsin treatment converted the polypeptide of molecular weight 140,000 to a polypeptide of molecular weight 112,000. We conclude that the cytoplasmic nitrate reductase of S. aureus has a large subunit of molecular weight 140,000, which can be modified by trypsin to a polypeptide of molecular weight 112,000 without loss of catalytic activity.
...
PMID:Partial purification and some properties of the Staphylococcus aureus cytoplasmic nitrate reductase. 45 98

Fours strains of nitrate reducing bacteria isolated from soil were studied for their behavior towards chlorate. They are facultative anaerobes, except for Bacillus megatherium (which is a strict aerobe) and they possess a nitrate reductase A. The growth of three strains of bacteria (Klebsiella pneumoniae, B. licheniformis and Micromonospora globosa) was slowed by sodium chlorate at a concentration of 0.06 to 0.1% while the other strain (B. megatherium) tolerated the CIO3- well. The delay of bacterial growth due to chlorate lasts for a certain period, after which the bacteria multiply again. The lag phase is due to small quantities of chlorite produced from the chlorate; the growth phase which follows is provoked by the multiplication of chlorate resistant mutants, most often nitrate reductase-negative and sometimes positive. Some reverse mutants nitrate reductase positive of K. pneumoniae no longer had the same characteristics as the wild strain: some resisted to chlorate or were different as to gas formation. The reduction of nitrate to ammonia by these bacteria is diminished in the presence of chlorate: the reduction of nitrate to nitrite was inhibited or not inhibited according to the type of strain. The bacteria broke down the chlorate partially or completely, according to the strains and the sustrates.
...
PMID:[A study of the action of sodium chlorate on strains of nitrate reducing soil bacteria (author's transl)]. 48 91

Assimilatory nitrate reductase (EC 1.6.6.1 NADH:nitrate oxidoreductase) from Chlorella vulgaris purified by affinity chromatography was found to be homogeneous as judged by electrophoresis on sodium dodecyl sulfate-polyacrylamide gel and by analytical ultracentrifugal techniques. The molecular weight of the intact enzyme and that of the enzyme dissociated in 6 M GuHCl, determined by sedimentation equilibrium studies, were 280,000 +/- 10,000 and 90,000 +/- 5,000, respectively. Comparable values were obtained using the S20,w value and the D20,w values in Svedberg's equation. The D20,w values were determined by laser light-scattering measurements. Active enzyme centrifugation showed that the monomer is an active species. A quantitative re-evaluation of the prosthetic groups present (FAD, heme, and molybdenum) was also made and was consistent with the conclusion that the active monomer contains three subunits as previously deduced by Solomonson et al. ((1975) J. Biol. Chem. 250, 4120). Electron micrographs showed images which corresponded to three subunits, supporting the data obtained by hydrodynamic studies. The enzyme is not cigar-shaped, as previously surmised, but has a roughly globular structure.
...
PMID:Physical studies on assimilatory nitrate reductase from Chlorella vulgaris. 50 Jun 68

Reduced nicotinamide adenine dinucleotide phosphate-dependent nitrate reductase activity in crude extracts of Trichoderma virde was significantly inhibited by physiological concentrations of ammonium chloride, sodium chloride, and potassium chloride, but not by ammonium or sodium sulfate. The chloride inhibition of nitrate reductase activity increased in a linear manner with chloride concentration.
...
PMID:Decrease in nitrate reductase activity in extracts of Trichoderma viride Incubated with chlorides. 55 76

Nitrate reductase, released from the membrane fraction of Escherichia coli by a neutral heat treatment, was purified to homogeneity by gel filtration chromatography. The purified enzyme behaved as an associating-dissociating system, exhibiting concentration-dependent sedimentation constants which ranged from 24 S at high concentrations in the ultracentrifuge down to 10 S at low concentrations in sucrose gradients. The molecular weight determined at high concentrations by sedimentation equilibrium was 880,000 +/- 30,000. Large and small enzyme species were detected on polyacrylamide disc gels run with diluted samples of enzyme. The ratio of the two species was concentration-dependent and the dissociation was reversible. The purified enzyme appeared to be homogeneous and monodisperse in the ultracentrifuge, on sucrose gradients, during gel filtration on Bio-Gel and on polyacrylamide gels, but it had a heterogeneous subunit composition as determined by sodium dodecyl sulfate gel electrophoresis. Enzyme species with different subunit compositions were partially resolved by gel filtration. The fractions with the highest specific activity contained subunits of 150,000 and 55,000 daltons in a ratio of approximately 1:1. Other fractions contained reduced amounts of the 55,000-dalton subunit and correspondingly increased amounts of 51,000-, 45,000-, and 10,000-dalton subunits, suggesting that the heterogeneity was the result of proteolytic degradation of the 55,000-dalton subunit. The enzyme contained approximately 12 non-heme irons, 12 acid-labile sulfides, 24 cysteine residues, and 1 molybdenum per 200,000 daltons.
...
PMID:Association-dissociation behavior and subunit structure of heat-released nitrate reductase from Escherichia coli. 77 Apr 63

Denitrification in a thermophile isolated on nitrite containing-medium (5 g/l) was studied by means of Warburg respirometry and gas chromatography. This strain seems to denitrify nitrite more rapidly than nitrate. Extracts of cells grown anaerobically on nitrate have dissimilatory nitrate reductase (type A); extracts of cells grown aerobically without nitrate have raised levels of the two types of nitrate reductase A and B. The optimal temperature for enzyme A activity is 60 degrees C. Nitrite reductase activity was measured using yeast extract as electron donor. For nitric oxide reductase activity, yeast extract is as efficient an electron donor as sodium lactate. Nitrous oxide reductase activity was found only in the 4 000 g supernatant showing the particulate nature of the enzyme. A mixture of FAD, FMN and NADH served as electron donor. Using acetylene as an inhibitor of nitrous oxide reduction in both whole cells and extracts, we showed that this gas is an intermediate compound in the reduction of NO to N2.
...
PMID:[Denitrification in a sporulating thermophilic bacterium]. 91 Nov 9


1 2 3 4 5 6 7 8 9 10 Next >>

---