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 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.
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PMID:Simple disk technique for detection of nitrate reduction by anaerobic bacteria. 32 77

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.
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PMID:Decrease in nitrate reductase activity in extracts of Trichoderma viride Incubated with chlorides. 55 76

Biochemical and microbiological studies were conducted to characterize the mechanism of bacterial formation of N-nitrosomorpholine from morpholine and nitrite at neutral pH. Nitrosating activity was markedly induced when bacteria were cultured anaerobically in minimal culture medium containing nitrate, while the presence of cysteine or tungsten in the medium inhibited induction. Of various metals, coenzymes and inhibitors tested for their effects on in vitro nitrosation of morpholine, potassium cyanide, sodium azide, NAD(P)H and nitrate strongly inhibited nitrosation. Several mutants of Escherichia coli A10 strain were prepared in order to examine whether nitrosation activity is linked to specific loci. Niridazole-resistant mutants, which lack nitroreductase, had as much nitrosating activity as the original E. coli A10, but chlorate-resistant mutants had completely lost this activity. A good correlation was observed between nitrate reductase activity and nitrosating activity in these mutants. These results indicate that bacterial nitrosation is an enzyme-mediated reaction closely associated with molybdenoenzymes such as the nitrate reductase/formate hydrogenlyase system.
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PMID:Biochemical studies on the catalysis of nitrosation by bacteria. 330 Oct 45

The molybdopterin cofactor from the formate dehydrogenase of Methanobacterium formicicum was studied. The cofactor was released by guanidine denaturation of homogeneous enzyme, which also released greater than 80% of the molybdenum present in the enzyme. The anoxically isolated cofactor was nonfluorescent, but after exposure to air it fluoresced with spectra similar to those of described molybdopterin cofactors. Aerobic release from acid-denatured formate dehydrogenase in the presence of I2 and potassium iodide produced a mixture of fluorescent products. Alkaline permanganate oxidation of the mixture yielded pterin-6-carboxylic acid as the only detectable fluorescent product. The results showed that the cofactor from formate dehydrogenase contained a pterin nucleus with a 6-alkyl side chain of unknown structure. Covalently bound phosphate was also present. The isolated cofactor was unable to complement the cofactor-deficient nitrate reductase of the Neurospora crassa nit-1 mutant.
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PMID:Molybdopterin cofactor from Methanobacterium formicicum formate dehydrogenase. 370 Mar 35

Twenty L-amino acids and several inorganic compounds were tested individually, as a sole nitrogen source, for ability to support the growth of Mycobacterium avium LM1 serovar 1. Of the amino acids tested, only L-glutamine provided nutritional support comparable to that of ammonium chloride at 1 mM. With either 1 mM potassium nitrate or nitrite substituted for ammonium chloride, similar numbers of CFU were produced. M. avium cells were grown in potassium nitrate or nitrite concentrations of 0.25, 0.5, 1.0, and 2.0 mM, and the medium was assayed for remaining nitrogen compound at several times during growth. Rates of utilization were of first-order kinetics, with nitrite removed more rapidly than nitrate. The rates were approximately 10 times as rapid at 0.25 mM than at 2 mM for either nitrogen source. Nine clinical isolates that included M. avium serovars 1, 4, and 8 and Mycobacterium scrofulaceum serovar 43 were tested for rate of utilization of ammonia, nitrate, or nitrite. Ammonia and nitrite were utilized with first-order kinetics by all strains. Nitrate utilization occurred but was not at the same level for all strains. Clinical tests indicate that M. avium is negative for nitrate reductase; this is because of the rapid reduction of nitrite produced from nitrate.
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PMID:Utilization of nitrate or nitrite as single nitrogen source by Mycobacterium avium. 381 23

1. In Aspergillus nidulans nitrate and nitrite induce nitrate reductase, nitrite reductase and hydroxylamine reductase, and ammonium represses the three enzymes. 2. Nitrate reductase can donate electrons to a wide variety of acceptors in addition to nitrate. These artificial acceptors include benzyl viologen, 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride, cytochrome c and potassium ferricyanide. Similarly nitrite reductase and hydroxylamine reductase (which are possibly a single enzyme in A. nidulans) can donate electrons to these same artificial acceptors in addition to the substrates nitrite and hydroxylamine. 3. Nitrate reductase can accept electrons from reduced benzyl viologen in place of the natural donor NADPH. The NADPH-nitrate-reductase activity is about twice that of reduced benzyl viologen-nitrate reductase under comparable conditions. 4. Mutants at six gene loci are known that cannot utilize nitrate and lack nitrate-reductase activity. Most mutants in these loci are constitutive for nitrite reductase, hydroxylamine reductase and all the nitrate-induced NADPH-diaphorase activities. It is argued that mutants that lack nitrate-reductase activity are constitutive for the enzymes of the nitrate-reduction pathway because the functional nitrate-reductase molecule is a component of the regulatory system of the pathway. 5. Mutants are known at two gene loci, niiA and niiB, that cannot utilize nitrite and lack nitrite-reductase and hydroxylamine-reductase activities. 6. Mutants at the niiA locus possess inducible nitrate reductase and lack nitrite-reductase and hydroxylamine-reductase activities. It is suggested that a single enzyme protein is responsible for the reduction of nitrite to ammonium in A. nidulans and that the niiA locus is the structural gene for this enzyme. 7. Mutants at the niiB locus lack nitrate-reductase, nitrite-reductase and hydroxylamine-reductase activities. It is argued that the niiB gene is a regulator gene whose product is necessary for the induction of the nitrate-utilization pathway. The niiB mutants either lack or produce an incorrect product and consequently cannot be induced. 8. Mutants at the niiribo locus cannot utilize nitrate or nitrite unless provided with a flavine supplement. When grown in the absence of a flavine supplement the activities of some of the nitrate-induced enzymes are subnormal. 9. The growth and enzyme characteristics of a total of 123 mutants involving nine different genes indicate that nitrate is reduced to ammonium. Only two possible structural genes for enzymes concerned with nitrate utilization are known. This suggests that only two enzymes, one for the reduction of nitrate to nitrite, the other for the reduction of nitrite to ammonium, are involved in this pathway.
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PMID:Genetic and biochemical studies of nitrate reduction in Aspergillus nidulans. 438 27

The assimilatory NADPH-nitrate oxidoreductase (EC 1.6.6.3) from Aspergillus nidulans was purified by means of affinity chromatography and analyzed by agarose isoelectric focusing and two-dimensional electrophoresis. NADPH-nitrate reductase activity was not activated by oxidation with potassium ferricyanide and was irreversibly inhibited by acrylamide. Electrophoresis of nitrate reductase in 7% polyacrylamide gels resulted in rapid loss of enzyme activity. Isoelectric focusing of purified enzyme in agarose gels resulted in the homogeneous band that exhibited NADPH-nitrate reductase, NADPH-cytochrome c reductase and reduced methyl viologen-nitrate reductase activities, which corresponded to an isoelectric point of 6.12 +/- 0.05 at 22 degrees C. Two-dimensional electrophoresis of focused nitrate reductase on SDS-polyacrylanide gel slabs yielded a single subunit of 54000 molecular weight. Acid treatment of the enzyme and subsequent isoelectric focusing resulted in a protein with a strongly acidic isoelectric point and reduced methyl viologen-nitrate reductase activity. It released another protein with a strongly basic isoelectric point which was inactive. It is postulated that the overall association of flavoprotein protomers with both heme and cytochrome b1 components confers a small net negative charge upon the native heteromultimer and accounts for its slightly acidic isoelectric point.
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PMID:Isoelectric focusing and two-dimensional analysis of purified nitrate reductase from Aspergillus nidulans. 675 5

Desulfovibrio desulfuricans (ATCC 27774), a strictly anaerobic sulfate-reducing bacteria, is able to perform anaerobic nitrate respiration in which nitrate is first reduced to nitrite by the action of nitrate reductase, and nitrite reductase then catalyzes the six-electron reduction of nitrite to ammonia. The nitrite reductase was found to be a membrane-bound enzyme and has been purified to electrophoretic homogeneity. The purified enzyme has a minimal Mr = 66,000 as judged by sodium dodecyl sulfate gel electrophoresis and contains 6 c-type heme groups/molecule. Pure nitrite reductase exhibits a typical c-type cytochrome absorption spectrum with reduced alpha-band at 552.5 nm. NADH and NADPH do not function as direct electron donors for the nitrite reductase. Desulfovibrio vulgaris hydrogenase, however, is able to transfer electrons from H2 to the nitrite reductase using FAD as the electron transfer mediator. The dithionite-reduced nitrite reductase was demonstrated to be auto-oxidizable even in the presence of potassium cyanide. On addition of nitrite, the dithionite-reduced enzyme is re-oxidized immediately. Hydroxylamine, however, can only partially re-oxidize the reduced enzyme. Ascorbate reduces the enzyme to a limited extent and the partially reduced enzyme is neither auto-oxidizable nor re-oxidizable by nitrite or hydroxylamine. Purified nitrite reductase has a pH optimum in the range of 8.0-9.5 and optimal activity at 57 degrees C. Purified nitrite reductase also has hydroxylamine reductase activity, and the Km for nitrite was determined to be 1.14 mM and that for hydroxylamine is 113.5 mM. The difference in Km values seems to exclude the possibility of hydroxylamine being a free intermediate in the reduction of nitrite.
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PMID:The isolation of a hexaheme cytochrome from Desulfovibrio desulfuricans and its identification as a new type of nitrite reductase. 730 57

Broad spectrum antibiotics are known to predispose towards oral candidiasis and gastroenteritis. Oral nitrite synthesis by commensal bacteria may be important in protecting the mouth and lower intestine from pathogenic organisms, including Candida albicans. The effect of 2 days administration of the broad spectrum antibiotic amoxycillin on salivary nitrite concentration, following a 200 mg potassium nitrate oral load, was studied in 10 healthy volunteers. The Cmax fell by 40% and the AUC was reduced by 1227 microM h (43%, 95% CI 273, 2181, P < 0.006) in the antibiotic treated group when compared with control. These findings suggest that destruction of nitrate reductase containing bacteria in the mouth by antibiotics may explain an increased incidence of infection with Candida and other pathogens.
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PMID:The effect of amoxycillin on salivary nitrite concentrations: an important mechanism of adverse reactions? 764 Jan 57

A rapid swab method using either a dry or moist swab soaked with potassium nitrate/benzalkonium chloride solution, and a method employing a single powdered reagent were assessed as possible alternatives to the conventional test for the detection of bacterial nitrate reductase activity. Results obtained by the use of the powdered reagent agreed 100% with those obtained by the conventional method. The moist swab method had a sensitivity and predictive value of the negative test of 80% and 73%, respectively. The dry swab method was least sensitive (72%) and had the lowest predictive value of the negative test (66%). The use of the single powdered reagent, which has a long shelf life, is a reliable alternative to the use of conventional reagents A and B. Results obtained by the rapid swab methods were inferior to those obtained by the conventional method.
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PMID:Detection of bacterial nitrate reductase activity by the use of a powdered reagent and rapid swab methods as compared to the conventional test. 821 93


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