Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.4 (nitrite reductase)
 1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitrite reductase was purified between 760- and 1300-fold from vegetable marrow (Cucurbita pepo L.) and residual hydroxylamine reductase activity was low or negligible by comparison. With ferredoxin as electron donor, nitrite loss and ammonia formation at pH7.5 were stoicheiometrically equivalent. Crude nitrite reductase preparations showed negligible activity with NADPH as electron donor maintained in the reduced state by glucose 6-phosphate, whereas by comparison, activity was high when either ferredoxin or benzyl viologen were also present and reduced by the NADPH-glucose 6-phosphate system, whereas FMNH(2) produced variable and relatively low activity under the same conditions. At pH values below 7, non-enzymic reactions occurred between reduced benzyl viologen and nitrite, and intermediate reduction products were inferred to be produced instead of ammonia. Activity with ferredoxin (0.1mm), reduced by chloroplast grana in the light, was 25 times that produced with ferredoxin (40mum) reduced with NADPH and glucose 6-phosphate. For an approximate molecular weight 61000-63000 derived by chromatography on Sephadex G-100 and G-200, and a specific activity of 46mumol of nitrite reduced/min per mg of protein with light and chloroplast grana, a minimum turnover number of 3x10(3)mol of nitrite reduced/min per mol of enzyme was found. Two hydroxylamine reductases were separated on Sephadex gels. One (HR1) was initially associated with nitrite reductase during gel filtration but disappeared during later fractionation. This HR1 fraction showed nearly comparable activity with reduced benzyl viologen, ferredoxin or FMNH(2). The other (HR2), of molecular weight approx. 35000, reacted with reduced benzyl viologen but showed negligible activity with ferredoxin or NADPH. Activity with FMNH(2) was associated with an irregular trailing boundary during gel filtration, with much diminished activity in the HR2 region. Activity with NADPH was about 30% of that with FMNH(2), reduced benzyl viologen or ferredoxin and was considered to reside in fraction HR1. Hydroxylamine yielded ammonia under all assay conditions. No activity with hyponitrite or sulphite was observed with reduced benzyl viologen as electron donor in either the nitrite reductase or the hydroxylamine reductase systems, but pyruvic oxime produced about 4% of the activity of hydroxylamine.
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PMID:Nitrite and hydroxylamine reduction in higher plants. Fractionation, electron donor and substrate specificity of leaf enzymes, principally from vegetable marrow (Cucurbita pepo L.). 439 27

The nitrate reductase in the mature root extract of 3-day maize (Zea mays) seedlings was relatively labile in vitro. Insoluble polyvinylpyrrolidone used in the extraction medium produced only a slight increase in the stability of the enzyme. Mixing the mature root extract with that of the root tip promoted the inactivation of nitrate reductase in the latter. The inactivating factor in the mature root was separated from nitrate reductase by (NH(4))(2)SO(4) precipitation. Nitrate reductase was found in the 40% (NH(4))(2)SO(4) precipitate, while the inactivating factor was largely precipitated by 40 to 55% (NH(4))(2)SO(4). The latter fraction of the mature root inactivated the nitrate reductase isolated from the root tip, mature root, and scutellum. The inactivating factor, which has a Q(10) 15 to 25 C of 2.2, was heat labile, and hence has been designated as a nitrate reductase inactivating enzyme. The reduced flavin mononucleotide nitrate reductase was also inactivated, while an NADH cytochrome c reductase in nitrate-grown seedlings was inactivated but at a slower rate. The inactivating enzyme had no influence on the activity of nitrite reductase, glutamate dehydrogenase, xanthine oxidase, and isocitrate lyase. The activity of the nitrate reductase inactivating enzyme was not influenced by nitrate and was also found in the mature root of minus nitrate-grown seedlings.
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PMID:A nitrate reductase inactivating enzyme from the maize root. 1665 31

The effect of tungsten on the development of endogenous and nitrate-induced NADH- and FMNH(2)-linked nitrate reductase activities in primary leaves of 10-day-old soybean (Glycine max [L.] Merr.) seedlings was studied. The seedlings were grown with or without exogenous nitrate. High levels of endogenous nitrate reductase activities developed in leaves of seedlings grown without nitrate. However, no endogenous nitrite reductase activity was detected in such seedlings. The FMNH(2)-linked nitrate reductase activity was about 40% of NADH-linked activity. Tungsten had little or no effect on the development of endogenous NADH- and FMNH(2)-linked nitrate reductase activities, respectively. By contrast, in nitrate-grown seedlings, tungsten only inhibited the nitrate-induced portion of NADH-linked nitrate reductase activity, whereas the FMNH(2)-linked activity was inhibited completely. Tungsten had no effect on the development of nitrate-induced nitrite reductase activity. The complete inhibition of FMNH(2)-linked nitrate reductase activity by tungsten in nitrate-grown plants was apparently an artifact caused by the reduction of nitrite by nitrite reductase in the assay system. The results suggest that in soybean leaves either the endogenous nitrate reductase does not require molybdenum or the molybdenum present in the seed is preferentially utilized by the enzyme complex as compared to nitrate-induced nitrate reductase.
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PMID:Differential effect of tungsten on the development of endogenous and nitrate-induced nitrate reductase activities in soybean leaves. 1666 75