Nitrite

About: Nitrite is a research topic. Over the lifetime, 15425 publications have been published within this topic receiving 484581 citations.

Chemical removal of nitrate from water

Abstract: HIGH levels of nitrate in ground water can pose a serious health risk. Reduction of nitrate to nitrite in the gut may cause methemoglobinaemia1both in newborn infants and in adults deficient in glucose-phosphate dehydrogenase2. Under abnormal circumstances, reduction to nitrite can also occur in the stomach to form N-nitrosamines, a postulated cause of stomach cancer3. Nitrate outflow onto shallow continental shelves can promote nearshore algal blooms. Both natural and anthropogenic sources contribute to nitrate pollution. In the United States4 and Europe5, legislation now specifies a maximum permissible nitrate level in drinking water. Techniques such as selective ion exchange6, reverse osmosis, electrodialysis and distillation exist to transfer nitrate between two bodies of water, but only biological processes are presently available for nitrate destruction. Here I describe a chemical process in which aluminium powder reduces nitrate to ammonia, nitrogen and nitrite. In a pH range of 9 to 10.5, selective reduction of nitrate relative to sulphate is possible, and between pH 9.1 and 9.3, loss of the reductant through decomposition of water can be minimized to less than 2%. Subsequent control of pH and concentrations of dissolved aluminium, nitrite and ammonia should be possible at a realistic cost, making this process potentially useful for combating nitrate pollution.

The Conversion of Nitrite to Nitrogen Oxide(s) by the Constitutive NAD(P)H-Nitrate Reductase Enzyme from Soybean

Abstract: A two-step purification protocol was used in an attempt to separate the constitutive NAD(P)H-nitrate reductase [NAD(P)H-NR, pH 6.5; EC 1.6.6.2] activity from the nitric oxide and nitrogen dioxide (NO(x)) evolution activity extracted from soybean (Glycine max [L.] Merr.) leaflets. Both of these activities were eluted with NADPH from Blue Sepharose columns loaded with extracts from either wild-type or LNR-5 and LNR-6 (lack constitutive NADH-NR [pH 6.5]) mutant soybean plants regardless of nutrient growth conditions. Fast protein liquid chromatography-anion exchange (Mono Q column) chromatography following Blue Sepharose affinity chromatography was also unable to separate the two activities. These data provide strong evidence that the constitutive NAD(P)H-NR (pH 6.5) in soybean is the enzyme responsible for NO(x) formation. The Blue Sepharose-purified soybean enzyme has a pH optimum of 6.75, an apparent Km for nitrite of 0.49 millimolar, and an apparent Km for NADPH and NADH of 7.2 and 7.4 micromolar, respectively, for the NO(x) evolution activity. In addition to NAD(P)H, reduced flavin mononucleotide (FMNH2) and reduced methyl viologen (MV) can serve as electron donors for NO(x) evolution activity. The NADPH-, FMNH2-, and reduced MV-NO(x) evolution activities were all inhibited by cyanide. The NADPH activity was also inhibited by p-hydroxymer-curibenzoate, whereas, the FMNH2 and MV activities were relatively insensitive to inhibition. These data indicate that the terminal molybdenum-containing portion of the enzyme is involved in the reduction of nitrite to NO(x). NADPH eluted both NR and NO(x) evolution activities from Blue Sepharose columns loaded with extracts of either nitrate- or zero N-grown winged bean (Psophocarpus tetragonolobus [L.]), whereas NADH did not elute either type of activity. Winged bean appears to contain only one type of NR enzyme that is similar to the constitutive NAD(P)H-NR (pH 6.5) enzyme of soybean.

Loss of Ammonia Monooxygenase Activity in Nitrosomonas europaea upon Exposure to Nitrite

Abstract: Nitrosomonas europaea, an obligate ammonia-oxidizing bacterium, lost an increasing amount of ammonia oxidation activity upon exposure to increasing concentrations of nitrite, the primary product of ammonia-oxidizing metabolism. The loss of activity was specific to the ammonia monooxygenase (AMO) enzyme, as confirmed by a decreased rate of NH4+-dependent O2 consumption, some loss of active AMO molecules observed by polypeptide labeling with 14C2H2, the protection of activity by substrates of AMO, and the requirement for copper. The loss of AMO activity via nitrite occurred under both aerobic and anaerobic conditions, and more activity was lost under alkaline than under acidic conditions except in the presence of large concentrations (20 mM) of nitrite. These results indicate that nitrite toxicity in N. europaea is mediated by a unique mechanism that is specific for AMO.