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Nitrite
About: Nitrite is a research topic. Over the lifetime, 15425 publications have been published within this topic receiving 484581 citations.
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TL;DR: As oxidation and reduction may occur the concentrations of nitrite plus nitrate in a product has to be controlled and measured especially if the residual amounts are regulated.
744 citations
TL;DR: It is concluded that in non-elicited leaves NO is produced in variable quantities by NR depending on the total NR activity, the NR activation state and the cytosolic nitrite and nitrate concentration.
Abstract: NO (nitric oxide) production from sunflower plants (Helianthus annuus L.), detached spinach leaves (Spinacia oleracea L.), desalted spinach leaf extracts or commercial maize (Zea mays L.) leaf nitrate reductase (NR, EC 1.6.6.1) was continuously followed as NO emission into the gas phase by chemiluminescence detection, and its response to post-translational NR modulation was examined in vitro and in vivo. NR (purified or in crude extracts) in vitro produced NO at saturating NADH and nitrite concentrations at about 1% of its nitrate reduction capacity. The K(m) for nitrite was relatively high (100 microM) compared to nitrite concentrations in illuminated leaves (10 microM). NO production was competitively inhibited by physiological nitrate concentrations (K(i)=50 microM). Importantly, inactivation of NR in crude extracts by protein phosphorylation with MgATP in the presence of a protein phosphatase inhibitor also inhibited NO production. Nitrate-fertilized plants or leaves emitted NO into purified air. The NO emission was lower in the dark than in the light, but was generally only a small fraction of the total NR activity in the tissue (about 0.01-0.1%). In order to check for a modulation of NO production in vivo, NR was artificially activated by treatments such as anoxia, feeding uncouplers or AICAR (a cell permeant 5'-AMP analogue). Under all these conditions, leaves were accumulating nitrite to concentrations exceeding those in normal illuminated leaves up to 100-fold, and NO production was drastically increased especially in the dark. NO production by leaf extracts or intact leaves was unaffected by nitric oxide synthase inhibitors. It is concluded that in non-elicited leaves NO is produced in variable quantities by NR depending on the total NR activity, the NR activation state and the cytosolic nitrite and nitrate concentration.
738 citations
01 Jan 1995
TL;DR: Strains of some species can use porphorinoids from the environment and exhibit activities of catalase, nitrite reduction or even cytochromes, and Pseudo-catalase is formed in strains of Lb.
Abstract: Lactobacilli are Gram-positive, non-spore-forming, rods or coccobacilli with a G+C content of DNA usually below 50 mol%. They are strictly fermentative, aero-tolerant or anaerobic, aciduric or acidophilic and have complex nutritional requirements (e.g. for carbohydrates, amino acids, peptides, fatty acid esters, salts, nucleic acid derivatives, and vitamins). They do not synthesize porphyrinoids and thus, are devoid of heme-dependent activities. Strains of some species can use porphorinoids from the environment and exhibit activities of catalase, nitrite reduction or even cytochromes (Meisel, 1991). Pseudo-catalase is formed in strains of Lb. mali. With glucose as a carbon source lactobacilli may be either homofermentative, producing more than 85% lactic acid, or hetero-fermentative, producing lactic acid, CO2, ethanol (and/or acetic acid) in equimolar amounts. In the presence of oxygen or other oxidants increased amounts of acetate may be produced at the expense of lactate or ethanol, whereby one additional mole of ATP is gained via the acetate kinase reaction. Thus, variations in the metabolic end products may occur. Various compounds (e.g. citrate, malate, tartrate, quinolate, nitrate, nitrite, etc.) may be metabolized, and used as energy source (e.g. via building up a proton motive force) or electron acceptors.
728 citations
Journal Article•
TL;DR: Results indicate that T cell lymphokines and IFN-gamma are powerful modulators of macrophage nitrite/nitrate synthesis during BCG infection and in vitro, and nitrite / nitrate synthesis appears to be common property of both primed and fully activated macrophages.
Abstract: Macrophage synthesis of nitrite and nitrate after activation by BCG infection or by treatment in vitro with both T cell-derived (lymphokines (LK) or recombinant murine interferon-gamma (IFN-gamma] and bacterial (lipopolysaccharide (LPS) and heat-killed bacillus Calmette-Guerin (hk BCG] agents was studied by using macrophages from C3H/He and C3H/HeJ mice. Spleen and peritoneal macrophages isolated from BCG-infected donors that were producing nitrate continued to synthesize nitrite and nitrate in culture. LPS treatment in vitro (25 or 50 micrograms/ml) additionally increased this nitrite/nitrate synthesis. Thioglycolate-elicited macrophages from non-infected C3H/HeJ mice treated with LK also produced nitrite/nitrate, and concurrent LPS (0.1 to 50 micrograms/ml) treatment resulted in enhanced synthesis. Recombinant IFN-gamma also stimulated nitrite/nitrate synthesis by C3H/He and CeH/HeJ macrophages as did LPS (C3H/He only) and hk BCG. When given concurrently with either LPS or hk BCG, IFN-gamma enhanced C3H/He and C3H/HeJ macrophage nitrite/nitrate synthesis over that produced by macrophages treated with either LPS or hk BCG alone. Macrophages activated in vitro exhibited a 4 to 12 hr lag time before engaging in nitrite/nitrate synthesis, which then proceeded for 36 to 42 hr at linear rates. Daily medium renewal did not alter the synthesis kinetics but increased the total amount of nitrite/nitrate produced. Nitrate and nitrite were stable under the conditions of culture and when added did not influence additional macrophage synthesis. Taken together, these results indicate that T cell lymphokines and IFN-gamma are powerful modulators of macrophage nitrite/nitrate synthesis during BCG infection and in vitro, and nitrite/nitrate synthesis appears to be common property of both primed and fully activated macrophage populations.
704 citations
TL;DR: It is shown that N2H4 is produced from the anammox substrates ammonium and nitrite and that nitric oxide is the direct precursor of N2 H4, which presents a new biochemical reaction forging an N–N bond and fills a lacuna in understanding of the biochemical synthesis of the N2 in the atmosphere.
Abstract: Two distinct microbial processes, denitrification and anaerobic ammonium oxidation (anammox), are responsible for the release of fixed nitrogen as dinitrogen gas (N(2)) to the atmosphere. Denitrification has been studied for over 100 years and its intermediates and enzymes are well known. Even though anammox is a key biogeochemical process of equal importance, its molecular mechanism is unknown, but it was proposed to proceed through hydrazine (N(2)H(4)). Here we show that N(2)H(4) is produced from the anammox substrates ammonium and nitrite and that nitric oxide (NO) is the direct precursor of N(2)H(4). We resolved the genes and proteins central to anammox metabolism and purified the key enzymes that catalyse N(2)H(4) synthesis and its oxidation to N(2). These results present a new biochemical reaction forging an N-N bond and fill a lacuna in our understanding of the biochemical synthesis of the N(2) in the atmosphere. Furthermore, they reinforce the role of nitric oxide in the evolution of the nitrogen cycle.
694 citations