Nitrite

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

Mechanisms and microbial structure of partial denitrification with high nitrite accumulation.

Abstract: Nitrite (NO2 (-)-N) accumulation in denitrification can provide the substrate for anammox, an efficient and cost-saving process for nitrogen removal from wastewater. This batch-mode study aimed at achieving high NO2 (-)-N accumulation over long-term operation with the acetate as sole organic carbon source and elucidating the mechanisms of NO2 (-)-N accumulation. The results showed that the specific nitrate (NO3 (-)-N) reduction rate (59.61 mg N VSS(-1) h(-1) at NO3 (-)-N of 20 mg/L) was much higher than specific NO2 (-)-N reduction rate (7.30 mg N VSS(-1) h(-1) at NO3 (-)-N of 20 mg/L), and the NO2 (-)-N accumulation proceeded well at the NO3 (-)-N to NO2 (-)-N transformation ratio (NTR) as high as 90 %. NO2 (-)-N accumulation was barely affected by the ratio of chemical oxygen demand (COD) to NO3 (-)-N concentration (C/N). With the addition of NO3 (-)-N, NO2 (-)-N accumulation occurred and the specific NO2 (-)-N reduction rate declined to a much lower level compared with the value in the absence of NO3 (-)-N. This indicated that the denitrifying bacteria in the system preferred to use NO3 (-)-N as electron acceptor rather than use NO2 (-)-N. In addition, the Illumina high-throughput sequencing analysis revealed that the genus of Thauera bacteria was dominant in the denitrifying community with high NO2 (-)-N accumulation and account for 67.25 % of total microorganism. This bacterium might be functional for high NO2 (-)-N accumulation in the presence of NO3 (-)-N.

Hydrogen Peroxide-Supported Oxidation of NG-Hydroxy-L-Arginine by Nitric Oxide Synthase

Abstract: The ability of murine macrophage nitric oxide synthase (NOS) to utilize peroxides in place of O2 and NADPH was investigated using hydrogen peroxide (H2O2), tert-butylhydroperoxide, and cumene hydroperoxide with both L-arginine and NG-hydroxy-L-arginine (L-NHA) as substrates. Of the three peroxides examined, only H2O2 was able to support product formation using L-NHA as a substrate. No product formation was observed from L-arginine with any peroxide tested. Therefore, the L-NHA/H2O2 reaction was examined in greater detail. The products of the reaction were citrulline and nitrite/nitrate (NO2-/NO3-) with a stoichiometry of approximately 0.75:1 (citrulline to NO2-/NO3-). Product formation was greater in the presence of oxygen. Both the Km and Vmax of the reaction, determined under aerobic conditions, were affected by (6R)-tetrahydro-L-biopterin (H4B). Chemiluminescence experiments failed to detect nitric oxide (.NO) as a reaction product. However, spectral spectral experiments with L-NHA and H2O2 under anaerobic conditions demonstrated the appearance of a ferrous heme-.NO complex with a Soret peak at 440 nm and a broad single alpha/beta peak at 578 nm, which is believed to arise from single electron transfer of a ferric-NO- (nitroxyl) complex. Preliminary experiments detected nitrous oxide (N2O) formation by gas chromatography under anaerobic conditions. Stable isotope labeling experiments with [18O]H2O2 conclusively established incorporation of label exclusively into the ureido position of citrulline. Based on these results, a mechanism of oxidation of L-NHA by H2O2 is proposed.

Degradation of 2,4-dinitrotoluene by the lignin-degrading fungus Phanerochaete chrysosporium

Abstract: Under ligninolytic conditions, the white rot basidiomycete Phanerochaete chrysosporium mineralizes 2,4-dinitrotoluene (I) The pathway for the degradation of I was elucidated by the characterization of fungal metabolites and oxidation products generated by lignin peroxidase (LiP), manganese peroxidase (MnP), and crude intracellular cell extracts The multistep pathway involves the initial reduction of I to yield 2-amino-4-nitrotoluene (II) II is oxidized by MnP to yield 4-nitro-1,2-benzoquinone (XII) and methanol XII is then reduced to 4-nitro-1,2-hydroquinone (V), and the latter is methylated to 1,2-dimethoxy-4-nitrobenzene (X) 4-Nitro-1,2-hydroquinone (V) is also oxidized by MnP to yield nitrite and 2-hydroxybenzoquinone, which is reduced to form 1,2,4-trihydroxybenzene (VII) 1,2-Dimethoxy-4-nitrobenzene (X) is oxidized by LiP to yield nitrite, methanol, and 2-methoxy-1,4-benzoquinone (VI), which is reduced to form 2-methoxy-1,4-hydroquinone (IX) The latter is oxidized by LiP and MnP to 4-hydroxy-1,2-benzoquinone, which is reduced to 1,2,4-trihydroxybenzene (VII) The key intermediate 1,2,4-trihydroxybenzene is ring cleaved by intracellular cell extracts to produce, after reduction, beta-ketoadipic acid In this pathway, initial reduction of a nitroaromatic group generates the peroxidase substrate II Oxidation of II releases methanol and generates 4-nitro-1,2-benzoquinone (XII), which is recycled by reduction and methylation reactions to regenerate intermediates which are in turn substrates for peroxidase-catalyzed oxidation leading to removal of the second nitro group Thus, this unique pathway apparently results in the removal of both aromatic nitro groups before ring cleavage takes place

The toxicology of nitrate, nitrite and n-nitroso compounds†

Abstract: Nitrate is essentially non-toxic to mammals but it can be reduced to nitrite either in improperly stored food, in the rumen of cattle, in the gastrointestinal tract of the human infant, and by the microflora of the human mouth The nitrite from these and other sources, including that purposely added to food, presents a toxic hazard both because of the direct toxicity of nitrite, and by the formation of carcinogenic N-nitroso compound by reaction with amino compounds Administration of toxic amounts of nitrite induces methaemoglobinaemia The nature of this disease, its importance in human medicine and the reason for the particular sensitivity of the infant, are briefly discussed The carcinogenic properties of N-nitroso compounds are described These compounds have been found in the environment and may be formed in the stomach from amines and nitrite Our knowledge of the amount of N-nitroso compounds to which man is exposed, is continually increasing but with the lack of epidemiologic evidence, the assessment of the significance to man of these traces of N-nitroso compounds depends upon the interpretation of animal experiments and their extrapolation to man This extrapolation would be more certain if there were a more clear understanding of the factors determining tissue selectivity by carcinogens and tissue sensitivity, and of the mechanism of cumulation of carcinogenic doses and of synergism between carcinogens Recent experiments suggest that there may soon be a significant breakthrough in the understanding of this These experiments are briefly discussed

Nitrite: A Physiological Store of Nitric Oxide and Modulator of Mitochondrial Function.

Abstract: Nitrite, long considered a biologically inert metabolite of nitric oxide (NO) oxidation, is now accepted as a physiological storage pool of NO that can be reduced to bioactive NO in hypoxic conditions to mediate a spectrum of physiological responses in blood and tissue. This graphical review will provide a broad overview of the role of nitrite in physiology, focusing on its formation and reduction to NO as well as its regulation of the mitochondrion—an emerging subcellular target for its biological actions in tissues.