nitric oxide

Colourless, toxic gas (NO), formed from nitrogen and oxygen by the action of electric sparks or high temperatures or, more conveniently, by the action of dilute nitric acid on copper or mercury. First prepared circa 1620 by Jan B. Helmont, it was first studied in 1772 by Joseph Priestley, who called it “nitrous air.” An industrial procedure for the manufacture of hydroxylamine is based on the reaction of nitric oxide with hydrogen in the presence of a catalyst. The formation of nitric oxide from nitric acid and mercury is applied in a volumetric method of analysis for nitric acid or its salts. The gas is synthesized via enzyme-catalyzed reactions in humans and other animals, where it serves as a signaling molecule. Among its numerous biological roles, it causes dilation of blood vessels and as such is an important regulator of blood pressure. Nitric oxide is one of the components of air pollution generated by internal-combustion engines.

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Inorganic compound, colourless, fuming, highly corrosive liquid, chemical formula HNO₃. A common laboratory reagent, it is important in the manufacture of fertilizers and explosives (including nitroglycerin), as well as in organic syntheses, metallurgy, ore flotation, and reprocessing of spent nuclear fuel. A strong acid, it is toxic and can cause severe burns. It attacks most metals and is used for etching steel and photoengraving.

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nitrous oxide + acceptor + H₂O $rightleftharpoons$ 2 nitric oxide + reduced acceptor

The 3 substrates of this enzyme are nitrous oxide, acceptor, and H₂O, whereas its two products are nitric oxide and reduced acceptor.

This enzyme belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with other acceptors. The systematic name of this enzyme class is nitrous-oxide:acceptor oxidoreductase (NO-forming). Other names in common use include nitrogen oxide reductase, and nitrous-oxide:(acceptor) oxidoreductase (NO-forming). This enzyme participates in nitrogen metabolism.

Structural studies

As of late 2007, 8 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , , and .

References

• Heiss B, Frunzke K, Zumft WG "Formation of the N-N bond from nitric oxide by a membrane-bound cytochrome bc complex of nitrate-respiring (denitrifying) Pseudomonas stutzeri". J. Bacteriol. 171 3288–97.

External links

The CAS registry number for this enzyme class is .

Gene Ontology (GO) codes