Definitions

# nitrous oxide

nitrous oxide or nitrogen (I) oxide, chemical compound, N2O, a colorless gas with a sweetish taste and odor. Its density is 1.977 grams per liter at STP. It is soluble in water, alcohol, ether, and other solvents. Although it does not burn, it supports combustion since it decomposes into oxygen and nitrogen when heated. The gas is prepared commercially by the thermal decomposition of ammonium nitrate, NH4NO3, at about 240°C; to produce nitrous oxide and water; the reaction must be carefully controlled to prevent explosive decomposition of the nitrous oxide. The gas is purified, liquified by compressing and cooling it, and stored in metal cylinders. A major use of nitrous oxide is in anesthesia, e.g., in dentistry. It is commonly called laughing gas since it produces euphoria and mirth when inhaled in small amounts. It is also used in making certain canned pressurized foods, e.g., instant whipped cream. Nitrous oxide was discovered (1772) by Joseph Priestley, who called it "diminished nitrous air"; he prepared it from "nitrous air" (nitric oxide, NO) by treatment with iron powder or a mixture of iron and sulfur powders. Its properties were further studied (1799) by Sir Humphry Davy.
or laughing gas

Inorganic compound, one of the oxides of nitrogen. A colourless gas with a pleasantly sweetish odour and taste, it has an analgesic effect when inhaled; it is used as an anesthetic (often called just “gas”) in dentistry and surgery. This effect is preceded by mild hysteria, sometimes with laughter, hence the name laughing gas. It is also used as a propellant in food aerosols and as a leak detector.

In enzymology, a nitrous-oxide reductase is an enzyme that catalyzes the chemical reaction

nitrogen + H2O + acceptor $rightleftharpoons$ nitrous oxide + reduced acceptor

The 3 substrates of this enzyme are nitrogen, H2O, and acceptor, whereas its two products are nitrous 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 nitrogen:acceptor oxidoreductase (N2O-forming). Other names in common use include nitrous oxide reductase, N2O reductase, and nitrogen:(acceptor) oxidoreductase (N2O-forming). This enzyme participates in nitrogen metabolism. It employs one cofactor, copper.

## Structural studies

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes , , and .

## References

• Coyle CL, Zumft WG, Kroneck PM, Korner H, Jakob W "Nitrous oxide reductase from denitrifying Pseudomonas perfectomarina. Purification and properties of a novel multicopper enzyme". Eur. J. Biochem. 153 459–67.