IUBMB Enzyme Nomenclature


Accepted name: nitric oxide reductase [NAD(P)+, nitrous oxide-forming]

Reaction: N2O + NAD(P)+ + H2O = 2 NO + NAD(P)H + H+

Other name(s): fungal nitric oxide reductase; cytochrome P450nor; NOR (ambiguous)

Systematic name: nitrous oxide:NAD(P) oxidoreductase

Comments: A heme-thiolate protein (P450). The enzyme from Fusarium oxysporum utilizes only NADH, but the isozyme from Trichosporon cutaneum utilizes both NADH and NADPH. The electron transfer from NAD(P)H to heme occurs directly, not requiring flavin or other redox cofactors.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. Shoun, H. and Tanimoto, T. Denitrification by the fungus Fusarium oxysporum and involvement of cytochrome P-450 in the respiratory nitrite reduction. J. Biol. Chem. 266 (1991) 11078-11082. [PMID: 2040619]

2. Shiro, Y., Fujii, M., Iizuka, T., Adachi, S., Tsukamoto, K., Nakahara, K. and Shoun, H. Spectroscopic and kinetic studies on reaction of cytochrome P450nor with nitric oxide. Implication for its nitric oxide reduction mechanism. J. Biol. Chem. 270 (1995) 1617-1623. [PMID: 7829493]

3. Zhang, L., Kudo, T., Takaya, N. and Shoun, H. The B' helix determines cytochrome P450nor specificity for the electron donors NADH and NADPH. J. Biol. Chem. 277 (2002) 33842-33847. [PMID: 12105197]

4. Oshima, R., Fushinobu, S., Su, F., Zhang, L., Takaya, N. and Shoun, H. Structural evidence for direct hydride transfer from NADH to cytochrome P450nor. J. Mol. Biol. 342 (2004) 207-217. [PMID: 15313618]

[EC created 2011]

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