IUBMB Enzyme Nomenclature


Accepted name: nitric-oxide synthase (flavodoxin)

Reaction: 2 L-arginine + 3 reduced flavodoxin + 4 O2 = 2 L-citrulline + 2 nitric oxide + 3 oxidized flavodoxin + 4 H2O (overall reaction)
(1a) 2 L-arginine + 2 reduced flavodoxin + 2 O2 = 2 Nω-hydroxy-L-arginine + 2 oxidized flavodoxin + 2 H2O
(1b) 2 Nω-hydroxy-L-arginine + reduced flavodoxin + 2 O2 = 2 L-citrulline + 2 nitric oxide + oxidized flavodoxin + 2 H2O

Glossary: nitric oxide = NO = nitrogen(II) oxide

Other name(s): nitric oxide synthetase (ambiguous); NO synthase (ambiguous)

Systematic name: L-arginine,reduced-flavodoxin:oxygen oxidoreductase (nitric-oxide-forming)

Comments: Binds heme (iron protoporphyrin IX) and tetrahydrobiopterin. The enzyme, found in bacteria and archaea, consist of only an oxygenase domain and functions together with bacterial ferredoxins or flavodoxins. The orthologous enzymes from plants and animals also contain a reductase domain and use only NADPH as the electron donor (cf. EC

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


1. Pant, K., Bilwes, A.M., Adak, S., Stuehr, D.J. and Crane, B.R. Structure of a nitric oxide synthase heme protein from Bacillus subtilis. Biochemistry 41 (2002) 11071-11079. [PMID: 12220171]

2. Adak, S., Aulak, K.S. and Stuehr, D.J. Direct evidence for nitric oxide production by a nitric-oxide synthase-like protein from Bacillus subtilis. J. Biol. Chem. 277 (2002) 16167-16171. [PMID: 11856757]

3. Wang, Z.Q., Lawson, R.J., Buddha, M.R., Wei, C.C., Crane, B.R., Munro, A.W. and Stuehr, D.J. Bacterial flavodoxins support nitric oxide production by Bacillus subtilis nitric-oxide synthase. J. Biol. Chem. 282 (2007) 2196-2202. [PMID: 17127770]

4. Agapie, T., Suseno, S., Woodward, J.J., Stoll, S., Britt, R.D. and Marletta, M.A. NO formation by a catalytically self-sufficient bacterial nitric oxide synthase from Sorangium cellulosum. Proc. Natl. Acad. Sci. USA 106 (2009) 16221-16226. [PMID: 19805284]

5. Holden, J.K., Lim, N. and Poulos, T.L. Identification of redox partners and development of a novel chimeric bacterial nitric oxide synthase for structure activity analyses. J. Biol. Chem. 289 (2014) 29437-29445. [PMID: 25194416]

[EC created 2012 as EC, transferred 2017 to EC]

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