ExplorEnz: EC 1.14.13.39

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1.14.13.39

Accepted name:

nitric-oxide synthase (NADPH)

Reaction:

2 L-arginine + 3 NADPH + 3 H⁺ + 4 O₂ = 2 L-citrulline + 2 nitric oxide + 3 NADP⁺ + 4 H₂O (overall reaction)
(1a) 2 L-arginine + 2 NADPH + 2 H⁺ + 2 O₂ = 2 N^ω-hydroxy-L-arginine + 2 NADP⁺ + 2 H₂O
(1b) 2 N^ω-hydroxy-L-arginine + NADPH + H⁺ + 2 O₂ = 2 L-citrulline + 2 nitric oxide + NADP⁺ + 2 H₂O

Glossary:

nitric oxide = NO = nitrogen(II) oxide

Other name(s):

NOS (gene name); nitric oxide synthetase (ambiguous); endothelium-derived relaxation factor-forming enzyme; endothelium-derived relaxing factor synthase; NO synthase (ambiguous); NADPH-diaphorase (ambiguous)

Systematic name:

L-arginine,NADPH:oxygen oxidoreductase (nitric-oxide-forming)

Comments:

The enzyme consists of linked oxygenase and reductase domains. The eukaryotic enzyme binds FAD, FMN, heme (iron protoporphyrin IX) and tetrahydrobiopterin, and its two domains are linked via a regulatory calmodulin-binding domain. Upon calcium-induced calmodulin binding, the reductase and oxygenase domains form a complex, allowing electrons to flow from NADPH via FAD and FMN to the active center. The reductase domain of the enzyme from the bacterium Sorangium cellulosum utilizes a [2Fe-2S] cluster to transfer the electrons from NADPH to the active center. cf. EC 1.14.14.47, nitric-oxide synthase (flavodoxin).

Links to other databases:

BRENDA, EXPASY, Gene, KEGG, MetaCyc, PDB, CAS registry number: 125978-95-2

References:

1.	Bredt, D.S. and Snyder, S.H. Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme. Proc. Natl. Acad. Sci. USA 87 (1990) 682–685. [DOI] [PMID: 1689048]
2.	Stuehr, D.J., Kwon, N.S., Nathan, C.F., Griffith, O.W., Feldman, P.L. and Wiseman, J. N^ω-hydroxy-L-arginine is an intermediate in the biosynthesis of nitric oxide from L-arginine. J. Biol. Chem. 266 (1991) 6259–6263. [PMID: 1706713]
3.	Stuehr, D., Pou, S. and Rosen, G.M. Oxygen reduction by nitric-oxide synthases. J. Biol. Chem. 276 (2001) 14533–14536. [DOI] [PMID: 11279231]
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. [DOI] [PMID: 19805284]
5.	Foresi, N., Correa-Aragunde, N., Parisi, G., Calo, G., Salerno, G. and Lamattina, L. Characterization of a nitric oxide synthase from the plant kingdom: NO generation from the green alga Ostreococcus tauri is light irradiance and growth phase dependent. Plant Cell 22 (2010) 3816–3830. [DOI] [PMID: 21119059]

[EC 1.14.13.39 created 1992, modified 2012, modified 2017]