IUBMB Enzyme Nomenclature


Accepted name: 22α-hydroxysteroid 23-monooxygenase

Reaction: (1) 3-epi-6-deoxocathasterone + [reduced NADPH—hemoprotein reductase] + O2 = 6-deoxotyphasterol + [oxidized NADPH—hemoprotein reductase] + H2O
(2) (22S,24R)-22-hydroxy-5α-ergostan-3-one + [reduced NADPH—hemoprotein reductase] + O2 = 3-dehydro-6-deoxoteasterone + [oxidized NADPH—hemoprotein reductase] + H2O

Other name(s): cytochrome P450 90C1; CYP90D1; CYP90C1; 3-epi-6-deoxocathasterone,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (C-23-hydroxylating); 3-epi-6-deoxocathasterone 23-monooxygenase

Systematic name: 22α-hydroxysteroid,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (C-23-hydroxylating)

Comments: A cytochrome P-450 (heme-thiolate) protein involved in brassinosteroid biosynthesis in plants. The enzyme has a relaxed substrate specificity, and C-23 hydroxylation can occur at different stages in the pathway. In Arabidopsis thaliana two isozymes, encoded by the CYP90C1 and CYP90D1 genes, have redundant activities.

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


1. Kim, G.T., Fujioka, S., Kozuka, T., Tax, F.E., Takatsuto, S., Yoshida, S. and Tsukaya, H. CYP90C1 and CYP90D1 are involved in different steps in the brassinosteroid biosynthesis pathway in Arabidopsis thaliana. Plant J. 41 (2005) 710-721. [PMID: 15703058]

2. Ohnishi, T., Szatmari, A.M., Watanabe, B., Fujita, S., Bancos, S., Koncz, C., Lafos, M., Shibata, K., Yokota, T., Sakata, K., Szekeres, M. and Mizutani, M. C-23 hydroxylation by Arabidopsis CYP90C1 and CYP90D1 reveals a novel shortcut in brassinosteroid biosynthesis. Plant Cell 18 (2006) 3275-3288. [PMID: 17138693]

[EC created 2010 as EC, transferred 2018 to EC, modified 2022]

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