IUBMB Enzyme Nomenclature


Accepted name: isoflavone 3'-hydroxylase

Reaction: formononetin + [reduced NADPH—hemoprotein reductase] + O2 = calycosin + [oxidized NADPH—hemoprotein reductase] + H2O

For diagram of reaction click here.

Glossary: calycosin = 3'-hydroxyformononetin

Other name(s): isoflavone 3'-monooxygenase; CYP81E9

Systematic name: formononetin,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (3'-hydroxylating)

Comments: A cytochrome P-450 (heme-thiolate) protein. Also acts on biochanin A and other isoflavones with a 4'-methoxy group. Involved in the biosynthesis of the pterocarpin phytoalexins medicarpin and maackiain.

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


1. Hinderer, W., Flentje, U. and Barz, W. Microsomal isoflavone 2'-hydroxylases and 3'-hydroxylases from chickpea (Cicer arietinum L) cell-suspensions induced for pterocarpan phytoalexin formation. FEBS Lett. 214 (1987) 101-106.

[EC created 1992 as EC, transferred 2018 to EC]

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