IUBMB Enzyme Nomenclature


Accepted name: 4'-methoxyisoflavone 2'-hydroxylase

Reaction: formononetin + [reduced NADPH—hemoprotein reductase] + O2 = 2'-hydroxyformononetin + [oxidized NADPH—hemoprotein reductase] + H2O

For diagram of reaction click here.

Other name(s): CYP81E1 (gene name); CYP81E3 (gene name); CYP81E7 (gene name); isoflavone 2'-monooxygenase (ambiguous); isoflavone 2'-hydroxylase (ambiguous)

Systematic name: formononetin,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (2'-hydroxylating)

Comments: A cytochrome P-450 (heme-thiolate) protein. Acts on isoflavones with a 4'-methoxy group, such as formononetin and biochanin A. Involved in the biosynthesis of the pterocarpin phytoalexins medicarpin and maackiain. EC, isoflavone 2'-hydroxylase, is less specific and acts on other isoflavones as well as 4'-methoxyisoflavones.

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.

2. Akashi, T., Aoki, T. and Ayabe, S.-I. CYP81E1, a cytochrome P450 cDNA of licorice (Glycyrrhiza echinata L.), encodes isoflavone 2'-hydroxylase. Biochem. Biophys. Res. Commun. 251 (1998) 67-70. [PMID: 9790908]

3. Liu, C.J., Huhman, D., Sumner, L.W. and Dixon, R.A. Regiospecific hydroxylation of isoflavones by cytochrome p450 81E enzymes from Medicago truncatula. Plant J. 36 (2003) 471-484. [PMID: 14617078]

[EC created 1992 as EC, modified 2005, transferred 2018 to EC]

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