Isoflavone 7-O-methyltransferase (EC 2.1.1.150) is an enzyme that catalyzes a general chemical reaction which converts 7-hydroxyisoflavones to their 7-methoxy derivatives. For example, genistein is converted to prunetin:
The methylation reaction requires the cofactor, S-adenosyl methionine (SAM), to provide the methyl group, leaving the byproduct S-adenosyl-L-homocysteine (SAH). The enzyme was characterised from alfalfa. It is also capable of methylating daidzein and these reactions are often induced by attack by a pathogen, with the plant responding to an elicitor by biosynthesis of a phytoalexin. This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:hydroxyisoflavone 7-O-methyltransferase.
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