Reaction: S-adenosyl-L-methionine + a 7-hydroxyisoflavone = S-adenosyl-L-homocysteine + a 7-methoxyisoflavone
See diagram for reaction in prunetin or isoformononetin biosynthesis.
Systematic name: S-adenosyl-L-methionine:hydroxyisoflavone 7-O-methyltransferase
Comments: The enzyme from alfalfa can methylate daidzein, genistein and 6,7,4'-trihydroxyisoflavone but not flavones or flavanones.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 136111-54-1
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2. He, X.Z. and Dixon, R.A. Genetic manipulation of isoflavone 7-O-methyltransferase enhances biosynthesis of 4'-O-methylated isoflavonoid phytoalexins and disease resistance in alfalfa. Plant Cell 12 (2000) 1689-1702. [PMID: 11006341]
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4. He, X.Z., Reddy, J.T. and Dixon, R.A. Stress responses in alfalfa (Medicago sativa L). XXII. cDNA cloning and characterization of an elicitor-inducible isoflavone 7-O-methyltransferase. Plant Mol. Biol. 36 (1998) 43-54. [PMID: 9484461]
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