Reaction: S-adenosyl-L-methionine + 3,5,7,3',4'-pentahydroxyflavone = S-adenosyl-L-homocysteine + 3-methoxy-5,7,3',4'-tetrahydroxyflavone
For diagram click here.
Other name(s): flavonol 3-O-methyltransferase; flavonoid 3-methyltransferase
Systematic name: S-adenosyl-L-methionine:3,5,7,3',4'-pentahydroxyflavone 3-O-methyltransferase
Comments: Specific for quercetin. Related enzymes bring about the 3-O-methylation of other flavonols, such as galangin and kaempferol.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 81295-55-8
References:
1. De Luca, V., Brunet, G., Khouri, H., Ibrahim, R. and Hrazdina, G. Flavonol 3-O-methyltransferase in plant-tissues. Z. Naturforsch. 37 (1982) 134-135.
2. De Luca, V. and Ibrahim, R.K. Enzymatic synthesis of polymethylated flavonols in Chrysosplenium americanum. I. Partial purification and some properties of S-adenosyl-L-methionine:flavonol 3-, 6-, 7-, and 4'-O-methyltransferases. Arch. Biochem. Biophys. 238 (1985) 596-605. [PMID: 3994393]
3. De Luca, V. and Ibrahim, R.K. Enzymatic synthesis of polymethylated flavonols in Chrysosplenium americanum. II. Substrate interaction and product inhibition studies of flavonol 3-, 6-, and 4'-O-methyltransferases. Arch. Biochem. Biophys. 238 (1985) 606-618. [PMID: 3994394]
4. Ibrahim, R.K. and De Luca,V. Polymethylated flavonol synthesis is catalyzed by distinct O-methyltransferases. Naturwissenschaften 69 (1982) 41-42.