Luteolin O-methyltransferase (EC 2.1.1.42) is an enzyme that catalyzes the chemical reaction
This is a methylation reaction in which the flavone, luteolin, is converted to chrysoeriol. The methyl group comes from the cofactor, S-adenosyl methionine (SAM), which loses its methyl group and becomes S-adenosyl-L-homocysteine (SAH). Luteolin O-methyltransferase can also act on flavanols and converts quercetin to isorhamnetin:
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:5,7,3',4'-tetrahydroxyflavone 3'-O-methyltransferase. Other names in common use include o-dihydric phenol methyltransferase, luteolin methyltransferase, luteolin 3'-O-methyltransferase, o-diphenol m-O-methyltransferase, o-dihydric phenol meta-O-methyltransferase, and S-adenosylmethionine:flavone/flavonol 3'-O-methyltransferase. This enzyme participates in flavonoid biosynthesis and reacts with flavones in the 3' position, preferring those with a second hydroxy group adjacent in the 4' position.
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