Tocopherol O-methyltransferase () is an enzyme that catalyzes the chemical reaction
This is a methylation reaction in which one of the vitamin E components, γ-tocopherol, is converted to the more commonly found α-tocopherol. The methyl group comes from the cofactor, S-adenosyl methionine (SAM), which becomes S-adenosyl-L-homocysteine (SAH).
The enzymes from Arabidopsis thaliana and Capsicum annuum can also convert δ-tocopherol into β-tocopherol and are effective on tocotrienols, by addition of a methyl group at the same relative position as in γ-tocopherol.
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:gamma-tocopherol 5-O-methyltransferase. This enzyme is also called gamma-tocopherol methyltransferase.
References