In enzymology, a methionine S-methyltransferase (EC 2.1.1.12) is an enzyme that catalyzes the chemical reaction Thus, the two substrates of this enzyme are S-adenosyl methionine and L-methionine, whereas its two products are S-adenosylhomocysteine and S-methyl-L-methionine.
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:L-methionine S-methyltransferase.
This enzyme participates in selenoamino acid metabolism.
It has 2 cofactors: manganese[citation needed], and zinc.