S-adenosyl-L-methionine-dependent methyltransferase. Involved in glucosinolate metabolism and defense against phytopathogens (By similarity). a thiol + S-adenosyl-L-methionine = a methyl thioether + H(+) + S-adenosyl-L-homocysteine No visible phenotype under normal growth conditions. Belongs to the class I-like SAM-binding methyltransferase superfamily. TPMT family.