This family consists of thiopurine S-methyltransferase (), thiol S-methyltransferase () and thiocyanate methyltransferase ().Thiopurine S-methyltransferase is a cytosolic enzyme that catalyses S-methylation of aromatic and heterocyclic sulphydryl compounds, including anticancer and immunosuppressive thiopurines []. Thiopurine is commonly used to suppress the immune system in the case of autoimmune disease, inflammatory bowel disease and to prevent transplanted organ rejection []. Thiopurine drugs can be toxic to cells but their effect can be mediated by the incorporation of thioguanine nucleotides into DNA [].Thiocyanate methyltransferase and thiol S-methyltransferase are involved in glucosinolate metabolism and defense against phytopathogens. Thiocyanate methyltransferase is highly reactive to thiocyanate (NCS-) derived from myrosinase-mediated hydrolysis of glucosinolates upon tissue damage [].
