This family represents the C-terminus (approximately 100 residues) of bacterial and eukaryotic Magnesium-protoporphyrin IX methyltransferase (EC:2.1.1.11). This converts magnesium-protoporphyrin IX to magnesium-protoporphyrin IX methylester using S-adenosyl-L-methionine as a cofactor [1].

1: Heterologous expression of the bchM gene product from Rhodobacter capsulatus and demonstration that it encodes S-adenosyl-L-methionine:Mg-protoporphyrin IX methyltransferase. Bollivar DW, Jiang ZY, Bauer CE, Beale SI; J Bacteriol 1994;176:5290-5296. PMID:8071204