This entry includes a group of methyltransferases such as leucine carboxyl methyltransferase 1 (known as Ppm1 in yeast and LCMT1 in mammals), leucine carboxyl methyltransferase 2 (Ppm2/LCMT2) and O-methyltransferase TcmP. Ppm1 regulates the activity of serine/threonine phosphatase 2A (PP2A) through methylation of the C-terminal leucine residue of the catalytic subunit of PP2A [, , ]. This affects the heteromultimeric composition of PP2A which in turn affects protein recognition and substrate specificity. Like many other methyltransferases Ppm1 uses S-adenosylmethionine (SAM) as the methyl donor. Ppm1 contains the common SAM-dependent methyltransferase core fold, with various insertions and additions creating a specific PP2A binding site []. Ppm2, a homologue of Ppm1, is a S-adenosyl-L-methionine-dependent methyltransferase that acts as a component of the wybutosine biosynthesis pathway, which is part of tRNA modification [].Streptomyces glaucescens TcmP is an O-methyltransferase that catalyses the methylation of the C-9 carboxy group of tetracenomycin E (TCM E) to yield TCM A2, which is then further processed to produce the antibiotic TCM C [].
