Methylates the carboxyl group of the C-terminal leucine residue of protein phosphatase 2A catalytic subunits to form alpha-leucine ester residues. [phosphatase 2A protein]-C-terminal L-leucine + S-adenosyl-L-methionine = [phosphatase 2A protein]-C-terminal L-leucine methyl ester + S-adenosyl-L-homocysteine Belongs to the methyltransferase superfamily. LCMT family.