Methylates the carboxyl group of the C-terminal leucine residue of protein phosphatase 2A catalytic subunits to form alpha-leucine ester residues. Acts on the two major protein phosphatase 2A catalytic subunits, PPH21 and PPH22. [phosphatase 2A protein]-C-terminal L-leucine + S-adenosyl-L-methionine = [phosphatase 2A protein]-C-terminal L-leucine methyl ester + S-adenosyl-L-homocysteine Inhibited by S-adenosyl-L-homocysteine. Belongs to the methyltransferase superfamily. LCMT family.