H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 manganese ions per subunit. Reversibly methyl esterified on Leu-309 by leucine carboxyl methyltransferase 1 (LCMT1) and protein phosphatase methylesterase 1 (PPME1). Carboxyl methylation influences the affinity of the catalytic subunit for the different regulatory subunits, thereby modulating the PP2A holoenzyme's substrate specificity, enzyme activity and cellular localization (By similarity). Belongs to the PPP phosphatase family. PP-2A subfamily.