Involved in glycogen accumulation. 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. Inactivated in a complex with phosphatase methylesterase PPE1 (PP2Ai). Interacts with phosphatase 2A activator RRD1, which can reactivate PP2Ai by dissociating the catalytic subunit from the complex. Interacts with TAP42. Reversibly methyl esterified on Leu-368 by leucine carboxyl methyltransferase 1 (PPM1) and protein phosphatase methylesterase 1 (PPE1). 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. Present with 1960 molecules/cell in log phase SD medium. Belongs to the PPP phosphatase family. PP-2A subfamily.