Essential role in cell cycle control. PP2A may be involved in controlling the entry into mitosis, possibly acting as an inhibitor. 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. Retarded cell growth is produced by disruption of ppa2. Belongs to the PPP phosphatase family. PP-2A subfamily.