Protein phosphatase activity in vitro. 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. Inhibited by okadaic acid, tautomycin and calyculin A. Inhibited by phosphatase inhibitor 2 (dpiA). Interacts with dpiA. Expressed throughout development. Belongs to the PPP phosphatase family.