Responsible, together with PTC2, for the dephosphorylation of the cyclin-dependent protein kinase CDC28. H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 magnesium or manganese ions per subunit. Present with 19700 molecules/cell in log phase SD medium. Belongs to the PP2C family.