Essential for the maintenance of cell size and integrity in response to osmotic stress. 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. Present with 189 molecules/cell in log phase SD medium. Belongs to the PPP phosphatase family. PP-Z subfamily.