Has an important role in osmotic stability and cell shape control. It may negatively regulate the osmosensing signal transmitted through wis1 map kinase. 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. Monomer. Belongs to the PP2C family.