May have a role in the recovery or adaptation response of photoreceptors. May have a role in development (By similarity). 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. Activated by calcium. Belongs to the PPP phosphatase family.