Is essential for the regulation of mitotic chromosomal segregation as well as regulation of chromatin condensation during interphase. 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. Interacts with Nop17l (PubMed:17007873). Interacts with uri; uri inhibits Pp1-87B phosphatase activity (PubMed:18412953). Interacts with Rif1 (PubMed:26022086, PubMed:29746464). Detected in embryos and larvae (at protein level). Belongs to the PPP phosphatase family. PP-1 subfamily.