phosphatase phosphoprotein phosphatase Catalysis role of the reaction: a phosphoprotein + H2O = a protein + phosphate. Together with protein kinases, these enzymes control the state of phosphorylation of cell proteins and thereby provide an important mechanism for regulating cellular activity. IMR:0000272 (obsolete) phosphoprotein phosphohydrolase protein phosphatase protein phosphatase-2A related molecular function GO:0004721