Protein phosphatases in developing Dictyostelium discoideum cells

Protein phosphatase activities in developing Dictyostelium discoideum cells were investigated. Substrates were prepared by phosphorylation of histone H2b and kemptide (Leu-Arg-Arg-Ala-Ser-Leu-Gly) using cAMP-dependent protein kinase. Two histone phosphatase activities (M_r 170 000 and 520 000) and one kemptide phosphatase activity (M_r 230 000) were found in the cytosolic cell fraction. Histone phosphatase was also present in the particulate fraction, kemptide phosphatase was not. All phosphatase activities were present throughout development. No differences in protein phosphatase activities were found in prespore and prestalk cells. A heat-stable factor which inhibits the particulate and both soluble histone phosphatase activities was isolated.