Myosin specific phosphatases isolated from Dictyostelium discoideum.

Using native myosin phosphorylated on either the heavy chain or the light chain, we have isolated myosin phosphatases from extracts of vegetative Dictyostelium amoeba. Two phosphatases were resolved by DEAE-cellulose chromatography. One of these phosphatases removed phosphate from heavy chain or light chain at approximately the same rate. The other phosphatase appeared to be much more specific for phosphorylated myosin heavy chain. Although these enzymes removed phosphate from other phosphoprotein substrates such as histone or casein, they did so at a much lower rate. Both enzymes required magnesium for activity, but appeared to be independent of calcium.