The separation and properties of two phosphoprotein phosphatases from the dimorphic fungus Mucor rouxii

Soluble preparations from mycelium of the dimorphic fungus Mucor rouxii contained detectable amounts of phosphoprotein phosphatase activity. This cytosolic phosphatase activity exhibited a molecular weight below 80,000 and could be resolved into two different forms (enzymes I and II) by chromatography on DEAE-cellulose followed by gel filtration on Sephacryl S-300. Enzyme I (M_r 64,000) was mainly a histone phosphatase activity, absolutely dependent on divalent cations, with a K_0.5 for MnCl₂ of 2 mm. Enzyme II (M_r 40,000) was active with histone and phosphorylase. Its activity was independent or slightly inhibited by Mn²⁺. This enzyme was strongly inhibited by 50 mm NaF or 1 mm ATP. When partially purified enzymes I and II were separately treated with ethanol, the catalytic properties of enzyme II were apparently not affected while those of enzyme I were drastically changed. The activity with histone, which was originally dependent on Mn²⁺, became independent or slightly inhibited by the cation. The treatment was accompanied by a notable increase in phosphorylase phosphatase activity which was strongly inhibited by Mn²⁺. Treated enzyme I eluted from DEAE-cellulose and Sephacryl S-300 columns at a position similar to that of enzyme II.