Purification and characterization of two phosphorylase phosphatases from rabbit liver

Two phosphorylase phosphatase activities (I and III) have been purified from rabbit liver, with respective molecular weights of 117,000 and 230,000. Phosphatase III contained three different subunits of molecular weights 35,000, 67,000 and 80,000. Phosphatase I although majoritary in the preparation, was not homogeneous. Both phosphatases were dissociated by 2-mercaptoethanol treatment, releasing a catalytic subunit with a molecular weight of about 35,000. Phosphatases I and III activities responded very differently to incubation with trypsin and to ethanol precipitation. Phosphatase III was much more sensitive to inactivation by several ions and ATP than phosphatase I. On the basis of the obtained data, phosphatase I can be classified as a type-1 phosphatase and phosphatase III as a type-1 phosphatase.