A novel glycogen synthase phosphatase from canine heart

Abstract

Summary Two molecular forms (M r =49,300 and 26,000) of a divalent cation-dependent (Mg 2+ =Mn 2+ >Co 2+ ) protein phosphatase, which represent the major glycogen synthase phosphatase activity in canine heart extracts, have been partially purified and characterized. Although a general protein phosphatase of M r =35,000 is also active toward synthase D, it represents the major phosphorylase phosphatase activity in heart muscle. The present findings indicate that the dephosphorylation of synthase D and phosphorylase a may be regulated by two distinct phosphatases rather than by a single nonspecific enzyme.