Phosphorylation of the glycogen‐binding subunit of protein phosphatase‐1G in response to adrenalin

Abstract

The glycogen‐binding (G) subunit of protein phosphatase‐1 is phosphorylated in vivo. In rabbits injected with propranolol the serine residue termed site‐1 was phosphorylated in 56% of the molecules isolated, and phosphorylation increased to 82% after administration of adrenalin. It is concluded that the G‐subunit is a physiological substrate for cyclic AMP‐dependent protein kinase. The G‐subunit remained largely bound to glycogen even after injection of adrenalin, whereas half of the protein phosphatase‐1 activity associated with glycogen was released into the cytosol. The results indicate that adrenalin induces dissociation of the catalytic subunit from the G‐subunit in vivo.