Multisite phosphorylation of glycogen synthase from rabbit skeletal muscle

Abstract

A casein kinase was highly purified from rabbit skeletal muscle whose substrate specificity and enzymatic properties were virtually identical to those of casein kinase‐I from rabbit reticulocytes. Prolonged incubation of glycogen synthase with high concentrations of skeletal muscle casein kinase‐I and Mg‐ATP resulted in the incorporation of >6 mol phosphate/mol subunit and decreased the activity ratio (∓ glucose‐6P) from 0.8 to in vivo to be evaluated.