Identification of a calmodulin‐dependent glycogen synthase kinase in rabbit skeletal muscle, distinct from phosphorylase kinase

Abstract
A glycogen synthase kinase that is completely dependent on Ca2+ and calmodulin has been identified in mammalian skeletal muscle, and purified ∼3000‐fold by chromatography on phosphocellulose and calmodulin—Sepharose. The presence of 50 mM NaCl in the homogenisation buffer was critical for extraction of the enzyme. The calmodulin‐dependent glycogen synthase kinase (app. M r 850 000) is distinct from myosin light‐chain kinase and phosphorylase kinase, but phosphorylates the same serine residue on glycogen synthase as phosphorylase kinase. The physiological role of the enzyme is discussed.