A multifunctional calmodulin-dependent protein kinase. Similarities between skeletal muscle glycogen synthase kinase and a brain synapsin I kinase

Calmodulin-dependent glycogen synthase kinase isolated from skeletal muscle and synapsin I kinase II isolated from brain have several properties that are very similar. These properties include: substrate and site-specificities, immunological cross-reactivity, and phosphopeptide maps following limited proteolysis. Both enzymes phosphorylate a wide variety of substrate proteins. The two kinases may represent different isozymes of a multifunctional calmodulin-dependent protein kinase that mediates many of the actions of Ca²⁺ in various tissues. Therefore, we propose the name 'calmodulin-dependent multi-protein kinase' for this broad specificity enzyme.