Substrate specificity of a multifunctional calmodulin-dependent protein kinase

Abstract

The substrate specificity of the multifunctional calmodulin-dependent protein kinase from skeletal muscle has been studied using a series of synthetic peptide corresponding to the NH2-terminal 10 residues of glycogne synthase, Pro-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ser-Ser-NH2, stoichiometrically at Ser-7, the same residue phosphorylated in the parent protein. The synthetic peptide was phosphorylatd with a V(max) of 12.5 μmol·min-1·mg-1 and an apparent K(m) of 7.5 μM compared to values of 1.2 μmol·min-1·mg-1 and 3.1 μM, respectively, for glycogen synthase. Similarly, a synthetic peptide corresponding to the NH2-terminal 23 residues of smooth muscle myosin light chain was readily phosphorylated on S..