A new heparin-inhibited and polyamine-activated protein kinase from bovine kidney

Two casein kinases, casein kinase-1 (CK-1) and casein kinase-2 (CK-2), have been characterized from many sources. In this study we describe the properties of a third casein kinase, designated casein kinase-3 (CK-3). CK-3 (Mr 32,000) is readily separated from CK-2 by gel filtration and from CK-1 by hydroxyapatite chromatography. CK-3 phosphorylates several proteins, including phosphorylase kinase. Phosphorylation of phosphorylase kinase by CK-3 results in a 10-fold enzyme activation. CK-3 is activated by spermine and inhibited by heparin, ADP, and divalent metal ions (Mn2+, Zn2+). Heparin inhibition of the kinase is reversed by spermine. The physical and regulatory properties of CK-3 are very similar to CK-1, suggesting that these kinases may be closely related.