A simple and rapid method for the assay of cyclic GMP-dependent protein kinase

A method for the isolation in partially purified cyclic GMP-dependent protein kinase (cGPK) from cerebellum is described. It involves a step-elution of an ion-exchange column charged with the post-mitochondrial supernatant of cerebellar homogenate. The cGPK activity is defined as the protein kinase activity in presence minus that in absence of cyclic GMP. Under the assay conditions used no interference by cyclic AMP-dependent protein kinase, and only negligible activities of cyclic nucleotide phosphodiesterase and phosphoprotein phosphatase could be detected.