Identifying protein kinases in crude extracts that phosphorylate cyclic GMP-binding cyclic-GMP specific phosphodiesterase.

The main protein kinase that phosphorylates cyclic GMP-binding cyclic GMP-specific phosphodiesterase (cG-BPDE) in crude extracts of bovine lung is cyclic GMP-dependent protein kinase. This can be shown by the use of either exogenous or endogenous cG-BPDE as substrate for endogenous cyclic GMP-dependent protein kinase. The characteristics of this phosphorylation suggest a physiological significance.