Cyclic Nucleotide-dependent Protein Kinases

Abstract

Abstract An enzyme which catalyzes the phosphorylation of histone by ATP, and is activated by low concentrations of guanosine 3',5'-monophosphate, has been found in lobster muscle and partially purified. The guanosine 3',5'-monophosphate-dependent protein kinase has been separated from an adenosine 3',5'-monophosphate-dependent protein kinase found in the same tissue. The rate of phosphorylation of histone, catalyzed by the guanosine 3',5'-monophosphate-dependent protein kinase, was increased about 5-fold by guanosine 3',5'-monophosphate at a concentration of 0.5 µm; the apparent Km of the enzyme was about 0.08 µm for guanosine 3',5'-monophosphate and about 4 µm for adenosine 3',5'-monophosphate. The apparent Km of the adenosine 3',5'-monophosphate-dependent protein kinase isolated from the same tissue was about 0.02 µm for adenosine 3',5'-monophosphate and about 1.2 µm for guanosine 3',5'-monophosphate.