Cyclic Nucleotide-Dependent Protein Kinases From Silkworm Eggs: Occurrence of Two Cyclic Nucleotide-Dependent Protein Kinases, Changes in Their Activities and Levels of Cyclic Nucleotides During Development of the Eggs

Abstract

Two cyclic nucleotide-dependent protein kinases, designated as protein kinase-I and -11, were obtained from the eggs of the silkworm, Bornbyx rnori. Protein kinase-I is highly dependent on cGMP, whereas protein kinase-I1 is dependent on CAMP. In developing non-diapause eggs, the level of cyclic nucleotide-dependent protein kinase activity is quite high but that in the diapause eggs is not. The developmental changes in the two protein kinases and the level of cyclic nucleotides were also studied during the development of the eggs.Protein kinases catalyze transfer of the terminal phosphate of ATP to a variety of protein substrates. The protein kinase which is stimulated by CAMP was first observed by WALSH et al. ( 1 968). Since that time, cyclic nucleotide-dependent protein kinases have been reported from various laboratories and their biological roles have also been discussed (WALSH and ASHBY, 1973). In insects, only a few reports concerning cyclic nucleotide-dependent protein kinases have been published.The first study on insect protein kinase was by Kuo et al. (1971), in which they reported the presence of CAMP-and cGMP-dependent protein kinases in cockroach, silkmoth and other insect species. Recently, TAKAHASHI et al. (1 974) obtained partially purified cGMP-dependent protein kinase from silkworm eggs and reported some o f its properties.