Calcium-dependent protein kinase: widespread occurrence in various tissues and phyla of the animal kingdom and comparison of effects of phospholipid, calmodulin, and trifluoperazine.

Abstract

A widespread occurrence of Ca2+-dependent protein kinase was shown in various tissues and phyla of the animal kingdom. Phosphatidylserine appeared to be more effective than calmodulin in supporting the Ca2+-dependent phosphotransferase activity. The phospholipid-sensitive Ca2+-dependent protein kinase activity, distributed in both the cytosolic and particulate fractions, was not inhibited by trifluoperazine, a specific inhibitor of calmodulin-sensitive, Ca2+-dependent reactions or processes. The enzyme activity levels, compared to those of cAMP-dependent and cGMP-dependent protein kinases, were exceedingly high in certain tissues (such as brain and spleen) and exhibited a much greater disparity among tissues. The Ka for Ca2+ was about 100 .mu.M in the presence of phosphatidylserine; the value was as low as 2 .mu.M in the presence of phosphatidylserine and diolein. Phospholipid-sensitive Ca2+-dependent protein kinase may mediate certain actions of Ca2+ in tissues, acting independently or in a complementary manner with other protein phosphorylation systems stimulated by calmodulin-Ca2+, cAMP, or cGMP. [The animals studied were the earthworm (Lumbricus), snail (Cepaea), lobster (Homarus), cockroach (Periplaneta), frog (Xenopus), goldfish (Carassius), duck (Anas) and dog (Canis).].