[Ca2+, phospholipid-dependent protein kinase (C-kinase) in the rat placental chorion]

C-kinase is one of the enzymes which phosphorylate cellular proteins, and is reported to be involved in transmission of the extracellular signals regarding hormones, etc. to inside the cell. This enzyme is widely distributed in many tissues and organs and several C-kinase-mediated cellular responses were reported. However, in the placenta, the presence of C-kinase has not been reported. In this paper we reported for the first time the purification of C-kinase from rat placental chorion and investigated the physiological functions of C-kinase. The results were as follows: A considerable amount of C-kinase was detected in the membrane fraction of rat placenta. C-kinase specifically phosphorylated several membrane proteins, and the phosphorylation pattern was different from those of mid pregnancy and late pregnancy. The C-kinase activity in late pregnancy was 6 times higher than that of mid pregnancy. Hemin and Polylysine inhibited partially-purified membrane-bound C-kinase. Substrate specificity C-kinase from rat placenta was similar to those from other organs.