Partial characterization of protein kinase C from an insect cell line

The characteristics of protein kinase C (EC 2.7.1.37) from an insect cell line (Choristoneura fumiferana) have been described. DEAE-cellulose chromatography produced a major peak of activity which eluded at 0.04-0.055 M NaCl. The enzyme was sensitive to phosphatidylserine in the presence of calcium. Phorbol 12-myristate 13-acetate (PMA) in nanomolar concentrations stimulated protein kinase C activity 8-fold over basal levels and reduced the enzymes requirement for Ca²⁺. The enzyme had a K_a of 10 nM for PMA. Diacylglycerols tested included diolein, dilinolein, diarachidonin, oleoyl-acetyl-glycerol, dioctonoyl-sn-glycerol, dipalmitin and distearin. A 2.5- to 3-fold activation was obtained in the presence of 26 μM diolein, 40 μM oleoyl-acetyl-glycerol and 46 μM dioctonoyl-sn-glycerol. The enzyme activity was sensitive to the inhibitor H-7 and 50% inhibition was achieved at a concentration of 52 μM H-7. Phosphatidylinositol enhanced enzyme activity in the absence of phosphatidylserine but phosphatidylethanolamine had no effect.