Abstract
A particulate associated, calcium and diacylglycerol-activated, phospholipid-dependent protein kinase (protein kinase C; PKC) has been demonstrated in the pupal brain of the tobacco hornworm, Manduca sexta. The particulate enzyme could be measured accurately only after its solubilization by non-ionic detergents, Triton X-100 being the most effective. The basic enzymatic properties of the particulate associated PKC are similar to those of the cytosolic brain enzyme. Maximal enzyme activity was obtained in the presence of 0.75 mM Ca 2+ and 200 μg/ml phosphatidylserine. Diacylglycerol (1,2 diolein; 50 μg/ml) further enhanced both PKC activity and Ca 2+ sensitivity in the presence of an optimal concentration of phosphatidylserine. Particulate PKC is inhibited by trifluoperazine in a dose-dependent manner with an IC 50 of approx. 30 μM. Subcellular distribution studies revealed that 86% of the pupal brain PKC activity is present in the soluble cellular fraction. A study of PKC activity during pupal-adult development revealed that the specific activity of day 9 pharate adult brain PKC was 6-fold higher than that observed for day 0 pupal brains. SDS-polyacrylamide gel electrophoresis and autoradiography demonstrated that a microsomal enriched 34 kDa peptide was phosphorylated by PKC in the presence of Ca 2+ and phosphatidylserine.
Published Version
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