Fatty acid activation of protein kinase C: Dependence on diacylglycerol

The kinetics of activation of protein kinase C by oleic acid have been reinvestigated, using highly purified preparations of the rat brain and bovine spleen enzymes. Activation of both enzymes by oleic acid is enhanced dramatically by diolein, contrary to previous reports. In the presence of 9.7 μM diolein, the concentrations of oleic acid required for half-maximal activation are 5 μM and 9 μM for the rat brain and bovine spleen enzymes respectively, indicating that the system is much more sensitive to activation by fatty acids than previously recognized. Both enzymes also exhibit a pronounced lag in the activation at low concentrations of oleic acid. The kinetics of activation are very similar to those reported by Hannun et al. (J. Biol. Chem 260, 10039-10043), who characterized the activation of the rat brain enzyme by mixed micelles containing Triton X-100, phosphatidylserine and diolein