Stimulation of cyclic nucleotide phosphodiesterase by products of phosphatidylinositol metabolism catalyzed by phospholipase A2

Products of phospholipase A₂-catalyzed hydrolysis of phosphatidylinositol, lysophosphatidylinositol, and unsaturated fatty acid are very effective stimulators of a partially purified bovine brain cyclic nucleotide phosphodiesterase. More than 10-fold of calcium-independent stimulation can be achived by lysophatidylinositol or oleic acid. The degree of stimulation is comparable to that by calcium-mediated calmodulin. The other lysophospholipid which shows comparable stimulation is lysophosphatidylserine although at a higher concentration. Diacylphosphoglycerides are inactive. Kinetic studies showed that lysophosphatidylinositol, like calmodulin, increased the V_max without affecting the apparent K_m for adenosine 3′,5′-cyclic phosphate (cAMP).