Phospholipase A1 acting on phosphatidic acid in porcine platelet membranes.

1-[14C]Palmitoyl-2-[3H]arachidonoyl-sn-glycerol 3-phosphate was hydrolyzed to form [14C]palmitic acid and 2-[3H]arachidonoyl-glycerophosphate by porcine platelet membranes. This phospholipase A1 activity was relatively specific for phosphatidic acid; the addition of several other phospholipids in equimolar amounts did not have a significant effect on the hydrolysis of radiolabeled phosphatidic acid, and the specific activity for phosphatidic acid hydrolysis was 20-fold higher than that of the hydrolysis of phosphatidylcholine, phosphatidylethanolamine, or phosphatidylinositol under the conditions used. This phospholipase A1 acting on phosphatidic acid has properties different from those reported for other phospholipases and lipases present in platelets.