A phospholipase A2 hydrolyzing arachidonoyl-phospholipids in mouse peritoneal macrophages.

A calcium-dependent phospholipase A2 with half-maximal activity at approx. 0.7 microM free Ca2+ has been identified in the cytosolic fraction from macrophages. The enzyme eluted as a 70 kDa protein upon gel chromatography and showed increased activity after 10 min pretreatment of the cells with 10 nM phorbol myristate acetate. No significant activity could be detected in the membrane fraction. The enzyme hydrolyzed arachidonic acid-containing phosphatidylcholine and -ethanolamine as well as phosphatidylinositol. The release of arachidonic acid in the in vitro assay was inhibited in a dose-dependent manner by nordihydroguaiaretic acid and quercetin that are also potent inhibitors of the mobilization of arachidonic acid in intact macrophages.