Protein kinase activation of phospholipase A2 in sonicates of mouse peritoneal macrophages

Mouse peritoneal macrophages have a phospholipase A2 activity which is optimally active at pH 8.5 (PLA8.5), requires 2 mM Ca2+ and is capable of hydrolyzing arachidonic acid from phosphatidylcholine and phosphatidylethanolamine. The specific activity of PLA8.5 can be greatly increased in macrophage sonicates by their incubation at 37 degrees C. This augmentation of PLA8.5 activity occurs maximally at pH 7.5, requires Ca2+, and is inhibited by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N',-tetraacetic acid and EDTA. The sulfhydryl-specific reagents N-ethylmaleimide and p-hydroxymercuribenzoate inhibit PLA8.5 activation but have no effect on the fully activated PLA8.5 enzyme itself. PLA8.5 activation is also augmented by ATP and is inhibited by pretreatment of the sonicates with ATPase and by beta-gamma-methylene ATP. The addition of the catalytic subunit of bovine heart cAMP-dependent protein kinase to macrophage sonicates in the presence of 1 mM reduced glutathione augments PLA8.5 activation. These data suggest that a protein kinase may be involved in the activation of PLA8.5 in mouse macrophage sonicates.