PHOSPHOLIPASE-D ACTIVITY OF ISOLATED RAT-BRAIN PLASMA-MEMBRANES

With [C-14]oleate-labeled phosphatidylcholine as a substrate for phosp holipase D the hydrolytic activity was measured by phosphatidic acid f ormation and the transphosphatidylation activity was measured by the p hosphatidylethanol formed in the presence of ethanol. The pH optimum w as 6.5 with dimethylglutarate as the buffer. EGTA inhibited the transp hosphatidylation activity to a greater extent than the hydrolytic acti vity. In contrast CaCl2, BaCl2, MgCl2 and SrCl2 stimulated the hydroly tic activity without effecting the transphosphatidylation activity. Be Cl2 another member of the group IIa transition metals was a very poten t inhibitor of both the hydrolytic and transphosphatidylation activity . GTP gamma S, an activator of G protein-mediated events, was an inhib itor of both activities.