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

With [C-14]oleate-labeled phosphatidylcholine as a substrate for phospholipase D the hydrolytic activity was measured by phosphatidic acid formation and the transphosphatidylation activity was measured by the phosphatidylethanol formed in the presence of ethanol. The pH optimum was 6.5 with dimethylglutarate as the buffer. EGTA inhibited the transphosphatidylation activity to a greater extent than the hydrolytic activity. In contrast CaCl2, BaCl2, MgCl2 and SrCl2 stimulated the hydrolytic activity without effecting the transphosphatidylation activity. BeCl2 another member of the group IIa transition metals was a very potent inhibitor of both the hydrolytic and transphosphatidylation activity. GTP gamma S, an activator of G protein-mediated events, was an inhibitor of both activities.