Dual role of interfacial phospholipid in phospholipase A2 catalysis.

Abstract

The results of crosslinking experiments with dimethyl suberimidate and gel filtration binding studies are used to delineate a detailed model for [cobra venom, Naja naja naja] phospholipase A2 (phosphatide 2-acyl-hydrolase, EC 3.1.1.4) action in the presence of Ca2+ on mixed micelles of Triton X-100 and phospholipid. Important features of the "dual-phospholipid" model are: the use of the nonionic surfactant as an inert matrix that may influence lipid conformation but does not interact with the enzyme; the involvement of 2 lipid molecules in a single cycle of catalysis as an explanation for the "surface dilution" phenomenon; the requirement of an ordered reaction whereby divalent metal ion binds prior to phospholipid binding; the induction of lipid substrate of an asymmetric dimer structure for the enzyme.