NMR STRUCTURES OF PHOSPHOLIPASE A(2) REVEAL CONFORMATIONAL-CHANGES DURING INTERFACIAL ACTIVATION

It has long been proposed that the higher activity of phospholipase A( 2) (PLA(2)) for substrates presented as multimolecular aggregates comp ared to dispersed molecules (interfacial activation) arises due to a c onformational change in the enzyme, X-ray studies have, however, faile d to identify any such change. Here we report the solution structures of porcine pancreatic PLA(2) both free and as a ternary complex with m icelles and a competitive inhibitor, Important differences between the se structures indicate that conformational changes may play an importa nt role in the mechanism of interfacial activation in PLA(2)s.