A molecular model for interfacial activation in phospholipase A2

Electrostatic calculations predict that amino-terminal conformation and ionisation contribute significantly to transition state stability in phospholipase A2, so that control of these factors by binding to aggregated substrate provides a plausible mechanism for interfacial activation. In particular, it is suggested that a part of the pH dependence of interfacial activity may arise from transient deprotonation of an ordered amino-terminus. Interface charge and the detailed structure of the interfacial complex are also predicted to influence catalytic activity. The model is compared with available biochemical data.