A MOLECULAR-MODEL FOR INTERFACIAL ACTIVATION IN PHOSPHOLIPASE A(2)

Electrostatic calculations predict that amino-terminal conformation an d ionisation contribute significantly to transition state stability in phospholipase A(2), so that control of these factors by binding to ag gregated substrate provides a plausible mechanism for interfacial acti vation. In particular, it is suggested that a part of the pH dependenc e of interfacial activity may arise from transient deprotonation of an ordered amino-terminus. Interface charge and the detailed structure o f the interfacial complex are also predicted to influence catalytic ac tivity. The model is compared with available biochemical data. (C) 199 7 Federation of European Biochemical Societies.