Theoretical studies of the electrostatic interactions in aspartic proteinases, intramolecular interactions in pepsin and penicillopepsin

A semi-empirical approach has been used to estimate the intramolecular electrostatic interactions in pepsin and penicillopepsin. The pH-dependence of the free energy electrostatic term was calculated, and the pH-dependence of the domain interactions has been estimated. As it was shown, the contribution of electrostatic interactions is rather small for the stabilization of the native structure. At the same time the electrostatic repulsion between domains increases with the increase of pH. The later can be the cause of the alkaline denaturation of pepsin and domain mobility.