The catalytic mechanism of alpha-amylases based upon enzyme crystal structures and model building calculations.

Based upon the known crystal structures of Taka-amylase A and the recently refined Porcine pancreatic alpha-amylase inhibitor complex a mechanism of catalysis in amylase active centers is proposed. The mechanism differs significantly from the well-known lysozyme model of catalysis. The hydrolysis is catalyzed by three carboxyl groups and its starts from a water nucleophilic attack and opening of the glucose ring in the catalytic center rather than from protonation of the glycosidic oxygen. The main supporting experimental observations are briefly discussed.