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 rece ntly refined Porcine pancreatic a-amylase inhibitor complex a mechanis m of catalysis in amylase active centers is proposed. The mechanism di ffers significantly from the well-known lysozyme model of catalysis. T he hydrolysis is catalyzed by three carboxyl groups and it starts from a water nucleophilic attack and opening of the glucose ring in the ca talytic center rather than from protonation of the glycosidic oxygen. The main supporting experimental observations are briefly discussed. ( C) 1994 Academic Press, Inc.