Crystallographic complexes of glucoamylase with maltoligosaccharide analogs: relationship of stereochemical distortions at the nonreducing end to the catalytic mechanism

The extent of stereochemical distortion as a function of pH for two related pseudotetrasaccharide inhibitors, acarbose and D-gluco-dihydrocarbose, were analyzed by high-resolution crystallographic studies of glucoamylase. Distortions in the nonreducing end of ligands bound to the active site of glucoamylase are relatively small, indicating that electrostatic charge stabilization of the transition state may be the dominant factor in promoting the development of a glucopyranosyl cation in the active site of glucoamylase.