Characterization of the subsite structure of the β-glucosidase from Aspergillus niger, an aspect of the mechanism of carbohydrate recognition

Steady-state kinetics on the reaction catalyzed by the β-glucosidase of Aspergillus niger were carried out to evaluate the kinetic parameters, Km and ko, for phenyl β-d-glucosides. The ko/Km values, which may relate to productive binding at subsites, were found to correlate with the substituent constant π (hydrophobicity), suggesting that subsite 2 has a hydrophobic character. A “hydrophobic-driven” mechanism is considered to contribute to the productive E–S complex for recognition of the substrate.