Mechanism of the adsorption of pancreatic alpha-amylase onto starch crystallites

The mechanism of the adsorption of alpha-amylase onto crystalline starch is still little understood despite its involvement in many industrial applications. Our purpose was first to identify the relationships between adsorption and catalysis, and secondly to characterise the mode of adsorption. Initially, the enzyme has a high affinity for starch crystallites as shown by its rapid adsorption onto the spherulite surface. The kinetics of adsorption ar well described by a logarithmic relationship. Adsorption precedes catalysis and is a prerequisite step for the hydrolysis of crystalline starch. Decrease in the rate of hydrolysis is accompanied by desorption of porcine pancreatic alpha-amylase. The resistance of crystalline starch to attack by amylase in vitro probably reflects the increasing amounts of enzyme-product complexes present in solution as the hydrolysis proceeds. The influence of electrostatic adsorption was studies by varying either the pH or the ionic strength.