Kinetic analysis and enzyme concentration effect relevant to dependence of amylolysis of starch granules on specific surface area concentration

The kinetics and enzyme concentration effects on the amylolysis of rice, maize, and potato starch granules by porcine pancreatic α-amylase (PPA) were analyzed. The Km values of the native starches, when expressed as a function of surface area concentration, were similar to each other. Inconsistencies in Vmax values can be attributed to the deviations from real values of the surface area concentration. The deviations were confirmed by that the initial rate differences among the native starches with the same apparent surface area concentration were observed at low enzyme concentrations. Kinetic parameters of dimethyl sulfoxide (DMSO)-solubilized native starches showed no significant difference, demonstrating that structural and compositional differences of starches do not affect amylolysis. The resistance of starch granules against amylolysis predominantly affects the Vmax, and as a result, the kcat is reduced compared with DMSO-solubilized starch. In conclusion, the kinetic analysis and enzyme concentration effect confirmed that surface area concentration mainly affects the initial hydrolysis rate of native starch granules.