The relation of physical properties of native starch granules to the kinetics of amylolysis catalysed by porcine pancreatic α-amylase

Various native starch granules were tested as substrates for porcine pancreatic α-amylase and enzyme kinetic parameters obtained from initial rate studies. Surface area per kg weight values and gelatinisation enthalpies (ΔHgel) for the different granules were measured. ΔHgel was used as an indication of the degree of disorder within the starch granules. Km values, that are indicative of starch availability, decreased with the particle size but not in a linear fashion. The catalytic efficiency of amylase and the initial rate of catalysed hydrolysis were both significantly correlated with the surface area. Also, Km, catalytic efficiency (kcat/Km) and initial hydrolysis rate were all significantly correlated with ΔHgel. Thus the surface area of granules and the degree of order of starch have important influences on the initial rate at which native starch is digested by amylase. We believe that this is the first systematic report linking kinetic data with surface area and gelatinisation parameters of native starch.