Synergistic and antagonistic effects of α-amylase and amyloglucosidase on starch digestion

The influence of biomacromolecular physical structure on the kinetics of degradation with exo-acting or a mixture of endo- and exo-acting enzymes was studied using three physical forms of maize and potato starch, amyloglucosidase (exo-acting) and α-amylase (endo-acting) as exemplars. For starch in granular form, there was synergism between the enzymes in the production of glucose. In contrast, endo- and exo-acting enzymes showed antagonistic effects in digestion of cooked starches. Antagonism was ascribed to the rapid production of low molecular weight oligomers by α-amylase, which are less efficiently digested by amyloglucosidase than polymeric substrates. The rates of digestion of swollen granule ghosts cooked under low shear conditions were slower than starches cooked under high shear conditions that prevent granule ghost formation. There was also an enzyme-resistant fraction present in granule ghosts, in contrast to high shear cooked starches that were fully digested under the conditions used.