Inhibition of α-amylase activity by cellulose: kinetic analysis and nutritional implications

We report on inhibition of α-amylase activity by cellulose based on in vitro experiments. The presence of cellulose in the hydrolysing medium reduced the initial velocity of starch hydrolysis in a concentration dependent manner. α-Amylase adsorption to cellulose was reversible, attaining equilibrium within 30 min of incubation, and showed a higher affinity at 37 °C compared to 20 and 0 °C. The adsorption was almost unchanged in the presence of maltose (2.5-20 mM) but was hindered in the presence of excess protein, suggesting non-specific adsorption of α-amylase to cellulose. Kinetic analyses of α-amylase hydrolysis of maize starch in the presence of cellulose showed that the inhibition is of a mixed type. The dissociation constant (K_ic) of the EI complex was found to be ca. 3 mg/mL. The observed inhibition of α-amylase activity suggests that cellulose in the diet can potentially attenuate starch hydrolysis.