A Kinetic Model to Explain the Maximum in alpha-Amylase Activity Measurements in the Presence of Small Carbohydrates

Baks, T.; Janssen, A.E.M.; Boom, R.M.


The effect of the presence of several small carbohydrates on the measurement of the -amylase activity was determined over a broad concentration range. At low carbohydrate concentrations, a distinct maximum in the -amylase activity versus concentration curves was observed in several cases. At higher concentrations, all carbohydrates show a decreasing -amylase activity at increasing carbohydrate concentrations. A general kinetic model has been developed that can be used to describe and explain these phenomena. This model is based on the formation of a carbohydrate-enzyme complex that remains active. It is assumed that this complex is formed when a carbohydrate binds to -amylase without blocking the catalytic site and its surrounding subsites. Furthermore, the kinetic model incorporates substrate inhibition and substrate competition. Depending on the carbohydrate type and concentration, the measured -amylase activity can be 75% lower than the actual -amylase activity. The model that has been developed can be used to correct for these effects in order to obtain the actual amount of active enzyme