Action of amyloglucosidase on oxidised amylose.

The Michaelis constant and maximal velocity of alpha-amylase-free amyloglucosidase decrease with increasing periodate oxidation of amylose. These kinetic features have been explained on the basis of competitive inhibition by the oxidised non-reducing end of the (1 leads to 4)-alpha-D-glucan chain with the active centres of the enzyme. A kinetic model is proposed to demonstrate this special kind of inhibition where the concentration of inhibitor is directly proportional to the substrate concentration. The experimental data fitted this model, and the plots of 1/Km and 1/V against the ratio of oxidised/unoxidised non-reducing end-groups were straight lines.