The kinetics of amylolysis : Part III. Effect of self-inhibition on the kinetic constants of beta-amylolysis

Abstract

For beta-amylolysis, the number of bonds split per effective enzyme-substrate encounter has been determined with amyloses having various degrees of polymerization (d.p.), labelled with 14C. The degradation is shifted in the direction of the “single chain mechanism” with increasing d.p. By taking into account the “inactive, non-reacting” collisions leading to “self-inhibition”, the number of bonds split per “reactive” and “non-reactive” enzyme-substrate encounter was established. From these data, and from the inhibition constant of the inner D-glucose residues of the amylose chain, in conjunction with the Michaelis constant extrapolated to d.p.  4, the actual rate constants for the formation and dissociation of the “reactive” enzyme-substrate complexes and for the formation and dissociation of the “non-reactive” enzyme-substrate complexes were determined. It was found that the rate constants for the formation of the “reactive” complexes decrease slowly with the increase of “self-inhibition”, whereas those for the dissociation of these complexes decrease to a greater extent.