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

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.