The kinetics of the combination reaction between enzyme and substrate

A stochastic analysis has been made for enzyme-substrate combination reaction systems. The relationship between diffusion-encounter and effective collision has been discussed. A new equation, derived for calculating the combination rates of multiple-active-site reaction systems, will serve to provide a theoretical basis for experimentally investigating the combination activation energies of liquid phase fast reaction systems. The calculated results show that the usual method employed to estimate the combination rates of multiple-active-site reaction systems is applicable only to the large activation energy concerned, but not to the small. In the latter case, the coupling effect among active sites should not be overlooked. In this paper, the kinetic characteristics of liquid phase fast reaction systems involving conformational changes are further discussed. A new method of separation of kinetic constants has been suggested and the relationship between measuring signal and multi-barrier reaction analyzed. On such a basis, we have derived a general equation which takes into account both the effect of the diffusion-limit and the effects of conformational changes and of solvents, in an attempt to provide a kinetic basis for further investigating the whole process of enzyme-substrate combination reactions.