Structure and Enzyme Reactions. Parts I and II

Abstract

THE question of the applicability of the law of mass action to reactions in the living organism has long been considered as one of the most important problems in the dynamics of life phenomena. The chief difficulty in the solution of this problem is that these reactions take place in a heterogeneous medium, in which, apart from purely chemical reactions, we encounter processes of diffusion, and the whole question is further complicated by the fact that most of the reacting substances are in the colloidal state. For this reason, all except ionic reactions and those connected with the last stages of disintegration or the first stages of synthesis, are reactions involving all those factors connected with reactions of hydrophile colloids in heterogeneous media, i.e. reactions of adsorption, and in general, all surface phenomena, to which the law of mass action is, at least in the state of presen day knowledge, inapplicable. In this paper we shall consider the questions of the applicability of the law of mass action to enzyme reactions. In general, in so far as the kinetics of enzyme reactions in homogeneous systems are concerned, if we can, in general, consider any enzyme system to be homogeneous, these conform to the law of mass action, as has been pointed out by Michaelis and Menten [1913] and Josephson [1925]. It is a question whether the same holds good for enzyme reactions in vivo, and whether reversible enzyme reactions may here be interpreted on the basis of the concentration of the substrates. Here we encounter a whole series of incomprehensible facts, apparently irreconcilable with the law of mass action, a classical example of this being the different behaviour of amylase in vitro and in vivo.