The Inactivation of Trypsin. I

In most of the early work of the kinetics of enzyme action it was tacitly assumed that enzyme reactions obeyed the law of mass action and that they represented a special case of homogeneous catalysis. As the individual enzymes were studied more carefully, however, itbecame apparent that few, if any, obeyed the law of mass action in its simplest form. Several authors have, therefore, taken the view that enzyme reactions should be considered as occurring in heterogeneous systems, and that owing to their colloidal nature they do not conform to the law of mass action. On the other hand, Tammann, Michaelis, Arrhenius, 1 Euler, ~ Taylor, 3 and others consider that in general the law of mass action does hold and that the apparent divergencies are due to secondary reactions. The author has found that the peculiarities of pepsin digestion may be accounted for in this way. I t seems possible to explain the kinetics of an enzyme hydrolysis fairly well from either point of view. I t is possible to find very close analogies on the one hand with ordinary homogeneous catalysis, and on the other hand with heterogeneous catalysis. From the theoretical side it has been stated that since most enzymes are admittedly colloidal it is not justifiable to apply the law of mass action to them. I t may be pointed out, however, that the work of Perrin and of Svedberg 4 has shown that colloidal solutions obey the gas laws very well, in fact, much better than do ionized substances. Since the law of mass