228 INACTIVATION OF TRYPSIN. I 



action can be derived from the gas laws and the two laws of thermody- 

 namics, there seems to be every reason to suppose that colloidal 

 solutions should obey the law of mass action. The question appears to 

 be one of experimental fact. If it is found that enzyme reactions may 

 be accounted for on the basis of the law of mass action there seems to 

 be no theoretical reason to disregard this fact and attempt an explana- 

 tion from the point of view of adsorption. Most of the experimental 

 evidence at hand, however, consists of data on the kinetics of the reac- 

 tions. It is a matter of experience that conclusions based on kinetics 

 alone are exceedingly uncertain especially when, as is the case with en- 

 zymes, the equations used contain at least two constants. It seems 

 better therefore to attack the question from another angle. It is 

 known that various substances retard the action of enzymes and that 

 there must therefore be some kind of a reaction between these sub- 

 stances and the enzyme (or the substrate). If it could be shown that 

 this reaction conformed accurately to the law of mass action it would 

 furnish experimental justification for the application of this law to the 

 enzyme reaction in general, at least as far as the particular enzyme is 

 concerned. It has been shown by the author that the equilibrium 

 between pepsin and the products formed by its action on proteins 

 does conform quite accurately to the law of mass action.^ Euler and 

 Svanberg^ have shown that the inactivation of invertase by various 

 crystalloid substances is due to an equilibrium which is accurately 

 expressed by the same law. The experiments described in this paper 

 were undertaken with the view of determining whether or not the 

 same condition is found in the case of trypsin. As wiU be seen from 

 these experiments, the reaction between trypsin and the substances 

 which inhibit its action may be accurately accounted for by the law 

 of mass action. 



It is known that various substances inhibit the action of trypsin. 

 Bayhss^ found that some, at least, of the products formed by the 

 action of the enzyme on proteins inhibited its action and also rendered 

 it more stable. He concluded, therefore, that they combined in some 



5 Northrop, J. H., /. Gen. Physiol , 1919-20, ii, 471. 



® von Euler, H., and Svanberg, O., FernientforscJmng, 1919-20, iii, 330; 1921, 

 iv, 142. 



'Bayliss, W. M., Arch. Biol, 1904, xi, Suppl. 261. 



