258 INACTIVATION OF TRYPSIN. II 



Does Trypsin Form a Compound with Gelatin? 



The hypothesis which has been found to account quantitatively for 

 the experiments described in this paper contains the assumption that 

 the velocity of hydrolysis is proportional to the concentration oi free 

 enzyme. That is, the enzyme would enter into the formula for the 

 kinetics of the reaction just as would the hydrogen ion concentration 

 in the case of a reaction catalyzed by hydrogen ions or as one of the 

 reactants in any chemical reaction and the time presumably consists 

 of the time required for a molecule of enzyme to come in contact with 

 a molecule of gelatin. The idea was proposed by Brown^ and has 

 since been elaborated by various authors that enzymes combine with 

 the substances which are hydrolyzed by them and that the velocity 

 of the reaction depends on the speed of decomposition of this com- 

 pound, while the time for the compound to form is negligible. If 

 this were true in the case of trypsin it is clear that the mechanism for 

 the equilibrium between trypsin and the inhibiting substance which 

 has been found to agree with the experiments could not be verified 

 since it would be necessary to allow for the amount of trypsin com- 

 bined with the gelatin. If this mechanism is correct therefore it seems 

 necessary to conclude that the amount of trypsin combined with the 

 gelatin at any one time is neghgibly small and that the limiting time 

 element is really the time required for the compound to form as is the 

 case in other chemical reactions. The same reasoning evidently applies 

 to pepsin hydrolysis and to invertase (Euler^), since in both these 

 cases it has been found that the equilibrium between the enzyme 

 and an inhibiting substance can be quantitatively accounted for by 

 the assumption that the rate of hydrolysis is proportional to the free 

 enzyme. This question will be discussed in another paper. 



Can the Results he Accounted for by the Adsorption Formula? 



The adsorption formula as given by Freundlich^ and as usually 

 used is written 



^ Brown, A. J., /. Chem. Soc, 1902, Ixxxi, 373. 



^ Freundlich, H., Kapillarchemie: Eine Darstellung der Chemie der Kolloide 

 und verwandter Gebiete, Leipsic, 1909. 



