JOHN H. NORTHROP 259 



— r = k . m 



C- 



n 



where x is the amount adsorbed, C is the concentration of the sub- 

 stance remaining in the solution, and m is the amount of adsorbent 

 (or the area of the adsorbing surface), k and n are constants. In 

 the present experiments it cannot well be assumed that the enzyme 

 is adsorbed by the inhibiting substance since there is no evidence 

 that this is in other than true solution. It would be necessary to 

 suppose therefore that the inhibiting substance is adsorbed by the 

 enzyme. The amount of enzyme would therefore be represented 

 by w in the above formula and there would be no way to determine 

 how much was combined and how much was free since there is no term 

 in the equation to represent the amount of the adsorbent (in this case 

 the enzyme) which is combined. 



Hedin'' has found that trypsin is adsorbed by charcoal and that 

 the equilibrium in this case is that demanded by the adsorption 

 formula. Hedin's experiments are, however, not contradictory to 

 those described in this paper since it is quite possible that trypsin may 

 be adsorbed by charcoal and yet react with other substances accord- 

 ing to the law of mass action. This is known to be the case with 

 acetic acid and many other substances. 



SUMMARY. 



1. A study has been made of the equilibrium existing between 

 trypsin and the substances formed in the digestion of proteins which 

 inhibit its action. 



2. This substance could not be obtained by the hydrolysis of the 

 proteins by acid or alkali. It is dialyzable. 



3. The equilibrium between this substance (inhibitor) and trypsin 

 is found to agree with the equation, 



trypsin -f^inhibitor ^ tr>-psin-inhibitor 



The equilibrium is reached instantaneously and is independent of the 

 substrate concentration. If it be further assumed that the rate of 



» Hedin, S., Biochem. J., 1906, i, 484; Z. physiol. Chem., 1906-07, i, 497. 



