242 



INACTIVATION OF TRYPSIN. I 



case.^^ The action of pepsin gives rise to substances which inhibit 

 pepsin but which are themselves attacked by trypsin. 



TABLE IV. 



Retarding Effect of Various Solutions of Hydrolyzed Gelatin or Casein on the 



Action of Trypsin. 



25 cc. of gelatin pH 6.2, specific conductivity 2 X 10-^, plus 1 cc. of solution 

 noted. 1 cc. of trypsin added and time required to cause a change of 10 points 

 (bridge reading) in the conductivity determined. In each case the amount of 

 hydrolyzed protein added is equivalent to 0.2 gm. of the original protein. 



Solution. 



(a) Gelatin hydrolyzed by trypsin . 

 (fi) Casein hydrolyzed by trypsin . . 



(c) Casein completely hydrolyzed 



(d) Gelatin completely hydrolyzed 



by acid . . 

 by alkali . 



by acid . 

 by alkali . 



(e) Solution (a) after 24 hrs. dialysis. 

 Solution (b) after 24 hrs. dialysis. 



Method of Determining the Amount of Retardation. 



It has already been shown that the rate of hydrolysis of gelatin 

 alone as determined by the change in conductivity is identical with 

 that found by the formol titration. Fig. 4 shows that this is also the 

 case when the hydrolysis has been retarded by the addition of inhibitor 



^* Northrop, J. H., /. Gen. Physiol., 1921-22, iv, 57. 



