504 



KINETICS OF TRYPSIN DIGESTION 



TABLE X. 



Rate of Hydrolysis of Casein, Gelatin, and a Mixture of Casein and Gelatin. 



4 cc. dialyzed trypsin were added to each solution at 34°C. 5 cc. samples were 

 removed after 0.10, 0.25, 0.50, 1.50, and 3.0 hrs. and run into 25 cc. of water con- 

 taining 10 cc. 0.20 N HCl. 2 cc. of this solution (equivalent to 0.33 cc. of original 

 solution) were analyzed for amino nitrogen by Van Slyke method. 



Casein solution. 4 gm. casein in 100 cc. phosphate buffer. m/IO, titrated to 

 pH 7.5. 



Gelatin solution. 3.5 gm. gelatin in 100 cc. phosphate buffer. pH7.5. 

 •Gelatin-casein solution. 4 gm. casein + 3.5 gm. gelatin in 100 cc. phosphate 

 buffer as above. pH 7.5. 



/. Rate of Hydrolysis Depends on the Concentration of the Enzyme 

 Substrate Compound. 



(a) The same enzyme acts on both casein and gelatin. 



In this case the rate of hydrolysis of the mixture must be less than 

 the rate of hydrolysis of the casein alone, since it has already been 

 assumed, in order to account for the rate-concentration curve, that 

 the enzyme is saturated by 4 per cent casein. The addition of gela- 

 tin to the system will therefore remove some enzyme from the casein 

 to combine with the gelatin and since the gelatin hydrolyzes more 

 slowly than the casein, the result will be a decrease in the rate of 

 digestion. This is contradicted by the experiment. 



