JOHN H. NORTIJROP 



67 



Action of Trypsin on Gelatin Partiu^y Biydrolyzed by Pepsin. 



The results of this experiment are she ,n in Fig. 6. The final point 

 reached by the trypsin hydrolysis is independent of the amount of 

 hydrolysis previously accomplished . ' the pepsin. The linkages 

 hydrolyzed by pepsin are therefore evic "- itly also hydrolyzed by tryp- 

 sin so that it is immaterial whether the /epsin acts on the protein or 

 not, as far as the final stage reached is c-t>ncerned. It is possible that 

 the rate of hydrolysis may be greater if ti>,e pepsin acts first since Fig. 2 

 showed that those linkages attacked byi pepsin are among the most 

 resistant to the action of trypsin. The experiment confirms the result 

 shown in Fig. 2, that trypsin hydrolyzes the same linkages as does 

 pepsin but also attacks others which are split slowly if at all by pepsin. 



TABLE IV. 



Addition of Trypsin to Gelatin Partially Hydrolyzed by Alkali. 



Action of Trypsin on Gelatin Previously Hydrolyzed by Alkali. 



The results of this experiment are given in Fig. 7 and Table IV. 

 Alkali hydrolysis evidently follows very nearly the same course as 

 does trypsin hydrolysis since the increased hydrolysis due to the 

 addition of trypsin becomes rapidly less and stops when the alkali 

 hydrolysis has reached about 13 cc. This corresponds to the point 

 reached by trypsin alone. The linkages split must therefore be the 

 same in both cases. In this case also no evidence of a reversal of the 

 action was observed although the experiment was carried much 

 further than is shown in the figure. 



