372 



CHEMICAL DYNAMICS 



kinase obtained from the succus entericus of the duodenum. 

 The result of these investigations was to show that the synthetic 

 polypeptids can be divided into two distinct classes, members 

 of the one class being hydrolysed or (if racemic) partially hydro- 

 lysed by the trypsin; members of the other class not being 

 hydrolysed by trypsin. The various polypeptids employed by 

 Fischer and Abderhalden were distributed between these two 

 classes as follows: 



Hydrolysed 



* Alanyl-glycin 



* Alanyl-alanin 



* Alanyl-leucin A 



* Leucyl-isoserin A 

 Glycyl-1-tyrosin 

 Leucyl-1-tyrosin 



* Alanyl-glycyl-glycin 



* Leucyl-glycyl-glycin 



* Glycyl-leucyl-alanin 



Not Hydrolysed 

 Glycyl-alanin 

 Glycyl-glycin 

 Alanyl-leucin B 

 Leucyl-alariin 

 Leucyl-glycin 

 Leucyl-leucin 

 Aminobutyryl-glycin 

 Aminobutyryl-aminobutyric acid A 

 Aminobutyryl-aminobutyric acid B 

 Valyl-glycin 



Alanyl-leucyl-glycin 



Dialanyl-cystin 



Dileucyl-cystin 



Tetraglycyl-glycin 



Triglycyl-glycin ester 



d-alanyl-d-alanin 



d-alanyl-1-leucin 



1-leucyl-l-leucin 



1-leucyl-d-glutamic acid 



Glycyl-phenylalanin 



Leucyl-prolin 



Diglycyl-glycin 



Triglycyl-glycin 



Dileucyl-glycyl-glycin 



d-alanyl-1-alanin 



1-alanyl-d-alanin 



1-leucyl-d-leucin 



d-leucyl-1-leucin 



The compounds which are marked by asterisks were racemic. 

 Of all these the hydrolysis proved to be asymmetric and only the 

 naturally-occurring stereo-isomer was attacked. 



There is thus a remarkable correlation between the ability of 

 these enzymes to attack certain amino-acid unions and the occur- 

 rence of these unions among the natural proteins which these 

 enzymes attack in the ordinary course of events. As we shall 

 see in the following chapter there are many excellent reasons 

 for believing that the action of the proteolytic enzymes, like 

 that of many of the inorganic catalysors, is dependent upon the 

 formation of intermediate compounds of the enzyme with the 

 substrate. It appears highly probable, therefore, that the enzyme 



