CHAPTER XV 

 THE HYDROLYSIS OF THE POLYPEPTmS 



1. The Hydrolysis of Polypeptids by Proteolytic Enzymes. — 



By the aid of the various hydrolysing agencies the synthetic poly- 

 peptids are capable of being spht, with successive additions of 

 the elements of water, into their constituent amino-acids. Among 

 these hydrolysing agencies must be reckoned a number of the 

 protein-splitting enzymes which are found in a variety of tissues, 

 tissue-extracts and secretions. 



The action of the enzymes of the pancreas (trypsin and, pre- 

 sumably, others) upon the dipeptids was first investigated by 

 Fischer and Bergell (12) who acted upon solutions of various 

 dipeptids with pancreas-extract. They found that: 



glycyl-glycin 



/3-naphthalenesiilphoglycyl-d-aIamn 

 /3-naphthalenesulpho-d-alanyl-glycin 

 Di-^-naphthalenesulphotyrosyl-dl-leucin 



while 



/S-naphthalenesulphoglycyl-l-tyrosin 



/S-naphthaleneglycyl-dl-leucin 



carboxethyl-glycyl-dl-leucin 



glycyl-l-tyrosin 



leucyl-alanin 



alanyl-leucin 



leucyl-leucin 



were not hydrolysed. 



were hydrolysed. 



In the course of these investigations the exceedingly interest- 

 ing fact was encountered that the racemic compounds are hydro- 

 lysed asymmetrically by the pancreas extract; thus only 1-leucin 

 was obtained by the action of the extract upon carboxethyl- 

 glycyl-d-1-leucin, the remainder (containing d-leucin) not being 

 acted upon. Now l-leucin is the naturally occurring variety, the 

 form, that is, which is found in the proteins. 



These investigations were greatly extended by Fischer and 

 Abderhalden (11) who employed a pancreatic juice prepared 

 by Pavlov from a pancreatic fistula and activated by entero- 



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