CHAPTER III 

 PROTEIN-DIGESTION IN THE INTESTINE 



Erepsin. In the preceding chapters we have dealt in 

 some detail with pepsin and trypsin. Our attention is now 

 turned to a third ferment directly involved in protein- diges- 

 tion, the erepsin of the intestinal secretion, the discovery of 

 which is due to the acuteness of observation of Otto 

 Cohnheim. 



Erepsin is an enzyme which does not act upon most of 

 the native albumins, but reduces albumoses and peptones to 

 crystallizable products. "In connection with the action of 

 erepsin upon the individual intermediate substances between 

 albumin and the amino acids," Cohnheim observes, "it 

 should be said that peptones, that is peptones corresponding 

 to Kiihne's conception, lose the ability to respond to the 

 biuret-reaction very quickly, within minutes or hours, when 

 in contact with erepsin-solutions, very much more rapidly 

 than I have ever observed when they are brought in contact 

 with active pancreatic extract. Erepsin acts much more 

 slowly upon the various albumoses, weeks elapsing before the 

 disappearance of the biuret-reaction, which is in fact a rather 

 deceptive phenomenon. Kutscher, Seemann and Weinland, 

 who have worked with erepsin only upon albumin and who 

 because of the slowness of the loss of biuret-reaction have 

 denied any real importance to erepsin in digestion, are con- 

 tradicted by these differences. ' ' The influence of erepsin is, 

 however, not limited to the protein derivatives of higher 

 molecular composition. Polypeptids are also split, as 

 shown by the investigations of Abderhalden and his associ- 

 ates and the studies of H. Euler. Thus the albumoses and 

 peptones formed from ingested proteins by the action of 



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