178 ORGANIC AGRICULTURAL CHEMISTRY 



This shows why it is always necessary for the pancreatic juice 

 and intestinal juice to act together in the same region and on 

 the same food mass. 



The hydrolytic action of trypsin takes place in alkaline 

 solutions and is similar to that of pepsin in its chemical nature. 

 It differs, however, in the end products of the hydrolysis. 

 While pepsin hydrolysis of proteins yields mostly derived 

 proteins, proteoses, peptones and polypeptides with a small 

 amount of amino-acids, the action of trypsin yields mostly 

 amino-acids and only small amounts of the derived proteins. 

 Trypsin may produce the amino-acids from either original 

 protein or from derived protein. The final result then of the 

 action of the enzymes of the pancreatic juice upon protein food 

 is to convert them largely into the final end products, amino- 

 acids. 



It should also be mentioned that according to some authori- 

 ties trypsinogen may be activated by calcium salts, while others 

 claim that trypsin is formed by the action of calcium salts 

 upon another zymogen than trypsinogen. 



Intestinal Juice. Erepsin. — The juice secreted by the epi- 

 thelial cells of the small intestine and known also as succus enteri- 

 cus contains another enzyme connected with the digestion of pro- 

 teins in addition to the enterokinase just mentioned. This is 

 the proteolytic enzyme erepsin. Erepsin differs from the two 

 proteolytic enzymes thus far considered in that its action is 

 almost wholly upon the derived proteins; proteoses, peptones 

 and polypeptides. These compounds are present after protein 

 food has been acted upon by pepsin and trypsin, and they are 

 hydrolyzed by erepsin to the final end products, amino-acids. 

 Erepsin does possess the power of hydrolyzing a few original 

 proteins, viz. caseinogen of milk and protamines and histones. 



This completes, therefore, the digestion of protein food, which 

 by the combined and supplementary action of the three pro- 

 teolytic enzymes, pepsin of the gastric juice, trypsin of the 

 pancreatic juice and erepsin of the intestinal juice, are hydrolyzed 

 to the final end products, amino-acids. The protein food is 



