124 PHYSIOLOGY OF ALIMENTATION. 



Alkali-pro teinase shows, in common with other ferments, 

 an increase in the velocity of reaction with an increase in the 

 concentration of the enzyme. This holds true, however, 

 only within certain limits of time, concentration of both 

 enzyme and protein, etc. In infinite time a small amount 

 of the ferment will bring about as much protein digestion 

 as a larger one. In no case is all the protein split into the 

 digestion products to be discussed below. Unless the 

 products of digestion are removed as soon as formed the 

 proteolysis is incomplete, or, as it is ordinarily put, an 

 accumulation of the products of digestion interferes with the 

 further action of the enzyme. This is probably due to the 

 fact that the activity of the enzyme is reversible. When the 

 products of the protein digestion are removed by dialysis as 

 soon as formed, a small amount of the enzyme will split an 

 indefinite amount of the protein. 



When alkali-proteinase is allowed to act upon proteins, 

 the protein molecule is broken up into a number of simpler 

 substances. According to the generally accepted view, the 

 decomposition of the protein is brought about by a series of 

 successive cleavages. Shortly after the ferment has begun 

 its work, there can be recognized the proteases, and later 

 the peptones, in the sense in which KUHNE used these terms. 

 Before the ultimate products of tryptic digestion are reached, 

 substances which in their chemical complexity stand between 

 them and the peptones,' the peptides of EMIL FISCHER and 

 ABDERHALDEN, 1 are formed. These peptides represent com- 

 binations of amino-acids, and depending upon whether two, 

 three, four, or many molecules of the same or different 

 amino-acids enter into the composition of the peptide, we 

 distinguish between di-, tri-, tetra-, and polypeptide bodies. 

 The ultimate products of tryptic digestion are mono- and 



1 EMIL FISCHER and ABDERHALDEN: Zeitschrift fur physiologische 

 Chemie, 1903, XXXIX, p. 81; ABDERHALDEN: Lehrbuch d. physiol. 

 Chemie, Berlin, 1906, Eiweissstoffe. 



