84 THE CHEMICAL COMPOSITION OF THE BODY 



AMINO ACIDS OBTAINED ON HYDROLYTIC CLEAVAGE OF WHEAT PROTEIN, 



It has been indicated that the synthesis in very simple proteins can be 

 attained by combining amino acids. A synthesis, however, can be brought 

 about by the reversible action of the digestive enzymes. Recently Taylor 

 has been able to synthesize a simple protein, a protamine, by the reversible 

 action of a trypsin on amino acids which were previously obtained by the 

 digestion of the protamine. Cleavage by enzymes is a hydrolysis of the 

 same type as that mentioned above by the use of the mineral acids. In 

 the concentration of the products of a digestion the enzymes act in the 

 reverse manner and resynthesize these substances on which they have pre- 

 viously acted. Robertson has demonstrated a similar reversible action of 

 pepsin on paranuclein derived from a digestion of casein. The reversible 

 action may be indicated by the equation: 



PROTEIN + WATER + AMINO ACIDS. 



These experiments lend a new stimulus to the efforts to build up proteins 

 in the chemical laboratory along the lines of catalytic action of enzymes. 

 The proteins of the various tissues of the body are quite different in character 

 and chemical constitution and are different from the protein of the diet. 

 In digestion there is a breaking down of the protein in the food into simple 

 combinations of amino acids or the acids themselves, and subsequently 

 there is a selection of certain amino acids and resynthesis of characteristic 

 proteins by the cells of the tissues. 



