106 THE AMINO ACIDS 



Acetone 

 Bodies 



CO a + H a O 

 CH a 



COOH 



Homogentisic acid 



In these transformations homogentisic acid is an 

 important intermediary product which at times appears 

 in the urine. (See Alkaptonuria.) In harmony with 

 the idea that homogentisic acid is an intermediary 

 product in the decomposition of tyrosine and pheny- 

 lalanine is the demonstration that the liver may form 

 acetone from homogentisic acid. 



Little definite is ^ known concerning intermediary 

 stages in the fate oi trytophane* in the human body. 



Arginine undoubtedly undergoes hydrolysis by the 

 enzyme arginase yielding urea and ornithine and the 

 latter may also yield urea. 



NH 3 



C = NH 

 I 

 NH.CH a .CH a .CH a .CH.NH a .COOH + H a O = 



Arginine 



