FURTHER FATE OF AMINO ACIDS 103 



As a general rule substances containing the aromatic 

 or benzene nucleus do not readily undergo complete 

 oxidation in the organism, the benzene nucleus remain- 

 ing unchanged. The amino acids derived from protein 

 hydrolysis, and containing this nucleus, namely, tyro- 

 sine, phenylalanine and tryptophane do suffer complete 

 disintegration, the benzene nucleus being disrupted. 

 There are at least two ways in which the aromatic 

 amino acids may be destroyed. In the first place the 

 following series of reactions may occur phenylalanine 

 being employed as a specific example. Phenylalanine 

 by oxidative deamination is first changed to phenyl- 

 pyruvic acid : 



COOH a ketone acid COOH 



I I 



CH.NH 8 C = O 



CH a ^vv^ CH 3 



I -5> - I 



C C 



/\ /\ 



HC CH HC CH 



II I II I 



HC CH HC CH 



CH CH 



Phenylalanine Phenyl-pyruvic acid 



