THE PROTEINS AND THEIR METABOLISM 



80 



3. Oniitliin or a-amino 5-amino valeriauic acid. 

 o-CH,NH 2 



Y-CIL 



a-CIINHo 



I 

 COOII 



3. Arginin or a-amino 5-guanidin valerianic acid. 

 NH 



ii 

 S-CHoNH C NH 2 



Y-CH 2 



o-CHNH, 



COOII 



These substances are strongly alkaline in reaction. The last substance, 

 on hydrolysis with alkali or an enzyme known as argina.se, splits into urea 

 and ornitliin. This latter substance is not found as such among the pro- 

 tein cleavage products. 



K. Aromatic amino acids. 



1. Phenyl-alanin or a-amino '/3-phenyl propionic acid. 



CH 



/ \ 

 HC CH 



HC 



CH 



\ 



c 



CHo 



CIINH 2 



COOII 



Phenvl radical 



Alanin radical 



