198 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



guanidine-a-amino-valerianic acid ; guanidine has the formula 

 NH=C(NH 2 ) 2 , and arginin, therefore, may be written 



NH 2 NH 2 



| H H H | / 



NH= C N C C C C C 

 H H H H H \ 



OH 



Arginin is really a compound of guanidine with ornithin a 

 derivative of which is found in the urine of birds. Ornithin 

 is a-S-di-amino-valerianic acid. 



Lysin is a-e-di-amino-normal-caproic acid, i.e. 



CH 2 NH 2 CH 2 CH 2 CH 2 CHNH 2 C0 2 H 

 It occurs in greatest quantities in casein and gelatine. 



Histidin has a rather more complex constitution than 

 either of the other two hexone bases. It is probably a 

 condensation product formed by elimination of NH 3 from 

 arginin and its constitutional formula may be provisionally 

 written thus : 



CH N 



C HN 



I 

 CH 2 



CH NH 2 

 COOH 



Amino-dicarboxylic Acids 



Of these the following may be mentioned, asparlic acid or 



CHNH 2 C0 2 H 

 amino-succinic acid, , and glutaminic acid or 



CH 2 C0 9 H 

 a-amino-glutaric acid, COOHCHNH 2 CH 2 CH 2 C0 3 H. 



