CHAPTER II. 



o> AMINO-ACIDS AND OTHER BASES DERIVED FROM PROTEIN CONTAINING 

 A CARBOXYL-GROUP (UROCANIC AND KYNURENIC ACIDS). 



IN the monamino-acids, formed by the hydrolysis of proteins, the 

 acidic properties of the carboxyl-group are neutralised more or less 

 completely by an adjoining amino-group in the a-position, and only 

 the diamino-acids histidine, lysine, and arginine are bases. When the 

 amino-group is not in the a-position the basic character is more pro- 

 nounced, and the so-called w-amino-acids are feeble bases, being pre- 

 cipitated by phosphotungstic acid ; several of them are formed from 

 protein fission products by putrefaction, and these are described in this 

 chapter. 



The influence of the position of the amino-group on the acid dis- 

 sociation constant K a and on the basic dissociation constant K 6 is 

 evident from the following table (Ley [1909, p. 358]) : 



An ammo-acid may also be rendered basic by complete methylation 

 of the nitrogen atom, as in the betaines described in Chapter III. 

 o>-Amino-acids are produced by putrefaction in three ways ; 



1. By partial deaminization of a diamino-acid, as in the formation 

 of S-amino-valeric acid from ornithine : 



NH 2 . CH 2 CH 2 CH a CH(NH 2 )COOH + 2H = NH 2 . CH 2 CH 2 CH 2 CH 2 COOH + NH 3 . 



2. By the partial decarboxylation of a dibasic amino-acid, e.g. 

 the production of 7-amino-butyric from glutamic acid : 



COOH . CH(NH 2 ) . CH 2 . CH 2 . COOH = NH 3 . CH 2 . CH a . CH 2 . COOH + CO 2 . 



3. By the reduction of a cyclic amino-acid. Ackermann [191 1, 2] 

 and Neuberg [191 1, l] have recently shown that a-pyrrolidine car- 

 boxylic acid (proline) yields S-amino-valeric acid in putrefaction : 



33 3 



