DERIVATIVES 



443 



AMINO ACIDS OBTAINED AS CLEAVAGE PRODUCTS OF 



PROTEINS. 



(i) Aliphatic Compounds. 



( Glycine or a-amino-acetic acid CH.^NHjCOOH 



Alanine or a-amino propionic acid CHgCHNHjCOOH 



Amino-butyric acid CH3CH0CHNH2COOH 



Amino-caproic acid CH3CH2CHXH.,CHNH2COOH 



Valine or a-amino-isovaleric acid 



CHaX 



>CH . CHNHoCOOH 

 CH3/ - 



Leucine or a-amino-isocaproic acid 



\CHCHXHNH,COOH 

 CH3/ 

 Isoleucine or a-amino-j3-methyl j3-ethyl propionic acid 



CVS \ 



' >CHCHNH,COOH 



Serine or a-amino jS-hydroxv propionic acid. 

 I CH2OHCHNH2COOH 



Mono-carboxylic 

 mono-amino acids. 



Dicarboxylic 

 mono-amino acids. 



Mono-carboxylic 

 di-amino acids 



Dicarboxylic 

 di-amino acid. 



I 



C Aspartic * or a-amino-succinic acid 

 j COOH CH^CHNHoCOOH 



I Glutamic * or a-amino-glutaric acid 

 '^ COOH CH2CHXHNHXOOH 



Ornithine or a-S-di-amino-valeric acid 



NH2CH2CH2CH.XHNH2COOH 

 Arginine or S-guanidine a-amino-valeric acid 

 /NH, 

 HN = C 



XnHCHsCH^CH^CHNHoCOOH 

 Lysine or a-e-di-amino-caproic acid 



NHoCHXHoCHaCH^CHNHaCOOH 

 Di-amino-trihydroxy-dodecanic acid j C12H26O5N2 



Cystine or di [j3-thio a-amino propionic] acid 

 CH,— S— S— CHjj 



CHNH2 

 COOH 



HNHa 

 OOH 



* The amides corresponding to these two acids, namely, asparagine 

 CONH2CH2CHNH2COOH and glutamine CONHaCHaCH^CHNHXOOH are 

 of considerable importance in plants. The former occurs in asparagus and 

 is produced in seeds which are allowed to germinate in the dark (Schulze, 

 " Landwirtsch. Gahrb.," 1878, 411), while the latter has been found in the 

 seeds of Cucurbita and many other plants (Schulze and Barbieri, " Ber. deut. 

 chem. Gesells.," 1877, 10, 199 ; Schulze, id., 1896, 29, 1882). Asparagine 

 and glutamine being readily hydrolysed by mineral acids, are not obtained 

 as cleavage products of proteins by the ordinary methods of chemical 

 hydrolysis, and for this reason are not quoted in the above list of cleavage 

 products. 



t The constitutional formula of this substance has not yet been 

 determined. 



