S. A. KOSER 245 



supplied in many different groupings. In addition, various methods of decomposition 

 are doubtless brought into play by different organisms and certain other factors exert 

 a pronounced influence upon the process, such as the supply of oxygen, the tonicity 

 of the medium, and the presence of other available nitrogenous and non-nitrogenous 

 compounds. 



The initial step in the process of utilization is usually a deamination or decar- 

 boxylation. Deamination may be accompHshed in a variety of ways: by reduction 

 with the formation of a saturated fatty acid, by oxidation with the formation of a 

 ketone acid, and by hydrolysis with the formation of a hydroxy acid. A simple mono- 

 amino acid such as alanine may be broken down as follows: 



CHj-CH-NH^-COOH-h H. . . . .CH3-CH.-COOH-1-NH3 



Propionic acid 

 CH3.CH-NH..C00H-h O . . . .CH3-CO-COOH+NH3 



Pyruvic acid 

 CH3-CH-NH.-C00H-HH,0. . . .CH3-CHOH-COOH-HNH3 



Lactic acid 



The ring structures such as those found in tyrosine, proline, histidine, and trypto- 

 phane, though not invulnerable, are more resistant to bacterial attack, and in many 

 instances only the side chain is used.' In tryptophane, for example, we have nitrogen 

 in the alanine side chain and in the indol ring. The side chain is utilized by many or- 

 ganisms while the ring structure is frequently left intact in the form of indol-propionic 

 or -acetic acid, skatol, or indol. Another type of change has been described by Raist- 

 rickj^" who found that histidine was converted to urocanic acid, an unsaturated acid, 

 by a number of organisms. 



HC 

 \ 



N— C • CH. • CH • NH. • COOH N— C • CH = CH • COOH 



/ 

 \ 



+NH3 



N— C N— C 



H H H H 



Decarboxylation of an amino acid results in the formation of an amine by the 

 loss of CO2: 



CH3-CH-NH.-C00H — > OTrCH.-NH.+ CO, . 



Ethyl amine 



The ethyl amine formed from alanine may in turn be hydrolyzed to form ethyl alcohol 

 and ammonia: 



CH3-CH.-NH.+H.0 > CH3CH.OH4-NH3. 



Other amino acids may be changed in a similar way. Histidine is converted into 

 histamine, lysine yields cadaverine, and tyrosine yields tyramine.^ It is of special in- 



• Raistrick, H.: Biochem. J., 13, 446. 1919; Raistrick, H., and Clark, A. B.: ibid., 15,76. 1921; 

 Hanke, M. T., and Koessler, K. K.: J. Biol. Ckem., 50, 131. 1922; Long, E. R.: Am. Rev. Tiiberc, 

 5, S57- 1922. 



-' Raistrick, H.: Biochem. J., 11, 71. 191 7. 



^ Hanke, M. T., and Koessler, K. K.: /. Biol. Chcm., 39, 539. 1919; 50, 131, 1922; 59, 835. 1924. 



