184 NUCLEIC ACIDS AND THE NITROGENOUS BASES 



AMINES DERIVED FROM AMINO-ACIDS. 



The proteolytic enzymes, such as Trypsin and Erepsin, accomplish 

 the conversion, by hydrolysis, of the proteins into their constituent 

 amino-acids. The next step in the degradation of nitrogenous food- 

 stuffs by animal tissues generally, appears to consist in Deaminization 

 with the splitting off of ammonia and the oxidation of the remainder 

 of the original amino-acid molecule to carbon dioxide and water. No 

 intermediate stages in this process have been definitely established, 

 and we have been unable to detect the presence in animal tissues of 

 enzymes capable of producing nitrogenous bases other than ammonia 

 from amino-acids. That such enzymes, perhaps highly localized, do 

 actually exist in animal tissues may be regarded as exceedingly prob- 

 able, from the variety and physiological importance of the nitrogenous 

 bases which are found to occur in animal tissues and their significant 

 chemical resemblance to certain of the amino-acids which are yielded by 

 the digestion of protein. 



Bacteria and other Fungi, however, constitute a group of organisms 

 which are able to rapidly produce from amino-acids a series of nitrog- 

 enous bases which arise by Decarboxylization of the amino-acid 

 molecule in accordance with the general equation: 

 R 



-| , R 



CHNH 2 



= CH 2 NH 2 + CO 2 

 COOH 



Amino-acid Amine 



At the same time that this is taking place, Deaminization is also 

 proceeding, and is evidenced by the production of ammonia. The 

 conditions determining the relative proportion of these two processes 

 are complex and have not as yet been fully determined, but it has 

 been observed that the presence of carbohydrates in a culture of 

 bacteria or fungi greatly diminishes the production of ammonia, 

 presumably because in the absence of carbohydrates the organisms 

 utilize amino-acids as a source of energy as well as a source of nitro- 

 gen, and consuming the carbon and hydrogen components for this 

 purpose, split off ammonia as a by-product. In studying the decar- 

 boxylization of individual amino-acids it has been found that the 

 addition of Peptone to the bacterial culture increases the yield of 

 amines, probably because the process of deaminization being shared 

 between the amino-acid and the peptone, a greater proportion of the 

 amino-acid remains available for decarboxylization. 



Decarboxylization may also, especially under anaerobic conditions, 

 be accompanied by reduction, in which case Formic Acid is produced 

 instead of carbon dioxide: 

 R 



I R 



CHNH 2 | 



+ H 2 = CH 2 NH 2 + HCOOH 

 COOH 

 Amino-acid Amine 



