DECOMPOSITION OF PROTEINS 483 



OH • C 6 H<CH 2 • CH • NH 2 • COOH = OH • C 6 H< • CH 2 • CH 2 • NH 2 + CO, 



tyrosine 



A mono-amino di-carboxylic acid may lose a C0 2 group, with the formation of a 

 mono-carboxylic acid: 



HOOC • CH 2 • CHNHjCOOH - CH 8 • NH 2 • CH 2 • COOH 4- CO s 

 Aspartic acid /S-alanine 



3. Reductive deaminization: 



R-CH-NHrCOOH + H 2 = RCH 2 COOH + NH, (6) 



or 



R-CHNH 2 COOH + H 2 = RCH, + NH, + CO* (7) 



This process of reduction is carried on by anaerobic bacteria, which reduce the 

 a-amino acids, with the formation of saturated fatty acids and ammonia. As 

 instances, one may cite the formation of acetic acid and ammonia, or methane, 

 C0 2 and ammonia, from glycocoll, as well as the following reactions: 



C 6 H 6 • CH 2 • CH • NH 2 ■ COOH + H 2 = C 6 H 6 • CH 2 • CH 2 • COOH + NH, 

 Phenyl-alanine Phenyl-propionic acid 



COOH • CH 2 • CH • NH 2 • COOH + H 2 = (CH 2 ) 2 • (COOH) 2 + NH, 

 aspartic acid succinic acid 



COOH • CH 2 • CH • NH 2 • COOH + H 2 = CH 3 • CH 2 • COOH + NH, + CO, 

 aspartic acid propionic acid 



The formation of butyric acid takes place according to the same reaction: 



COOH • CH 2 • CH 2 • CH • NH 2 • COOH + H, - 

 glutamic acid 



CH, • CH 2 • CH 2 • COOH + NH, + C0 2 

 butyric acid 



4. Anaerobic bacteria may produce ammonia from amino acids, without 

 reduction. 33 



RCH 2 CHNH 2 COOH = RCH:CHCOOH -f- NH, (8) 



5. Oxidative deaminization: 



RCH-NH 2 COOH + 2 = RCOOH + NH, + CO, (9) 



This process is carried out by aerobic organisms, especially by fungi. 34 As 



33 Raistrick, H. Studies on the cycloclastic power of bacteria. I. A quanti- 

 tative study of the aerobic decomposition of histidine by bacteria. Biochem. 

 Jour., 13: 446-458. 1919. 



34 Dakin, H. D. Oxidations and reductions in the animal body. 2nd ed., 

 Longmans, Green & Co. 1922; Ehrlich and Jacobsen, 1912 (p. 481). 



