DECOMPOSITION OF PROTEINS 481 



When proteins are hydrolyzed by means of acids or enzymes, only 

 10 per cent of the total nitrogen in casein and 25 per cent in gliadin 

 is liberated as ammonia, as a result of the breaking of the acid amide 

 ( — CO-NH 2 ) linkages. When proteins are acted upon by microor- 

 ganisms, especially when those are used as sources of energy, large 

 quantities of ammonia will be produced as a waste product. Seventy- 

 five per cent or more of the protein-nitrogen can be found to accumulate 

 in the soil in the form of ammonia within a few days, with proteins 

 as the only source of energy. The ammonia is produced by a series 

 of chemical changes which depend upon the nature of the organism, 

 presence of nutrients other than amino acids (such as available carbo- 

 hydrates), oxygen tension, and other conditions under which the 

 reactions take place. 



Ammonia formation from amino acids may involve processes of 

 hydrolysis, oxidation or reduction, or a combination of two or all, 

 resulting in the splitting of the amino group or the carboxyl group or 

 both. The various reactions may be summarized, as follows: 



1. Hydrolytic decomposition: 



NH • C(NH 2 ) • NH • (CH 2 ) 3 • CH(NH 2 ) • COOH + H 2 = 



arginine 

 CH 2 (NH 2 ) ■ CH 2 • CH 2 • CH(NH 2 ) • COOH + CO(NH 2 ) 2 

 ornithine urea 



The hydrolysis of an amino acid may result in the formation of a lower fatty 

 acid and ammonia, of an alcohol, C0 2 and ammonia, or of an aldehyde, lower 

 acid and ammonia, as shown by the general formulae: 



RCH-NH 2 -COOH + H 2 = RCHOH-COOH + NH 3 (1) 



RCH<NH 2 -COOH + H 2 = R-CH 2 OH + C0 2 + NH 3 (2) 



R-CH-NHrCOOH + H 2 = R-CHO + HCOOH + NH 3 (3) 



These processes are carried out by various aerobic organisms. 28 Formula 

 (2) is of common occurrence among bacteria, 29 fungi and yeasts, 30 as in the case 

 of formation of isoamyl alcohol from leucine. 



28 Dakin, H. D. The oxidation of leucin and amido-isovaleric acid and of 

 amido-n valeric acid with hydrogen peroxide. Jour. Biol. Chem., 4: 63-76. 

 1908; Ehrlich, F., and Jacobsen, A. Uber die Umwandlung von Aminosauren 

 in Oxysiiuren durch Schimmelpilze. Ber. deut. Chem. Gesell., 44: 888. 1911; 

 (Centrbl. Bakt. II, 33: 346-347. 1912). 



29 Nawiasky, P. Uber die Umsetzung von Aminosauren durch Bac. proleus 

 vulgaris. Arch. Hyg., 66: 209-243. 1908; also 64: 33-61. 1908. 



30 Ehrlich, F. Ueber die Entstehung des Fuselols. Ztschr. Ver. Deut. 

 Zuckerind. Tech. T. N. S., 42: 539-567. 1905. 



