DECOMPOSITION OF PROTEINS 479 



environmental conditions but also upon the organisms concerned. In 

 the great majority of cases, especially in the study of the activities of 

 soil microorganisms, the measurement of ammonia was used as an 

 index of protein decomposition. 19 



But even in the case of protein decomposition in soil, where one 

 group of organisms readily acts upon the products formed by another, 

 various protein derivatives are found, in addition to ammonia. 



Lathrop, 20 for example, found that histidine, hypoxanthine, cytosine, 

 xanthine, nucleic acid, creatinine, cyanuric acid are of common occur- 

 rence in the soil; arginine, lysine, adenine, choline, trimethylamine 

 occur only infrequently in the soil. This leads to the assumption that 

 a part of the proteins and other organic nitrogenous compounds are 

 accumulating in the soil, originating from plant residues, stable manure, 

 green manure, organic fertilizers and the bodies of microorganisms. 

 Lathrop analyzed, by the Van Slyke method, soils to which proteins 

 (dried blood) had been added, at the beginning of the experiment and 

 at the end of various periods of incubation. Even after a 240-day 

 period of decomposition of dried blood in the soil, proteins, or protein- 

 like complexes, insoluble in distilled water, but extractable by dilute 

 alkaline solution, were found to be present in the soil. It is not known, 

 however, whether these proteins are residues from the dried blood 

 which have resisted decomposition by the soil microorganisms, or 

 whether they are synthesized materials or constituents of the bodies 

 of the latter. Evidence was obtained to indicate that a formation of 

 new protein material takes place in the soil in the course of decom- 

 position of proteins and this new protein is perhaps somewhat resistant 

 to decomposition. Protein-like bodies giving reactions for proteoses 

 and peptones have also been isolated from the soil. 21 



Miyake 22 found that fatty amino compounds seem to be transformed 

 into ammonia more easily than aromatic compounds; aromatic imino 

 compounds are decomposed with greater difficulty than the aromatic 

 amino compounds. The nature of the other group in the molecule 



19 A detailed review of the extensive literature on ammonia formation in the 

 decomposition of organic matter, up to 1910, is given by Voorhees and Lipman, 

 1907 (p. 491) and Lohnis, 1910 (p. xiii). 



20 Lathrop, 1917 (p. 474). 



21 Walters, 1915 (p. 474). 



22 Miyake, K. Influence of the chemical structure of the compounds to be 

 ammonified upon the rate of ammonification. Jour. Amer. Chem. Soc, 39: 

 2378-2382. 1917. 



