DECOMPOSITION OF PROTEINS 487 



Uric acid can also be decomposed by various bacteria according to 

 the following reactions: 



(1) C5H4N4O3 + 8 H,0 + 1§ (0 8 ) = 4NH 4 HCO, + CO, 



(2) C6H4N4O3 + 4H 2 - C3H4O6 + 2 CO (NH,), 



tartronic 

 acid 



(3) C 6 H<N<0 3 + 2H 2 + 1} (0 2 ) = 2 CO (NH 2 ) 2 + 3 CO, 



Hippuric acid is first hydrolyzed by an enzyme produced by certain 

 fungi: 



C 6 H 6 • CO • NH • CH 2 • COOH + H 2 = C 6 H 5 • COOH + NH, • CH, • COOH 

 Hippuric acid Benzoic Glycocoll 



acid 



Among the other nitrogenous substances which have to be first 

 decomposed by microorganisms before they can be assimilated by 

 plants, we find urea 43 and cyanamide. Urea is hydrolized, with the 

 formation of ammonia, by a large number of soil microorganisms as 

 well as by specific groups of bacteria, which utilize the energy liberated 

 in the process. 



NH 2 



CO/ + 2 H 2 = (NH<) 2 CO3 - C0 2 + 2 NH 3 + H 2 

 NH 2 



According to Yamazaki, 44 the decomposition of urea takes place in 

 two definite stages with the formation of ammonium carbonate as the 

 intermediary product. 



Fearon 46 maintains that the enzyme urease decomposes urea first 

 into cyanic acid and ammonia: 



HN:C-0->HN:C:0 + NH, 



v 



NH, 

 Urea (cylic) Cyanic acid 

 form) 



Cyanic acid is hydrolyzed, in the presence of water: 



HN : C : O + H 2 = NH 3 + C0 2 . 



43 A detailed study of the chemistry of urea is given by E. A. Warner. The 

 Chemistry of Urea. Longmans, Green & Co., New York. 1923. 



44 Yamazaki, E. Chemical reaction of the system urease-urea. Jour. Tokyo 

 Chem. Soc, 39: 125-184. 1918; Sci. Rept. Tokoku Imp. Univ., 9: 97, 136. 1920. 



45 Fearon, W. R. Urease. I. The chemical changes involved in the zymol- 

 ysis of urea. Biochem. Jour., 17: 84-93. 1923; Physiol. Rev., 6: 399-439. 1926. 



