THE METABOLISM OF THE PURIN BODIES 

 I. NH-CO 



C-NH 



389 



NH-CO 



CO CO+CO 



NH. 



CO 



I II X > 



NH-C-NH/ NH-CO 



Uric acid (treated with cold HNO 3 ). Alloxan. 



\NH, 



Urea. 



NH - CO 



= CO 



+ 00, 



II. NH-CO 



CO CO + O 



I 

 NH - CO 



Alloxan (treated with warm HNO 3 ). Parabanic acid. 

 III. NH-CO 



NH - CO 



NH - CO 



CO I +H.,O -CO 



I 

 NH - CO 



Parabanic add (heated with alkali). Oxaluric acid. 



NH 2 COOH 



IV. NH - CO 

 CO 

 NH COOH 



NH, 



H 2 



CO 



\ 



NH, 



COOH 



i 



COOH 



Oxaluric acid (boiled with water). Urea. Oxalic acid. 



These intermediate bodies can be prepared by other means 

 than those described above, and the accuracy of their -structural 

 formulae thereby proven. 



By using a milder oxidising agent, such as potassium per- 

 manganate, uric acid first of all forms a substance called allantoin. 

 This has the empirical formula C 4 H 6 N 4 3 , and the reaction is as 

 follows : 



C 5 H 4 N 4 3 + O + H 2 = C 4 H 6 N 4 3 + CO 2 



(uric acid) (allantoin) 



The structural formula for allantoin is 



/NH-CH-NH\ 



CO | CO 



\NH-CO NH 2 / 



from which it is seen to be very like uric acid, possessing two 

 urea molecules and a central carbon chain. By further oxidation 



