BIOSYNTHESIS OF PURINES AND PYRIMIDINES 



283 



I 4 II 8> = 



H H 



Uric acid 







II 



HNf 6 



1 5 



CH3I 



KOH = C' 3 'C. 9/ 



I 

 CH 



H II H 



H H I 



CHj 



8C=0 



3 -(Kl/ 



3-Methyluric acid 



9-Methyluric acid 



KCIO3 

 HCl 



* 1; 



o=c: 



3 lc=o 



Metiiylalloxan 



PbOj 



HN C=0 



I I 



o=c 



H 



Alloxan 



C=0 



H2O 



-*► NH3 + CH5NH, 



Fig. 2. Degradation of uric acid according to Lagerkvist.'" 



TABLE IV 



Synthesis of Uric Acid from Ni*H4C1 and Ni^-labeled Aspartic Acid in the 



Pigeon'" 



The method was appHed to uric acid obtained from pigeons after the 

 administration of N^^-labeled ammonium salts and N^Mabeled aspartic 

 acid. As shown in Table IV the experiments with ammonia demonstrated 

 a preferential incorporation of the isotope into positions 3 and 9. Aspartate- 

 N^^ was incorporated into all nitrogen atoms to about the same extent. 



The metabolic origin of the nitrogen atoms of hypoxanthine has been 

 investigated by Sonne et al.^^'^^ using pigeon liver extracts. Use was made 



" J. C. Sonne and I. Lin, Federation Proc. 11, 290 (1952). 

 3-» J. C. Sonne and I. Lin, Federation Proc. 12, 271 (1953). 

 35 J. C. Sonne, I. Lin, and J. M. Buchanan, J. Am. Chem. Soc. 75, 1516 (1953). 



