BIOSYNTHESIS OF PURINES AND PYRIMIDINES 287 



Fig. 4. 



2. The Role of the Carboxamide and the Enzymic Synthesis 



OF Inosinic Acid 



By growing Escherichia coli in the presence of bacteriostatic amounts of 

 sulfonamides, Stetten and Fox^^ were able to demonstrate the accumula- 

 tion of a diazotizable amine in the substrate. The amine was isolated but 

 its constitution was not elucidated. Subsequently Shive et al}^ identified 

 this amine as 4-amino-5-imidazolecarboxamide (Fig. 4). These authors 

 proposed that the carboxamide was an intermediate in the biogenesis of 

 purines. In addition to the structural similarity, several other hnes of 

 evidence supported this view. The inhibition caused by sulfonamides could, 

 to some extent, be reversed by purines, as was shown by Shive and 

 Roberts. ^'^ Shive^^ also found that the normal strain of Lactobacillus arabino- 

 sus could utilize the carboxamide instead of purines, as could a mutant 

 strain of Ophiostoma multiannulatum}'^ and a hypoxanthine-requiring 

 mutant of E. coli.^^ In the latter case the formyl derivative was more ac- 

 tive than the unsubstituted carboxamide. 



The carboxamide was also accumulated by normal E. coli during in- 

 hibition with aminopterin** and by a purine-requiring mutant of E. coli}^ 

 Recently it has been shown by Stewart and Sevag^® that the carboxamide 

 is produced by a ^^ild strain of E. coli B during normal growth. 



Carboxamide-C^'* was found to be incorporated into the polynucleotide 

 purines and into allantoin of the rat,^^ into hypoxanthine in pigeon liver 



«M. R. Stetten and C. L. Fox, Jr., J. Biol. Chem. 161, 333 (1945). 



" W. Shive, W. W. Ackermann, M. Gordon, M. E. Getzendaner, and R. E. Eakin, 



/. Am. Chem. Soc. 69, 725 (1947). 

 50 W. Shive and E. C. Roberts, /. Biol. Chem. 162, 463 (1946). 

 " W. Shive, Ann. N. Y. Acad. Sci. 52, 1212 (1950). 



" N. Fries, S. Bergstrom, and M. Rottenberg, Physiol. Plantarum 2, 210 (1949). 

 " R. Ben-Ishai, B. Volcani, and E. D. Bergmann, Arch. Biochem. and Biophys. 32, 



229 (1951). 

 " D. W. Woolley and R. B. Pringle, J. Am. Chem. Soc. 72, 634 (1950). 

 " J. S. Gots, Arch. Biochem. 29, 222 (1950). 



*« R. C. Stewart and M. G. Sevag, Arch. Biochem.. and Biophys. 41, 9 (1952). 

 " C. S. Miller, S. Gurin, and D. W. Wilson, Science 112, 654 (1950). 



