Pfizer Handbook of Microbial Metabolites 



558 



cule,"'^ but C-4 of the purine nucleus is equivalent to C-4a 

 in riboflavin, and C-5 of purine to C-9a of riboflavin.^"* 

 The C-4 of riboflavin is furnished by carbon dioxide (cf. 

 C-6 in purines), and C-2 from formate (cf. C-2 in pu- 

 rines). These relationships are shown in generalized 

 diagram. 



Sources of the Carbon Atoms in Purines, Pteridines and Flavines 



co; 



i 



o 



HCOOH 



y 



IN iT| 



\ 



HCOOH HCOOH 



Purine 



HCOOH 



The pyrimidine rings in all these systems seem to have 

 a common origin, and perhaps purines are precursors of 

 the other two classes of heterocycles. 



Guanine-5-C^ * was converted to labeled riboflavin and to 

 labeled G-compound by Eremothecium ashbyii, Ashbya 

 gossypii, Candida fiareri, C. guilliermondii and C. parapsi- 

 lopsis.'^-' Pyrimidines and pteridines were not used di- 

 rectly, and, when labeled G-compound was added to grow- 

 ing cultures, it was not converted to riboflavin by E. 

 ashbyii nor was labeled 4,5-diaminouracil. V-Compound 

 was shown to be formed rather easily from G-compound 

 by air oxidation of a stored alkaline solution. While G- 

 compound was not used by growing whole cells, cell-free 

 extracts of E. ashbyii, Ashbya gossypii, Mycobacterium 

 smegmatis and M. avium were able to incorporate it into 

 the riboflavin molecule.-^'" ■" 



33 Walter S. McNutt, 7. Biol. Chem. 210 511 (1954). 



3*G. W. E. Plaut, ibid. 208 513 (1954). 



"•"' Friedhelm Korte, Hans Ulrich Aldag, Gerhard Ludwig, Wilfried 

 Paulus and Klaus Storiko, Ann. 619 70 (1958). 



3« Friedhelm Korte and Hans Ulrich Aldag, Ann. 628 144 (1959). 



3" G. F. Maley and G. W. E. Plaut, /. Am. Chem. Soc. 81 2025 

 (1959). 



