84 BACTERIAL FERMENTATIONS 



imidazole is enzymatically decarboxylated to 4-aminoimida- 

 zole which accumulates in the presence of ethylenediamine- 

 tetraacetic acid. The aminoimidazole is readily decomposed 

 to ammonia and formiminoglycine by crude extracts of 

 CI. cylindrosporum* 5 Formiminoglycine (FIG) is also the 

 product accumulating in the decomposition of xanthine by 

 crude extracts. In earlier experiments on xanthine decom- 

 position by extracts, FIG was mistakenly identified as a 

 mixture of glycine, formate, and ammonia, because these 

 compounds are readily formed non-enzymatically from FIG 

 under conditions commonly used for their estimation. The 

 conversion of 4-aminoimidazole to FIG is apparently a com- 

 plex reaction involving more than one step. The enzyme 

 responsible for 4-aminoimidazole decomposition has been 

 partially purified and shown not to form formiminoglycine 

 directly, but an unidentified compound (X in Fig. 6) which 

 can be hydrolyzed non-enzymatically to glycine in the pres- 

 ence of either acid or alkali. This compound is not an 

 intermediate in the fermentation, since it is not converted 

 to formiminoglycine by crude extracts. Probably it is 

 formed from the true intermediate by a non-enzymatic 

 side reaction. 



One of the most interesting parts of the purine fermenta- 

 tion is the conversion of FIG to glycine, ammonia, and 

 formate. This conversion, which evidently requires several 

 enzymes, can provide useful energy to the organism in the 

 form of ATP. Rabinowitz and Pricer 66 have shown that 



FIG + ADP + P» — > 



GLYCINE + HCOOH + NH 3 + ATP (12) 



under certain conditions the over-all reaction may be repre- 

 sented by equation 12. This reaction sequence is depend- 

 ent upon the presence of tetrahydrofolic acid (THFA) or 



