BACTERIAL FERMENTATIONS 



In the fermentation of purines by living cultures of C. 

 acidi-urici, glycine and formate do not accumulate in considerable 

 amounts, whereas acetate is a major product. Tracer experi- 

 ments have established that both glycine and formate are con- 

 verted in part to acetate. Formate carbon goes into the methyl 

 group of acetate. The methylene carbon of glycine enters both 

 carbons of acetate, whereas the carboxyl carbon of glycine is 

 converted mainly to carbon dioxide. The mechanism of acetate 

 formation from glycine and formate has not been established 

 definitely, but a pathway involving serine is indicated by in- 

 direct evidence (30). Serine is rapidly converted to pyruvate 

 by cell-free extracts and pyruvate is oxidized to acetate and 

 carbon dioxide. Also glycine can be oxidized to acetate. 



A schematic representation of uric acid fermentation by C. 

 acidi-urici and C. cylindrosporum as presently understood is given 

 in Figure 1. 



Many aspects of the purine fermentation remain to be 

 elucidated. The steps in the conversion of 4-amino-imidazole 

 to glycine are not known. It is likely that this process involves 

 an "active formate" which facilitates the conversion of glycine 

 or a glycine precursor to serine. Energy useful for synthetic 

 purposes may also be generated during the conversion of xan- 

 thine to glycine ; otherwise it is difficult to see what purpose this 

 process serves. It is unlikely that this reaction sequence serves 

 only to provide precursors of serine and pyruvate, because these 

 compounds cannot replace purines as fermentation substrates. 

 At present there is no indication of the participation of purine 

 or imidazole nucleotides in the breakdown of purines, but in 

 view of the general similarity between the mechanisms of the 

 fermentation and purine syntheses in animals, a possible role of 

 nucleotides in the purine fermentation should be investigated 

 more closely. 



References 



1. Bard, R. C, and I. C. Gunsalus, J. Bacterial., 59, 387 (1950). 



2. Barker, H. A., and J. V. Beck, J. Biol. Chern., 747, 3 (1941). 



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