76 BACTERIAL FERMENTATIONS 



cannot convert urea to ammonia, it may also be concluded 

 that at least one of the ureido groups of allantoic acid is 

 decomposed before being separated from the two-carbon 

 chain. The latter is ultimately oxidized in part to oxamic 

 acid, carbon dioxide, and formate, and partly reduced to 

 glycolate and acetate by paths that are yet to be determined. 

 Orotic Acid Fermentation by Zymobacterium orofl- 

 cuiti. Not all of the fermentation products of orotic acid 

 have been identified, but ammonia, carbon dioxide, acetate, 

 and one or more four-carbon dicarboxylic acids appear to 

 be formed. The early reactions in the fermentation of 

 orotic acid by this bacterium have been extensively studied 

 by Lieberman and Romberg 14 - 15 by the use of cell-free 

 extracts. The first reaction is the DPN-linked reduction of 

 orotic acid to L-dihydroorotic acid. This is followed by a 

 hydrolytic cleavage of the pyrimidine ring to give L-ureido- 

 succinic acid. 



HN— CO HN— CO 



II II 



OC CH +DPNH+H+ :^=± OC CH 2 +DPN+ 



I II II 



HN— C— COOH HN— CH— COOH 



Orotic acid L-Dihydroorotic acid 



±H 2 



COOH 



I I I 



CH 2 +CO2+NH3 OC CH 2 



I I I 



H 2 N— CH— COOH ^- HN— CH— COOH 



L-Aspartic acid L-Ureidosuccinic acid 



The ureido group of the latter compound is degraded with 

 the formation of ammonia, carbon dioxide, and L-aspartic 

 acid. The further transformations of aspartic acid have not 

 been analyzed in detail, but it is probable in view of the 



