68 



BACTERIAL FERMENTATIONS 



derived from glutamate carbon atoms 3 and 4, gives rise 

 to an active acetyl group which is preferentially converted 

 to butyrate. The acetyl group and carbon dioxide might 

 well be formed from pyruvate derived from carbon atoms 

 5, 4, and 3. Therefore, a fission of the glutamate carbon 



^OOH 1 



2 CHNH 2 f 



I J 



3 CH 2 



I 

 4 CH 2 



5 COOH 



^OOH 

 2 CH 3 



■ 3 CH 3 ■ 



I 

 4 CO 



L 5 coohJ 



IT 1 



L 4 co— xj 



r CH 3 COOH 



CH3CH2CH2COOH 



4 CO 

 + 



5 co 2 



Fig. 2. Fermentation of C 14 -Glutamate by Clostridium fetanomorphum. 



chain between carbon atoms 2 and 3 to give acetate and 

 pyruvate is consistent with the tracer experiments. The 

 results exclude the occurrence of a tricarboxylic acid cycle 

 in a reverse as well as a forward direction. The operation 

 of the cycle in the reverse direction, i.e., from a-ketogluta- 

 rate to oxalacetate and acetate via citrate, would give an 

 acetyl group in which the methyl carbon atom was derived 

 from glutamate carbon atom 4, instead of carbon atom 3 

 as observed. 



The further exploration of the pathway of glutamate 

 fermentation has been done with enzyme preparations. 

 Wachsman 41 found that cell-free extracts of CI. tetano- 



