The role of alpha-ketoglutarate and mesaconate in glutamate fermentation by Clostridium tetanomorphum.

The products of L-glutamate fermentation by resting or growing cells of Clostridium tetanomorphum are acetate, butyrate, hydrogen, and approximately stoichiometric amounts of carbon dioxide and ammonia (14). Experiments with C14-labeled glutamate have shown that acetate, butyrate, and carbon dioxide originate preferentially from glutamate carbons 1 and 2, 3 and 4, and 5, respectively, and that glutamate carbon atom 4 is the precursor of butyrate carbons 1 and 3 (5, 6). These findings are consistent with a path of glutamate fermentation that involves the formation of 2 different. CZ units, one active in acetate formation and the other a precursor of butyrate, and exclude the operation of a tricarboxylic acid cycle in the oxidative direction. Experiments on the mechanism of this fermentation carried out, with cell-free preparations have furnished evidence for the involvement of both a-ketoglutaric and mesaconic acids.