Tracer experiments on the mechanism of synthesis of valeric and caproic acids by Clostridium kluyveri.

This synthesis is a complex process involving numerous steps, but the net result is a condensation of a Cz compound with a Cd compound to give a CS compound. The condensation could occur theoretically in either or both of two ways. The carbinol carbon of ethanol could condense with the y-carbon of butyric acid, or the carboxyl carbon of the acid could condense with the a-carbon of the alcohol. Several years ago (1) an attempt was made to distinguish between these two possibilities by preparing caproic acid from butyric acid labeled in its carboxyl group with C14. Decarboxylation of the resulting labeled caproic acid showed that it did not contain an appreciable amount of Cl4 in its carboxyl group. This was taken to indicate that the only condensation that occurred was between the carboxyl carbon of butyric acid and the a-carbon of the ethanol. This conclusion has now been confirmed by degrading the caproic acid in such a way as to show that it is labeled only in the p position. In addition we have investigated by tracer methods the condensations that occur when valeric acid and other compounds are formed by a fermentation of ethanol and propionic acid.