Tracer experiments on the mechanism of uric acid decomposition and acetic acid synthesis by Clostridium acidi-urici.

The relatively high yield of acetic acid from hypoxanthine is of considerable significance because a direct decomposition of the Ca chain in 1 mole of hypoxanthine cannot give more than 1 mole of a Cz compound. The observed yield of approximately 1.25 moles of acetic acid indicates that the formation of at least part of the acetic acid must involve a condensation either between two CB compounds, or between a Cs and a Cl compound, or between two C1 compounds. The Cl compound could be carbon dioxide or a derivative of the ureide carbons of the purine. The possibility that carbon dioxide is used to form acetic acid was tested qualitatively several years ago by allowing uric acid or other purines to be fermented in the presence of C”OZ (2). It was found that carbon dioxide is incorporated into both the methyl and the carboxyl groups of acetic acid. Later experiments of the same type done with Cl402 provided quantitative data from which it was possible to conclude that a large part of the carboxyl carbon of acetic acid is derived directly from uric acid (3). The data also indicated that part of the methyl group may be derived from the same source, although other interpretations were not excluded. There is considerable evidence to show that glycine is an intermediate in the decomposition of uric acid and other pukes by anaerobic bacteria (1,3). Although Clostridium acidi-urici does not form appreciable amounts