Nicotinic Acid Metabolism

Extracts of nicotinate-grown Clostridum barkeri ferment [7-14C]nicotinate to 14CO2 and a mixture of volatile and non-volatile acidic products. This conversion is markedly stimulated by the addition of certain intermediates of the over-all fermentation pathway, namely pyruvate, α-methyleneglutarate, methylitaconate, or dimethylmaleate. In large scale experiments [14C]α-methyleneglutarate, [14C]methylitaconate, and [14C]dimethylmaleate were detected among the products of [7-14C]nicotinate metabolism. When specifically labeled α-methyleneglutarate and dimethylmaleate were fermented, the distribution of 14C among the final products (acetate, propionate, and carbon dioxide) was as predicted from the earlier tracer experiments. The carboxyl carbon of pyruvate is the most likely precursor of carbon dioxide in the fermentation.