Forms part of the nicotinate-fermentation catabolism pathway in?Eubacterium barkeri. Other enzymes involved in this pathway are EC?1.17.1.5?(nicotinate dehydrogenase), EC?1.3.7.1?(6-hydroxynicotinate reductase), EC?3.5.2.18?(enamidase), EC?1.1.1.291?(2-hydroxymethylglutarate dehydrogenase), EC?5.4.99.4?(2-methyleneglutarate mutase), EC?4.2.1.85?(dimethylmaleate hydratase) and EC?4.1.3.32?(2,3-dimethylmalate lyase).