Involved in the fermentation of nicotinate to ammonia, propionate, acetate and carbon dioxide. 2-methyleneglutarate = 2-methylene-3-methylsuccinate Contains a mixture of adenosylcobalamin and oxygen-stable cob(II)alamin. Inhibited by intrinsic factor and iodoacetic acid. Competitively inhibited by itaconate, mesaconate, succinate, 1-methyl-1,2-trans-clycopropane, dicarboxylate and L-malate. Non-competitively inhibited by glutaconate and 1-methyl-1,2-cis-cyclopropanedicarboxylate. Not inhibited by acrylate or by the chelating agents alpha,alpha-dipyridyl or EDTA. Not activated by Fe(2+), Mg(2+), Mn(2+) or Ca(2+). Unaffected by K(+), Na(+), NH4(+), Rb(+) or Li(+). Activity decreases rapidly below pH 7.5 in phosphate buffer, and below pH 8.0 in Tris buffer. Cofactor degradation; nicotinate degradation; propanoate and pyruvate from 6-hydroxynicotinate: step 5/8. Homotetramer. By nicotinate.