A biotin‐dependent sodium pump: glutaconyl‐CoA decarboxylase from Acidaminococcus fermentans

Abstract

The decarboxylation of glutaconyl‐CoA to crotonyl‐CoA in the anaerobic bacterium Acidaminococcus fermentans is catalysed by a membrane‐bound, biotin‐dependent enzyme which requires Na⁺ for activity. Inverted vesicles from A. fermentans accumulated Na⁺ only if glutaconyl‐CoA was decarboxylated. The Na⁺ uptake was inhibited by avidin but not by the avidin biotin complex. Detergents and ionophores such as monensin also prevented the Na⁺ transport. The results indicate that the enzyme is able to convert the free energy of decarboxylation (ΔG ^o′ ≈−30 kJ/mol) into a Na⁺ gradient.