• Methanosarcina barkeri;
  • Ech hydrogenase;
  • Formylmethanofuran dehydrogenase;
  • Methanogenesis


A Methanosarcina barkeri mutant lacking Ech hydrogenase does not catalyze CH4 formation from H2/CO2 since, as was shown previously, the energy-driven reduction of CO2 to formylmethanofuran by H2 is blocked. CH4 formation by this mutant could be restored in the presence of CO or pyruvate. Furthermore, CH4 formation from H2/CO2 plus CO by the Δech mutant was not inhibited by the protonophore TCS. These data show that in vivo the reduction of CO2 to formylmethanofuran can be coupled to the oxidation of CO or pyruvate via a common electron carrier and that the reduction of this electron carrier by H2, catalyzed by Ech hydrogenase, is the energy-driven step in formylmethanofuran-synthesis from CO2, H2 and methanofuran.