Respiration of Dehalobacter restrictus is based on reductive dechlorination of tetrachloroethene. The terminal component of the respiratory chain is the membrane-bound tetrachloroethene reductase. The metal prosthetic groups of the purified enzyme have been studied by optical and EPR spectrescopy. The 60-kDa monomer contains one cobalamin with E(m)(Co(1+/2+)) = -350 mV and E(m)(Co(2+/3+)) >150 mV two electron-transferring [4Fe-4S]((2+;1+)) clusters with rather low redox potentials of E(m)~ -480 mV. The cob(II)alamin is present in the base-off configuration. A completely reduced enzyme sample reacted very rapidly with tetrachloroethene yielding base off cob(II)alamin rather than trichlorovinyl-cob(III)alamin.
Schumacher, W., Holliger, C., Zehnder, A. J. B., & Hagen, W. R. (1997). Redox chemistry of cobalamin and iron-sulfur cofactors in the tetrachloroethene reductase of Dehalobacter restrictus. FEBS Letters, 409(3), 421–425. https://doi.org/10.1016/S0014-5793(97)00520-6