Open AccessThermodynamics of the Formylmethanofuran Dehydrogenase Reaction in Methanobacterium Thermoautotrophicum
Author(s) -
Bertram Peter A.,
Thauer Rudolf K.
Publication year - 1994
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1994.t01-1-00811.x
Subject(s) - methanobacterium , methanogenesis , chemistry , thermophile , dehydrogenation , dehydrogenase , electron donor , stereochemistry , biochemistry , enzyme , methane , catalysis , organic chemistry , archaea , gene
Purified formylmethanofuran dehydrogenase from Methanobacterium thermoautotrophicum , which is a thermophilic methanogenic Archaeon growing on H 2 and CO 2 , was shown to catalyze the reversible reduction of CO 2 to N ‐formylmethanofuran with 1,1′,2,2′‐tetramethylviologen ( E′ o =− 550 mV) as electron donor. The rate of CO 2 reduction was approximately 25 times higher than the rate of N ‐formylmethanofuran dehydrogenation. From determinations of equilibrium concentrations at 60°C and pH 7.0 a midpoint potential ( E′ o ) for the CO 2 + methanofuran/formylmethanofuran couple of approximately – 530 mV was estimated. The initial step of methanogenesis from CO 2 thus has a midpoint potential considerably more negative than that of the H + /H 2 couple ( E′ o =−460 mV at 60°C). Evidence is described indicating that the as‐yet unidentified physiological electron donor of the formylmethanofuran dehydrogenase is present in the soluble cell fraction.