Recent studies have revealed that NAD-dependent formate dehydrogenase (FDH1) isolated from the a-proteobacterium Methylobacterium extorquens AM1 showed extraordinary stability under aerobic conditions. The enzyme was found to be a heterodimer of two subunits (a1b1) of 107 and 61 kDa, respectively. The a-subunit harbors the molybdopterin cofactor and at least one iron�sulfur cluster. Sequence identity was highest to the catalytic subunits of the tungsten- and selenocysteine containing formate dehydrogenases characterized from Eubacterium acidaminophilum and Moorella thermoacetica (Clostridium thermoaceticum).FDH1 exhibited higher formate oxidation activity when tungstate was present in the growth medium. In the absence of molybdate or tungstate, NAD-dependent FDH activity was detected as minute levels. In this study, in the presence of molybdate or tungstate, FDH1 a-subunit from M. extorquens AM1 was expressed heterologously in Escherichia coli (E. coli)at low temperature (20?). Recombinant FDH1 a-subunit showed the formate oxidation activity with the concomitant reduction of benzyl viologen. This implies formate oxidation catalyzed by FDH1 a-subunit can be coupled with artificial electron acceptor such as viologen. The reverse reaction, the reduction of CO2 to formate, was demonstrated as well. Based on the reversible interconversion of CO2 and formate catalyzed by FDH1 alpha subunit, the recombinant enzyme can be promisingly used as catalyst for the reduction of CO2 by using electrons supplemented from cathode.

Expression of recombinant NAD-independent FDH1 alpha subunit from Methylobacterium extorquens AM1 in Escherichia coli and reversible interconversion of carbon dioxide and formate

247th National Meeting (2014)

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