EPR studies on Formate Dehydrogenase from Desulfovirio desulfuricans (Dd FDH) ATCC 27774.

M.G. RIVAS; C.D. BRONDINO; I. MOURA

Fátima (Portugal)

Otro; 3rd Encontro do Requimte.; 2004

Requimte- FCT-UNL

FDH capable of converting formate to carbon dioxide are a diverse group of enzymes found in both prokaryotes and eukaryotes. FDHs from anaerobes contain metal cofactors, the type of metals and cofactors vary widely. Dd FDH was purified through five chromatographic steps and was preliminary characterized by UV-Vis and EPR spectroscopy. This preliminary characterization showed that the protein contains three types of redox-active canters: four c-types hemes, two [4Fe-4S]2+/1+ clusters and a molybdenum-pterin site. The as-prepared state of the enzyme shows the typical EPR signals associated with ferric heme in a low spin configuration and Mo(V) ion species having high redox potentials. Upon reduction with formate and/or reducing agents, these signals are replaced by EPR signals associated with iron/sulfur clusters of the [4Fe-4S]+ and Mo(V) ion species having low redox potentials. Previous EPR studies revealed the presence of two iron-sulfur centers, but the recent determination of the structure and EPR characterization of the closely related Desulfovibrio gigas and Desulfovibrio alaskensis FDH, respectively, showed that the enzyme is composed of 4×[4Fe-4S] clusters. Taking into consideration these new evidences, we are currently reinterpreting the spectroscopic data and the species produced under turnover conditions.