Properties of formate dehydrogenase from Desulfovibrio gigas

Abstract

The formate dehydrogenase from extracts of Desulfovibrio gigas was partially purified to a specific activity of 5600 nmol CO2 ∙ min−1 ∙ mg protein−1. Uniquely for a formate dehydrogenase from anaerobes, the enzyme was stable when stored aerobically. Nevertheless, thiols were required in the assay mixture for enzymatic activity. If the enzyme first catalyzed the transfer of electrons from thiols to benzyl viologen (a diaphorase activity), then formate was oxidized rapidly without a lag period. The enzyme had a molecular weight of approximately 240 000, a pH optimum of 7.5–8.0, and a temperature optimum of 56 °C. Activity with cytochrome c3 (molecular radius (Mr) = 13 000) was about twice that with ferredoxin or flavodoxin as the electron acceptor. These results suggest that the formate dehydrogenase from D. gigas can be activated by transferring electrons from thiols to an electron acceptor and uses cytochrome c3 as the natural electron carrier for the oxidation of formate.

Purification and Characterization of a Tungsten-Containing Formate Dehydrogenase from Desulfovibrio gigas

“…The early observation that the D. gigas FDH activity in soluble extract was air-insensitive made the enzyme purification easier (17). This contrasts with the reports that most FDHs isolated from anaerobes lose activity when stored aerobically and thus must be purified under strictly anaerobic conditions.…”

“…This enzyme was partially purified by Riederer-Henderson and Peck (17). These authors proposed a periplasmatic localization for this protein.…”

Two W‐containing formate dehydrogenases (CO2‐reductases) involved in syntrophic propionate oxidation by Syntrophobacter fumaroxidans

“…Similar reducing conditions were also required to maintain the enzyme stability during purification: a concentration of 100 µ m dithionite in the buffers was sufficient to obtain reasonable (> 50%) recoveries per purification step. Unlike the W‐containing FDH from D. gigas [16,38], strong reducing conditions were also required to purify the W‐containing FDHs from M. thermoacetica [15] and E. acidaminophilum [17].…”

NAD+-dependent formate dehydrogenase

“…They may be classified into two major families. The first includes a diverse group of conjugated iron-sulphur metalcontaining proteins of microbial origin differing in physiological role, cellular location, substrate specificity, nature of the physiological electron acceptor, content and type of prosthetic groups [29][30][31][32][33][34][35][36][37]. These enzymes are distinguished by their high molecular mass, complex quaternary structure, the presence of various prosthetic groups and their lability towards oxygen.…”