Formate: Cytochrome Oxidoreductase of Desulfovibrio vulgaris

Formate dehydrogenase and its electron acceptor were isolated and purified from Desulfovibriovulgaris. The optimum pH of the enzyme (K3Fe(CN),6 as an acceptor) is 6–7. Km for formate is 7.4×10−6M. NAD³, NADP³, FAD, FMN, cytochrome c3 and clostridial ferredoxin are not reduced by the enzyme in the presence of formate. The enzyme is not inhibited by p-chloromercuribenzoate, iodoacetamide, sodium hypophosphite, EDTA or o-phenanthroline, but strongly inhibited by KCN. The natural electron acceptor is a c-type cytochrome. The absorption spectrum of its reduced form has α, β and γ peaks at 553, 523 and 416 mμ, respectively. Its molecular weight is about 6500. Desulfovibrio formate dehydrogenase is, thus, formate: ferricytochrome c 553 (mol. wt., 6500) oxidoreductase, a new entry in EC class 1.2.2.