Abstract
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.

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