Reconstitution of a formate-NADP+ oxidoreductase from formate dehydrogenase and a 5-deazaflavin-linked NADP+ reductase isolated from Methanococcus vannielii.

The formate-dependent reduction of NADP+ by extracts of Methanococcus vannielii is catalyzed by a coupled system consisting of formate dehydrogenase, a 5-deazaflavin cofactor, and 5-deazaflavin-dependent NADP+ reductase. All three components were purified from crude extracts of M. vannielii. Recombination of these components reconstituted the formate-NADP+ oxidoreductase system. The formate dehydrogenase also can utilize FAD, FMN, and a number of artificial dyes as electron acceptors, but these do not replace the 5-deazaflavin cofactor in the coupled enzyme system. The reduced form of 5-deazaflavin binds readily to the NADP+ reductase apoprotein and is not dissociated by ammonium sulfate treatment at neutral pH under anaerobic conditions. This electron transfer cofactor from M. vannielii is identical in many of its properties to the 5-deazaflavin isolated from other methane-producing bacteria.