Nicotinamide adenine dinucleotide-dependent formate dehydrogenase from Rhodopseudomonas palustris

Summary Formate dehydrogenase in extracts of the facultative phototroph, Rhodopseudomonas palustris was shown to be soluble and NAD-linked. The flavin nucleotides, FMN and FAD, stimulated the rate of NAD reduction about fourfold. Reduction of artificial electron acceptors such as DCPIP and cytochrome c was also stimulated by FMN and FAD. The pH optimum for the reduction of NAD was pH 8.0, in contrast to pH 6.8 for cytochrome c and DCPIP reduction. The apparent K_mfor formate as measured by NAD reduction was 2.6×10^-4 M. Although the addition of thiosulfate or yeast extract to the formate medium increased both the growth rate and yield of Rhps. palustris, they had little effect on the activity of formate dehydrogenase.