Factor 420-dependent pyridine nucleotide-linked formate metabolism of Methanobacterium ruminantium.

Methanobacterium ruminantium was shown to possess a formate dehydrogenase which is linked to factor 420 (F420) as the first low-molecular-weight or anionic electron transfer coenzyme. Reduced F420 obtained from the formate dehydrogenase can be further linked to the formation of hydrogen via the previously described F420-dependent hydrogenase reaction, thus constituting an apparently simple formate hydrogenlyase system, or to the reduction of nicotinamide adenine dinucleotide phosphate via F420:nicotinamide adenine dinucleotide phosphate oxidoreductase. The results indicate that hydrogen and formate, the only known energy sources for M. ruminantium and many other methanogenic bacteria, should be essentially equivalent as sources of electrons in the metabolism of this organism.