ELECTRON-TRANSFER REACTIONS FOR THE REDUCTION OF NADP(-STADTMANAE() IN METHANOSPHAERA)

Methanosphaera stadtmanae, a member of the Methanobacteriales reduces methanol, but not CO2 with H-2 or 2-propanol to produce methane. In ce ll-free extracts of M. stadtmanae the activities of several enzymes in volved in electron transfer were measured. The activities of an F-420- nonreactive hydrogenase, NADP(+):F-420 oxidoreductase, NADP(+)-depende nt 2-propanol dehydrogenase, and a methyl viologen dependent F-420 deh ydrogenase were observed. Based on the presence of these particular en zyme activities, their cofactor requirements and the absence of F-420- dependent hydrogenase activity, a model of the electron transport path way through the coenzyme F-420 to provide electrons for biosynthesis, was formulated.