Factor 420 dependent pyridine nucleotide linked hydrogenase system on Methanobacterium ruminantium

Abstract

M. ruminantium was shown to possess a nicotinamide adenine dinucleotide phosphate (NADP) linked factor 420 (F420) dependent hydrogenase system. This system was also shown to be present in Methanobacterium strain MOH. The hydrogenase system of M. ruminantium also links directly to F420, flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN), methyl viologen, and Fe3+. It has a pH optimum of about 8 and an apparent Km for F420 of about 5x10-6M at pH 8 when NADP is the electron acceptor. The F420 NADP oxidoreductase activity is inactive toward nicotinamide adenine dinucleotide (NAD) and no NADPH:NAD or FADH2(FMNH2):NAD transhydrogenase system was detected. Neither crude ferredoxin nor boiled crude extract of Clostridium pasteurianum could replace F420 in the NADP linked hydrogenase reaction of M. ruminantium. Also, neither F420 nor a crude 'ferredoxin' fraction from M. ruminantium extracts could substitute for ferredoxin in the pyruvate ferredoxin oxidoreductase reaction of C. pasteurianum.