title: Function of coenzyme F420-dependent NADP reductase in methanogenic archaea containing an NADP-dependent alcohol dehydrogenase.
abstract: Methanogenic archaea growing on ethanol or isopropanol as the electron donor for CO2 reduction to CH4 contain either an NADP-dependent or a coenzyme F420-dependent alcohol dehydrogenase. We report here that in both groups of methanogens, the N5, N10-methylenetetrahydromethanopterin dehydrogenase and the N5, N10-methylenetetrahydromethanopterin reductase, two enzymes involved in CO2 reduction to CH4, are specific for F420. This raised the question how F420H2 is regenerated in the methanogens with an NADP-dependent alcohol dehydrogenase. We found that these organisms contain catabolic activities of an enzyme catalyzing the reduction of F420 with NADPH. The F420-dependent NADP reductase from Methanogenium organophilum was purified and characterized. The N-terminal amino acid sequence showed 42% sequence identity to a putative gene product in Methanococcus jannaschii, the total genome of which has recently been sequenced.
authors.affiliation: Max-Planck-Institut für terrestrische Mikrobiologie, Abteilung Biochemie, Karl-von-Frisch-Strasse, D-35043 Marburg, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Berk
authors.forename: R K
authors.initials: RK
authors.lastname: Thauer
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000595:Amino Acid Sequence; D019605:Euryarchaeota / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism; D011622:Pterins / Q000378:metabolism; D012256:Riboflavin / Q000031:analogs & derivatives* / Q000378:metabolism; D017421:Sequence Analysis
chemical_list: C091917:N(5),N(10)-methylene-tetrahydromethanopterin; D011622:Pterins; D009249:NADP; C015084:coenzyme F420; D000429:Alcohol Oxidoreductases; C084155:alcohol dehydrogenase (NAD(P)+); D000587:Oxidoreductases Acting on CH-NH Group Donors; C047126:methylenetetrahydromethanopterin dehydrogenase; D009247:NADH, NADPH Oxidoreductases; C109941:F420-dependent NADP reductase; D012256:Riboflavin