title: A tungsten-containing active formylmethanofuran dehydrogenase in the thermophilic archaeon Methanobacterium wolfei.
abstract: Methanobacterium wolfei is a thermophilic methanogenic archaeon which requires tungsten or molybdenum for growth. We have found that the organism contains two formylmethanofuran dehydrogenases, one of which is a tungsten enzyme. Indirect evidence indicates that the other formylmethanofuran dehydrogenase is a molybdenum enzyme. The tungsten enzyme was purified and characterized. The native enzyme had an apparent molecular mass of 130 kDa. SDS/PAGE revealed a composition of three subunits of apparent molecular mass 35, 51 and 64 kDa, the N-terminal amino acid sequences of two of which were determined. 0.3-0.4 mol tungsten/mol enzyme was found but no molybdenum. The pterin cofactor was identified as molybdopterin guanine dinucleotide. The purified enzyme exhibited a specific activity of 8.3 mumol.min-1.mg protein-1 and an apparent Km for formylmethanofuran and methylviologen of 13 microM and 0.4 mM, respectively. The optimum temperature for activity was 65 degrees C. At 40-60 degrees C, the rate increased with a Q10 of 1.9; the activation energy of the reaction was 45 kJ/mol. The enzyme was found to require potassium ions for thermostability. The oxygen-sensitive enzyme was not inactivated by cyanide.
authors.affiliation: Laboratorium für Mikrobiologie, Philipps-Universität Marburg, Federal Republic of Germany.
authors.forename: R A
authors.initials: RA
authors.lastname: Schmitz
authors.forename: M
authors.initials: M
authors.lastname: Richter
authors.forename: D
authors.initials: D
authors.lastname: Linder
authors.forename: R K
authors.initials: RK
authors.lastname: Thauer
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D002384:Catalysis; D006358:Hot Temperature; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D017014:Methanobacterium / Q000201:enzymology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D008982:Molybdenum / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry; D011189:Potassium Chloride / Q000494:pharmacology; D011489:Protein Denaturation / Q000187:drug effects; D013057:Spectrum Analysis; D014414:Tungsten / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D011189:Potassium Chloride; D008982:Molybdenum; D007501:Iron; D000445:Aldehyde Oxidoreductases; C060639:formylmethanofuran dehydrogenase; D014414:Tungsten