Formylmethanofuran

Bertram PA, RA Schmitz, D Linder, RK Thauer (1994) Tungsten can substitute for molybdate in sustaining growth of Methanobacterium thermoautotrophicum identification and characterization of a tungsten isoenzyme of formylmethanofuran dehydrogenase. Arch Microbiol 161 220-228. 

Methanogenesis is induced by the activity of the formylmethanofuran dehydrogenase system. Initially, carbon dioxide is fixed by methanofuran (11) and... 

This enzyme [EC 2.3.1.101] catalyzes the reaction of N-formylmethanofuran with 5,6,7,8-tetrahydromethanopt-erin to yield methanofuran and 5-formyl-5,6,7,8-tetrahy-dromethanopterin. 

Formic acid irradiation of, 3 183 reaction with hydrogen atom, 3 191 Formylium cation, 9 231 Formylmethanofuran dehydrogenase, Methano-bacterium wolfei, 40 73 Fossil fuel, radiocarbon and, 3 311-312 Four-coordinated metal centers, 37 19 Fourier-transform infrared spectroscopy, NiFe hydrogenase, 47 295-298, 299, 303 Fourier-transform ion cyclotron resonance... 

C02 to formylmethanofuran. A complex of proteins that is unstable in oxygen is also needed. The principal component of the methyl reductase binds two molecules... 

A number of other reductases and dehydrogenases, including dissimilatory nitrate reductases of E. coli and of denitrifying bacteria (Chapter 18), belong to the DMSO reductase family. Other members are reductases for biotin S-oxide,649 trimethylamine N-oxide, and polysulfides as well as formate dehydrogenases (Eq. 16-63), formylmethanofuran dehydrogenase (Fig. 15-22,... 

Tungsten- and sometimes Se-containing formate dehydrogenases together with N-formylmethanofuran dehydrogenases (Fig. 15-22, step b) form a second family. 

Formylmethanofuran dehydrogenase Bacterial aPySe (MPTpG)Mo(S), (MPTpA)Mo(S), (MPTpA)Mo(S) (MPTpG)W(S)/ Unknown Fe2S2 46,274-279... 

FIGURE 1. Examples of reactions catalyzed by molybdenum containing enzymes. From top to bottom, hydroxylation of xanthine, hydroxylation of acetaldehyde, dehydrogenation of carbon monoxide, transhydroxylation of pyrogallol, oxidation of sulfite, reduction of nitrate, reduction of dimethylsulfoxide, oxidation of formate, reduction of polysulfide and formation of formylmethanofuran. 

Schmitz, R. A., Albracht, S. P. J., and Thauer, R. K., 1992, A molybdenum and a tungsten isoenzyme of formylmethanofuran dehydrogenase in the thermophilic archaeon Methanobacterium wolfei, Eur. J. Biochem. 209 1013nl018. 

FDH = Formate dehydrogenase CAR = Carboxyhc acid reductase FMDH = Formylmethanofuran dehydrogenase MFR = Methanofuran AOR = Aldehyde ferredoxin oxi-doreductase MPT = Molybdopterin Fdox = Oxidized ferredoxin Fdred = Reduced ferredoxin FOR = Formaldehyde ferredoxin oxidoreductase EXAFS = X-ray absorption edge fine structure kDa = Kilodaltons EPR = Electron paramagnetic resonance. 

The growth of Methanobacterium wolfei is dependent on the presence of molybdenum or tungsten, and one of the two formylmethanofuran dehydrogenases from this bacterium is a tungsten enzyme (285). The reversible reaction catalyzed by these enzymes (Eq. (29)) is the first step in methane formation from CO2 in all methanogenic Archaea (286). 

An enzyme-bound molybdopterin is found in methanogen formate dehydrogenase, and formylmethanofuran dehydrogenase [123,124]. It is distinct from the H4MPT coenzymes used in the methanogenic pathway (see the enzyme sections for detail). 

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