| Type: | Family | Name: | Formylmethanofuran dehydrogenase, subunit A |
| Description: | Formylmethanofuran dehydrogenases () is found in methanogenic and sulphate-reducing archaea. The enzyme contains molybdenum or tungsten, a molybdopterin guanine dinuceotide cofactor (MGD) and iron-sulphur clusters []. It catalyses the reversible reduction of CO2and methanofuran via N-carboxymethanofuran (carbamate) to N-formylmethanofuran, the first and second steps in methanogenesis from CO2[, ]. This reaction is important for the reduction of CO2to methane, in autotrophic CO2fixation, and in CO2formation from reduced C1units []. The synthesis of formylmethanofuran is crucial for the energy metabolism of archaea. Methanogenic archaea derives the energy for autrophic growth from the reduction of CO2with molecular hydrogen as the electron donor []. The process of methanogenesis consists of a series of reduction reactions at which the one-carbon unit derived from CO2is bound to C1carriers.There are two isoenzymes of formylmethanofuran dehydrogenase: a tungsten-containing isoenzyme (Fwd) and a molybdenum-containing isoenzyme (Fmd). The tungsten isoenzyme is constitutively transcribed, whereas transcription of the molybdenum operon is induced by molybdate []. The archaea Methanobacterium thermoautotrophicumcontains a 4-subunit (FwdA, FwdB, FwdC, FwdD) tungsten formylmethanofuran dehydrogenase and a 3-subunit (FmdA, FmdB, FmdC) molybdenum formylmethanofuran dehydrogenase []. This entry represents subunit A (FmdA and FwdA) of formylmethanofuran dehydrogenases. The other subunits are subunit B (), subunit C (), subunit D (), subunit E (), and subunit F (). Some organisms also encode a fusion of the C and D subunits(). Members of this entry share sequence similarity with the two highly conserved regions of dihydroorotase () (an amidohydrolase): the first is located at the N-terminal end and contains two histidine residues suggested to be involved in binding a zinc ion []; the second conserved region is at the C terminus [].In Methylobacterium extorquens, homologues of FmdA, FmdB and FmdC subunits were found and shown to copurify with a functional formyltransferase complex. However, there is no evidence that the complex catalyses the oxidation of formylmethanofuran []. | Short Name: | Formylmethanofuran_DH_asu |
