title: Formate dehydrogenase of Clostridium pasteurianum.
abstract: Formate dehydrogenase was purified to electrophoretic homogeneity from N2-fixing cells of Clostridium pasteurianum W5. The purified enzyme has a minimal Mr of 117,000 with two nonidentical subunits with molecular weights of 76,000 and 34,000, respectively. It contains 2 mol of molybdenum, 24 mol of nonheme iron, and 28 mol of acid-labile sulfide per mol of enzyme; no other metal ions were detected. Analysis of its iron-sulfur centers by ligand exchange techniques showed that 20 iron atoms of formate dehydrogenase can be extruded as Fe4S4 centers. Fluorescence analysis of its isolated molybdenum centers suggests it is a molybdopterin. The clostridial formate dehydrogenase has a pH optimum between 8.3 and 8.5 and a temperature optimum of 52 degrees C. The Km for formate is 1.72 mM with a Vmax of 551 mumol of methyl viologen reduced per min per mg of protein. Sodium azide competes competitively with formate (K1 = 3.57 microM), whereas the inactivation by cyanide follows pseudo-first-order kinetics with K = 5 X 10(2) M-1 s-1.
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D003013:Clostridium / Q000201:enzymology*; D004579:Electron Transport; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D008982:Molybdenum / Q000032:analysis; D009097:Multienzyme Complexes; D013045:Species Specificity; D013379:Substrate Specificity; D013440:Sulfides / Q000032:analysis
chemical_list: D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D013440:Sulfides; D008982:Molybdenum; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase