title: Formate dehydrogenase molybdenum and tungsten sites--observation by EXAFS of structural differences.
abstract: Preliminary EXAFS data has been collected on the molybdenum (K-edge) in C. pasteurianum formate dehydrogenase and the tungsten (LIII-edge) in C. thermoaceticum formate dehydrogenase. In the presence of dithionite, the tungsten enzyme was devoid of W = O bonds, and exhibited average W-(O, N) and W-S bond lengths of 2.13 +/- 0.03 A and 2.39 +/- 0.03 A, respectively. In sharp contrast, the C. pasteurianum molybdenum site has three Mo = O bonds with an average bond length of 1.74 +/- 0.03 A. It is also the first molybdenum enzyme found lacking Mo-S bonds, and does not appear to be redox active in the presence of formate or dithionite. Model compounds WO2(8-hydroxyquinoline)2 = WO2(ox)2, and WO2(8 mercaptoquinoline)2 = WO2(tox)2, were also examined. Respective predicted bond lengths for WO2(ox)2 and WO2(tox)2 were W = O of 1.71, 1.73 A; W-N of 2.31, 2.29 A; W-O or W-S of 1.92 or 2.40 A, with estimated uncertainties of +/- 0.03 A.
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000378:metabolism*; D000494:Allosteric Regulation; D001665:Binding Sites; D003013:Clostridium / Q000201:enzymology* / Q000378:metabolism; D005560:Formate Dehydrogenases / Q000378:metabolism*; D005583:Fourier Analysis; D008982:Molybdenum / Q000378:metabolism*; D014414:Tungsten / Q000378:metabolism*
chemical_list: D008982:Molybdenum; D005560:Formate Dehydrogenases; D000445:Aldehyde Oxidoreductases; D014414:Tungsten