Redox characteristics of the tungsten DMSO reductase of Rhodobacter capsulatus |
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Authors: | Hagedoorn Peter Leon Hagen Wilfred R Stewart Lisa J Docrat Arefa Bailey Susan Garner C David |
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Affiliation: | Kluyver Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, Delft, The Netherlands. p.l.hagedoorn@tnw.tudelft.nl |
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Abstract: | The dimethylsulfoxide reductase (DMSOR) from Rhodobacter capsulatus is known to retain its three-dimensional structure and enzymatic activity upon substitution of molybdenum, the metal that occurs naturally at the active site, by tungsten. The redox properties of tungsten-substituted DMSOR (W-DMSOR) have been investigated by a dye-mediated reductive titration with the concentration of the W(V) state monitored by EPR spectroscopy. At pH 7.0, E(m)(W(VI)/W(V)) is -194 mV and E(m)(W(V)/W(IV)) is -134 mV. Each E(m) value of W-DMSOR is significantly lower (220 and 334 mV, respectively) than that of the corresponding couple of Mo-DMSOR. These redox potentials are consistent with the ability of Mo-DMSOR to catalyze both the reduction of DMSO to DMS and the back reaction, whereas W-DMSOR is very effective in catalyzing the forward reaction, but shows no ability to catalyze the oxidation of DMS to DMSO. |
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Keywords: | Dimethylsulfoxide reductase Tungsten Molybdenum Midpoint potential Electron paramagnetic resonance |
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