Redox characteristics of the tungsten DMSO reductase of Rhodobacter capsulatus

• Published in: FEBS letters 2003-12, Vol.555 (3), p.606-610
• Main Authors: Hagedoorn, Peter-Leon, Hagen, Wilfred R., Stewart, Lisa J., Docrat, Arefa, Bailey, Susan, Garner, C.David
• Format: Article
• Language: English
• Subjects: Catalysis; Dimethyl Sulfoxide - chemistry; Dimethyl Sulfoxide - metabolism; Dimethylsulfoxide reductase; Electron paramagnetic resonance; Electron Spin Resonance Spectroscopy; Hydrogen-Ion Concentration; Iron-Sulfur Proteins; Midpoint potential; Molybdenum; Molybdenum - chemistry; Molybdenum - metabolism; Oxidation-Reduction; Oxidoreductases - chemistry; Oxidoreductases - metabolism; Rhodobacter capsulatus; Rhodobacter capsulatus - enzymology; Titrimetry - methods; Tungsten; Tungsten - chemistry; Tungsten - metabolism
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(03)01359-0

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.