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The enzyme DMSOase, Dimethylsulfoxide Reductase, is found in many bacteria and fungi. This enzyme catalyzes the reaction
O=S(CH3)2 + 2e- + 2H+ S(CH3)2 + H2O
The conversion of water soluble DMSO to the insoluble and volatile dimethylsulfide generates energy for bacteria by stripping electrons from organic matter. The crystal structure of the oxidized enzyme is shown here in wireframe display.
th sulfur atom has a long 3.3 Å partial bond to Mo and partial disulfide bond to a neighbouring sulfur and possibly a hydrogen bond to the oxygen of Ser 147. Each pterin moiety is attached to one of the nucleotides, in this case GMP. All Mo-containing enzymes except nitrogenase are found to contain at least one pterin cofactor.
3(O-ser)). The geometry of this site is poorly resolved and more work needs to be done to determine the exact geometry.
The oxidation state of the Mo is ambiguous because of the partial bonds. There also appears to be partial bonding between the oxo group and a neighbouring sulfur at 2.2 Å. The enzyme is reduced when electrons and protons travel to the molybdenum and the oxo ligand is converted to water. The electrons are supplied by an electron transport protein.
3(O-ser) structure has been removed to produce the distorted site Mo(S)3(O-ser). This ligand deficient metal could probably only exist in the protected confines of a protein where other ligands are prevented from coordinating. DMSO can coordinate at this vacant site via the oxygen. The oxo group is abstracted from the substrate during oxidation and becomes attached to molybdenum in an exothermic reaction.