Rachel Udelhoven

The DMSO reductase family consists of proteins that catalyze oxygen atom transfer reactions. These proteins are characterized by a mononuclear Mo center that is ligated by one or two molybdopterin cofactors (through the two thiolates). DMSO reductase itself is ligated by two molybdopterin cofactors and catalyzes the reduction of dimethyl sulfoxide to dimethyl sulfide. This reaction is important in the overall environmental cycle of sulfur. Using techniques such as x-ray crystallography, x-ray absorption spectroscopy, resonance Raman, and EPR, the structure and mechanism of the protein have been probed and characterized. Introduction Molybdenum is one of the most important second row transition metals biologically because it is the only one that shows activity when bound by cofactors [19]. Molybdenum proteins can be put into two different classes, nitrogenases that have an iron-molybdenum cofactor and molybdoenzymes (Moco-dependent enzymes) that have a mononuclear molybdenum center. The Moco enzymes contain three different families of proteins, the xanthine oxidase family, the sulfite reductase family and the DMSO reductase family. They catalyze oxygen atom transfers to and from substrates; in case of the hydroxylases (the xanthine family) the oxygen atom from water is inserted into C-H bonds, and the oxotransferases (the sulfite and DMSO reductase families) transfer an oxygen atom to or from one of the substrates (Eq. 1 and 2).