Xanthine oxidase families models

W-substituted Model Compounds for the DMSOR and Xanthine Oxidase Families... 

Figure 6.16 Tungsten-substituted model complexes for the DMSOR and xanthine oxidase families.

This contribution has reviewed the history, relevant background chemistry, synthetic strategies and progress towards the modelling of Mo hydroxylases (the xanthine oxidase family of enzymes). Work to date has achieved the synthesis of important active site components but their combination in idealized MoHMs (active site replicates) is complicated by the redox interplay of Mo and S and the thermodynamic instability of mononuclear. 

The bis(l,2-enedithiolate) complexes discussed closely resemble the metal centers found in the dmso reductase family of Mo enzymes and in the tungsten enzymes. The reactivity of mono(l,2-enedithiolate) complexes remains a continuing challenge as synthetic chemists pursue accurate models for the xanthine oxidase and sulfite oxidase families of metal sites. New 1,2-dithiolate ligands [70,71] and complexes are needed to demonstrate ligand effects to help elucidation reaction mechanism. 

The initial contribution to this volume provides a detailed overview of how spectroscopy and computations have been used in concert to probe the canonical members of each pyranopterin Mo enzyme family, as well as the pyranopterin dithiolene ligand itself. The discussion focuses on how a combination of enzyme geometric structure, spectroscopy and biochemical data have been used to arrive at an understanding of electronic structure contributions to reactivity in all of the major pyranopterin Mo enzyme families. A unique aspect of this discussion is that spectroscopic studies on relevant small molecule model compounds have been melded with analogous studies on the enzyme systems to arrive at a sophisticated description of active site electronic structure. As the field moves forward, it will become increasingly important to understand the structure, function and reaction mechanisms for the numerous non-canonical [ie. beyond sulfite oxidase, xanthine oxidase, DMSO reductase) pyranopterin Mo enzymes. 

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