Bioinorganic chemistry of molybdenum and tungsten enzymes: A structural–functional modeling approach

Chemical approaches toward the bioinorganic chemistry of molybdenum and tungsten enzymes had been either biomimetic (structural modeling) or bioinspired (functional modeling). Among the dithiolene type of ligands, bdt (1,2-benzene dithiolate) and related aromatic molecules as model ene–dithiolene ligands were used to react with pre-designed molybdenum complexes in organic solvents. Whereas in the alternative approach mnt (maleonitrile dithiolate) is used to mimic the ligand backbone of the central atom in the active sites of these enzymes using molybdate or tungstate as the metal source in water. Structural–functional models are known for some selected enzymes, namely, sulfite oxidase, aldehyde ferredoxin oxidoreductase, tungsten formate dehydrogenase, acetylene hydratase, polysulfide reductase and dissimilatory nitrate reductase. The protocols and methodologies adopted to achieve these model systems compared with various other model systems described in this review give testimony to chemist's ability, through chemical manipulations, to achieve the model systems which may potentially serve as structural–functional mimics of natural enzyme systems.

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