Molybdenum is one of the only 4d transition metals used by biological systems and is critical for life on this planet. Molybdenum-dependant enzymes are present in almost every living organism and play a central role in mammalian sulfur catabolism, anaerobic respiration in bacteria, and nitrate assimilation in plants. These enzymes complete oxygen atom transfers on a large variety of substrates, utilizing a molybdenum cofactor (Moco) composed of a molybdenum metal center and one or two highly conserved pyranopterin dithiolene ligands (MPT). There are a total of eight electron equivalents between the Mo center and MPT, making Moco one of the most redox rich cofactors in all of biology. Due to the instability of Moco outside of the protein matrix, there is still little known about the contributions of MPT on catalytic function. It is, however, clear that without MPT, the enzyme loses a marked amount of catalytic efficiency. In order to investigate the role of the MPT ligand in catalytic function, the Burgmayer lab has developed a family of synthetic models with the structure [TEA][Tp*Mo(X)pterin-C(CH3)2R-dithiolene], where TEA is tetraethylammonium, Tp* is tris(3,5-dimethylpyrazolyl)hydroborate, X is either oxygen or sulfur, and R is either hydroxyl or methyl. In this poster we present recent results using these synthetic models to investigate the chemical reactivity of the pterin and its potential effect on catalysis. These conclusions are supported through NMR, FT-IR, Mass Spectrometry, and Cyclic Voltammetry.

Models of the molybdenum cofactor: Synthesis and reactivity

255th National Meeting (2018)

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