AEI 67 |
| The ubiquitous binuclear copper enzyme tyrosinase activates O2 to form a μ-η2:η2-peroxodicopper(II) complex, which oxidizes phenols to catechols. A synthetic, spectroscopically faithful model complex, capable of aromatic hydroxylation at –80 °C, forms a reactive intermediate upon phenolate addition at extreme temperature in solution (–120 °C). Detailed spectroscopic characterization supports a bis-μ-oxodicopper(III)-phenolate complex as the electrophilic oxidant, in which the O–O bond is cleaved. Overall, the evidence for sequential O–O bond cleavage and C–O bond formation suggests an alternative intimate mechanism for phenol hydroxylation. Other studies have focused on 1-aminocyclopropane-1-carboxylic acid oxidase (ACC oxidase), a non-heme iron enzyme that produces the plant hormone ethylene, important in many aspects of plant growth and development. Steady- and pre-steady-state kinetic analyses and 18O kinetic isotope effect measurements were employed to determine the order of substrate binding, the nature of the activated iron-oxygen species involved in substrate oxidation, and to characterize the intermediates that accumulate during catalytic turnover. Several ACC substrate analogues that can inhibit ethylene production have been kinetically investigated with the goal of designing a mechanism-based inhibitor. The use of radioactively labeled analogues has been employed to determine the fate of substrate breakdown products and the role of active site residues in catalysis. |
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Academic Employment Initiative
8:00 PM-10:00 PM, Monday, August 20, 2007 BCEC -- Exhibit Hall - B2, Sci-Mix
Academic Employment Initiative |