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  • Experimental Evidence and Mechanistic Description of the Phenolic H-Transfer to the Cu2O2 Active Site of oxy-Tyrosinase. Journal of the American Chemical Society Kipouros, I., Stańczak, A., Dunietz, E. M., Ginsbach, J. W., Srnec, M., Rulíšek, L., Solomon, E. I. 2023


    Tyrosinase is a ubiquitous coupled binuclear copper enzyme that activates O2 toward the regioselective monooxygenation of monophenols to catechols via a mechanism that remains only partially defined. Here, we present new mechanistic insights into the initial steps of this monooxygenation reaction by employing a pre-steady-state, stopped-flow kinetics approach that allows for the direct measurement of the monooxygenation rates for a series of para-substituted monophenols by oxy-tyrosinase. The obtained biphasic Hammett plot and the associated solvent kinetic isotope effect values provide direct evidence for an initial H-transfer from the protonated phenolic substrate to the Cu2O2 core of oxy-tyrosinase. The correlation of these experimental results to quantum mechanics/molecular mechanics calculations provides a detailed mechanistic description of this H-transfer step. These new mechanistic insights revise and expand our fundamental understanding of Cu2O2 active sites in biology.

    View details for DOI 10.1021/jacs.3c07450

    View details for PubMedID 37844210