Experimental Evidence and Mechanistic Description of the Phenolic H-Transfer to the Cu2O2 Active Site of oxy-Tyrosinase

0576720 - ÚOCHB 2024 RIV US eng J - Journal Article
Kipouros, I. - Stanczak, Agnieszka - Dunietz, E. M. - Ginsbach, J. W. - Srnec, Martin - Rulíšek, Lubomír - Solomon, E. I.
Experimental Evidence and Mechanistic Description of the Phenolic H-Transfer to the Cu2O2 Active Site of oxy-Tyrosinase.
Journal of the American Chemical Society. Roč. 145, č. 42 (2023), s. 22866-22870. ISSN 0002-7863. E-ISSN 1520-5126
R&D Projects: GA ČR(CZ) GA23-05940S
Research Infrastructure: e-INFRA CZ - 90140
Institutional support: RVO:61388963 ; RVO:61388955
Keywords : copper * hydroxylation * monooxygenase
OECD category: Physical chemistry; Physical chemistry (UFCH-W)
Impact factor: 15, year: 2022
Method of publishing: Limited access
https://doi.org/10.1021/jacs.3c07450

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.
Permanent Link: https://hdl.handle.net/11104/0346146