Author: ["Cooper Citek","Christopher T. Lyons","Erik C. Wasinger","T. Daniel P. Stack"]
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Abstract
The enzyme tyrosinase contains two CuI centres, trigonally coordinated by imidazole nitrogens of six conserved histidine residues. The enzyme activates O2 to form a µ-η2:η2-peroxo–dicopper(II) core, which hydroxylates tyrosine to a catechol in the first committed step of melanin biosynthesis. Here, we report a family of synthetic peroxo complexes, with spectroscopic and chemical features consistent with those of oxygenated tyrosinase, formed through the self-assembly of monodentate imidazole ligands, CuI and O2 at −125 °C. An extensively studied complex reproduces the enzymatic electrophilic oxidation of exogenous phenolic substrates to catechols in good stoichiometric yields. The self-assembly and subsequent reactivity support the intrinsic stability of the Cu2O2 core with imidazole ligation, in the absence of a polypeptide framework, and the innate capacity to effect hydroxylation of phenolic substrates. These observations suggest that a foundational role of the protein matrix is to facilitate expression of properties native to the core by bearing the entropic costs of assembly and precluding undesired oxidative degradation pathways. A functional active-site mimic of the oxy-tyrosinase enzyme forms through self-assembly of monodentate imidazole ligands, copper(I) and oxygen at −125 °C. The fidelity of this copper–dioxygen complex to the native enzyme, its inherent stability and hydroxylation reactivity suggest that an organizational role of the protein matrix suffices to realize function. Cite this article
Citek, C., Lyons, C., Wasinger, E. et al. Self-assembly of the oxy-tyrosinase core and the fundamental components of phenolic hydroxylation. Nature Chem 4, 317–322 (2012). https://doi.org/10.1038/nchem.1284 