Ramsden, CA and Riley, PA (2014) Tyrosinase: The four oxidation states of the active site and their relevance to enzymatic activation, oxidation and inactivation. Bioorganic & Medicinal Chemistry, 22 (8). 2388 - 2395. ISSN 0968-0896

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Tyrosinase is an enzyme widely distributed in the biosphere. It is one of a group of proteins with a strongly conserved bicopper active centre able to bind molecular oxygen. Tyrosinase manifests two catalytic properties; monooxygenase and oxidase activity. These actions reflect the oxidation states of the active centre. Tyrosinase has four possible oxidation states and the details of their interaction are shown to give rise to the unusual kinetic behaviour of the enzyme. The resting state of the enzyme is met-tyrosinase [Cu(II)2] and activation, associated with a ‘lag period’, involves reduction to deoxy-tyrosinase [Cu(I)2] which is capable of binding dioxygen to form oxy-tyrosinase [Cu(II)2·O2]. Initially the conversion of met- to deoxy-tyrosinase is brought about by a catechol that is indirectly formed from an ortho-quinone product of tyrosinase action. The primary function of the enzyme is monooxygenation of phenols to ortho-quinones by oxy-tyrosinase. Inactivation of the enzyme results from monooxygenase processing of catechols which can lead to reductive elimination of one of the active-site copper ions and conversion of oxy-tyrosinase to the inactive deact-tyrosinase [Cu(II)Cu(0)]. This review describes the tyrosinase pathways and the role of each oxidation state in the enzyme’s oxidative transformations of phenols and catechols.

Item Type: Article
Additional Information: The final accepted version of this publication is available online at https://www.sciencedirect.com/science/article/pii/S0968089614001540?via%3Dihub
Uncontrolled Keywords: Tyrosinase; Monooxygenase; Oxidase; Quinones; Melanin
Subjects: Q Science > Q Science (General)
Q Science > QD Chemistry
Divisions: Faculty of Natural Sciences > School of Physical and Geographical Sciences
Depositing User: Symplectic
Date Deposited: 09 Aug 2019 07:41
Last Modified: 09 Aug 2019 13:09
URI: https://eprints.keele.ac.uk/id/eprint/6669

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