Tyrosinase-catalyzed hydroxylation of hydroquinone, a depigmenting agent, to hydroxyhydroquinone: A kinetic study

García-Molina, María del Mar, Muñoz Muñoz (Munoz), Jose Luis, Martinez-Ortiz, Francisco, Martinez, José Rodriguez, García-Ruiz, Pedro Antonio, Rodriguez-López, José Neptuno and García-Cánovas, Francisco (2014) Tyrosinase-catalyzed hydroxylation of hydroquinone, a depigmenting agent, to hydroxyhydroquinone: A kinetic study. Bioorganic & Medicinal Chemistry, 22 (13). pp. 3360-3369. ISSN 0968-0896

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Official URL: https://doi.org/10.1016/j.bmc.2014.04.048


Hydroquinone (HQ) is used as a depigmenting agent. In this work we demonstrate that tyrosinase hydroxylates HQ to 2-hydroxyhydroquinone (HHQ). Oxy-tyrosinase hydroxylates HQ to HHQ forming the complex met-tyrosinase-HHQ, which can evolve in two different ways, forming deoxy-tyrosinase and p-hydroxy-o-quinone, which rapidly isomerizes to 2-hydroxy-p-benzoquinone or on the other way generating met-tyrosinase and HHQ. In the latter case, HHQ is rapidly oxidized by oxygen to generate 2-hydroxy-p-benzoquinone, and therefore, it cannot close the enzyme catalytic cycle for the lack of reductant (HHQ). However, in the presence of hydrogen peroxide, met-tyrosinase (inactive on hydroquinone) is transformed into oxy-tyrosinase, which is active on HQ. Similarly, in the presence of ascorbic acid, HQ is transformed into 2-hydroxy-p-benzoquinone by the action of tyrosinase; however, in this case, ascorbic acid reduces met-tyrosinase to deoxy-tyrosinase, which after binding to oxygen, originates oxy-tyrosinase. This enzymatic form is now capable of reacting with HQ to generate p-hydroxy-o-quinone, which rapidly isomerizes to 2-hydroxy-p-benzoquinone. The formation of HHQ during the action of tyrosinase on HQ is demonstrated by means of high performance liquid chromatography mass spectrometry (HPLC–MS) by using hydrogen peroxide and high ascorbic acid concentrations. We propose a kinetic mechanism for the tyrosinase oxidation of HQ which allows us the kinetic characterization of the process. A possible explanation of the cytotoxic effect of HQ is discussed.

Item Type: Article
Uncontrolled Keywords: Tyrosinase, Hydroquinone, Kinetic2-Hydroxy-p-benzoquinone, Hydrogen peroxide, Ascorbic acid
Subjects: C700 Molecular Biology, Biophysics and Biochemistry
Department: Faculties > Health and Life Sciences > Applied Sciences
Depositing User: Elena Carlaw
Date Deposited: 11 Feb 2019 11:37
Last Modified: 10 Oct 2019 23:48
URI: http://nrl.northumbria.ac.uk/id/eprint/37923

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