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      Tyrosinase: The four oxidation states of the active site and their relevance to enzymatic activation, oxidation and inactivation

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      Bioorganic & Medicinal Chemistry

      Elsevier BV

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          Abstract

          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.

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          Author and article information

          Journal
          Bioorganic & Medicinal Chemistry
          Bioorganic & Medicinal Chemistry
          Elsevier BV
          09680896
          April 2014
          April 2014
          : 22
          : 8
          : 2388-2395
          Article
          10.1016/j.bmc.2014.02.048
          24656803
          © 2014

          https://www.elsevier.com/tdm/userlicense/1.0/

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