Proposed Metabolic Pathways of Hydroquinone Oxidation by Tyrosinase (IMAGE)

Fujita Health University

Proposed Metabolic Pathways of Hydroquinone Oxidation by Tyrosinase

Caption

Tyrosinase (Tyr) catalyzes hydroquinone (HQ) oxidation via two main pathways. The HBQ pathway directly oxidizes HQ to 2-hydroxy-1,4-benzoquinone (HBQ), which dimerizes and forms hydroquinone-eumelanin (HQ-EM). The BQ pathway involves dopaquinone (DQ)-mediated redox exchange producing p-benzoquinone (BQ), which reacts with cysteine (Cys) to form 2-S-cysteinylhydroquinone (Cys-HQ) and further oxidizes to hydroquinone-pheomelanin (HQ-PM). These pathways illustrate the enzymatic formation of reactive metabolites linked to exogenous ochronosis.

Credit

Emeritus Professor Shosuke Ito from Fujita Health University, Japan

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