Tyrosinase-catalyzed hydroxylation of hydroquinone, a depigmenting agent, to hydroxyhydroquinone: A kinetic study.
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.
GENZ: Grupo de Investigación de Enzimología, Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Campus de Excelencia Internacional 'Mare Nostrum', Universidad de Murcia, Espinardo, Murcia E-30100, Spain.
María del Mar
Mdel M
García-Molina
GENZ: Grupo de Investigación de Enzimología, Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Campus de Excelencia Internacional 'Mare Nostrum', Universidad de Murcia, Espinardo, Murcia E-30100, Spain.
Jose Luis
JL
Muñoz Muñoz
Grupo de Investigación de Electroquímica Teórica y Aplicada, Departamento de Física-Química, Facultad de Química, Campus de Excelencia Internacional 'Mare Nostrum', Universidad de Murcia, Espinardo, Murcia E-30100, Spain.
Francisco
F
Martinez-Ortiz
SUIC (Servicio de Instrumentación Científica), Universidad de Murcia, Spain.
José Rodriguez
JR
Martinez
QCBA: Grupo de Química de Carbohidratos y Tecnología de Alimentos, Departamento de Química Orgánica, Facultad de Química, Campus de Excelencia Internacional 'Mare Nostrum', Universidad de Murcia, Espinardo, Murcia E-30100, Spain.
Pedro Antonio
PA
García-Ruiz
GENZ: Grupo de Investigación de Enzimología, Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Campus de Excelencia Internacional 'Mare Nostrum', Universidad de Murcia, Espinardo, Murcia E-30100, Spain.
José Neptuno
JN
Rodriguez-López
GENZ: Grupo de Investigación de Enzimología, Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Campus de Excelencia Internacional 'Mare Nostrum', Universidad de Murcia, Espinardo, Murcia E-30100, Spain. Electronic address: canovasf@um.es.
Francisco
F
García-Cánovas
D001205:Ascorbic Acid / Q000737:chemistry; D055162:Biocatalysis; D006861:Hydrogen Peroxide / Q000737:chemistry; D006873:Hydroquinones / Q000737:chemistry / Q000378:metabolism*; D006900:Hydroxylation; D007700:Kinetics; D015394:Molecular Structure; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D062327:Skin Lightening Preparations / Q000737:chemistry / Q000378:metabolism*
D006873:Hydroquinones; D062327:Skin Lightening Preparations; C013038:hydroxyhydroquinone; D006861:Hydrogen Peroxide; D014442:Monophenol Monooxygenase; D001205:Ascorbic Acid; C031927:hydroquinone
2-Hydroxy-p-benzoquinone; Ascorbic acid; Hydrogen peroxide; Hydroquinone; Kinetic; Tyrosinase