title: Kinetic study of the oxidation of 4-hydroxyanisole catalyzed by tyrosinase.
abstract: Despite the importance of the substrate 4-hydroxyanisole in melanoma therapy, the kinetics of its oxidation catalyzed by tyrosinase has never been properly characterized. This approach is reported here for the first time. The applicability to 4-hydroxyanisole of the reaction mechanism of tyrosinase previously proposed for other monophenols has been corroborated. The Michaelis constant for the oxidation of 4-hydroxyanisole catalyzed by mushroom tyrosinase was (62 +/- 1.5) microM at pH 7 and increased when the pH decreased, reaching a value of (195 +/- 5) microM at pH 5.5. However the maximum steady-state rate, whose value was (0.54 +/- 0.01) microM/min, did not change with the pH. The apparent catalytic constant was (184 +/- 5) s-1, around twenty three times higher than that previously described for L-tyrosine (8 s-1).
authors.affiliation: Departamento de Bioquímica y Biología Molecular-A, Facultad de Biología, Universidad de Murcia, Spain.
authors.forename: J C
authors.initials: JC
authors.lastname: Espín
authors.forename: R
authors.initials: R
authors.lastname: Varón
authors.forename: J
authors.initials: J
authors.lastname: Tudela
authors.forename: F
authors.initials: F
authors.lastname: García-Cánovas
mesh_terms: D000840:Anisoles / Q000737:chemistry* / Q000378:metabolism; D052160:Benzothiazoles; D002384:Catalysis; D006835:Hydrazones; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D010636:Phenols / Q000378:metabolism; D012044:Regression Analysis; D013053:Spectrophotometry; D013379:Substrate Specificity; D013844:Thiazoles / Q000737:chemistry
chemical_list: D000840:Anisoles; D052160:Benzothiazoles; D006835:Hydrazones; D010636:Phenols; D013844:Thiazoles; C009760:mequinol; D014442:Monophenol Monooxygenase; C002536:3-methyl-2-benzothiazolone hydrazone