title: Chemical and enzymic oxidation by tyrosinase of 3,4-dihydroxymandelate.
abstract: Tyrosinase usually catalyses the conversion of monophenols into o-diphenols and the oxidation of diphenols to the corresponding o-quinones. Sugumaran [(1986) Biochemistry 25, 4489-4492] has previously proposed an unusual oxidative decarboxylation of 3,4-dihydroxymandelate catalysed by tyrosinase. Our determination of the intermediates involved in the reaction demonstrated that 3,4-dihydroxybenzaldehyde is not the first intermediate appearing in the medium during the enzymic reaction. Re-examination of this new activity of tyrosinase has demonstrated that the product of the enzyme action is the o-quinone, which, owing to its instability, evolves to the final product, 3,4-dihydroxybenzaldehyde, by a chemical reaction of oxidative decarboxylation.
authors.affiliation: Departamento de Bioquímica, Universidad de Murcia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Cabanes
authors.forename: A
authors.initials: A
authors.lastname: Sanchez-Ferrer
authors.forename: R
authors.initials: R
authors.lastname: Bru
authors.forename: F
authors.initials: F
authors.lastname: García-Carmona
mesh_terms: D001205:Ascorbic Acid; D001487:Basidiomycota / Q000201:enzymology; D004156:Catechol Oxidase / Q000378:metabolism*; D003653:Decarboxylation; D008333:Mandelic Acids / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D013997:Time Factors
chemical_list: D008333:Mandelic Acids; C000989:3,4-dihydroxymandelic acid; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase; D001205:Ascorbic Acid