title: Spectrophotometric Characterization of the Action of Tyrosinase on p-Coumaric and Caffeic Acids: Characteristics of o-Caffeoquinone.
abstract: New methods are proposed to determine the activity of tyrosinase on caffeic and p-coumaric acids. Because o-quinone from caffeic acid is unstable in its presence, it has been characterized through spectrophotometric measurements of the disappearance of coupled reducing agents, such as nicotinamide adenine dinucleotide reduced form. It has also been characterized by a chronometric method, measuring the time that a known concentration of ascorbic acid takes to be consumed. The activity on p-coumaric acid has been followed by measuring the formation of o-quinone of caffeic acid at the isosbestic point originated between caffeic acid and o-caffeoquinone and measuring the formation of o-quinone at 410 nm, which is stable in the presence of p-coumaric acid (both of them in the presence of catalytic amounts of caffeic acid, maintaining the ratio between p-coumaric acid and caffeic acid constant; R = 0.025). The kcatvalue of tyrosinase obtained for caffeic acid was higher than that obtained for p-coumaric acid, while the affinity was higher for p-coumaric acid. These values agree with those obtained in docking studies involving these substrates and oxytyrosinase.
authors.forename: Antonio
authors.initials: A
authors.lastname: Garcia-Jimenez
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University , Newcastle upon Tyne NE2 4HH, United Kingdom.
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Munoz-Munoz
authors.forename: Francisco
authors.initials: F
authors.lastname: García-Molina
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Teruel-Puche
authors.forename: Francisco
authors.identifier: http://orcid.org/0000-0002-8869-067X
authors.initials: F
authors.lastname: García-Cánovas
mesh_terms: D000363:Agaricales / Q000201:enzymology*; D016227:Benzoquinones / Q000737:chemistry*; D055162:Biocatalysis; D002109:Caffeic Acids / Q000737:chemistry*; D003373:Coumaric Acids / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry*; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000737:chemistry*; D011422:Propionates; D013053:Spectrophotometry / Q000379:methods*
chemical_list: D016227:Benzoquinones; D002109:Caffeic Acids; D003373:Coumaric Acids; D005656:Fungal Proteins; D011422:Propionates; C004532:quinone; D014442:Monophenol Monooxygenase; C495469:p-coumaric acid; C040048:caffeic acid
keywords: caffeic acid; docking; p-coumaric acid; spectrophotometric characterization; tyrosinase