title: P-hydroxycinnamic acids as natural mediators for laccase oxidation of recalcitrant compounds.
abstract: The capabilities of p-coumaric acid (PCA), ferulic acid (FA), and sinapic acid (SA) as laccase mediators are compared in oxidation of industrial dyes and polycyclic aromatic hydrocarbons (PAH). SA behaved as highly efficient mediator in decolorization of dyes, including the recalcitrant Reactive Black 5. This mediating capacity was related to the specificity constant of the enzyme oxidizing this p-hydroxycinnamic acid, which was 16 times higher than for the typical substrate 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). The kinetics of ABTS oxidation by laccase in the presence of p-hydroxycinnamic acids suggested that the stable phenoxyl radical of a SA transformation product acts as laccase mediator. On the other hand, FA and, especially PCA, easily mediated benzo[a]pyrene oxidation, the latter also promoting the oxidation of the more recalcitrant phenanthrene. Phenanthrene transformation by laccase-PCA was enhanced by Tween 80. This fact, together with the detection of TBARS (thiobarbituric acid-reactive-substances) from unsaturated fatty acids, revealed that laccase can also initiate lipid peroxidation reactions in the presence of p-hydroxycinnamic acids enabling oxidation of the most recalcitrant PAH.
authors.affiliation: Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain. susanacam@cib.csic.es
authors.forename: Susana
authors.initials: S
authors.lastname: Camarero
authors.forename: Ana I
authors.initials: AI
authors.lastname: Cañas
authors.forename: Paula
authors.initials: P
authors.lastname: Nousiainen
authors.forename: Eric
authors.initials: E
authors.lastname: Record
authors.forename: Anne
authors.initials: A
authors.lastname: Lomascolo
authors.forename: Maria Jesús
authors.initials: MJ
authors.lastname: Martínez
authors.forename: Angel T
authors.initials: AT
authors.lastname: Martínez
mesh_terms: D001564:Benzo(a)pyrene / Q000737:chemistry; D003116:Color; D004396:Coloring Agents / Q000737:chemistry; D003373:Coumaric Acids / Q000737:chemistry*; D007700:Kinetics; D042845:Laccase / Q000737:chemistry*; D015227:Lipid Peroxidation; D010084:Oxidation-Reduction; D010616:Phenanthrenes / Q000737:chemistry; D011422:Propionates; D013056:Spectrophotometry, Ultraviolet
chemical_list: D004396:Coloring Agents; D003373:Coumaric Acids; D010616:Phenanthrenes; D011422:Propionates; D001564:Benzo(a)pyrene; C031181:phenanthrene; D042845:Laccase; C495469:p-coumaric acid