Comparative characterization of four laccases from Trametes versicolor concerning phenolic C-C coupling and oxidation of PAHs

The laccase genes Icc alpha, Icc beta, Icc gamma and Icc delta encoding four isoenzymes from Trametes versicolor have been cloned and expressed in Pichia pastoris. Biochemical characterization allowed classification of these laccases into two distinct groups: Lcc alpha and Lcc beta possessed higher thermal stability, but lower catalytic activity towards 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulpbonic acid) (ABTS) compared to Lcc gamma and Lcc delta. Activities of the laccases were quite different as well. Laccase Lcc delta showed highest phenolic C-C coupling activity with sinapic acid, but lowest oxidizing activity towards polycyclic aromatic hydrocarbons (PAHs). Highest activity towards PAHs was observed with Lcc beta. After 72 h, more than 80% of fluorene, anthracene, acenaphthene and acenaphthylene were oxidized by Lcc beta in the presence of ABTS. Investigation of the structural basis of the different activities of the laccases demonstrated the impact of positions 164 and 265 in the substrate binding site on oxidation of PAHs. (C) 2008 Elsevier Inc. All rights reserved