Oxidation of anthracene and benzo[a]pyrene by laccases from Trametes versicolor

The in vitro oxidation of the two polycyclic aromatic hydrocarbons anthracene and benzo[a]pyrene, which have ionization potentials of less than or equal to 7.45 eV, is catalyzed by laccases from Trametes versicolor. Crude laccase preparations were able to oxidize both anthracene and the potent carcinogen benzo[a]pyrene. Oxidation of benzo [a] pyrene was enhanced by the addition of the cooxidant 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), while an increased anthracene oxidizing ability was observed in the presence of the low-molecular-weight culture fluid ultrafiltrate. Two purified laccase isozymes from T. versicolor were found to have similar oxidative activities towards anthracene and benzo[a]pyrene. Oxidation of anthracene by the purified isozymes was enhanced in the presence of ABTS, while ABTS was essential for the oxidation of benzo[a]pyrene. In all cases anthraquinone was identified as the major end product of anthracene oxidation, These findings indicate that laccases may have a role in the oxidation of polycyclic aromatic hydrocarbons by white rot fungi.