Oxidation of PAH and PAH-derivatives by fungal and plant oxidoreductases

The in vitro-oxidation of the three- and four-ring polycyclic aromatic hydrocarbons (PAH) anthracene, phenanthrene, pyrene and fluoranthene by preparations of extracellular lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase (Lacc) of the white rot fungus Nematoloma frowardii and by mushroom tyrosinase (Tyr) and horseradish peroxidase (HRP) was investigated. LiP transformed 58.6% of anthracene and 34.2% of pyrene, whereas 31.5% of anthracene and 11.2% pyrene were oxidized by MnP. In the presence of the mediating substances veratryl alcohol (for LiP), GSH (for MnP), and ABTS (for Lacc, Tyr, HRP), the conversion of PAH was enhanced in most cases. Inclusion of PAH-derivatives, known as intermediates or potential dead-end-products of microbial PAH metabolism, in the in vitro-oxidation studies, demonstrated that the hydroxylated PAH metabolites served as substrates for all oxidoreductases tested, whereas PAH-quinones and oxo-metabolites were not transformed.