Products of laccase catalyzed reaction of 1-hydroxypyrene

The formation of residues in soils and sediments which are not readily extractable is an important fate for hydrophobic organic contaminants. Reaction of 1-hydroxypyrene, a known fungal and terrestrial invertebrate metabolite and photo-oxidation product of pyrene, with a commercially prepared laccase (an oxidoreductive enzyme) in solution provides a test system to study the fate of residues in nature. The reaction of dissolved 1-hydroxypyrene with laccase produced a distinct color change and caused a precipitate to form. At least six products were shown by HPLC analysis with photodiode array detection. The most prominent peak was composed of 1,6- and 1,8-pyrene-dione as confirmed by proton NMR analysis. LC/MS data on remaining peaks indicate that radical coupling produces acetonitrile soluble dimers and at least one trimer. Proposed structures consistent with MS and photodiode array data indicate that pyrene subunits are linked predominantly by ether bonds. Additional products, insoluble in acetonitrile, were also formed. The formation of complex products in vitro, indicates that the same mechanisms could produce bound residues in soil.