A Trametes villosa laccase, produced as a recombinant protein in Aspergillus oryzae, was purified to an electrophoretically homogeneous state and employed in studies on the metabolism of bisphenol A. Structural analysis of the bisphenol A reaction products by the enzyme indicated that the dimer, trimer, tetramer, pentamer, and hexamer of bisphenol A with C-C and/or C-O bonds between phenol moieties, were formed as the result of successive oxidative-condensation. The reaction mixture also contained oligomers fragments, each with phenol molecules, suggesting the occurrence of cleavage of the formed oligomers to release 4-isopropenylphenol. A luciferase reporter assay using COS-7 cells revealed that both the soluble and insoluble fractions of the bisphenol A reaction products had no estrogenic activity even at rather high concentrations. (C) 2004 Society of Chemical Industry.