Phthalates, which are used as plasticizers in the plastics industry, are widely used and have been dispersed into the environment. A white-rot basidiomycete Phlebia tremellosa, which showed good growth in media containing various hormone-mimicking compounds, degraded benzylbutylphthalate and diethylphthalate by up to 30% and 80%, respectively, under liquid culture conditions for 9 days. A laccase cDNA from P. tremellosa was cloned by a rapid amplification of cDNA ends (RACE)-PCR technique, and found to encode 1832 nucleotides. Its deduced amino acid sequence showed 80.7% identity when compared with that of Phlebia radiata, and 64.8% identity when compared with that of Trametes versicolor. When this fungus was grown under suitable conditions for degrading phthalic esters, the laccase activity and its transcript level were both highly increased.

A white-rot basidiomycete, Phlebia tremellosa, produced a laccase that showed increased activity during degradation of phthalates. A laccase was purified through the ion exchange chromatography and preparative gel electrophoresis, and the estimated molecular weight was 75 kDa. The optimum pH and temperature of the purified laccase was pH 4.0 and 20 degrees C, respectively. The K(m) value of the enzyme was 55.7 microM, and the V(max) was 0.0541 OD min(-1) U(-1) for o-tolidine. Purified laccase reduced the estrogenic activity of four different endocrine-disrupting chemicals. However, this effect was reduced by a laccase inhibitor, kojic acid, which confirmed that the laccase was involved in the removal of estrogenic activity.

Irpex lacteus was genetically transformed using an laccase expression vector to get increased laccase producing strains. Stable integration of the vector was confirmed by PCR using the vector-specific primers, and the transformants showed increased laccase activities. When the transformants were grown with several endocrine disrupting chemicals, laccase activity of each transformant was induced up to six times higher than that of the wild type. They showed increased degrading activities against EDCs as well as increased removal rates of estrogenic activities generated by the EDCs than the wild type, and the laccase expression was increased during the degradations of the EDCs.