DEGRADATION OF 2,4,6-TRICHLOROPHENOL BY PHANEROCHAETE-CHRYSOSPORIUM -INVOLVEMENT OF REDUCTIVE DECHLORINATION

Under secondary metabolic conditions, the lignin-degrading basidiomyce te Phanerochaete chrysosporium mineralizes 2,4,6-trichlorophenol. The pathway for the degradation of 2,4,6-trichlorophenol has been elucidat ed by the characterization of fungal metabolites and oxidation product s generated by purified lignin peroxidase (LIP) and manganese peroxida se (MnP). The multistep pathway is initiated by a LIP- or MnP-catalyze d oxidative dechlorination reaction to produce 2,6-dichloro-1,4-benzoq uinone. The quinone is reduced to 2,6-dichloro-1,4-dihydroxybenzene, w hich is reductively dechlorinated to yield 2-chloro-1,4 dihydroxybenze ne. The latter is degraded further by one of two parallel pathways: it either undergoes further reductive dechlorination to yield 1,4-hydroq uinone, which is ortho-hydroxylated to produce 1,2,4-trihydroxybenzene , or is hydroxylated to yield 5-chloro-1,2,4 trihydroxybenzene, which is reductively dechlorinated to produce the common key metabolite 1,2, 4 trihydroxybenzene. Presumably, the latter is ring cleaved with subse quent degradation to CO2. In this pathway, the chlorine at C-4 is oxid atively dechlorinated, whereas the other chlorines are removed by a re ductive process in which chlorine is replaced by hydrogen. Apparently, all three chlorine atoms are removed prior to ring cleavage. To our k nowledge, this is the first reported example of aromatic reductive dec hlorination by a eukaryote.