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Journal of Bacteriology, October 1998, p. 5159-5164, Vol. 180, No. 19
Department of Biochemistry and Molecular
Biology, Oregon Graduate Institute of Science and Technology,
Portland, Oregon 97291-1000
Received 10 April 1998/Accepted 22 July 1998
Under secondary metabolic conditions, the lignin-degrading
basidiomycete Phanerochaete chrysosporium mineralizes
2,4,6-trichlorophenol. The pathway for the degradation of
2,4,6-trichlorophenol has been elucidated by the characterization of
fungal metabolites and oxidation products generated by purified lignin
peroxidase (LiP) and manganese peroxidase (MnP). The multistep pathway
is initiated by a LiP- or MnP-catalyzed oxidative dechlorination
reaction to produce 2,6-dichloro-1,4-benzoquinone. The quinone is
reduced to 2,6-dichloro-1,4-dihydroxybenzene, which is reductively
dechlorinated to yield 2-chloro-1,4-dihydroxybenzene. The latter is
degraded further by one of two parallel pathways: it either undergoes
further reductive dechlorination to yield 1,4-hydroquinone, 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
subsequent degradation to CO2. In this pathway, the
chlorine at C-4 is oxidatively dechlorinated, whereas the other
chlorines are removed by a reductive process in which chlorine is
replaced by hydrogen. Apparently, all three chlorine atoms are removed prior to ring cleavage. To our knowledge, this is the first reported example of aromatic reductive dechlorination by a eukaryote.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Degradation of 2,4,6-Trichlorophenol by Phanerochaete
chrysosporium: Involvement of Reductive Dechlorination
*
Corresponding author. Mailing address: Department of
Biochemistry and Molecular Biology, Oregon Graduate Institute of
Science and Technology, P.O. Box 91000, Portland, OR 97291-1000. Phone: (503) 748-1076. Fax: (503) 748-1464. E-mail:
mgold{at}bmb.ogi.edu.
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