Oxidative 4-dechlorination of polychlorinated phenols is catalyzed by extracellular fungal lignin peroxidases
The extracellular lignin peroxidases (ligninases) of Phanerochaete chrysosporium catalyzed H/sub 2/O/sub 2/-dependent spectral changes in several environmentally significant polychlorinated phenols: 2,4-dichloro-, 2,4,5-trichloro-, 2,4,6-trichloro-, and pentachlorophenol. Gas chromatography/mass spectrometry of reduced and acetylated reaction products showed that, in each case, lignin peroxidase catalyzed a 4-dechlorination of the starting phenol to yield a p-benzoquinone. The oxidation of 2,4-dichlorophenol also yielded a dechlorinated coupling dimer, tentatively identified as 2-chloro-6-(2,4-dichlorophenoxy)-p-benzoquinone. Experiments on the stoichiometry of 2,4,6-trichlorophenol oxidation showed that this substrate was quantitatively dechlorinated to give the quinone and inorganic chloride. H/sub 2//sup 18/O-labeling experiments on 2,4,6-trichlorophenol oxidation demonstrated that water was the source of the new 4-oxo substituent in 2,6-di-chloro-p-benzoquinone. The results indicate a mechanism whereby lignin peroxidase oxidizes a 4-chlorinated phenol to an electrophilic intermediate, perhaps the 4-chlorocyclohexadienone cation. Nucleophilic attack by water and elimination of HCl then ensue at the 4-position, which produces the quinone. Lignin peroxidases have previously been implicated in the degradation by Phanerochaete of several nonphenolic aromatic pollutants. It appears likely from their results that these peroxidases could also catalyze the initial dechlorination of certain polychlorinated phenols in vivo.
- Research Organization:
- State Univ. of New York, Syracuse (USA)
- OSTI ID:
- 6326308
- Journal Information:
- Biochemistry; (United States), Vol. 27:17
- Country of Publication:
- United States
- Language:
- English
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CHLORINATED AROMATIC HYDROCARBONS
DECHLORINATION
LABELLED COMPOUNDS
PEROXIDASES
BIOCHEMISTRY
GAS CHROMATOGRAPHY
HYDROCHLORIC ACID
LIGNIN
MASS SPECTROSCOPY
OXYGEN 18
PHANEROCHAETE
PHENOLS
WATER
AROMATICS
CARBOHYDRATES
CHEMICAL REACTIONS
CHEMISTRY
CHROMATOGRAPHY
DEHALOGENATION
ENZYMES
EUMYCOTA
EVEN-EVEN NUCLEI
FUNGI
HALOGENATED AROMATIC HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INORGANIC ACIDS
ISOTOPES
LIGHT NUCLEI
NUCLEI
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDOREDUCTASES
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PLANTS
POLYSACCHARIDES
SACCHARIDES
SEPARATION PROCESSES
SPECTROSCOPY
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques