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EFFECT OF HUMIC CONSTITUENTS ON THE TRANSFORMATION OF CHLORINATED PHENOLS AND ANILINES IN THE PRESENCE OF OXIDOREDUCTIVE ENZYMES OR BIRNESSITE. (R823847)
Citation:
Park, J., J. Dec, J. Kime, AND J. Bollag. EFFECT OF HUMIC CONSTITUENTS ON THE TRANSFORMATION OF CHLORINATED PHENOLS AND ANILINES IN THE PRESENCE OF OXIDOREDUCTIVE ENZYMES OR BIRNESSITE. (R823847). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 33:2028-2034, (1999).
Description:
Chlorinated phenols and anilines are transformed and detoxified in soil
through oxidative coupling reactions mediated by enzymes or metal oxides. The
reactions may be influenced by humic constituents, such as syringaldehyde or
catechol, that originate from lignin decomposition and are also subject to
oxidative coupling. In this study, the effect of humic constituents on
xenobiotic transformation was evaluated in vitro based on the determination of
unreacted chlorophenols and chloroanilines. In experiments with peroxidase,
laccase, and birnessite (src="/ncer/pubs/images/delta.gif">-MnO2), the transformation of most
chlorophenols was considerably enhanced by the addition of syringaldehyde. Less
enhancement was observed using 4-hydroxybenzoic acid, and the addition of
catechol resulted in a reduction of most transformations. The opposite was
observed in experiments with tyrosinase, in which case catechol caused
considerable enhancement of chlorophenol transformation. The varying effect of
catechol can be explained by different transformation mechanisms involving
either o-quinone coupling (with tyrosinase) or free radical coupling
(with peroxidase, laccase, or birnessite). Regardless of the agent used to
mediate the reactions, chloroanilines seemed to undergo nucleophilic addition to
quinone oligomers, which resulted from coupling of the humic constituents.
Catechol, which readily forms quinones and quinone oligomers, was most efficient
in enhancing these reactions.