Purification and characterization of a tetrachloro-p-hydroquinone reductive dehalogenase from a Flavobacterium sp

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Abstract
Tetrachloro-p-hydroquinone (TeCH) is the first intermediate in pentachlorophenol (PCP) degradation by Flavobacterium sp. strain ATCC 39723. We previously purified a PCP hydroxylase that oxidized PCP to TeCH. Subsequently, we identified the reductive dehalogenation of TeCH to 2,3,6-trichloro-p-hydroquinone and then to 2,6-dichloro-p-hydroquinone in a cell extract with the reduced form of glutathione as the reducing agent under anaerobic conditions. Here we report the purification of a TeCH reductive dehalogenase that reductively dehalogenated TeCH to trichlorohydroquinone and then to dichlorohydroquinone. The enzyme was purified by protamine sulfate treatment, ammonium sulfate fractionation, and phenyl-agarose, anion-exchange, and gel filtration column chromatographies. As determined by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses, the protein has a molecular weight of about 30,000; nondenaturing polyacrylamide gel electrophoresis analysis suggests that the native enzyme exists as a dimer. The enzyme used glutathione but not NADPH, NADH, dithiothreitol, or ascorbic acid as the reducing agent. The optimal pH was close to neutral.