Characterization of 2,6-Dichloro-p-hydroquinone 1,2-Dioxygenase (PcpA) of Sphingomonas chlorophenolica ATCC 39723

Pentachlorophenol (PCP) is a general biocide and a major environmental pollutant. The initial steps of PCP degradation by Sphingomonas chlorophenolica ATCC 39723 have been studied and characterized. Two enzymes are responsible for converting PCP to 2,6-dichloro-p-hydroquinone (2,6-DiCH) which is a common metabolic intermediate of the biodegradation of polychlorinated phenols. 2,6-DiCH is degraded by PcpA from strain ATCC 39723, but the reaction end product has been misidentified as 6-chlorohydroxyquinol and has been elusive to detection. We report here the overproduction of PcpA in Escherichia coli and the demonstration of quantitative conversion of 2,6-DiCH to 2-chloromaleylacetate with the coconsumption of one equivalent O2 and release of one equivalent Cl− by purified PcpA. On the basis of the reaction stoichiometry, the enzyme is proposed to be 2,6-DiCH 1,2-dioxygenase.