The Maintenance Role Of A Glutathionyl-Quinol Lyase (PcpF) In Pentachlorophenol Degradation By Sphingobium Chlorophenolicum ATCC 39723

Pentachlorophenol(PCP) is a toxic pollutant.Its biodegradation has been extensively studied in Sphingobium chlorophenolicum ATCC 39723.All enzymes required to convert PCP to a common metabolic intermediate before entering the tricarboxylic acid cycle for complete mineralization have been characterized.One of the enzymes is tetrachloro-p-quinol reductive dehalogenase(PcpC),which is a glutathione S-transferase(GST).PcpC catalyzes the GSH-dependent conversion of tetrachloro-p-quinol to trichloro-p-quinol(TriCH) and then to dichloro-p-quinol (DiCH) in the PCP degradation pathway.PcpC is readily oxidatively damaged,and the damaged PcpC produces glutathionyl GS-TriCH and GS-DiCH conjugates,which cannot be further metabolized by the enzyme.Accumulation of GS-quinol conjugates inside the cells could be detrimental to the cells,as the conjugates could undergo oxidation and reduction,generating reactive oxygen species.A hypothetical GST gene (pcpF) is next to pcpC on the bacterial chromosome.The pcpF gene was cloned,and PcpF was purified.The purified PcpF was able to convert GS-TriCH and GS-DiCH conjugates to TriCH and DiCH with the co-consumption of GSH.The GS-quinol lyase reactions catalyzed by PcpF are rather unusual for a GST.The inactivation of pcpF in S.chlorophenolicum made the mutant Jose the GS-quinol lyase activities.The mutant became more sensitive to PCP toxicity and significantly decreased the PCP degradation rates.Thus,PcpF played a maintenance role in PCP degradation and converted GS-quinol conjugates back to the intermediates of PCP degradation pathway.