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Journal of Bacteriology, June 2006, p. 4424-4430, Vol. 188, No. 12
0021-9193/06/$08.00+0     doi:10.1128/JB.01849-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

A Glutathione S-Transferase Catalyzes the Dehalogenation of Inhibitory Metabolites of Polychlorinated Biphenyls

Pascal D. Fortin, Geoff P. Horsman, Hao M. Yang, and Lindsay D. Eltis*

Departments of Microbiology and Biochemistry, University of British Columbia, Vancouver, BC V6T 1Z3, Canada

Received 5 December 2005/ Accepted 3 April 2006

BphK is a glutathione S-transferase of unclear physiological function that occurs in some bacterial biphenyl catabolic (bph) pathways. We demonstrated that BphK of Burkholderia xenovorans strain LB400 catalyzes the dehalogenation of 3-chloro 2-hydroxy-6-oxo-6-phenyl-2,4-dienoates (HOPDAs), compounds that are produced by the cometabolism of polychlorinated biphenyls (PCBs) by the bph pathway and that inhibit the pathway's hydrolase. A one-column protocol was developed to purify heterologously produced BphK. The purified enzyme had the greatest specificity for 3-Cl HOPDA (kcat/Km, ~104 M–1 s–1), which it dechlorinated approximately 3 orders of magnitude more efficiently than 4-chlorobenzoate, a previously proposed substrate of BphK. The enzyme also catalyzed the dechlorination of 5-Cl HOPDA and 3,9,11-triCl HOPDA. By contrast, BphK did not detectably transform HOPDA, 4-Cl HOPDA, or chlorinated 2,3-dihydroxybiphenyls. The BphK-catalyzed dehalogenation proceeded via a ternary-complex mechanism and consumed 2 equivalents of glutathione (GSH) (Km for GSH in the presence of 3-Cl HOPDA, ~0.1 mM). A reaction mechanism consistent with the enzyme's specificity is proposed. The ability of BphK to dehalogenate inhibitory PCB metabolites supports the hypothesis that this enzyme was recruited to facilitate PCB degradation by the bph pathway.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of British Columbia, 1365-2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada. Phone: (604) 822-0042. Fax: (604) 822-6041. E-mail: leltis{at}interchange.ubc.ca.

Journal of Bacteriology, June 2006, p. 4424-4430, Vol. 188, No. 12
0021-9193/06/$08.00+0     doi:10.1128/JB.01849-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Bhowmik, S., Horsman, G. P., Bolin, J. T., Eltis, L. D. (2007). The Molecular Basis for Inhibition of BphD, a C-C Bond Hydrolase Involved in Polychlorinated Biphenyls Degradation: LARGE 3-SUBSTITUENTS PREVENT TAUTOMERIZATION. J. Biol. Chem. 282: 36377-36385 [Abstract] [Full Text]  
  • Tocheva, E. I., Fortin, P. D., Eltis, L. D., Murphy, M. E. P. (2006). Structures of Ternary Complexes of BphK, a Bacterial Glutathione S-Transferase That Reductively Dechlorinates Polychlorinated Biphenyl Metabolites. J. Biol. Chem. 281: 30933-30940 [Abstract] [Full Text]  


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