Dechlorination of pesticides by a specific bacterial glutathione-S-transferase, BphKLB400: Potential for bioremediation

Abstract

The bphK gene located in the bph operon of Burkholderia xenovorans LB400 encodes a protein, BphKLB400, with significant sequence similarity to glutathione-S-transferases (GSTs). GSTs are a superfamily of enzymes involved in the detoxification of many endobiotic and xenobiotic substances. Recently, BphKLB00 was shown to catalyze the dechlorination of a number of toxic chlorinated organic compounds. Comparison of the amino acid sequence of BphKLB400 with GSTs from other bacteria that degrade polychlorinated biphenyls identified a number of highly conserved amino acids in the C-terminal region of the protein thought to be associated with substrate specificity. Mutating the conserved amino acid at position 180 of BphKLB400 from an alanine to a proline residue resulted in an increase in GST activity of bacterial cell extracts towards a number of chlorinated organic substrates tested including commonly used pesticides. Laboratory scale plant protection experiments suggested that E. coli expressing BphKLB400 [wild-type and mutant (Alal80Pro)] could protect pea plants from the effects of chloromequat chloride. Therefore, BphKLB400, identified as having dechlorination activity towards toxic chlorinated organic compounds used in the environment, could have potential in bioremediation. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.