title: Recruitment of a double bond isomerase to serve as a reductive dehalogenase during biodegradation of pentachlorophenol.
abstract: Tetrachlorohydroquinone dehalogenase catalyzes the replacement of chlorine atoms on tetrachlorohydroquinone and trichlorohydroquinone with hydrogen atoms during the biodegradation of pentachlorophenol by Sphingomonas chlorophenolica. The sequence of the active site region of tetrachlorohydroquinone dehalogenase is very similar to those of the corresponding regions of maleylacetoacetate isomerases, enzymes that catalyze the glutathione-dependent isomerization of a cis double bond in maleylacetoacetate to the trans configuration during the catabolism of phenylalanine and tyrosine. Furthermore, tetrachlorohydroquinone dehalogenase catalyzes the isomerization of maleylacetone (an analogue of maleylacetoacetate) at a rate nearly comparable to that of a bona fide bacterial maleylacetoacetate isomerase. Since maleylacetoacetate isomerase is involved in a common and presumably ancient pathway for catabolism of tyrosine, while tetrachlorohydroquinone dehalogenase catalyzes a more specialized reaction, it is likely that tetrachlorohydroquinone dehalogenase arose from a maleylacetoacetate isomerase. The substrates and overall transformations involved in the dehalogenation and isomerization reactions are strikingly different. This enzyme provides a remarkable example of Nature's ability to recruit an enzyme with a useful structural scaffold and elaborate upon its basic catalytic capabilities to generate a catalyst for a newly needed reaction.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology and Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Campus Box 216, Boulder, Colorado 80309-0216, USA.
authors.forename: K
authors.initials: K
authors.lastname: Anandarajah
authors.forename: P M
authors.initials: PM
authors.lastname: Kiefer
authors.forename: B S
authors.initials: BS
authors.lastname: Donohoe
authors.forename: S D
authors.initials: SD
authors.lastname: Copley
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001673:Biodegradation, Environmental; D019143:Evolution, Molecular; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006867:Hydrolases / Q000235:genetics / Q000378:metabolism*; D007535:Isomerases / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010416:Pentachlorophenol / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D011549:Pseudomonas / Q000201:enzymology; D016415:Sequence Alignment; D020578:Sphingomonas / Q000201:enzymology*; D014443:Tyrosine / Q000378:metabolism; D019745:cis-trans-Isomerases / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D014443:Tyrosine; D010649:Phenylalanine; D010416:Pentachlorophenol; D005982:Glutathione Transferase; D006867:Hydrolases; C078610:2,3,5,6-tetrachloro-4-hydroquinone reductive dehalogenase; D007535:Isomerases; D019745:cis-trans-Isomerases; C021531:maleylacetoacetate isomerase; D005978:Glutathione