Journal of Biological Chemistry
Volume 276, Issue 44, 2 November 2001, Pages 40991-40997
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ENZYME CATALYSIS AND REGULATION
Characterization of the B12- and Iron-Sulfur-containing Reductive Dehalogenase fromDesulfitobacterium chlororespirans*210

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The United Nations and the U.S. Environmental Protection Agency have identified a variety of chlorinated aromatics that constitute a significant health and environmental risk as “priority organic pollutants,” the so-called “dirty dozen.” Microbes have evolved the ability to utilize chlorinated aromatics as terminal electron acceptors in an energy-generating process called dehalorespiration. In this process, a reductive dehalogenase (CprA), couples the oxidation of an electron donor to the reductive elimination of chloride. We have characterized the B12 and iron-sulfur cluster-containing 3-chloro-4-hydroxybenzoate reductive dehalogenase from Desulfitobacterium chlororespirans. By defining the substrate and inhibitor specificity for the dehalogenase, the enzyme was found to require an hydroxyl grouportho to the halide. Inhibition studies indicate that the hydroxyl group is required for substrate binding. The carboxyl group can be replaced by other functionalities, e.g. acetyl or halide groups, ortho or meta to the chloride to be eliminated. The purified D. chlororespirans enzyme could dechlorinate an hydroxylated PCB (3,3′,5,5′-tetrachloro-4,4′-biphenyldiol) at a rate about 1% of that with 3-chloro-4-hydroxybenzoate. Solvent deuterium isotope effect studies indicate that transfer of a single proton is partially rate-limiting in the dehalogenation reaction.

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Published, JBC Papers in Press, August 31, 2001, DOI 10.1074/jbc.M106217200

*

This work was supported by National Science Foundation Grant MCB9974836 (to S. W. R).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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The on-line version of this article (available athttp://www.jbc.org) contains Supplemental Figures 1S and 2S.