title: A chlorine isotope effect for enzyme-catalyzed chlorination.
abstract: Several chlorinated organic compounds (COCs) that have been detected in a wide range of human, animal, and environmental samples may be derived from natural or anthropogenic sources. To determine whether the Cl isotope ratios of these compounds could be used to differentiate sources, we investigated the chlorine isotope effect for enzyme-catalyzed chlorination. Two aromatic substrates, 1,3,5-trimethylbenzene (TMB) and 3,5-dimethylphenol (DMP), were treated with a chloroperoxidase isolated from the fungus Caldariomyces fumago. A kinetic isotope effect (KIE) (in terms of k35/k37) was calculated to be 1.012 for TMB and 1.011 for DMP. A similar reaction, but not catalyzed, with hypochlorite yielded a much smaller KIE. These results indicate that a substantial KIE exists for this process. Furthermore, natural COCs synthesized by this enzymatic pathway may have Cl isotope ratios that will be easily distinguished from anthropogenic COCs.
authors.affiliation: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA. creddy@whoi.edu
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Reddy
authors.forename: Li
authors.initials: L
authors.lastname: Xu
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Drenzek
authors.forename: Neil C
authors.initials: NC
authors.lastname: Sturchio
authors.forename: Linnea J
authors.initials: LJ
authors.lastname: Heraty
authors.forename: Clare
authors.initials: C
authors.lastname: Kimblin
authors.forename: Alison
authors.initials: A
authors.lastname: Butler
mesh_terms: D002711:Chloride Peroxidase / Q000737:chemistry* / Q000378:metabolism; D002713:Chlorine / Q000737:chemistry*; D004785:Environmental Pollutants / Q000032:analysis / Q000378:metabolism; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry* / Q000378:metabolism; D007554:Isotopes; D007700:Kinetics
chemical_list: D004785:Environmental Pollutants; D006843:Hydrocarbons, Chlorinated; D007554:Isotopes; D006418:Heme; D002713:Chlorine; D002711:Chloride Peroxidase