title: Identification and localization of a stable sulfenic acid in peroxide-treated tetrachlorohydroquinone dehalogenase using electrospray mass spectrometry.
abstract: BACKGROUND
  Tetrachlorohydroquinone dehalogenase catalyzes the reductive dehalogenation of tetrachlorohydroquinone to trichlorohydroquinone and then to 2,6-dichlorohydroquinone. This enzyme undergoes oxidative damage during purification which causes it to form aberrant products. The damage is reversible by treatment with dithiothreitol. Possible types of oxidative damage include an inappropriate disulfide bond, a cysteine sulfenic acid, or a methionine sulfoxide.
  
  
  RESULTS
  Using electrospray liquid chromatography / mass spectrometry, we have demonstrated that oxidation of tetrachlorohydroquinone dehalogenase with H2O2 results in formation of a sulfenic acid at Cys13. Further oxidation to a sulfinic acid was also observed.
  
  
  CONCLUSIONS
  Oxidation of Cys 13 to a sulfenic acid prevents the normal reductive dehalogenation reaction from being completed. This finding is consistent with previous work which suggested that Cys 13 acts as a nucleophile during the conversion of tetrachlorohydroquinone to trichlorohydroquinone. The technique described for identification and localization of the cysteine sulfenic acid should be applicable to a wide variety of biological systems.
authors.affiliation: Department of Chemistry and Biochemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO 80309, USA. copley@cires.colorado.edu
authors.forename: W S
authors.initials: WS
authors.lastname: Willett
authors.forename: S D
authors.initials: SD
authors.lastname: Copley
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D006867:Hydrolases / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D013434:Sulfenic Acids / Q000032:analysis*
chemical_list: D013434:Sulfenic Acids; D006861:Hydrogen Peroxide; D006867:Hydrolases; C078610:2,3,5,6-tetrachloro-4-hydroquinone reductive dehalogenase