title: Catalase-peroxidase from synechocystis is capable of chlorination and bromination reactions.
abstract: Catalase-peroxidases (KatGs) are multifunctional heme peroxidases exhibiting an overwhelming catalase activity and a substantial peroxidase activity of broad specificity. Here, we show that catalase-peroxidases are also haloperoxidases capable of oxidizing chloride, bromide, and iodide in a peroxide- and enzyme-dependent manner. Recombinant KatG and the variants R119A, W122F, and W122A from the cyanobacterium Synechocystis PCC 6803 have been tested for their halogenation activity. Halogenation of monochlorodimedon (MCD), formation of triiodide and tribromide, and bromide- and chloride-mediated oxidation of glutathione have been tested. Halogenation of MCD by chloride, bromide, and iodide was shown to be catalyzed by wild-type KatG and the variant R119A. Generally, rates of halogenation increased in the order Cl(-) < Br(-) < I(-) and/or by decreasing pH. The halogenation activity of R119A was about 7-9% that of the wild-type enzyme. Upon exchange of the distal Trp122 by Phe and Ala, both the catalase and halogenation activities were lost but the overall peroxidase activity was increased. The findings suggest that the same redox intermediate is involved in H(2)O(2) and halide oxidation and that distal Trp122 is involved in both two-electron reactions. That halides compete with H(2)O(2) for the same redox intermediate is also emphasized by the fact that the polarographically measured catalase activity is influenced by halides, with bromide being more effective than chloride.
authors.affiliation: Institute of Chemistry, Institute of Applied Microbiology, University of Agricultural Sciences, Muthgasse 18, Vienna, A-1190, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Jakopitsch
authors.forename: G
authors.initials: G
authors.lastname: Regelsberger
authors.forename: P G
authors.initials: PG
authors.lastname: Furtmüller
authors.forename: F
authors.initials: F
authors.lastname: Rüker
authors.forename: G A
authors.initials: GA
authors.lastname: Peschek
authors.forename: C
authors.initials: C
authors.lastname: Obinger
mesh_terms: D000409:Alanine / Q000737:chemistry; D001426:Bacterial Proteins / Q000378:metabolism*; D001966:Bromine / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism*; D002713:Chlorine / Q000378:metabolism*; D000458:Cyanobacteria / Q000201:enzymology*; D004583:Electrons; D029968:Escherichia coli Proteins; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007455:Iodine / Q000378:metabolism; D008956:Models, Chemical; D016297:Mutagenesis, Site-Directed; D009195:Peroxidase / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism*; D010649:Phenylalanine / Q000737:chemistry; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors; D014364:Tryptophan / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; D010649:Phenylalanine; D002713:Chlorine; D014364:Tryptophan; D007455:Iodine; D006861:Hydrogen Peroxide; D010544:Peroxidases; C081610:catalase-peroxidase, bacteria; D002374:Catalase; C051253:katG protein, E coli; D009195:Peroxidase; D000409:Alanine; D001966:Bromine