title: Formation of cyanogen iodide by lactoperoxidase.
abstract: The haem protein lactoperoxidase (LPO) is an important component of the anti-microbial immune defence in external secretions and is also applied as preservative in food, oral care and cosmetic products. Upon oxidation of SCN(-) and I(-) by the LPO-hydrogen peroxide system, oxidised species are formed with bacteriostatic and/or bactericidal activity. Here we describe the formation of the inter(pseudo)halogen cyanogen iodide (ICN) by LPO. This product is formed when both, thiocyanate and iodide, are present together in the reaction mixture. Using (13)C nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry we could identify this inter(pseudo)halogen after applying iodide in slight excess over thiocyanate. The formation of ICN is based on the reaction of oxidised iodine species with thiocyanate. Further, we could demonstrate that ICN is also formed by the related haem enzyme myeloperoxidase and, in lower amounts, in the enzyme-free system. As I(-) is not competitive for SCN(-) under physiologically relevant conditions, the formation of ICN is not expected in secretions but may be relevant for LPO-containing products.
authors.affiliation: Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany. Electronic address: denise.schlorke@medizin.uni-leipzig.de.
authors.forename: Denise
authors.initials: D
authors.lastname: Schlorke
authors.affiliation: Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Flemmig
authors.affiliation: Institute of Analytical Chemistry, Department of Chemistry and Mineralogy, University of Leipzig, Leipzig, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Birkemeyer
authors.affiliation: Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Arnhold
mesh_terms: D000818:Animals; D055162:Biocatalysis; D002417:Cattle; D006861:Hydrogen Peroxide / Q000737:chemistry; D007454:Iodides / Q000138:chemical synthesis*; D007784:Lactoperoxidase / Q000737:chemistry*; D008892:Milk / Q000201:enzymology; D017672:Nitrogen Compounds / Q000138:chemical synthesis*; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry
chemical_list: D007454:Iodides; D017672:Nitrogen Compounds; D006861:Hydrogen Peroxide; D007784:Lactoperoxidase; D009195:Peroxidase
keywords: Cyanogen iodide; Iodide oxidation; Lactoperoxidase; Myeloperoxidase; Thiocyanate oxidation