title: Mechanism of halide-stimulated activity of chloroperoxidase evidence for enzymatic formation of free hypohalous acid.
abstract: In acidic solutions, bromide stimulates H2O2 decomposition catalyzed by chloroperoxidase or horseradish peroxidase, altogether similar to stimulation, by chloride and bromide, of H2O2 oxidation by HOCl. Low levels of an ultra-pure NaCl inhibited chloroperoxidase catalatic activity whereas very high concentrations of this salt stimulated the reaction. The stimulation reflects low bromide contamination of the ultra-pure NaCl, which is considerably less than Br levels in most AR grade chloride salts. In all of these systems, bromide functions as a catalyst which is first oxidized to Br2 by HOX (added directly or generated enzymatically), and subsequently regenerated by H2O2 reduction of Br2. These results provide strong support for a dissociable species, most likely HOX, as the first product of chloroperoxidase catalyzed oxidation of Br- and Cl- by H2O2.
mesh_terms: D001959:Bromates / Q000378:metabolism*; D001965:Bromides / Q000494:pharmacology*; D001966:Bromine / Q000378:metabolism*; D002711:Chloride Peroxidase / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology*; D004789:Enzyme Activation; D006735:Horseradish Peroxidase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006997:Hypochlorous Acid / Q000378:metabolism*; D007700:Kinetics; D010544:Peroxidases / Q000378:metabolism*
chemical_list: D001959:Bromates; D001965:Bromides; D002712:Chlorides; D006997:Hypochlorous Acid; D006735:Horseradish Peroxidase; D010544:Peroxidases; D002711:Chloride Peroxidase; C027664:hypobromous acid; D001966:Bromine