title: Lipid deterioration: beta-carotene destruction and oxygen evolution in a system containing lactoperoxidase, hydrogen peroxide and halides.
abstract: A model system containing lactoperoxidase/H2O2/halide decomposed beta-carotene in a reaction greatly affected by the concentration of H2O2. The optimal concentrations of H2O2 for activation of iodide and bromide were 2 mM and 10 microM, respectively. The oxidation of chloride by a lactoperoxidase, using beta-carotene destruction as a sensitive method to determine the activity of the enzyme, is reported herein. In the presence of optimal amounts of H2O2, the rate of beta-carotene destruction increases slowly until a critical concentration of the halides, followed by a rapid increase in the rate when halide concentrations were further increased. A lactoperoxidase/H2O2/iodide and/or bromide system generates oxygen in the presence of high H2O2 and halide concentrations. beta-Carotene inhibited the evolution of oxygen. A possible mechanism of beta-carotene destruction and triplet unexcited oxygen evolution by a lactoperoxidase/H2O2/halide system are proposed.
mesh_terms: D002338:Carotenoids / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D006219:Halogens; D006861:Hydrogen Peroxide; D007784:Lactoperoxidase / Q000378:metabolism*; D050356:Lipid Metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000302:isolation & purification; D010544:Peroxidases / Q000378:metabolism*; D019207:beta Carotene
chemical_list: D006219:Halogens; D019207:beta Carotene; D002338:Carotenoids; D006861:Hydrogen Peroxide; D007784:Lactoperoxidase; D010544:Peroxidases; D010100:Oxygen