title: The role of superoxide radicals in lactoperoxidase-catalysed H2O2-metabolism and in irreversible enzyme inactivation.
abstract: Irreversible inactivation of lactoperoxidase in the presence of excess H2O2 has been investigated. Serial overlay absorption spectra of the Soret region show that the rate and total amount of enzyme inactivation depend on the proton concentration. Perhydroxyl or superoxide radicals (HO.2 or O-2) cannot be established as the inactivating species in this mechanism, but they influence the rate of reconversion of the intermediate lactoperoxidase-compound III back to the resting ferric form of the enzyme.
mesh_terms: D005609:Free Radicals; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007784:Lactoperoxidase / Q000037:antagonists & inhibitors*; D010544:Peroxidases / Q000037:antagonists & inhibitors*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*
chemical_list: D005609:Free Radicals; D013481:Superoxides; D006861:Hydrogen Peroxide; D007784:Lactoperoxidase; D010544:Peroxidases; D013482:Superoxide Dismutase