title: Chemiluminescence from activated heme compounds detected in the reaction of various xenobiotics with oxyhemoglobin: comparison with several heme/hydrogen peroxide systems.
abstract: Chemiluminescence was detected in the reaction of oxyhemoglobin with various hydroxylamines and phenols, which have previously been shown to produce free radicals. The emitted light intensity correlated roughly with the methemoglobin formation rate, indicating the involvement of a photoemissive species as a reaction intermediate. In our previous work, we postulated the involvement of a catalase-insensitive, heme-bound hydrogen peroxide species in the methemoglobin formation reaction. In a series of experiments, we showed that intensive chemiluminescence occurred when hydrogen peroxide was mixed with either methemoglobin or metmyoglobin but not with hematin, which lacks the globin moiety. This suggests the involvement of the globin moiety in the light-emitting reaction sequence. The detection of paramagnetic globin species exhibiting similar kinetics as the corresponding light-emitting compound demonstrated that the assumed H2O2-heme compound has strong oxidizing properties. Accordingly, addition of bovine serum albumin to the hematin-hydrogen peroxide system also resulted in a strong chemiluminescence due to the formation of a paramagnetic transient species which could be detected by electron spin resonance (ESR). Several other heme compounds, such as cytochrome c or cytochrome c oxidase which have no vacant ligand site, did not show any light emission under similar conditions. This means that hydrogen peroxide must have access to a free-binding position on the heme. Chemiluminescence most probably stems from the transition of the initially formed heme-H2O2 adduct to the compound II type species. Due to their oxidizing nature, these species might be responsible for deleterious toxic effects such as lipid peroxidation and protein degradation.
authors.affiliation: Institute of Pharmacology and Toxicology, Veterinary University of Vienna, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Nohl
authors.forename: K
authors.initials: K
authors.lastname: Stolze
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007700:Kinetics; D008163:Luminescent Measurements; D008706:Methemoglobin / Q000378:metabolism; D008786:Metmyoglobin / Q000378:metabolism; D010108:Oxyhemoglobins / Q000378:metabolism*; D015262:Xenobiotics / Q000378:metabolism*
chemical_list: D010108:Oxyhemoglobins; D015262:Xenobiotics; D008786:Metmyoglobin; D006418:Heme; D008706:Methemoglobin; D006861:Hydrogen Peroxide