title: Mechanisms of generation of oxygen radicals and reductive mobilization of ferritin iron by lipoamide dehydrogenase.
abstract: The oxidase reaction of lipoamide dehydrogenase with NADH generates superoxide radicals and hydrogen peroxide under aerobic conditions. ESR spin trapping using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was applied to characterize the oxygen radical species generated by lipoamide dehydrogenase and the mechanism of their generation. During the oxidase reaction of lipoamide dehydrogenase, DMPO-OOH and DMPO-OH signals were observed. The DMPO-OOH signal disappeared on addition of superoxide dismutase. These results demonstrate that the DMPO-OOH adduct was produced from the superoxide radical generated by lipoamide dehydrogenase. In the presence of dimethyl sulfoxide, a DMPO-CH3 signal appeared at the expense of the DMPO-OH signal, indicating that the DMPO-OH adduct was produced directly from the hydroxyl radical rather than by decomposition of the DMPO-OOH adduct. The DMPO-OH signal decreased on addition of superoxide dismutase, catalase, or diethylenetriaminepentaacetic acid, indicating that the hydroxyl radical was generated via the metal-catalyzed Haber-Weiss reaction from the superoxide radical and hydrogen peroxide. Addition of ferritin to the NADH-lipoamide dehydrogenase system resulted in a decrease of the DMPO-OOH signal, indicating that the superoxide radical interacted with ferritin iron.
authors.affiliation: Institute for Enzyme Research, University of Tokushima.
authors.forename: Y
authors.initials: Y
authors.lastname: Bando
authors.forename: K
authors.initials: K
authors.lastname: Aki
mesh_terms: D002374:Catalase / Q000378:metabolism; D003497:Cyclic N-Oxides; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005293:Ferritins / Q000378:metabolism*; D006878:Hydroxides / Q000378:metabolism; D017665:Hydroxyl Radical; D009243:NAD / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D003497:Cyclic N-Oxides; D006878:Hydroxides; D009243:NAD; D017665:Hydroxyl Radical; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D005293:Ferritins; D002374:Catalase; D013482:Superoxide Dismutase; D008058:Dihydrolipoamide Dehydrogenase; D010100:Oxygen