title: Cryogenic absorption spectra of hydroperoxo-ferric heme oxygenase, the active intermediate of enzymatic heme oxygenation.
abstract: Using radiolysis with (32)P enriched phosphate as an internal source of ionizing radiation, the formation of hydroperoxo-ferric complex from oxy-ferrous precursor with a high yield was monitored at 77 K in heme oxygenase (HO) by means of optical absorption spectroscopy. Well-resolved absorption spectra (maxima at 421 nm, 530 nm, 557 nm) of hydroperoxo-ferric intermediate of this heme enzyme were measured in 70% glycerol/buffer frozen glasses. After annealing at 210-215 K this complex converts to the product complex, alpha-meso hydroxyheme-HO. No heme degradation products were formed in control experiments with ferric HO or other heme proteins.
authors.affiliation: Department of Biochemistry, University of Illinois, 116 Morrill Hall, 505 S. Goodwin Avenue, Urbana-Champaign, IL 61801, USA.
authors.forename: Ilia G
authors.initials: IG
authors.lastname: Denisov
authors.forename: Masao
authors.initials: M
authors.lastname: Ikeda-Saito
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yoshida
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Sligar
mesh_terms: D002384:Catalysis; D003080:Cold Temperature; D004789:Enzyme Activation; D005290:Ferric Compounds / Q000737:chemistry / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000737:chemistry* / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010545:Peroxides / Q000737:chemistry / Q000378:metabolism; D013053:Spectrophotometry
chemical_list: D005290:Ferric Compounds; D010545:Peroxides; D006418:Heme; D006419:Heme Oxygenase (Decyclizing); D010100:Oxygen