title: Hydroxylamine and hydrazine bind directly to the heme iron of the heme-heme oxygenase-1 complex.
abstract: We investigated whether or not hydroxylamine (HA) and hydrazine (HZ) interact with heme bound to heme oxygenase-1. Anaerobic addition of either HA or HZ to the ferric heme-enzyme complex produced a low-spin heme species. Titration studies at different pHs revealed that the neutral form of each of HA and HZ selectively binds to the heme with dissociation constants of 9.8 and 1.8 mM, respectively. Electron spin resonance analysis suggested that the nitrogen atom of each amine is coordinated to the ferric heme iron. With a concentrated solution of the heme-enzyme complex, however, another species of HA binding appeared, in which the oxygen atom of HA is coordinated to the iron. This species showed an unusual low-spin signal which is similar to that of the ferric hydroperoxide species in the heme oxygenase reaction.
authors.affiliation: Department of Medical Biochemistry, Kurume University School of Medicine, 67 Asahi-machi, Kurume 830-0011, Japan. sakamoto@med.kurume-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sakamoto
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Higashimoto
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Hayashi
authors.forename: Masakazu
authors.initials: M
authors.lastname: Sugishima
authors.forename: Keiichi
authors.initials: K
authors.lastname: Fukuyama
authors.forename: Graham
authors.initials: G
authors.lastname: Palmer
authors.forename: Masato
authors.initials: M
authors.lastname: Noguchi
mesh_terms: D000818:Animals; D006418:Heme / Q000737:chemistry*; D006419:Heme Oxygenase (Decyclizing) / Q000737:chemistry*; D051547:Heme Oxygenase-1; D006834:Hydrazines / Q000737:chemistry*; D019811:Hydroxylamine / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D051381:Rats
chemical_list: D006834:Hydrazines; C029424:hydrazine; D019811:Hydroxylamine; D006418:Heme; D007501:Iron; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1