title: A stable tyrosyl radical in monoamine oxidase A.
abstract: We present spectroscopic evidence consistent with the presence of a stable tyrosyl radical in partially reduced human monoamine oxidase (MAO) A. The radical forms following single electron donation to MAO A and exists in equilibrium with the FAD flavosemiquinone. Oxidative formation of the tyrosyl radical in MAO is not reliant on neighboring metal centers and uniquely requires reduction of the active site flavin to facilitate oxidation of a tyrosyl side chain. The identified tyrosyl radical provides the key missing link in support of the single electron transfer mechanism for amine oxidation by MAO enzymes.
authors.affiliation: Department of Biological Sciences, Queen Mary College, University of London, London E1 4NS, United Kingdom.
authors.forename: Stephen E J
authors.initials: SE
authors.lastname: Rigby
authors.forename: Robert M G
authors.initials: RM
authors.lastname: Hynson
authors.forename: Rona R
authors.initials: RR
authors.lastname: Ramsay
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Munro
authors.forename: Nigel S
authors.initials: NS
authors.lastname: Scrutton
mesh_terms: D000588:Amines / Q000737:chemistry; D001665:Binding Sites; D004227:Dithionite / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005609:Free Radicals; D006801:Humans; D008956:Models, Chemical; D008995:Monoamine Oxidase / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D011809:Quinones / Q000737:chemistry; D013053:Spectrophotometry; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D000588:Amines; D005609:Free Radicals; D011809:Quinones; C001636:flavosemiquinone; D004227:Dithionite; D014443:Tyrosine; D008995:Monoamine Oxidase; D010100:Oxygen