title: 2,4,5-Trihydroxyphenylalanine quinone biogenesis in the copper amine oxidase from Hansenula polymorpha with the alternate metal nickel.
abstract: Copper amine oxidase (CAO) is a dual-functioning enzyme that catalyzes the biosynthesis of a self-derived coenzyme and subsequent oxidative deamination of primary amines. The organic cofactor, 2,4,5-trihydroxyphenylalanine quinone (TPQ), is generated from the post-translational modification of an active site tyrosine (Y405) in a reaction shown to be dependent on both molecular oxygen and a mononuclear copper center. Previous investigations of Cu(II)-dependent cofactor formation in the Hansenula polymorpha amine oxidase (HPAO) provided evidence for the coordination of the precursor tyrosine in forming a ligand-to-metal charge transfer complex as a means of activating the tyrosyl ring for direct attack by triplet-state dioxygen. To further delineate the role of the metal in facilitating this complex series of reactions, apo-HPAO was reconstituted with alternate metals of varying reduction potentials and Lewis acidities [Ni(II), Co(II), Mn(II), Fe(II), and Fe(III)] and the consequence of each substitution on TPQ biogenesis examined. Ni(II) was found to support the transformation of the precursor tyrosine to the quinone cofactor to yield a mature enzyme competent for methylamine oxidation. Detailed kinetic analysis of the mechanism of TPQ biogenesis for the Ni(II)-substituted enzyme has led to the proposal of a direct electron transfer from the metal-coordinated tyrosinate to dioxygen as the dominant rate-limiting step.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Samuels
authors.forename: Judith P
authors.initials: JP
authors.lastname: Klinman
mesh_terms: D006631:Amine Oxidase (Copper-Containing) / Q000378:metabolism*; D001665:Binding Sites; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000378:metabolism; D007700:Kinetics; D008670:Metals / Q000737:chemistry / Q000378:metabolism; D009532:Nickel / Q000737:chemistry* / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010843:Pichia / Q000201:enzymology*; D011499:Protein Processing, Post-Translational; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism
chemical_list: C086758:2,4,5-trihydroxyphenylalanine quinone; D008670:Metals; D014443:Tyrosine; D004295:Dihydroxyphenylalanine; D009532:Nickel; D006631:Amine Oxidase (Copper-Containing); D010100:Oxygen