title: Reassessment of copper stoichiometry in ascorbate oxidase.
abstract: A very pure ascorbate oxidase solution was obtained by dissolving a crystalline sample of the enzyme. The ratio between 280 and 610 nm absorbancies was 22.5. It contained 8.0 +/- 0.2 Cu ions, 50% EPR detectable, per dimeric molecule (140,000 M.W.) with a molar extinction coefficient of 10,000 cm-1 at 610 nm. Two Cu ions were removed by treatment with N,N-diethyldithiocarbamate. The optical blue absorption band was unaffected, while two EPR detectable Cu ions were lost, with disappearance of the type 2 Cu signal. It is concluded that native ascorbate oxidase contains two type 1, two type 2, and four type 3 Cu ions.
authors.affiliation: Dipartimento di Scienze Biochimiche, Università di Roma, La Sapienza, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Morpurgo
authors.forename: I
authors.initials: I
authors.lastname: Savini
authors.forename: G
authors.initials: G
authors.lastname: Gatti
authors.forename: M
authors.initials: M
authors.lastname: Bolognesi
authors.forename: L
authors.initials: L
authors.lastname: Avigliano
mesh_terms: D001204:Ascorbate Oxidase; D001426:Bacterial Proteins; D003300:Copper; D003460:Crystallization; D004578:Electron Spin Resonance Spectroscopy; D008667:Metalloproteins; D010088:Oxidoreductases; D014674:Plant Proteins, Dietary; D013053:Spectrophotometry
chemical_list: D001426:Bacterial Proteins; D008667:Metalloproteins; D014674:Plant Proteins, Dietary; C017079:mauC protein, Methylobacterium extorquens; D003300:Copper; D010088:Oxidoreductases; D001204:Ascorbate Oxidase