title: Reinvestigation of metal ion specificity for quinone cofactor biogenesis in bacterial copper amine oxidase.
abstract: The topa quinone (TPQ) cofactor of copper amine oxidase is generated by copper-assisted self-processing of the precursor protein. Metal ion specificity for TPQ biogenesis has been reinvestigated with the recombinant phenylethylamine oxidase from Arthrobacter globiformis. Besides Cu2+ ion, some divalent metal ions such as Co2+, Ni2+, and Zn2+ were also bound to the metal site of the apoenzyme so tightly that they were not replaced by excess Cu2+ ions added subsequently. Although these noncupric metal ions could not initiate TPQ formation under the atmospheric conditions, we observed slow spectral changes in the enzyme bound with Co2+ or Ni2+ ion under the dioxygen-saturating conditions. Resonance Raman spectroscopy and titration with phenylhydrazine provided unambiguous evidence for TPQ formation by Co2+ and Ni2+ ions. Steady-state kinetic analysis showed that the enzymes activated by Co2+ and Ni2+ ions were indistinguishable from the corresponding metal-substituted enzymes prepared from the native copper enzyme (Kishishita, S., Okajima, T., Kim, M., Yamaguchi, H., Hirota, S., Suzuki, S., Kuroda, S., Tanizawa, K., and Mure, M. (2003) J. Am. Chem. Soc. 125, 1041-1055). X-ray crystallographic analysis has also revealed structural identity of the active sites of Co- and Ni-activated enzymes with Cu-enzyme. Thus Cu2+ ion is not the sole metal ion assisting TPQ formation. Co2+ and Ni2+ ions are also capable of forming TPQ, though much less efficiently than Cu2+.
authors.affiliation: Department of Structural Molecular Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan. tokajima@sanken.osaka-u.ac.jp
authors.forename: Toshihide
authors.initials: T
authors.lastname: Okajima
authors.forename: Sei'ichiro
authors.initials: S
authors.lastname: Kishishita
authors.forename: Yen-Chen
authors.initials: YC
authors.lastname: Chiu
authors.forename: Takeshi
authors.initials: T
authors.lastname: Murakawa
authors.forename: Misa
authors.initials: M
authors.lastname: Kim
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Shun
authors.initials: S
authors.lastname: Hirota
authors.forename: Shun'ichi
authors.initials: S
authors.lastname: Kuroda
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Tanizawa
mesh_terms: D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry* / Q000378:metabolism*; D001173:Arthrobacter / Q000201:enzymology*; D016227:Benzoquinones / Q000378:metabolism*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D007477:Ions / Q000737:chemistry / Q000378:metabolism; D019216:Metals, Heavy / Q000737:chemistry / Q000378:metabolism*; D013057:Spectrum Analysis
chemical_list: D016227:Benzoquinones; D007477:Ions; D019216:Metals, Heavy; C004532:quinone; D006631:Amine Oxidase (Copper-Containing)