Probing the Catalytic Mechanism of Copper Amine Oxidase from Arthrobacter globiformis with Halide Ions.
The catalytic reaction of copper amine oxidase proceeds through a ping-pong mechanism comprising two half-reactions. In the initial half-reaction, the substrate amine reduces the Tyr-derived cofactor, topa quinone (TPQ), to an aminoresorcinol form (TPQamr) that is in equilibrium with a semiquinone radical (TPQsq) via an intramolecular electron transfer to the active-site copper. We have analyzed this reductive half-reaction in crystals of the copper amine oxidase from Arthrobacter globiformis. Anerobic soaking of the crystals with an amine substrate shifted the equilibrium toward TPQsq in an "on-copper" conformation, in which the 4-OH group ligated axially to the copper center, which was probably reduced to Cu(I). When the crystals were soaked with substrate in the presence of halide ions, which act as uncompetitive and noncompetitive inhibitors with respect to the amine substrate and dioxygen, respectively, the equilibrium in the crystals shifted toward the "off-copper" conformation of TPQamr. The halide ion was bound to the axial position of the copper center, thereby preventing TPQamr from adopting the on-copper conformation. Furthermore, transient kinetic analyses in the presence of viscogen (glycerol) revealed that only the rate constant in the step of TPQamr/TPQsq interconversion is markedly affected by the viscogen, which probably perturbs the conformational change. These findings unequivocally demonstrate that TPQ undergoes large conformational changes during the reductive half-reaction.
From the Department of Biochemistry, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan.
Takeshi
T
Murakawa
the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan.
Akio
A
Hamaguchi
the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan.
Shota
S
Nakanishi
the School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan, the Advanced Photon Technology Division, RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan.
Misumi
M
Kataoka
the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan.
Tadashi
T
Nakai
the Advanced Photon Technology Division, RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan.
Yoshiaki
Y
Kawano
the School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan, the Advanced Photon Technology Division, RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan.
Hiroshi
H
Yamaguchi
the Department of Chemistry, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan, and.
Hideyuki
H
Hayashi
the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan, the Center of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, 783 71 Olomouc, Czech Republic.
Katsuyuki
K
Tanizawa
the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan, the Department of Chemistry, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan, and tokajima@sanken.osaka-u.ac.jp.
Toshihide
T
Okajima
D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry*; D001173:Arthrobacter / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D017434:Protein Structure, Tertiary
D001426:Bacterial Proteins; D003300:Copper; D006631:Amine Oxidase (Copper-Containing)
catalytic intermediate; catalytic mechanism; conformational change; copper amine oxidase; electron transfer; oxidase; quinone; radical; topa quinone; x-ray crystallography