A novel mixed valence form of Rhus vernicifera laccase and its reaction with dioxygen to give a peroxide intermediate bound to the trinuclear center.
Rhus vernicifera laccase, in a novel mixed valence state [T1oxT23red: type 1 Cu as Cu(II), and type 2 and 3 Cus as Cu(I)], was formed by reacting Cu(I) on the type 2 Cu-depleted laccase [T1oxT3red: type 1 Cu as Cu(II) and type 3 Cus as Cu(I)] under argon. Contrary to T1oxT3red, T1oxT23red was highly reactive with dioxygen, and gave the three transient bands at 340, 475, and 680 nm due to the two-electron reduced form of dioxygen [charge transfer bands from peroxide to Cu(II)]. The first order decays were highly dependent on pH, which led to the successful detection of the intermediate for ca. 2 h at pH 7.5. Another mixed valence derivative, T12oxT3red [type 1 and type 2 Cus as Cu(II), and type 3 Cus as Cu(I)] prepared through the action of Cu(II) on T1oxT3red was not reactive with dioxygen, but showed high enzyme activity as to the oxidation of N,N-dimethyl-p-phenylenediamine. The whole reaction mechanism of the reduction of dioxygen by laccase was proposed based on the present results together with data for the former detection and characterization of the three-electron reduced form of dioxygen [Huang, H. et al. (1999) J. Biol. Chem. 274, 46, 32718-32724].
Zoppellaro
G
G
Department of Chemistry, Faculty of Science, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan.
Sakurai
T
T
Huang
H
H
D001665:Binding Sites; D003300:Copper / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D042845:Laccase; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010545:Peroxides / Q000378:metabolism*; D010947:Plants, Toxic; D012251:Toxicodendron / Q000201:enzymology*
D010545:Peroxides; D003300:Copper; D010088:Oxidoreductases; D042845:Laccase; D010100:Oxygen