Hydrogen atom abstraction by Cu(II)- and Zn(II)-phenoxyl radical complexes, models for the active form of galactose oxidase

Masayasu Taki, Hideyuki Kumei, Shinobu Itoh, Shunichi Fukuzumi

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25 Scopus citations


The Cu(II) and Zn(II) complexes of phenoxyl radical species [M(II)(L1(.))(NO3)]+ (M=Cu or Zn, L1H: 2-methylthio-4-tert-butyl-6-[[bis[2-(2-pyridyl)ethyl]amino]methyl]phenol) and [M(II)(L2(.))(NO3)]+ (M=Cu or Zn, L2H: 2,4-di-tert-butyl-6-[[bis[2-(2-pyridyl)ethyl]amino]methyl]phenol) are prepared as model complexes of the active form of galactose oxidase (GAO). Hydrogen atom abstraction of 1,4-cyclohexadiene and tert-butyl substituted phenols by the GAO model complexes proceeds very efficiently to give benzene and the corresponding phenoxyl radical or its C-C coupling dimer as the oxidation products, respectively. Kinetic analyses on the oxidation reactions have shown that the hydrogen atom abstraction of the phenol substrates is significantly enhanced by the coordinative interaction of the OH group to the metal ion center of the complex, providing valuable insight into the enzymatic mechanism of the alcohol oxidation. Details of the substrate-activation process have been discussed based on the activation parameters (ΔH(≠) and ΔS(≠)) of the reactions. Copyright (C) 1999 Elsevier Science Inc.

Original languageEnglish
Pages (from-to)1-5
Number of pages5
JournalJournal of Inorganic Biochemistry
Issue number1
StatePublished - 15 Jan 2000

Bibliographical note

Funding Information:
The present study was financially supported in part by a Grant-in-Aid for Scientific Research on Priority Area (Molecular Biometallics: 10129218 and 11116219; Electrochemistry of Ordered Interface: 10131242 and 11118244; Creation of Delocalized Conjugated Electronic System: 10146232; Active Oxygen Species: 11228206) from the Ministry of Education, Science, Sports, and Culture of Japan, and by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists (No. 02410).


  • Copper(II) complexes
  • Galactose oxidase model
  • Hydrogen atom abstraction
  • Phenoxyl radical
  • Zinc(II) complexes


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