Radical copper oxidases, one electron at a time

James Whittaker, Mei M. Whittaker

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

Radical copper oxidases (including the fungal enzymes galactose oxidase and glyoxal oxidase) are emerging as an important family of metalloenzymes based on the free radical-coupled copper catalytic motif. The active sites of these enzymes combine a redox active copper ion with a stable protein free radical, forming a two-electron redox unit capable of oxidizing a variety of alcohols and aldehydes with reduction of dioxygen to hydrogen peroxide. This active site is remarkable in the extent to which the ligands participate in catalysis. One of the tyrosine residues dissociates from the metal center and abstracts a proton to activate substrate for oxidation, while a second tyrosine (post-translationally modified to form a tyrosine-cysteine dimer) serves as the free radical redox site. Computational studies of the substituted phenoxyl indicates that in the ground state the majority of the unpaired electron is localized on the phenoxyl oxygen and thioether sulfur atoms, accounting for the special properties of this site. Isotope kinetics have been investigated for the substrate oxidation half-reaction indicating a dramatic isotope effect (kH/kD∼20) consistent with homolytic cleavage of the methylene C-H bond and hydrogen atom transfer to the phenoxyl in the transition state.

Original languageEnglish (US)
Pages (from-to)903-910
Number of pages8
JournalPure and Applied Chemistry
Volume70
Issue number4
StatePublished - Apr 1998

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Free radicals
Free Radicals
Tyrosine
Copper
Isotopes
Electrons
Enzymes
Galactose Oxidase
Oxygen
Atoms
Oxidation
Hydrogen
Sulfides
Substrates
Aldehydes
Sulfur
Hydrogen peroxide
Dimers
Ground state
Hydrogen Peroxide

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Whittaker, J., & Whittaker, M. M. (1998). Radical copper oxidases, one electron at a time. Pure and Applied Chemistry, 70(4), 903-910.

Radical copper oxidases, one electron at a time. / Whittaker, James; Whittaker, Mei M.

In: Pure and Applied Chemistry, Vol. 70, No. 4, 04.1998, p. 903-910.

Research output: Contribution to journalArticle

Whittaker, J & Whittaker, MM 1998, 'Radical copper oxidases, one electron at a time', Pure and Applied Chemistry, vol. 70, no. 4, pp. 903-910.
Whittaker J, Whittaker MM. Radical copper oxidases, one electron at a time. Pure and Applied Chemistry. 1998 Apr;70(4):903-910.
Whittaker, James ; Whittaker, Mei M. / Radical copper oxidases, one electron at a time. In: Pure and Applied Chemistry. 1998 ; Vol. 70, No. 4. pp. 903-910.
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