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- Title
Tyrosine or Tryptophan? Modifying a Metalloradical Catalytic Site by Removal of the Cys-Tyr Cross-Link in the Galactose 6-Oxidase Homologue GlxA.
- Authors
Chaplin, Amanda K.; Bernini, Caterina; Sinicropi, Adalgisa; Basosi, Riccardo; Worrall, Jonathan A. R.; Svistunenko, Dimitri A.
- Abstract
The concerted redox action of a metal ion and an organic cofactor is a unique way to maximize the catalytic power of an enzyme. An example of such synergy is the fungal galactose 6-oxidase, which has inspired the creation of biomimetic copper oxidation catalysts. Galactose 6-oxidase and its bacterial homologue, GlxA, possess a metalloradical catalytic site that contains a free radical on a covalently linked Cys-Tyr and a copper atom. Such a catalytic site enables for the two-electron oxidation of alcohols to aldehydes. When the ability to form the Cys-Tyr in GlxA is disrupted, a radical can still be formed. Surprisingly, the radical species is not the Tyr residue but rather a copper second-coordination sphere Trp residue. This is demonstrated through the introduction of a new algorithm for Trp-radical EPR spectra simulation. Our findings suggest a new mechanism of free-radical transfer between aromatic residues and that the Cys-Tyr cross-link prevents radical migration away from the catalytic site.
- Subjects
TYROSINE; TRYPTOPHAN; RADICALS (Chemistry); GALACTOSE oxidase; COPPER catalysts; METAL ions
- Publication
Angewandte Chemie, 2017, Vol 129, Issue 23, p6602
- ISSN
0044-8249
- Publication type
Article
- DOI
10.1002/ange.201701270