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Nature of the intermediate formed in the reduction of O(2) to H(2)O at the trinuclear copper cluster active site in native laccase.
- Source :
-
Journal of the American Chemical Society [J Am Chem Soc] 2002 May 29; Vol. 124 (21), pp. 6180-93. - Publication Year :
- 2002
-
Abstract
- The multicopper oxidases contain at least four copper atoms and catalyze the four-electron reduction of O(2) to H(2)O at a trinuclear copper cluster. An intermediate, termed native intermediate, has been trapped by a rapid freeze-quench technique from Rhus vernicifera laccase when the fully reduced form reacts with dioxygen. This intermediate had been described as an oxygen-radical bound to the trinuclear copper cluster with one Cu site reduced. XAS, however, shows that all copper atoms are oxidized in this intermediate. A combination of EXAFS, multifrequency EPR, and VTVH MCD has been used to understand how this fully oxidized trinuclear Cu cluster relates to the fully oxidized resting form of the enzyme. It is determined that in the native intermediate all copper atoms of the cluster are bridged by the product of full O(2) reduction. In contrast, the resting form has one copper atom of the cluster (the T2 Cu) magnetically isolated from the others. The native intermediate decays to the resting oxidized form with a rate that is too slow to be in the catalytic cycle. Thus, the native intermediate appears to be the catalytically relevant fully oxidized form of the enzyme, and its role in catalysis is considered.
- Subjects :
- Binding Sites
Copper metabolism
Electron Spin Resonance Spectroscopy
Laccase
Models, Chemical
Oxidation-Reduction
Oxidoreductases metabolism
Oxygen metabolism
Plant Proteins chemistry
Plant Proteins metabolism
Rhus enzymology
Spectrometry, X-Ray Emission
Spectrophotometry, Ultraviolet
Water metabolism
Copper chemistry
Oxidoreductases chemistry
Oxygen chemistry
Water chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 0002-7863
- Volume :
- 124
- Issue :
- 21
- Database :
- MEDLINE
- Journal :
- Journal of the American Chemical Society
- Publication Type :
- Academic Journal
- Accession number :
- 12022853
- Full Text :
- https://doi.org/10.1021/ja0114052