Nature of the intermediate formed in the reduction of O2 to H2O at the trinuclear copper cluster active site in native laccase

被引:262
作者
Lee, SK
George, SD
Antholine, WE
Hedman, B
Hodgson, KO
Solomon, EI [1 ]
机构
[1] Stanford Univ, Dept Chem, Stanford, CA 94305 USA
[2] Med Coll Wisconsin, Biophys Res Inst, Natl Biomed ESR Ctr, Milwaukee, WI 53226 USA
[3] Stanford Univ, Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA
关键词
D O I
10.1021/ja0114052
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The multicopper oxidases contain at least four copper atoms and catalyze the four-electron reduction of O-2 to H2O 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 02 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.
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页码:6180 / 6193
页数:14
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