O2 activation by binuclear Cu sites:: Noncoupled versus exchange coupled reaction mechanisms
O2 activation by binuclear Cu sites:: Noncoupled versus exchange coupled reaction mechanisms
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DOI：
10.1073/pnas.0402114101
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发表时间：
2004-09-07
影响因子：
11.1
通讯作者：
Solomon, EI
中科院分区：
文献类型：
--
作者：
Chen, P;Solomon, EI
双核铜蛋白在生物学中对O-2的结合和活化起着重要作用，根据双核铜中心之间的磁性相互作用，双核铜蛋白可分为偶联和非偶联双核两种。偶联的双核铜蛋白包括血蓝蛋白、酪氨酸酶和儿茶酚氧化酶。这些蛋白质具有两个Cu中心，通过直接桥连配体强磁性耦合，所述直接桥连配体提供了将O-2还原为μ-η（2）：η（2）侧上过氧化物桥连的Cu-II/O-2物质的机制。这种侧桥过氧-Cu-2（II）物种被激活的亲电攻击的酚环的基板。非偶联的双核铜蛋白包括肽酰甘氨酸α-羟基化单加氧酶和多巴胺β-单加氧酶。这些蛋白质具有双核Cu活性位点，这些活性位点是遥远的，没有表现出交换相互作用，并且在单个Cu中心激活O-2以产生反应性Cu-II/O-2物种，用于从底物的C-H键中提取H原子。在耦合双核铜酶的O-2中间体可以被捕获和光谱研究。在非耦合双核铜蛋白可能的中间体可以通过相关的单核铜-II/O-2模型复合物来定义。这两类双核铜蛋白中的不同中间体表现出不同的反应性，这与它们不同的电子结构和双核铜中心之间的交换耦合相互作用有关。这些研究提供了深入了解在其反应机制的Cu中心之间的交换耦合的作用。
Binuclear Cu proteins play vital roles in O-2 binding and activation in biology and can be classified into coupled and noncoupled binuclear sites based on the magnetic interaction between the two Cu centers. Coupled binuclear Cu proteins include hemocyanin, tyrosinase, and catechol oxidase. These proteins have two Cu centers strongly magnetically coupled through direct bridging ligands that provide a mechanism for the 2-electron reduction Of O-2 to a mu-eta(2):eta(2) side-on peroxide bridged Cu-II/O-2 species. This side-on bridged peroxo-Cu-2(II) species is activated for electrophilic attack on the phenolic ring of substrates. Noncoupled binuclear Cu proteins include pepticlylglycine alpha-hydroxylating moncoxygenase and dopamine beta-monooxygenase. These proteins have binuclear Cu active sites that are distant, that exhibit no exchange interaction, and that activate O-2 at a single Cu center to generate a reactive Cu-II/O-2 species for H-atom abstraction from the C-H bond of substrates. O-2 intermediates in the coupled binuclear Cu enzymes can be trapped and studied spectroscopically. Possible intermediates in noncoupled binuclear Cu proteins can be defined through correlation to mononuclear Cu-II/O-2 model complexes. The different intermediates in these two classes of binuclear Cu proteins exhibit different reactivities that correlate with their different electronic structures and exchange coupling interactions between the binuclear Cu centers. These studies provide insight into the role of exchange coupling between the Cu centers in their reaction mechanisms.