Direct Electrochemistry of CueO and Its Mutants at Residues to and Near Type I Cu for Oxygen-Reducing Biocathode
Direct Electrochemistry of CueO and Its Mutants at Residues to and Near Type I Cu for Oxygen-Reducing Biocathode
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DOI：
10.1002/fuce.200800027
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发表时间：
2009-02-01
期刊：
影响因子：
2.8
通讯作者：
Kano, K.
中科院分区：
文献类型：
--
作者：
Miura, Y.;Tsujimura, S.;Kano, K.
CueO是一种存在于大肠杆菌中的多铜氧化酶（MCO），在碳气凝胶电极上以直接电子转移（DET）机制催化O-2的四电子还原，具有非常高的电催化活性。然而，CueO的过电位大于其他MCO。通过了解CueO的氧化还原性质，我们试图降低这种过电位。CueO在碳气凝胶电极上的直接电化学显示了一对源自I型（T1）Cu位点的氧化还原波，其氧化还原电位（E-T1（o ′））为0.28 V，相对于Ag垂直棒AgCl，pH 5.0。E-T_1（O_2）对pH的依赖性表明了质子转移和某些氨基酸残基的酸碱平衡的参与。催化电流的形状与DET生物电催化O-2中T1位点是电子入口的情况一致，在这种情况下，可以通过将E-T1（o）'向正电位移动来降低过电位。为了实现这一点，我们在M510处产生了CueO的突变体，M510是T1 Cu的轴向配体，而D439与His 443形成氢键，His 443与T1 Cu配位。两个突变体，M510 L和D439 A，成功地降低了过电位。
CueO, a multi-copper oxidase (MCO) occurring in Escherichia coli, catalyses a four-electron reduction of O-2 in a direct electron transfer (DET) mechanism with very high electrocatalytic activity on carbon aerogel electrodes. However, the overpotential of CueO is greater than that in other MCOs. By understanding the redox properties of CueO, we attempted to reduce this overpotential. Direct electrochemistry of CueO on carbon aerogel electrodes showed a pair of redox waves derived from the type I (T1) Cu site with a redox potential (E-T1(o)') of 0.28 V versus Ag vertical bar AgCl at pH 5.0. Dependence of E-T1(o)', on pH suggests the participation of proton transfer and acid-base equilibrium of some amino acid residue. The shape of the catalytic current is consistent with the T1 site being an inlet of electrons in the DET bioelectrocatalysis of O-2, in which case the overpotential could be reduced by shifting E-T1(o)' towards the positive potential. To achieve this, we created mutants of CueO at M510, which is the axial ligand of the T1 Cu, and at D439, which forms a hydrogen bond with His443 coordinated with the T1 Cu. Two mutants, M510L and D439A, successfully reduced the overpotential.