Original Research Paper

Direct Electrochemistry of CueO and Its Mutants at Residues to and Near Type I Cu for Oxygen-Reducing Biocathode

  1. Y. Miura1,
  2. S. Tsujimura1,
  3. S. Kurose2,
  4. Y. Kamitaka1,
  5. K. Kataoka2,
  6. T. Sakurai2,
  7. K. Kano1

Article first published online: 24 JUL 2008

DOI: 10.1002/fuce.200800027

Issue

Fuel Cells

Fuel Cells

Special Issue: “Biofuel Cells”

Volume 9, Issue 1, pages 70–78, February, 2009

Additional Information

How to Cite

Miura, Y., Tsujimura, S., Kurose, S., Kamitaka, Y., Kataoka, K., Sakurai, T. and Kano, K. (2009), Direct Electrochemistry of CueO and Its Mutants at Residues to and Near Type I Cu for Oxygen-Reducing Biocathode. Fuel Cells, 9: 70–78. doi: 10.1002/fuce.200800027

Author Information

  1. 1

    Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan

  2. 2

    Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan

Publication History

  1. Issue published online: 11 FEB 2009
  2. Article first published online: 24 JUL 2008
  3. Manuscript Accepted: 24 JUN 2008
  4. Manuscript Received: 24 MAR 2008

Funded by

  • NEDO
  • Ministry of Education, Science, Sports and Culture of Japan. Grant Numbers: 19310070, 19350081
  • COE for Microbial Process at Kyoto University

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Keywords:

  • Carbon Aerogel Electrode;
  • CueO;
  • Multi-Copper Oxidase;
  • Redox Potential;
  • Site-Directed Mutagenesis;
  • Type I Cu Site

Abstract

CueO, a multi-copper oxidase (MCO) occurring in Escherichia coli, catalyses a four-electron reduction of O2 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 (equation image) of 0.28 V versus Ag|AgCl at pH 5.0. Dependence of equation image 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 O2, in which case the overpotential could be reduced by shifting equation image 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.

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