A water-soluble supramolecular complex that mimics the heme/copper hetero-binuclear site of cytochrome c oxidase.

Hiroaki Kitagishi,Jean Weiss,Yasuhiro Kudo,Daiki Shimoji,Koji Kano,Ryo Kamiya,Takashi Hayashi,Takehiro Ohta,Jennifer A Wytko,Akira Onoda

doi:10.1039/c7sc04732k

Abstract

In mitochondria, cytochrome c oxidase (CcO) catalyses the reduction of oxygen (O2) to water by using a heme/copper hetero-binuclear active site. Here we report a highly efficient supramolecular approach for the construction of a water-soluble biomimetic model for the active site of CcO. A tridentate copper(ii) complex was fixed onto 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(iii) (FeIIITPPS) through supramolecular complexation between FeIIITPPS and a per-O-methylated β-cyclodextrin dimer linked by a (2,2':6',2''-terpyridyl)copper(ii) complex (CuIITerpyCD2). The reduced FeIITPPS/CuITerpyCD2 complex reacted with O2 in an aqueous solution at pH 7 and 25 °C to form a superoxo-type FeIII-O2-/CuI complex in a manner similar to CcO. The pH-dependent autoxidation of the O2 complex suggests that water molecules gathered at the distal Cu site are possibly involved in the FeIII-O2-/CuI superoxo complex in an aqueous solution. Electrochemical analysis using a rotating disk electrode demonstrated the role of the FeTPPS/CuTerpyCD2 hetero-binuclear structure in the catalytic O2 reduction reaction.

Highlights

Cytochrome c oxidase (CcO) is the terminal enzyme in the mitochondrial respiratory chain
The pH-dependent autoxidation of the O2 complex suggests that water molecules gathered at the distal Cu site are possibly involved in the FeIII–O2À/CuI superoxo complex in an aqueous solution
The synthetic route of a supramolecular FeIIITPPS/CuIITerpyCD2 complex is shown in Scheme 1 and experimental details are described in (ESI‡)

Summary

Introduction

Cytochrome c oxidase (CcO) is the terminal enzyme in the mitochondrial respiratory chain. The pH-dependent autoxidation of the O2 complex suggests that water molecules gathered at the distal Cu site are possibly involved in the FeIII–O2À/CuI superoxo complex in an aqueous solution.

Results

Conclusion