Coupling of Proton Transport across Planar Lipid Bilayer and Electron Transport Catalyzed by Membrane-bound Enzyme D-Fructose Dehydrogenase

Abstract

Proton transport from an aqueous phase (W1) to another one (W2) across a planar bilayer lipid membrane (BLM) was driven by the electron transport system. The electron transport system was composed of the oxidation of D-fructose by an oxidized form of D-fructose dehydrogenase (FDH) at the W1|BLM interface, the oxidation of a reduced form of FDH by an oxidized form of 7,7,8,8-tetracyanoquinodimethane (TCNQ) at the W1|BLM interface and the oxidation of a reduced form of TCNQ by [Fe(CN)₆]³⁻ at the W2|BLM interface. Then the negative current due to the electron transfer from W1 to W2 was clearly observed around 0 V. The zero-current potential varied to hold the electroneutrality in all phases by balancing the proton transport with the electron transport.