Function of a bound ubiquinone in Escherichia coli quinoprotein glucose dehydrogenase

Issue title: The Fifth Conference of the International CoQ10 Association, Kobe 2007 – 50th anniversary of CoQ10 discovery

Article type: Research Article

Authors: Mustafa, Golam | Ishikawa, Yoshinori | Kobayashi, Kazuo | Migita, Catharina T. | Tagawa, Seiichi | Yamada, Mamoru^;

Affiliations: Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi, Japan | Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University, Ube, Japan | The Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan

Note: [] Address for correspondence. Tel.: +81 83 933 5869, Fax: +81 83 933 5820; E-mail: [email protected]

Abstract: Membrane-bound glucose dehydrogenase (mGDH) is a single integral protein in the respiratory chain in Escherichia coli which oxidizes D-glucose and feeds electrons to ubiquinol oxidase via bulk ubiquinone (UQ). mGDH contains a bound UQ, CoQ_{8}, for its intramolecular electron transfer in addition to pyrroloquinoline quinone (PQQ) as a coenzyme. Pulse radiolysis analysis revealed that the bound UQ exists very close to PQQ at a distance of 11–13 Å Studies on mGDH mutants with substitutions for amino acid residues around PQQ showed that Asp-466 and Lys-493, which are crucial for catalytic activity, interact with bound UQ. Based on these findings, we propose that the bound UQ is involved in the catalytic reaction in addition to the intramolecular electron transfer in mGDH.

Keywords: Glucose dehydrogenase, pyrroloquinoline quinone, ubiquinone, intramolecular electron transfer

Journal: BioFactors, vol. 32, no. 1-4, pp. 23-29, 2008