title: Bimolecular Rate Constants for FAD-Dependent Glucose Dehydrogenase from Aspergillus terreus and Organic Electron Acceptors.
abstract: The flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) fromAspergillusspecies require suitable redox mediators to transfer electrons from the enzyme to the electrode surface for the application of bioelectrical devices. Although several mediators for FAD-GDH are already in use, they are still far from optimum in view of potential, kinetics, sustainability, and cost-effectiveness. Herein, we investigated the efficiency of various phenothiazines and quinones in the electrochemical oxidation of FAD-GDH fromAspergillus terreus. At pH 7.0, the logarithm of the bimolecular oxidation rate constants appeared to depend on the redox potentials of all the mediators tested. Notably, the rate constant of each molecule for FAD-GDH was approximately 2.5 orders of magnitude higher than that for glucose oxidase fromAspergillussp. The results suggest that the electron transfer kinetics is mainly determined by the formal potential of the mediator, the driving force of electron transfer, and the electron transfer distance between the redox active site of the mediator and the FAD, affected by the steric or chemical interactions. Higherk₂ values were found for ortho-quinones than for para-quinones in the reactions with FAD-GDH and glucose oxidase, which was likely due to less steric hindrance in the active site in the case of the ortho-quinones.
authors.affiliation: Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan. nozomu.tsuruoka1@gmail.com.
authors.forename: Nozomu
authors.initials: N
authors.lastname: Tsuruoka
authors.affiliation: Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan. takumegu0804@gmail.com.
authors.forename: Takuya
authors.initials: T
authors.lastname: Sadakane
authors.affiliation: Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan. hayashi.rika.gf@un.tsukuba.ac.jp.
authors.forename: Rika
authors.initials: R
authors.lastname: Hayashi
authors.affiliation: Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan. seiya@ims.tsukuba.ac.jp.
authors.forename: Seiya
authors.initials: S
authors.lastname: Tsujimura
mesh_terms: D001230:Aspergillus / Q000201:enzymology*; D016227:Benzoquinones / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D005948:Glucose Dehydrogenases / Q000378:metabolism*; D007700:Kinetics; D010084:Oxidation-Reduction; D010640:Phenothiazines / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D005656:Fungal Proteins; D010640:Phenothiazines; D005182:Flavin-Adenine Dinucleotide; C004532:quinone; D005948:Glucose Dehydrogenases; C031637:phenothiazine
keywords: flavin adenine dinucleotide; glucose dehydrogenase; phenothiazine; quinone; redox mediator