Highly Efficient Flavin–Adenine Dinucleotide Glucose Dehydrogenase Fused to a Minimal Cytochrome C Domain

Flavin–adenine dinucleotide (FAD) dependent glucose dehydrogenase (GDH) is a thermostable, oxygen insensitive redox enzyme used in bioelectrochemical applications. The FAD cofactor of the enzyme is buried within the proteinaceous matrix of the enzyme, which makes it almost unreachable for a direct communication with an electrode. In this study, FAD dependent glucose dehydrogenase was fused to a natural minimal cytochrome domain in its c-terminus to achieve direct electron transfer. We introduce a fusion enzyme that can communicate with an electrode directly, without the use of a mediator molecule. The new fusion enzyme, with its direct electron transfer abilities displays superior activity to that of the native enzyme, with a k cat that is ca. 3 times higher than that of the native enzyme, a k cat / K M that is more than 3 times higher than that of GDH and 5 to 7 times higher catalytic currents with an onset potential of ca. (−) 0.15 V vs Ag/AgCl, affording higher glucose sensing selectivity. Taking these parameters into consideration, the fusion enzyme presented can serve as a good candidate for blood glucose monitoring and for other glucose based bioelectrochemical systems.