The application of engineered glucose dehydrogenase to a direct electron-transfer-type continuous glucose monitoring system and a compartmentless biofuel cell

Continuous glucose monitoring (CGM) is expected to become an ideal way to monitor glycemic levels in diabetic patients. On the other hand, biofuel cells can be used as an alternative energy source in future implantable devices, such as implantable glucose sensors in the artificial pancreas. Glucose dehydrogenase from Acinetobacter calcoaceticus, which harbors pyrroloquinoline quinone as the prosthetic group (PQQGDH), is one of the enzymes most attractive as a glucose sensor constituent and as the anode enzyme in biofuel cells, due to its high catalytic activity and insensitivity to oxygen. However, the application of PQQGDH for these purposes is inherently limited because an electron mediator is required for the electron transfer to the electrode. We have recently reported on the development of an engineered enzyme, quinohemoprotein glucose dehydrogenase (QH-GDH), in which the cytochrome c domain of the quinohemoprotein ethanol dehydrogenase (QH-EDH) was fused with PQQGDH, to enable electron transfer to the electrode in the absence of an artificial mediator. In this study, we constructed a direct electron-transfer-type CGM system employing QH-GDH. This CGM system showed sufficient current response and high operational stability. Furthermore, we successfully constructed a compartmentless biofuel cell employing QH-GDH.