Study for structure and function of a flavoenzyme designed to a novel diagnostic enzyme

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FAD-dependent D-glucose dehydrogenase [GDH, EC 1.1.99.10] from A. oryzae catalyzes a reaction from D-glucose to D-glucono-1, 5-lactone using FAD as a cofactor. During the oxidative half-reaction, the reduced FAD is re-oxidized by electron acceptors, for instance 2, 6-dichlorophenol-indophenol and p-benzoquinone. It is expected that GDH would be utilized as a diagnostic enzyme for a biosensor that monitors the blood glucose level of diabetic patients. On the other hand, FAD-dependent D-glucose oxidase [GOX, EC 1.1.3.4] from A. niger, which shows a sequence identity of 29% with the GDH, catalyzes the same reductive half-reaction but different oxidative half-reaction; the reduced FAD is re-oxidized by O2. An oxygen reactivity of GDH is slower than that of GOX. To clarify the catalytic-reaction and substrate-binding mechanisms of GDH and how structural features govern the oxidative half-reaction between GDH and GOX, we investigated the GDH using X-ray crystallography.