Structural and Bioelectrochemical Elucidation of Direct Electron Transfer-type Membrane-bound Fructose Dehydrogenase

Flavin adenine dinucleotide (FAD)-dependent fructose dehydrogenase (FDH) from Gluconobacter japonicus NBRC3260, a membrane-bound flavohemoprotein capable of direct electron transfer (DET)-type bioelectrocatalysis, was investigated from the viewpoints of structural biology and bioelectrochemistry. As FDH provides a strong DET-type catalytic signal, extensive research has been conducted. Structural analysis using cryo-electron microscopy (cryo-EM) and single-particle analysis revealed the entire FDH structure. The electron transfer (ET) pathway during the catalytic oxidation of D-fructose was investigated using thermodynamic and kinetic approaches in bioelectrochemistry, as well as structural information. Key amino acid residues that play important roles in substrate specificity and ET acceleration have also been proposed.