9:30 AM - 11:30 AM
[16a-P3-11] Direct Electron Transfer between Single-Walled Carbon Nanotube and Flavin Adenine Dinucleotide-Dependent Glucose Dehydrogenase The Second Report
Keywords:flavin adenine dinucleotide-dependent glucose dehydrogenase, single-walled carbon nanotube, biosensor
An amperometric glucose biosensor based on Thermoascus crustaceus flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) is reported. Recombinant versions of this enzyme were expressed in the bacterium Escherichia coli (EcGDH) and in the yeasts Pichia pastoris (PpGDH) and Saccharomyces cerevisiae (ScGDH). The three GDHs had different molecular masses (EcGDH: 60 kDa, PpGDH: 90-150 kD, ScGDH: 110-250 kD) due to glycoform variations. This research investigated how the glycoforms of these novel FAD-GDHs influence the characteristics of the enzyme biosensor. To conduct a clear evaluation, a simple layer-by-layer process based on single-walled carbon nanotubes (CNT) and a plasma-polymerized thin film was adopted. The EcGDH and PpGDH electrodes provided larger electrochemical responses to glucose than did a FAD-glucose oxidase electrode used as a control, suggesting that CNT can position within electron transfer distance of FAD in the GDH molecule. It is remarkable that the current response of the glycan chain-rich PpGDH electrode is twice as high as that of the deglycosylated EcGDH electrode, whereas the electrode with the most glycan-rich ScGDH protein barely responds to glucose. A possible explanation is that PpGDH contains a suitable amount of glycan chain that does not disturb electron transfer between FAD and CNT in the absence of denaturation of the enzyme.