DIRECT ELECTRON TRANSFER AT PH = 7 OF PQQ SOLUBLE GLUCOSE DEHYDROGENASE

VICTORIA FLEXER; DURAND, F.; TSUJIMURA, S.; MANO, N.

Cracovia

Simposio; XXI INTERNATIONAL SYMPOSIUM ON BIOELECTROCHEMISTRY AND BIOENERGETICS; 2011

Bioelectrochemical Society

Soluble PQQ-glucose dehydrogenase (PQQ-sGDH) has now become the major enzyme used in biosensors systems for self monitoring of blood glucose because of its high activity and, unlike glucose oxidase, its insensitivity to O2. Here we present a comprehensive study of the direct electron transfer reaction of PQQ-sGDH from Acinetobacter calcoaceticus. WT PQQ-sGDH non-specifically immobilized on carbon cryogel electrodes1 retained its enzymatic activity for glucose and maltose oxidation at pH = 7.2 and 37oC. The cyclic voltammograms in the absence of enzymatic substrate showed 2 redox peaks that can be attributed to the two step two electron oxidation/reduction of PQQ.Calibration curves showed a linear amperometric response for glucose concentration up to 50 mM. At saturation, the catalytic current reached 0.9 mA cm-2. A new mutant enzyme, N428C, developed in our group2 that shows almost twice the maximum catalytic activity in homogeneous experiments in solution, also showed a DET signal on carbon cryogel electrodes for glucose electrooxidation. Interestingly, the ratio of the amperometric signal for glucose and maltose electrooxidation was close to the ratio of the enzyme activity in solution. The higher activity for the mutant enzyme was also verified on the electrode surface.