Effect of Degree of Glycosylation on Charge of Glucose Oxidase and Redox Hydrogel Catalytic Efficiency

For most redox enzymes, the reaction center is deeply buried inside the protein structure. [1] The peptide chain of both native enzymes produced in fungi and enzymes overexpressed in eukaryotic cells are surrounded by a sugar shell, increasing both the molecular size and the distance between the active redox center and the outside surface. This latter characteristic is of upmost importance for electron transfer, either via a redox mediator or directly to an electrode surface. This is for instance the case of the FAD/FADH 2 redox centers of glucose oxidase (GOX). [2] We have recently shown that a monolayer of an almost fully deglycosylated GOX from Aspergillus niger is able to directly oxidize glucose starting at a potential close to that of FAD/FADH 2 . [3] Later, in an attempt to further increase the rate of electron transfer from the FADH 2 centers to the Os 3+ mediators in an enzyme/polymer hydrogel matrix, we compared native and deglycosylated GOXs from A. niger. [4] Interestingly we found that the latter forms a more efficient redox hydrogel structure that yields up to 38% improved glucose oxidation, but that the intrinsic electron-transfer rate remains the same as for the native enzyme.