Tyrosine-specific bioconjugation allowing hole hopping along aromatic chains of glucose oxidase

Abstract

The potential of bioconjugated glucose oxidase enzymes for bioelectronic applications has been revealed in this research. By selectively modifying the enzyme with redox-active groups, we aimed to enhance the electrochemical properties of the enzyme while maintaining its biocatalytic activity. The phenothiazin-5-oxide and phenoxazine groups were selectively bioconjugated to the tyrosine residues on the enzyme surface. This bioconjugation was confirmed by mass spectrometry after enzymatic digestion of the protein. The self-assembly monolayer of modified enzyme exhibited improved bioelectrochemical behaviour, with enhanced anodic currents compared to the native enzyme. Marcus theory-based theoretical calculations revealed that hole hopping through the internal residues and from the electrode to the bioconjugated residues of the enzyme is thermodynamically favourable. The rate-limiting step for the bioelectrocatalytic process was identified as hole injection from the electrode to the bioconjugated enzyme surface. These findings demonstrate the potential of bioconjugated glucose oxidase for single molecule-based biosensing and bioelectronics.