Laccase is a multi-copper center enzyme that is able to oxidize phenolic substrates and undergo a four electron reduction of O₂ to H₂O. The interaction of laccase with different environmental toxins has been reported, whereby laccase can either oxidize pollutants (polyphenols, polyamines and paradiphenols) as fuels or be inhibited by the toxin (mercury and azide).^[1] Laccase is also commonly employed within enzymatic fuel cells (EFCs) yielding a biocathode that bioelectrocatalytically reduces O₂ to H₂O.

Self-powered biosensors are advantageous in terms of portability because they are not reliant on external power sources. In the past, glucose/O₂ EFCs have been widely used as self-powered biosensors utilizing laccase as the cathodic biocatalyst.^[2] Self-powered biosensors that sense based on enzymatic inhibition by an analyte are an important category of self-powered biosensors and have been extensively studied.^[3]

This study reports the first experimental evidence on the inhibition of laccase by two arsenic species (arsenite and arsenate). The mechanism for both inhibitors was determined to follow an uncompetitive inhibition model via UV-Vis assays using 2,2'azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as the oxidant/indicator. Enzymatic inhibition was also studied electrochemically via amperometric i-t experiments. Furthermore, laccase cathodes were employed as part of a conceptual self-powered arsenite/arsenate biosensor, demonstrating sensitivities of 0.91 ± 0.07 mV/mM for arsenite and 0.98 ± 0.02 mV/mM for arsenate. 

[1]              S. R. Couto, J. L. T. Herrera, Biotechnology advances 2006, 24, 500-513.

[2]              E. Katz, A. F. Bückmann, I. Willner, Journal of the American Chemical Society 2001, 123, 10752-10753.

[3]              D. Wen, L. Deng, S. Guo, S. Dong, Analytical chemistry 2011, 83, 3968-3972.