Superoxide versus peroxide activation of dye decolorizing peroxidases for bioelectrocatalysis

Abstract

Here we show that dye decolorizing peroxidases can be electrochemically activated for substrate oxidation without addition of exogenous H2O2, yielding activities similar or better than in their conventional operation. The method is based on the in situ generation of O2•−, •OH and H2O2. These species bind the heme to form catalytically competent oxoiron intermediates. Activation of the Pseudomonas putida enzyme is mainly mediated by O2•−, while those from Thermobifida fusca and Saccharomonospora viridis show preferential activation by H2O2. This differential reactivity is explained by the dynamics of a conserved distal aspartate residue. In contrast to previous reports on the Bacillus subtilis enzyme, none of the peroxidases studied here show significant •OH mediated activation, as this radical is quenched by reactive amino acids abundant in these proteins. These results pave the way for the development of bioelectrocatalytic reactors based on dye decolorizing peroxidases for water remediation and biomass processing.