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Updated: May 26, 2025

Author Spotlight: Advancing Mitochondrial Research - mtHyper7 Biosensor for Subcellular Analysis
Published on: June 2, 2023
Mechanistic Insights into HRP-Catalyzed Oxidation of the Near-Infrared Fluorescent Dye Sulfo-cyanine 7
Gabriela Manrique1, Jérémie Gottraux1, Simon Matoori1
1Faculté de Pharmacie, Université de Montréal, Montréal, Québec H3T 1J4, Canada.
Abstract:
Horseradish peroxidase (HRP) is a widely used enzyme that oxidizes a range of substrates in the presence of its co-substrate hydrogen peroxide (H2O2). In the past, we identified sulfo-cyanine 7 (S7) as a novel near-infrared substrate of HRP, which loses its fluorescence upon enzymatic oxidation in a hydrogen peroxide-dependent manner. However, the catalytic mechanism and the chemical structure of the oxidation products were not well understood. In this study, we investigate the catalytic mechanism of S7 oxidation by HRP and identify two radical products formed during the reaction. Our results point to the formation of non-near-infrared fluorescent species, and the regeneration of S7. These results strongly point to a disproportionation reaction that was described for other HRP substrates, namely the structurally related ABTS (2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)).
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