Dębski 2016 Free Radic Biol Med

Dębski D, Smulik R, Zielonka J, Michałowski B, Jakubowska M, Dębowska K, Adamus J, Marcinek A, Kalyanaraman B, Sikora A (2016) Mechanism of oxidative conversion of Amplex® Red to resorufin: pulse radiolysis and enzymatic studies. Free Radic Biol Med 95:323-32.

» PMID:27021961 Open Access

Dębski D, Smulik R, Zielonka J, Michałowski B, Jakubowska M, Dębowska K, Adamus J, Marcinek A, Kalyanaraman B, Sikora A (2016) Free Radic Biol Med

Abstract: Amplex® Red (10-acetyl-3,7-dihydroxyphenoxazine) is a fluorogenic probe widely used to detect and quantify hydrogen peroxide in biological systems. Detection of hydrogen peroxide is based on peroxidase-catalyzed oxidation of Amplex® Red to resorufin. In this study we investigated the mechanism of one-electron oxidation of Amplex® Red and we present the spectroscopic characterization of transient species formed upon the oxidation. Oxidation process has been studied by a pulse radiolysis technique with one-electron oxidants (N3(•), CO3(•-),(•)NO2 and GS(•)). The rate constants for the Amplex® Red oxidation by N3(•) ((2)k=2.1·10(9)M(-1)s(-1), at pH=7.2) and CO3(•-) ((2)k=7.6·10(8)M(-1)s(-1), at pH=10.3) were determined. Two intermediates formed during the conversion of Amplex® Red into resorufin have been characterized. Based on the results obtained, the mechanism of transformation of Amplex® Red into resorufin, involving disproportionation of the Amplex® Red-derived radical species, has been proposed. The results indicate that peroxynitrite-derived radicals, but not peroxynitrite itself, are capable to oxidize Amplex® Red to resorufin. We also demonstrate that horseradish peroxidase can catalyze oxidation of Amplex® Red not only by hydrogen peroxide, but also by peroxynitrite, which needs to be considered when employing the probe for hydrogen peroxide detection.

Cited by

• Komlódi T, Sobotka O, Gnaiger E (2021) Facts and artefacts on the oxygen dependence of hydrogen peroxide production using Amplex UltraRed. Bioenerg Commun 2021.4. https://doi:10.26124/BEC:2021-0004

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