Fig. 3.

Spectral analysis of MPO reacting with hydrogen peroxide. 1.5 μM MPO was incubated with 60 μM H₂O₂ (A), 250 μM H₂O₂ (B) and 1.5 mM H₂O₂ (C) in 50 mM phosphate buffer, pH 7.4, 100 μM DTPA. Time resolved spectra were recorded over time. The black spectrum depicts the spectral signature of ferric MPO before addition of H₂O₂, arrows indicate direction of spectral changes. Insets represent consumption of hydrogen peroxide over time as measured by the FOX assay as well as the residual peroxidase activity determined with the TMB-assay.