VPO1-mediated HOSCN generation. (A) pH-dependent HOSCN generation by VPO1. One hundred microliters of reaction containing 20 mM phosphate buffer, pH range from 4 to 8 as indicated, 500 nM rVPO1, 100 µM H2O2, 100 µM KSCN, and 100 µM TNB was carried out at 37 °C for 30 min. The absorbance at 412 nm was recorded. (B) VPO1 dose-dependent HOSCN generation. Experiments were carried out as in A at pH 5.5 and VPO1 concentration as indicated. (C) HOSCN dose-dependent generation by VPO1. Experiments were carried out as in A at pH 5.5. rVPO1 concentration was 500 nM and KSCN concentrations are indicated. The data are from three independent experiments. Error bars, SD.