Insulin disulfide reductase activity of OsTRXh1 and H2O2 tolerance assay in the yeast mutant EMY63 expressing OsTRXh1. A, GST-OsTRXhC43S, GST-OsTRXh1, and GST were expressed in E. coli, and the purified proteins were subjected to SDS-PAGE. B, The insulin reduction rate was measured using a 650-nm optical absorption in reaction assays containing the following purified proteins: 5 or 2.5 μm GST-OsTRXh1, 5 or 2.5 μm GST-OsTRXhC43S, and 5 μm GST. C, The growth performance of the transformed yeast mutant EMY63 under synthetic dextrose/Gal/-Ura agar medium containing 0 mm H2O2 and 0.7 mm H2O2. The yeast ScTrx1 and the empty vector were used as controls.