Peroxidase Activity Assay

POD activity was determined with guaiacol as a substrate, as described previously (Kwak et al., 1995). Briefly, 0.1 g FW of sweetpotato tissues was homogenized in 0.1 M potassium phosphate buffer (pH 6.0) on ice. After centrifugation, protein concentration in the extracts was measured using a spectropho which comprise the active sites of desaturase enzymes tometer, according to the Bradford assay (Bradford, 1976). To determine the specific POD activity, 0.46% guaiacol, 13 mM H₂O₂, and 5 μg of crude protein were mixed with distilled water. The absorbance of the sample was recorded at 470 nm every 20 s for 3 min. The measurement was performed three times with 3 independent tuberous roots.