APX activity was measured with the method of Nakano and
Asada (1981). The reaction mixture contained 50 mM phosphate
buffer (pH 7), 1 mM sodium ascorbate and 25 mM H2O2. Following
addition of ascorbate to the mixture, the reaction was monitored
via the absorbance at 290 nm (ε = 2.8 mM−1 cm−1).