... membranes. Both isoforms are involved in the water–water cycle, asystem to scavenge reactive oxygen species in chloro-plasts and dissipate excess excitation energy of photo-systems [2]. The ... brokenline. Fe, nitrogen, oxygen and the cation near Trp265 are shown in cyan, blue, red and magenta, respectively. Residue numbers refer to stro-mal APX of spinach; see Fig. 1. These structures ... thanwhen an excess amount of hydrogen peroxide isexogenously added, and we could determine the half-time of the inactivation quantitatively.Whereas recombinant APX-B retained its initialactivity...