Occurs in almost all aerobically respiring organisms and serves to protect cells from the toxic effects of hydrogen peroxide (By similarity). Involved in environmental stress response. Promotes drought stress tolerance and recovery (Ref.10). 2 H2O2 = 2 H2O + O2 Strongly inhibited by beta-mercaptoethanol, sodium azide and potassium cyanide. Slightly repressed by 3-amino-1,2,4-triazole (3-AT). Activity is repressed proportionally to increased concentration of NaCl, KCl and MgCl(2), and, to a lower extent, of LiCl. kcat is 6.6 min(-1) with H(2)O(2) as substrate (at pH 7.5). Optimum pH is 8. Optimum temperature is 30 degrees Celsius. Homotetramer (By similarity). Interacts with STRK1 at the plasma membrane (PubMed:29581216). Mostly expressed in young leaves (blades and sheaths) and seeds (Ref.10, PubMed:21979082, PubMed:21398647, PubMed:22106097, PubMed:26900141, PubMed:28969789, PubMed:29464319). Abundant in leaf sheath and moderately expressed in leaf blade and root (PubMed:21398647, PubMed:22106097, PubMed:29464319). Also present at a high levels in panicles, but barely in culms (PubMed:22106097, Ref.10). Observed in stems and anthers (PubMed:29464319). Abundance in leaves follows a photoperiod-dependent circadian rhythm with an oscillating expression pattern peaking late in the light period (PubMed:21398647, Ref.10). Inhibited by water stress (PubMed:21398647). Repressed by abscisic acid (ABA), drought, high salinity (NaCl) and hydrogen peroxide (H(2)O(2)) treatments (Ref.10). Triggered by zinc oxide nanoparticles (ZnO NPs); this induction is reversed by sodium nitroprusside (SNP, a NO donor) (PubMed:25958266). Accumulates upon infection by the bacterial blight agent X.oryzae pv. Oryzae (Xoo) strain PXO99 (PubMed:27185545). Influenced by heat stress (HS); up-regulated in conditons 35 degrees Celsius day / 27 degrees Celsius night, but repressed in conditions 38 degrees Celsius day / 30 degrees Celsius night (PubMed:29464319). Belongs to the catalase family.