Occurs in almost all aerobically respiring organisms and serves to protect cells from the toxic effects of hydrogen peroxide. Responsible for the redox homeostasis in leaves. Prevents nitric oxide (NO) accumulation and subsequent NO-mediated leaf cell death as well as the S-nitrosylation of specific proteins (e.g. glyceraldehyde 3-phosphate dehydrogenase and thioredoxin) by degrading H(2)O(2) (PubMed:22106097, PubMed:23331502). Involved in photorespiration. Promotes drought stress tolerance and recovery (Ref.13). Involved in NO-mediated enhanced tolerance to zinc oxide nanoparticles (ZnO NPs)-induced phytotoxicity (PubMed:25958266). Participates in melatonin-mediated detoxification (PubMed:25912474). 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, LiCl and MgCl(2). kcat is 0.5 min(-1) with H(2)O(2) as substrate (at pH 7.5) (PubMed:21979082). kcat is 28 sec(-1) with H(2)O(2) as substrate (at pH 7.4 and 30 degrees Celsius) (PubMed:26900141). Optimum pH is 7. Optimum temperature is 30 degrees Celsius. Homotetramer (By similarity). Interacts with GLO1 and GLO4; these interactions are disturbed by alpha-hydroxy-2-pyridinemethanesulfonic acid (HPMS) and salicylic acid (SA) (PubMed:26900141). Interacts with STRK1 at the plasma membrane (PubMed:29581216). Highly expressed in mature leaves (PubMed:21979082, PubMed:21398647, PubMed:22106097, PubMed:23331502, PubMed:26900141, PubMed:28969789, PubMed:29464319). Mainly expressed in leaf blades, stems, panicles, leaf sheaths, and culms, but barely in roots (PubMed:22106097, PubMed:23331502, PubMed:29464319). Abundance in leaves follows a light-dependent rhythm with an oscillating expression pattern peaking early in the light period (PubMed:21398647, PubMed:23331502). Inhibited by water stress and abscisic acid (ABA) in a concentration-dependent manner (PubMed:21398647, PubMed:23331502). Enhanced by ABA biosynthesis inhibitors nordihydroguaiaretic acid and tungstate under water stress (PubMed:21398647). Slightly affected by high salinity and hydrogen peroxide (H(2)O(2)) treatments (PubMed:23331502). Accumulates upon infection by the bacterial blight agent X.oryzae pv. Oryzae (Xoo) strain PXO99 (PubMed:27185545). Repressed by cadmium (Cd) (PubMed:28969789). Activated by STRK1-mediated phosphorylation at Tyr-210 upon salt and oxidative stress. Impaired catalase activity in leaves. Accumulation of hydrogen peroxide (H(2)O(2)) in leaves, which consequently promotes nitric oxide (NO) production via the activation of nitrate reductase, thus leading to subsequent NO-mediated leaf cell death, as well as increased S-nitrosylation of specific proteins including glyceraldehyde 3-phosphate dehydrogenase and thioredoxin (PubMed:22106097, PubMed:23331502). Leaf bleaching and cell death; these phenotypes are reversed by melatonin treatment (PubMed:25912474). Increased tolerance to zinc oxide nanoparticles (ZnO NPs) (PubMed:25958266). Belongs to the catalase family.