Decomposes hydrogen peroxide into water and oxygen; serves to protect cells from the toxic effects of hydrogen peroxide. 2 H2O2 = 2 H2O + O2 Strongly inhibited by sodium azide and sodium cyanide, and slightly inhibited by 3-amino-1,2,4-triazole. Optimum temperature is 30 degrees Celsius. Active over a temperature range from 20 to 70 degrees Celsius. Retains 100% of its initial activity following incubation at 40 degrees Celsius, and 82% of its activity following incubation at 50 degrees Celsius. The activity decreases significantly to 30% of the initial activity following incubation at 60 degrees Celsius. Homotetramer. Up-regulated during stationary phase. Belongs to the catalase family.