Decomposes hydrogen peroxide into water and oxygen; serves to protect cells from the toxic effects of hydrogen peroxide. Could protect cells in nodules which have a high potential to produce hydrogen peroxide because of the strong reducing conditions required for nitrogen fixation and the action of several proteins. 2 H2O2 = 2 H2O + O2 A threefold increase of the activity arises after exposure to heat stress (37 degrees Celsius), to sodium chloride or ethanol for one hour. Not inducible by hydrogen peroxide. Either KatA or KatC is absolutely required for the protection of the nitrogen fixation process. Belongs to the catalase family. HPII subfamily.