The primary function of the enzyme catalase is to catalyze the decomposition of hydrogen peroxide (H2O2) into water and oxygen. Catalase is critical for protecting cells from oxidative damage caused by hydrogen peroxide, a harmful byproduct of various metabolic processes. By facilitating this reaction, catalase helps maintain cellular homeostasis and prevent oxidative stress. Its efficiency in breaking down hydrogen peroxide makes it one of the fastest enzymes known, highlighting its importance in biological systems.