Catalase is a commonly occurring antioxidant enzyme that catalyzes the decomposition of hydrogen peroxide (H2O2) to produce water and oxygen. Hydrogen peroxide exists in eukaryotic cells as a byproduct of various oxidase and superoxide dismutase. The aggregation of hydrogen peroxide in cells can cause oxidation of DNA, proteins, and lipids, leading to gene mutations and cell death. Catalase can remove H2O2 from cells and protect living cells from oxidative damage. The role of catalase in oxidative stress-related diseases has been widely studied.