Catalase protein occurs in almost all aerobically respiring organisms and serves to protect cells from the toxic effects of hydrogen peroxide. It promotes growth of cells including T-cells，B-cells，myeloid leukemia cells，melanoma cells，mastocytoma cells and normal and transformed fibroblast cells. Catalase is a key antioxidant enzyme in the body’s defense against oxidative stress. Catalase is a heme enzyme that is present in the peroxisome of nearly all aerobic cells. Catalase converts the reactive oxygen species hydrogen peroxide to water and oxygen and thereby mitigates the toxic effects of hydrogen peroxide. Oxidative stress is hypothesized to play a role in the development of many chronic or late-onset diseases such as diabetes，asthma，Alzheimer's disease，systemic lupus erythematosus，rheumatoid arthritis，and cancers.
