Catalase (CAT, EC 220.127.116.11) is widely distributed antioxidant enzyme that protects cells from oxidative damage by reactive oxygen species (ROS). Removal of ROS (especially H2O2) from the cell by catalase provides protection against oxidative damage to the cell. Acatalasemia, also known as acatalasia, is a condition characterized by very low or no levels of catalase. CAT contains four ferriprotoporphyrin groups per molecule. Catalase has a double function; (1) The catalytic activity, which degrades hydrogen peroxide (H2O2), a ROS, into water and oxygen, and (2) The peroxidatic activity of the enzyme, which low molecular alcohols such as ethanol and methanol serve as electron donor.