Human Erythrocyte Catalase (HEC) is an enzyme that catalyzes the 2-step decomposition of hydrogen peroxide, H2O2, to water and oxygen inside the red blood cells of humans. In 1 second, HEC can decompose up to 1 million molecules of H2O2. H2O2, is a byproduct of aerobic respiration. It can become a free radical and damage the membrane proteins and lipids of red blood cells, resulting in heme degradation. HEC has also been shown to protect somatic cells from the oxidative damage caused by H2O2. We need H2O2 in our body as a way to help fight off infection. H2O2it is produced by leukocytes to help fight infections because it is an antibacterial agent.