What is catalase and how does it work in H2O2-based assays?

Catalase is an important enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals), protecting cells from oxidative damage by reactive oxygen species (ROS).  Catalase catalyzes the decomposition of hydrogen peroxide to water and oxygen with optimum pH ~7 (pH 6.8 ~7.5).

 

In H2O2-based assays, a small amount of catalase is often used to reduce the background signals derived from H2O2 contamination in buffers and enzyme mixtures. However, large amounts of catalase could affect the H2O2 response by competing with peroxide enzymes for H2O2 substrates.