InterPro

Catalases (EC:1.11.1.6) are antioxidant enzymes that catalyse the conversion of hydrogen peroxide to water and molecular oxygen, serving to protect cells from its toxic effects [PMID: 11351128]. Hydrogen peroxide is produced as a consequence of oxidative cellular metabolism and can be converted to the highly reactive hydroxyl radical via transition metals, this radical being able to damage a wide variety of molecules within a cell, leading to oxidative stress and cell death. Catalases act to neutralise hydrogen peroxide toxicity, and are produced by all aerobic organisms ranging from bacteria to man. Most catalases are mono-functional, haem-containing enzymes, although there are also bifunctional haem-containing peroxidase/catalases (IPR000763) that are closely related to plant peroxidases, and non-haem, manganese-containing catalases (IPR007760) that are found in bacteria [PMID: 14745498]. Based on a phylogenetic analysis, catalases can be classified into clade 1, 2 and 3. Clade 1 contains small subunit catalases from plants and a subset of bacteria; clade 2 contains large subunit catalases from fungi and a second subset of bacteria; and clade 3 contains small subunit catalases from bacteria, fungi, protists, animals, and plants [PMID: 9287428, PMID: 12557185].

Mono-functional, haem-containing catalases have a core that includes a haem-containing active site deeply buried in a beta-barrel structure with two or three channels providing access to the haem. This entry covers a tyrosine residue that serves as the haem proximal side ligand and includes a conserved arginine that participates in haem-binding.