Catalase is a ubiquitous enzyme found in both prokaryotes and eukaryotes, which is involved in the protection of cells from the toxic effects of peroxides. It catalyzes the conversion of hydrogen peroxide to water and molecular oxygen. Catalases also utilize hydrogen peroxide to oxidize various substrates such as alcohol or phenols. Clade 1 catalases are found in bacteria, algae, and plants; they have a relatively small subunit size of 55 to 69 kDa, and bind a protoheme IX (heme b) group buried deep inside the structure. They appear to form tetramers. In eukaryotic cells, catalases are located in peroxisomes.
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