Catalases 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. Most catalases are mono-functional, haem-containing enzymes, although there are also bifunctional haem-containing peroxidase/catalases that are closely related to plant peroxidases, and non-haem, manganese-containing catalases that are found in bacteria PMID:14745498. They are composed of a long amino-terminal arm, an antiparallel eight-stranded beta-barrel, an extended wrapping loop, a four-helical domain and, in large catalases, a carboxy-terminal domain with flavodoxin-like topology joined by a long loop PMID:23519415. This entry represents the helical domain of catalases.

PMID:11351128 PMID:14745498 PMID:23519415