| Description | Haem-containing catalase-peroxidases are bifunctional antioxidant enzymes that exhibit both catalase ( ) and peroxidase ( ) activity, and which are present predominantly in bacterial species [ ]. Several evolutionary lineages are present also in archaeal, fungal, and protistan species. These enzymes provide protection against oxidative stress by dismutating hydrogen peroxide to oxygen and water []. Phylogenetically they are closely related to ascorbate peroxidases and cytochrome c peroxidases [] and can be divided in two distinct clades []. They do not share sequence similarity with mono-functional, haem-containing catalases () that are ubiquitous in aerobic organisms, nor with non-haem manganese-containing catalases found in bacteria ( ). Catalases perform a unique two-step reaction cycle that cleaves two hydrogen peroxide molecules heterolytically to alternately oxidise and reduce the haem iron thus releasing water and molecular oxygen [ ]. Contrary, peroxidases use hydrogen peroxide only to oxidise the haem iron, but use different electron donors such as NADH or ascorbate to then reduce the haem.The structure of the catalase-peroxidase from the archaeon, Haloarcula marismortui (Halobacterium marismortui), reveals a dimer of two identical subunits [ ], although some catalase-peroxidases can exist also as homotetramers. The general topology, as well as the arrangement of the catalytic residues and haem in the active site, are similar to other class I peroxidases. However, the location of the haem group deeply buried inside the domain is typical of a catalase. The primary structure of the subunit can be divided into two similar halves, which very probably arose from a gene duplication event [, ]. A similar structure was obtained also for a catalase-peroxidase from the proteobacterium Burkholderia pseudomallei []. | Name | Catalase-peroxidase haem |
| Short Name | Catalase_peroxidase | Type | Family |
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