Peroxidases orperoxide reductases (EC number1.11.1.x) are a large group ofenzymes which play a role in various biological processes. They are named after the fact that they commonly break upperoxides, and should not be confused with other enzymes thatproduce peroxide, which are oftenoxidases.
Peroxidases typically catalyze a reaction of the form:
For many of these enzymes the optimalsubstrate ishydrogen peroxide, but others are more active with organichydroperoxides such aslipid peroxides. Peroxidases can contain ahemecofactor in their active sites, or alternatelyredox-activecysteine orselenocysteine residues.
The nature of theelectron donor is very dependent on the structure of the enzyme.
Protein families that serve as peroxidases include:[1]
Theglutathione peroxidase family consists of 8 known human isoforms. Glutathione peroxidases useglutathione as an electron donor and are active with bothhydrogen peroxide and organic hydroperoxide substrates.Gpx1,Gpx2, Gpx3, andGpx4 have been shown to beselenium-containing enzymes, whereas Gpx6 is aselenoprotein in humans with cysteine-containing homologues in rodents.
Amyloid beta, when bound to heme, has been shown to have peroxidase activity.[2]
A typical group of peroxidases are thehaloperoxidases. This group is able to form reactive halogen species and, as a result, natural organohalogen substances.
A majority of peroxidase protein sequences can be found in thePeroxiBase database.
While the exact mechanisms have yet to be determined, peroxidases are known to play a part in increasing a plant's defenses against pathogens.[3] Many members of the Solanaceae, notablySolanum melongena (eggplant/aubergine) andCapsicum chinense (the habanero/Scotch bonnet varieties of chili peppers) useGuaiacol and the enzyme guaiacol peroxidase as a defense against bacterial parasites such asRalstonia solanacearum: the gene expression for this enzyme commences within minutes of bacterial attack.[4]
Peroxidase can be used for treatment of industrial waste waters. For example,phenols, which are important pollutants, can be removed by enzyme-catalyzed polymerization usinghorseradish peroxidase. Thus phenols are oxidized to phenoxy radicals, which participate in reactions where polymers and oligomers are produced that are less toxic than phenols. It also can be used to convert toxic materials into less harmful substances.
There are many investigations about the use of peroxidase in many manufacturing processes like adhesives, computer chips, car parts, and linings of drums and cans. Other studies have shown that peroxidases may be used successfully to polymerize anilines and phenols in organic solvent matrices.[5]
Peroxidases are sometimes used ashistological markers.Cytochrome c peroxidase is used as a soluble, easily purified model forcytochrome c oxidase.
