Editing Peroxidase

{{Short description|Peroxide-decomposing enzyme}}
{{Use dmy dates|date=April 2020}}
[[File:GlutPeroxidase-1GP1.png|thumb|right|Glutathione Peroxidase 1 ({{PDB|1GP1}})]]

'''Peroxidases''' or '''peroxide reductases''' ([[Enzyme Commission number|EC number]] [https://web.archive.org/web/20090430141010/http://www.chem.qmul.ac.uk/iubmb/enzyme/EC1/11/1/ 1.11.1.x]) are a large group of [[enzyme]]s which play a role in various biological processes. They are named after the fact that they commonly break up [[peroxide]]s, and should not be confused with other enzymes that ''produce'' peroxide, which are often [[oxidases]].

==Functionality==
Peroxidases typically catalyze a reaction of the form:

:<chem>ROOR' + \overset{electron\atop donor}{2e^-} + 2H+ ->[\ce{Peroxidase}] {ROH} + R'OH</chem>

===Optimal substrates===
For many of these enzymes the optimal [[Substrate (biochemistry)|substrate]] is [[hydrogen peroxide]], but others are more active with organic [[hydroperoxide]]s such as [[lipid peroxide]]s. Peroxidases can contain a [[heme]] [[cofactor (biochemistry)|cofactor]] in their active sites, or alternately [[redox|redox-active]] [[cysteine]] or [[selenocysteine]] residues.

The nature of the [[nucleophile|electron donor]] is very dependent on the structure of the enzyme.
* For example, [[horseradish peroxidase]] can use a variety of organic compounds as electron donors and acceptors. Horseradish peroxidase has an accessible [[active site]], and many compounds can reach the site of the reaction.
* On the other hand, for an enzyme such as [[cytochrome c peroxidase]], the compounds that donate electrons are very specific, due to a very narrow active site.

=== Classification ===
Protein families that serve as peroxidases include:<ref>{{cite web |title=RedOxiBase: Peroxidase Classes |url=http://peroxibase.toulouse.inra.fr/infos/intro |access-date=30 May 2019}}</ref>

* Haem-using
** [[haem peroxidase]] and the related [[animal heme-dependent peroxidases]]
** [[DyP-type peroxidase family]]
** [[Catalase]]
** some [[haloperoxidase]]
** [[Di-haem cytochrome c peroxidase]]
* Non-heme
** Thiol: [[glutathione peroxidase]], [[peroxiredoxin]]
** [[vanadium bromoperoxidase]]
** Alkyl hydroperoxide reductase
** [[Manganese peroxidase]]
** [[NADH peroxidase]]

==Characterization==
The [[glutathione peroxidase]] family consists of 8 known human isoforms. Glutathione peroxidases use [[glutathione]] as an electron donor and are active with both [[hydrogen peroxide]] and organic hydroperoxide substrates. [[GPX1|Gpx1]], [[GPX2 (gene)|Gpx2]], Gpx3, and [[GPX4|Gpx4]] have been shown to be [[selenium]]-containing enzymes, whereas Gpx6 is a [[selenoprotein]] in humans with cysteine-containing homologues in rodents.

[[Amyloid beta]], when bound to heme, has been shown to have peroxidase activity.<ref>{{cite journal | vauthors = Atamna H, Boyle K | title = Amyloid-beta peptide binds with heme to form a peroxidase: relationship to the cytopathologies of Alzheimer's disease | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 9 | pages = 3381–6 | date = Feb 2006 | pmid = 16492752 | pmc = 1413946 | doi = 10.1073/pnas.0600134103 | doi-access = free | bibcode = 2006PNAS..103.3381A }}</ref>

A typical group of peroxidases are the [[haloperoxidase]]s. 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 the [[PeroxiBase]] database.

==Pathogenic resistance==
While the exact mechanisms have yet to be determined, peroxidases are known to play a part in increasing a plant's defenses against pathogens.<ref>{{cite journal | vauthors = Karthikeyan M, Jayakumar V, Radhika K, Bhaskaran R, Velazhahan R, Alice D | title = Induction of resistance in host against the infection of leaf blight pathogen (Alternaria palandui) in onion (Allium cepa var aggregatum) | journal = Indian Journal of Biochemistry & Biophysics | volume = 42 | issue = 6 | pages = 371–7 | date = Dec 2005 | pmid = 16955738 }}</ref> Many members of the Solanaceae, notably [[Eggplant|''Solanum melongena'']] (eggplant/aubergine) and ''[[Capsicum chinense]]'' (the habanero/Scotch bonnet varieties of chili peppers) use [[Guaiacol]] and the enzyme guaiacol peroxidase as a defense against bacterial parasites such as ''[[Ralstonia solanacearum]]'': the gene expression for this enzyme commences within minutes of bacterial attack.<ref>Prakasha, A, Umesha, S. Biochemical and Molecular Variations of Guaiacol Peroxidase and Total Phenols in Bacterial Wilt Pathogenesis of Solanum melongena. Biochemistry & Analytical Biochemistry, 5,292, 2016</ref>

==Applications==
Peroxidase can be used for treatment of industrial waste waters. For example, [[phenols]], which are important pollutants, can be removed by enzyme-catalyzed polymerization using [[horseradish 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.<ref>Tuhela, L., G. K. Sims, and O. Tuovinen. 1989. Polymerization of substituted anilines, phenols, and heterocyclic compounds by peroxidase in organic solvents. Columbus, Ohio: The Ohio State University. 58 pages.</ref>

Peroxidases are sometimes used as [[histology|histological]] markers. [[Cytochrome c peroxidase]] is used as a soluble, easily purified model for [[cytochrome c oxidase]].

== See also ==
{{Portal|Biology}}
* [[Ascorbate peroxidase]]
* [[Chloride peroxidase]]
* [[Cytochrome c peroxidase]]
* [[Haloperoxidase]]
* [[Hemoprotein]]
* [[Immunoperoxidase]]
* [[Lactoperoxidase]]
* [[Myeloperoxidase]] (MPO)
* [[Thyroid peroxidase]]

== References ==
{{Reflist}}

==External links==
* [http://peroxibase.toulouse.inra.fr/infos/intro Peroxibase], a database of peroxidases

{{Peroxidases}}
{{Enzymes}}
{{Authority control}}

[[Category:EC 1.11.1|*]]
[[Category:Hemoproteins]]