Peroxidases or peroxide reductases ( EC numberbr>1.11.1.x
are a large group of

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

s which play a role in various biological processes. They are named after the fact that they commonly break up

peroxide In chemistry, peroxides are a group of compounds with the structure , where R = any element. The group in a peroxide is called the peroxide group or peroxo group. The nomenclature is somewhat variable. The most common peroxide is hydrogen p ...

Functionality

Peroxidases typically catalyze a reaction of the form: :ROOR' + \overset + 2H+ -> ce + R'OH

Optimal substrates

For many of these enzymes the optimal substrate is

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3 ...

, but others are more active with organic

hydroperoxide Hydroperoxides or peroxols are compounds containing the hydroperoxide functional group (ROOH). If the R is organic, the compounds are called organic hydroperoxides. Such compounds are a subset of organic peroxides, which have the formula ROOR. ...

s such as

lipid peroxide Lipid peroxidation is the chain of reactions of oxidative degradation of lipids. It is the process in which free radicals "steal" electrons from the lipids in cell membranes, resulting in cell damage. This process proceeds by a free radical chain ...

s. Peroxidases can contain a

heme Heme, or haem (pronounced / hi:m/ ), is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver. In biochemical terms, heme is a coordination complex "consis ...

cofactor in their active sites, or alternately redox-active

cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, some ...

selenocysteine Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the ...

residues. The nature of the electron donor is very dependent on the structure of the enzyme. * For example,

horseradish peroxidase The enzyme horseradish peroxidase (HRP), found in the roots of horseradish, is used extensively in biochemistry applications. It is a metalloenzyme with many isoforms, of which the most studied type is C. It catalyzes the oxidation of various o ...

can use a variety of organic compounds as electron donors and acceptors. Horseradish peroxidase has an accessible

active site In biology and biochemistry, the active site is the region of an enzyme where substrate molecules bind and undergo a chemical reaction. The active site consists of amino acid residues that form temporary bonds with the substrate ( binding site) ...

, and many compounds can reach the site of the reaction. * On the other hand, for an enzyme such as

cytochrome c peroxidase Cytochrome ''c'' peroxidase, or CCP, is a water-soluble heme-containing enzyme of the peroxidase family that takes reducing equivalents from cytochrome ''c'' and reduces hydrogen peroxide to water: :CCP + H2O2 + 2 ferrocytochrome ''c'' + 2H+ � ...

, the compounds that donate electrons are very specific, due to a very narrow active site.

Classification

Protein families that serve as peroxidases include: * Haem-using ** haem peroxidase and the related animal heme-dependent peroxidases ** DyP-type peroxidase family **

Catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...

** some haloperoxidase **

Di-haem cytochrome c peroxidase In molecular biology, the di-haem cytochrome c peroxidase family is a group of distinct cytochrome c peroxidases (CCPs) that contain two haem groups. Similar to other cytochrome c peroxidases, they reduce hydrogen peroxide to water using c-type hae ...

* Non-heme ** Thiol: glutathione peroxidase,

peroxiredoxin Peroxiredoxins (Prxs, ; HGNC root symbol ''PRDX'') are a ubiquitous family of antioxidant enzymes that also control cytokine-induced peroxide levels and thereby mediate signal transduction in mammalian cells. The family members in humans are P ...

** vanadium bromoperoxidase ** Alkyl hydroperoxide reductase ** Manganese peroxidase ** NADH peroxidase

Characterization

The glutathione peroxidase family consists of 8 known human isoforms. Glutathione peroxidases use

glutathione Glutathione (GSH, ) is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by sources such as reactive oxygen species, free radicals, pe ...

as an electron donor and are active with both

and organic hydroperoxide substrates. Gpx1, Gpx2, Gpx3, and Gpx4 have been shown to be

selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...

-containing enzymes, whereas Gpx6 is a selenoprotein in humans with cysteine-containing homologues in rodents.

Amyloid beta Amyloid beta (Aβ or Abeta) denotes peptides of 36–43 amino acids that are the main component of the amyloid plaques found in the brains of people with Alzheimer's disease. The peptides derive from the amyloid precursor protein (APP), which is ...

, when bound to heme, has been shown to have peroxidase activity. A typical group of peroxidases are the haloperoxidases. 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. Many members of the Solanaceae, notably ''Solanum melongena'' (eggplant/aubergine) and ''

Capsicum chinense ''Capsicum chinense'', commonly known as a "habanero-type pepper", is a species of chili pepper native to the Americas. ''C. chinense'' varieties are well known for their unique flavors and many have exceptional heat. The hottest peppers in th ...

'' (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 ''Ralstonia solanacearum'' is an aerobic non-spore-forming, Gram-negative, plant pathogenic bacterium. ''R. solanacearum'' is soil-borne and motile with a polar flagellar tuft. It colonises the xylem, causing bacterial wilt in a very wide range ...

'': the gene expression for this enzyme commences within minutes of bacterial attack.

Applications

Peroxidase can be used for treatment of industrial waste waters. For example,

phenols In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl groups (— O H) bonded directly to an aromatic hydrocarbon group. The simplest is phenol, . Phenolic compounds are ...

, which are important pollutants, can be removed by enzyme-catalyzed polymerization using

. 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.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. Peroxidases are sometimes used as

histological Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...

markers.

Cytochrome c peroxidase Cytochrome ''c'' peroxidase, or CCP, is a water-soluble heme-containing enzyme of the peroxidase family that takes reducing equivalents from cytochrome ''c'' and reduces hydrogen peroxide to water: :CCP + H2O2 + 2 ferrocytochrome ''c'' + 2H+ � ...

is used as a soluble, easily purified model for

cytochrome c oxidase The enzyme cytochrome c oxidase or Complex IV, (was , now reclassified as a translocasEC 7.1.1.9 is a large transmembrane protein complex found in bacteria, archaea, and mitochondria of eukaryotes. It is the last enzyme in the respiratory elect ...

References

External links

Peroxibase
a database of peroxidases {{Use dmy dates, date=April 2020 * Hemoproteins