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. A ...

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 peroxides. 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 "consisti ...

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, sometime ...

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 s ...

residues. The nature of the

electron donor In chemistry, an electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process. Typical reducing agents undergo permanent chem ...

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 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) a ...

, 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 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 "consist ...

and the related animal heme-dependent peroxidases **

DyP-type peroxidase family In molecular biology, the DyP-type peroxidase family is a family of haem peroxidase enzymes. Haem peroxidases were originally divided into two superfamilies, namely, the animal peroxidases and the plant peroxidases (which are subdivided into class ...

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 Haloperoxidases are peroxidases that are able to mediate the oxidation of halides by hydrogen peroxide. Both halides and hydrogen peroxide are widely available in the environment. The Nernst equation shows that hydrogen peroxide can oxidize chlori ...

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 Glutathione peroxidase (GPx) () is the general name of an enzyme family with peroxidase activity whose main biological role is to protect the organism from oxidative damage. The biochemical function of glutathione peroxidase is to reduce lipid h ...

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 PRDX ...

vanadium bromoperoxidase Vanadium bromoperoxidases are a kind of enzymes called haloperoxidases. Its primary function is to remove hydrogen peroxide which is produced during photosynthesis from in or around the cell. By producing hypobromous acid (HOBr) a secondary reac ...

** Alkyl hydroperoxide reductase **

Manganese peroxidase Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

NADH peroxidase In enzymology, a NADH peroxidase () is an enzyme that catalyzes the chemical reaction :NADH + H+ + H2O2 \rightleftharpoons NAD+ + 2 H2O The presumed function of NADH peroxidase is to inactivate H2O2 generated within the cell, for example by gl ...

Characterization

The

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, pero ...

as an electron donor and are active with both

and organic hydroperoxide substrates.

Gpx1 Glutathione peroxidase 1, also known as GPx1, is an enzyme that in humans is encoded by the ''GPX1'' gene on chromosome 3. This gene encodes a member of the glutathione peroxidase family. Glutathione peroxidase functions in the detoxification of hy ...

, Gpx2, Gpx3, and

Gpx4 Glutathione peroxidase 4, also known as GPX4, is an enzyme that in humans is encoded by the ''GPX4'' gene. GPX4 is a phospholipid hydroperoxidase that protects cells against membrane lipid peroxidation. Function The antioxidant enzyme glutat ...

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 molecular biology a selenoprotein is any protein that includes a selenocysteine (Sec, U, Se-Cys) amino acid residue. Among functionally characterized selenoproteins are five glutathione peroxidases (GPX) and three thioredoxin reductases, (TrxR/TX ...

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

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. 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 the ...

'' (the habanero/Scotch bonnet varieties of chili peppers) use

Guaiacol Guaiacol () is an organic compound with the formula C6H4(OH)(OCH3). It is a phenolic compound containing an methoxy functional group. Guaiacol appears as a viscous colorless oil, although aged or impure samples are often yellowish. It occurs wid ...

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 rang ...

'': 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 c ...

, 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.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 electr ...

References

External links

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