Catalase

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Symbol = cat
Name = Catalase


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Pfam= PF00199
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Catalase is a common enzyme found in nearly all living organisms, where it functions to catalyze the decomposition of hydrogen peroxide to water and oxygen.cite web | title = Catalase: An Enzyme at Work| work = Science Education Outreach | url=http://crystal.uah.edu/~carter/enzyme/catalase.htm | accessdate=2007-02-11] Catalase has one of the highest turnover numbers of all enzymes; one molecule of catalase can convert millions of molecules of hydrogen peroxide to water and oxygen per second. [cite web | title = Catalase | work = Molecule of the Month | publisher = RCSB Protein Data Bank | url = http://www.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb57_1.html | date = 2004-09-01 | accessdate = 2007-02-11]

Catalase is a tetramer of four polypeptide chains, each over 500 amino acids long.cite web | author = Boon EM, Downs A, Marcey D |title = Catalase: H₂O₂: H₂O₂ Oxidoreductase | work = Catalase Structural Tutorial Text | url = http://biology.kenyon.edu/BMB/Chime/catalase/frames/cattx.htm | accessdate = 2007-02-11] It contains four porphyrin heme (iron) groups that allow the enzyme to react with the hydrogen peroxide. The optimum pH for catalase is approximately 7,cite book | authors = Maehly A, Chance B | title = The Assay of Catalases and Peroxidases "in" Methods of Biochemical Analysis | pages = 357 | year = 1954 | id = ISBN ] while the optimum temperature varies by species.cite web | title = A Quantitative Enzyme Study; CATALASE | url = http://web.archive.org/web/20000612104029/http://www.facstaff.bucknell.edu/toner/gb/lab121/labs34.html | accessdate = 2007-02-11]

History

Catalase was first noticed as a substance in 1811 when Louis Jacques Thénard, who discovered H₂O₂ (hydrogen peroxide), suggested that its breakdown is caused by a substance. In 1900, Oscar Loew was the first to give it the name catalase, and found its presence in many plants and animals [cite journal
title=A New Enzyme of General Occurrence in Organisms
author=Loew, Oscar
journal=Science
volume=11
issue=279
pages=701–2
month=May
year=1900
doi = 10.1126/science.11.279.701 ] . In 1937 catalase from beef liver was crystallised by James B. Sumner [cite journal
journal=Science
title=Cystalline Catalase
author=Sumner, J.B.
authorlink=James B. Sumner
coauthors=Dounce, A. L.
volume=87
issue=18
year=1938 | pages = 284
doi = 10.1126/science.87.2256.284 ] and the molecular weight worked out in 1938 [cite journal
title=The Molecular Weight of Crystalline Catalase
author=Sumner, James B.
coauthors=Gralen, Nils
journal=Science
volume=87
issue=2256
pages=284
month=Mar
year=1938 | doi = 10.1126/science.87.2256.284 ] .In 1969 the amino acid sequence of bovine catalase was worked out [cite journal
author=Schroeder WA
coauthors=Shelton JR; Shelton JB; Robberson B; Apell G.
title=The amino acid sequence of bovine liver catalase: a preliminary report.
journal=Arch Biochem Biophys
year=1969
month=May
volume=131|issue=2|pages=653–5
pmid=4892021
doi = 10.1016/0003-9861(69)90441-X ] . Then in 1981, the 3D structure of the protein was revealed [cite journal
title=Structure of beef liver catalase.
author=Murthy MR
coauthors=Reid TJ 3rd; Sicignano A; Tanaka N; Rossmann MG.
journal=J Mol Biol
year=1981
month=Oct
volume=152|issue=2|pages=465–99
pmid=7328661
doi = 10.1016/0022-2836(81)90254-0 ] .

Action of catalase

The reaction of catalase in the decomposition of hydrogen peroxide is:

: 2 H₂O₂ → 2 H₂O + O₂cite web | title = Catalase: A Closer Look | work = Science Education Outreach | url=http://crystal.uah.edu/~carter/enzyme/closer.htm | accessdate=2007-02-11]

In microbiology, the "catalase test" is used to differentiate between bacterial species in the lab. [http://www2.austin.cc.tx.us/microbugz/html/catalase_test.html] The test is done by placing a drop of hydrogen peroxide on a microscope slide. Using an applicator stick, a scientist touches the colony and then smears a sample into the hydrogen peroxide drop. If bubbles or froth forms, the organism is said to be "catalase-positive"; if not, the organism is "catalase-negative". [http://dentistry.ouhsc.edu/intranet-web/courses/dmi_8351/Catalase.html] This test is particularly useful in distinguishing staphylococci and micrococci, which are catalase-positive, from streptococci and enterococci, which are catalase-negative. [http://www2.austin.cc.tx.us/microbugz/html/catalase_test.html] While the catalase test alone cannot identify a particular organism, combined with other tests, it can aid diagnosis. The presence of catalase in bacterial cells depends on both the growth condition and the medium used to grow the cells.

Molecular mechanism

While the complete mechanism of catalase is not currently known, the reaction is believed to occur in two stages:

: H₂O₂ + Fe(III)-E → H₂O + O=Fe(IV)-E(.+)

: H₂O₂ + O=Fe(IV)-E(.+) → H₂O + Fe(III)-E + O₂cite web | author = Boon EM, Downs A, Marcey D | title = Proposed Mechanism of Catalase "in" Catalase: H₂O₂: H₂O₂ Oxidoreductase | work = Catalase Structural Tutorial Text | url = http://biology.kenyon.edu/BMB/Chime/catalase/frames/cattx.htm#Proposed%20Mechanism%20of%20Catalase | accessdate = 2007-02-11]

: Here Fe()-E represents the iron centre of the heme group attached to the enzyme. Fe(IV)-E(.+) ís a mesomeric form of Fe(V)-E, meaning that iron is not completely oxidized to +V but receives some "supporting electron" from the heme ligand. This heme has to be drawn then als radical cation (.+).

As hydrogen peroxide enters the active site, it interacts with the amino acids Asn147 (asparagine at position 147) and His74, causing a proton (hydrogen ion) to transfer between the oxygen atoms. The free oxygen atom coordinates, freeing the newly-formed water molecule and Fe(IV)=O. Fe(IV)=O reacts with a second hydrogen peroxide molecule to reform Fe(III)-E and produce water and oxygen. The reactivity of the iron center may be improved by the presence of the phenolate ligand of Tyr357 in the fifth iron ligand, which can assist in the oxidation of the Fe(III) to Fe(IV). The efficiency of the reaction may also be improved by the interactions of His74 and Asn147 with reaction intermediates. In general, the rate of the reaction can be determined by the Michaelis-Menten equation. [http://www.madsci.org/posts/archives/aug98/900981784.Bc.r.html]

Catalase can also oxidize different toxins, such as formaldehyde, formic acid, phenols, and alcohols. In doing so, it uses hydrogen peroxide according to the following reaction:

: H₂O₂ + H₂R → 2H₂O + R

Again, the exact mechanism of this reaction is not known.

Any heavy metal ion (such as copper cations in copper(II) sulfate) will act as a noncompetitive inhibitor on catalase. Also, the poison cyanide is a competitive inhibitor of catalase, strongly binding to the heme of catalase and stopping the enzyme's action.

Three-dimensional protein structures of the peroxidated catalase intermediates are available at the Protein Data Bank. This enzyme is commonly used in laboratories as a tool for learning the effect of enzymes upon reaction rates.

Cellular role

Hydrogen peroxide is a harmful by-product of many normal metabolic processes: To prevent damage, it must be quickly converted into other, less dangerous substances. To this end, catalase is frequently used by cells to rapidly catalyze the decomposition of hydrogen peroxide into less reactive gaseous oxygen and water molecules.cite journal | author = Gaetani G, Ferraris A, Rolfo M, Mangerini R, Arena S, Kirkman H | title = Predominant role of catalase in the disposal of hydrogen peroxide within human erythrocytes. | journal = Blood | volume = 87 | issue = 4 | pages = 1595–9 | year = 1996 | pmid = 8608252]

The true biological significance of catalase is not always straightforward to assess: Mice genetically engineered to lack catalase are phenotypically normal, indicating that this enzyme is dispensable in animals under some conditions.cite journal | author = Ho YS, Xiong Y, Ma W, Spector A, Ho D | title = Mice Lacking Catalase Develop Normally but Show Differential Sensitivity to Oxidant Tissue Injury. | journal = J Biol Chem | volume = 279 | issue = 31 | pages = 32804–812 | year = 2004 | pmid = 15178682 | doi = 10.1074/jbc.M404800200 ]

Some human beings have very low levels of catalase (acatalesimia), yet show few ill effects. It is likely that the predominant scavengers of H2O2 in normal mammalian cells are peroxiredoxins rather than catalase.

Catalase works at an optimum temperature of 37 °C, which is approximately the temperature of the human body.

Catalase is usually located in a cellular organelle called the peroxisome.cite book | author = Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P | title = Peroxisomes, "in" "Molecular Biology of the Cell" | edition = 4th ed. | publisher = Garland | year = 2002 | id = [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=catalase+AND+mboc4%5Bbook%5D+AND+373476%5Buid%5D&rid=mboc4.section.2194 (via NCBI Bookshelf)] ISBN 0815332181] Peroxisomes in plant cells are involved in photorespiration (the use of oxygen and production of carbon dioxide) and symbiotic nitrogen fixation (the breaking apart of diatomic nitrogen (N₂) to reactive nitrogen atoms).

Hydrogen peroxide is used as a potent antimicrobial agent when cells are infected with a pathogen. Pathogens that are catalase-positive, such as "Mycobacterium tuberculosis", "Legionella pneumophila", and "Campylobacter jejuni", make catalase in order to deactivate the peroxide radicals, thus allowing them to survive unharmed within the host. [http://mic.sgmjournals.org/cgi/content/full/149/9/2635]

Distribution among organisms

All known animals use catalase in every organ, with particularly high concentrations occurring in the liver. One unique use of catalase occurs in bombardier beetle. The beetle has two sets of chemicals ordinarily stored separately in its paired glands. The larger of the pair, the storage chamber or reservoir, contains hydroquinones and hydrogen peroxide, whereas the smaller of the pair, the reaction chamber, contains catalases and peroxidases. To activate the spray, the beetle mixes the contents of the two compartments, causing oxygen to be liberated from hydrogen peroxide. The oxygen oxidizes the hydroquinones and also acts as the propellant. cite journal| pmid = 10449758 | title = Spray aiming in the bombardier beetle: photographic evidence. | author = T Eisner and DJ Aneshansley | journal = Proc Natl Acad Sci U S A | date = 1999 Aug | volume = 96 | issue = 17 | pages = 9705–9 | doi = 10.1073/pnas.96.17.9705

Catalase is also universal among plants, but not among fungi, although some species have been found to produce the enzyme when growing in an environment with a low pH and warm temperatures. [cite journal| pmid = 16503295 | title = Production of catalase by fungi growing at low pH and high temperature. | author = K. Isobe, et al. | journal = J Biosci Bioeng | date = 2006 Jan | volume = 101 | issue = 1 | pages = 73–6 | doi = 10.1263/jbb.101.73 ]

Very few aerobic microorganisms are known that do not use catalase. [http://madsci.org/posts/archives/jun99/929507203.Gb.r.html] . "Streptococcus" species are an example of aerobic bacteria that do not possess catalase. Catalase has also been observed in some anaerobic microorganisms, such as Methanosarcina barkeri. [cite journal | doi = 10.1099/mic.0.28542-0 | title = The catalase and superoxide dismutase genes are transcriptionally up-regulated upon oxidative stress in the strictly anaerobic archaeon Methanosarcina barkeri. | author = Andrei Brioukhanov, Alexander Netrusov, and Rik Eggen. | journal = Microbiology | volume = 152 | pages = 1671–1677 | year = 2006 | pmid = 16735730]

Human applications

Catalase is used in the food industry for removing hydrogen peroxide from milk prior to cheese production. [http://www.worthington-biochem.com/CTL/default.html] Another use is in food wrappers, where it prevents food from oxidizing. [http://madsci.org/posts/archives/mar99/921636249.Gb.r.html] Catalase is also used in the textile industry, removing hydrogen peroxide from fabrics to make sure the material is peroxide-free. [http://www.p2pays.org/ref/11/10842.htm] A minor use is in contact lens hygiene - a few lens-cleaning products disinfect the lens using a hydrogen peroxide solution; a solution containing catalase is then used to decompose the hydrogen peroxide before the lens is used again. [US patent|5521091] Recently, catalase has also begun to be used in the aesthetics industry. Several mask treatments combine the enzyme with hydrogen peroxide on the face with the intent of increasing cellular oxygenation in the upper layers of the epidermis.

The catalase test is also one of the main three tests used by microbiologists to identify species of bacteria. The presence of catalase enzyme in the test isolate is detected using hydrogen peroxide. This when exposed to a small amount of a bacterial isolate will bubble if the bacteria possess this enzyme.

Pathology

The peroxisomal disorder acatalasia is due to a deficiency in the function of catalase.

See also

* Enzyme kinetics
* Peroxidases
* Superoxide dismutase

References

External links

* [http://genomics.senescence.info/genes/entry.php?hugo=CAT CAT] at the GenAge database.
* [http://madsci.org/FAQs/catalase.html Catalase Enzymatics, Expression and Applications "MadSci Network"]
* [http://www.tgw1916.net/movies.html Bacteria catalase test video]
* [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.11.1.6 BRENDA database entry for catalase.]
* [http://peroxibase.isb-sib.ch/ Systematic sequence analysis of catalases and peroxidases]

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