Editing Hydrogen peroxide (section)

==Biochemistry==
[[File:Ascaridol.svg|class=skin-invert-image|thumb|upright=0.5|[[Ascaridole]]]]

===Production===
The aerobic oxidation of [[glucose]] in the presence of the enzyme [[glucose oxidase]] produces hydrogen peroxide. The conversion affords [[gluconolactone]]:<ref>{{cite journal |doi=10.1007/s00253-008-1407-4 |title=Glucose oxidase: Natural Occurrence, Function, Properties and Industrial Applications |date=2008 |last1=Wong |first1=Chun Ming |last2=Wong |first2=Kwun Hei |last3=Chen |first3=Xiao Dong |journal=Applied Microbiology and Biotechnology |volume=78 |issue=6 |pages=927–938 |pmid=18330562 |s2cid=2246466}}</ref>
:{{chem2|C6H12O6 + O2 -> C6H10O6 + H2O2}}

[[Superoxide dismutase]]s (SOD)s are [[enzyme]]s that promote the [[disproportionation]] of [[superoxide]] into [[oxygen]] and hydrogen peroxide.<ref>Löffler G. and Petrides, P. E. ''Physiologische Chemie''. 4 ed., pp. 321–322, Springer, Berlin 1988, {{ISBN|3-540-18163-6}} (in German)</ref>

:{{chem2| 2 O2- + 2 H+ -> O2 + H2O2 }}
:{{chem2| 2 H2O2 -> O2 + 2 H2O }}

[[Peroxisome]]s are [[organelle]]s found in virtually all [[eukaryotic]] cells.<ref name="pmid20124343">{{cite journal |vauthors = Gabaldón T |title = Peroxisome diversity and evolution |journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |volume = 365 |issue = 1541 |pages = 765–773 |date = March 2010 |pmid = 20124343 |pmc = 2817229 |doi = 10.1098/rstb.2009.0240}}</ref> They are involved in the [[catabolism]] of [[very long chain fatty acid]]s, [[Branched-chain-fatty-acid kinase|branched chain fatty acids]], [[D-amino acid|<small>D</small>-amino acids]], [[polyamine]]s, and biosynthesis of [[plasmalogens]] and [[ether phospholipid]]s, which are found in mammalian brains and lungs.<ref name="pmid16756494">{{cite journal |vauthors = Wanders RJ, Waterham HR |title = Biochemistry of mammalian peroxisomes revisited |journal = Annual Review of Biochemistry |volume = 75 |issue = 1 |pages = 295–332 |year = 2006 |pmid = 16756494 |doi = 10.1146/annurev.biochem.74.082803.133329}}</ref> They produce hydrogen peroxide in a process catalyzed by [[flavin adenine dinucleotide]] (FAD):<ref>{{cite book |vauthors = Nelson D, Cox C, Lehninger AL, Cox MM |url = https://books.google.com/books?id=wuLQCAOtC4MC&pg=PA663 |title = Lehninger Biochemie |archive-url = https://web.archive.org/web/20170228175147/https://books.google.com/books?id=wuLQCAOtC4MC&pg=PA663 |archive-date = 28 February 2017 |pages = 663–4 |publisher = Springer |date = 2001 |isbn = 3-540-41813-X |language = German}}</ref>

:{{chem2| R\-CH2\-CH2\-CO\-SCoA + O2 }}<chem>->[\ce{FAD}]</chem> {{chem2| R\-CH\dCH\-CO\-SCoA + H2O2 }}

Hydrogen peroxide arises by the degradation of [[adenosine monophosphate]], which yields [[hypoxanthine]]. Hypoxanthine is then oxidatively [[catabolism|catabolized]] first to [[xanthine]] and then to [[uric acid]], and the reaction is catalyzed by the enzyme [[xanthine oxidase]]:<ref name="lehninger932">Nelson, David; Cox, Michael; Lehninger, Albert L. and Cox, Michael M. [https://books.google.com/books?id=wuLQCAOtC4MC&pg=PA932 Lehninger Biochemie], p. 932, Springer, 2001, {{ISBN|3-540-41813-X}} (in German)</ref>

{{Image frame
|align=center
| content={{Biochem reaction subunit
|compound=Hypoxanthine
|class=skin-invert-image
|image=Hypoxanthin.svg}}
{{Biochem reaction subunit
|enzyme=Xanthine oxidase
|for_subst={{H2O-nl}}, {{chem2|O2}}
|for_prod={{chem2|H2O2}}}}
{{Biochem reaction subunit
|compound=Xanthine
|class=skin-invert-image
|image=Xanthin.svg}}
{{Biochem reaction subunit
|enzyme=Xanthine oxidase
|for_subst={{H2O-nl}}, {{chem2|O2}}
|for_prod={{chem2|H2O2}}}}
{{Biochem reaction subunit
|compound=Uric acid
|class=skin-invert-image
|image=Harnsäure Ketoform.svg
|imagesize=120px}}
|caption=Degradation of hypoxanthine through xanthine to uric acid to form hydrogen peroxide
|width=600}}

The degradation of [[guanosine monophosphate]] yields xanthine as an intermediate product which is then converted in the same way to uric acid with the formation of hydrogen peroxide.<ref name="lehninger932" />

===Consumption===
[[Catalase]], another peroxisomal enzyme, uses this {{chem2|H2O2}} to oxidize other substrates, including [[phenols]], [[formic acid]], [[formaldehyde]], and [[ethanol|alcohol]], by means of a peroxidation reaction:
:{{chem2| H2O2 + R'H2 -> R' + 2 H2O }}
thus eliminating the poisonous hydrogen peroxide in the process.

This reaction is important in liver and kidney cells, where the peroxisomes neutralize various toxic substances that enter the blood. Some of the [[ethanol]] humans drink is oxidized to [[acetaldehyde]] in this way.<ref>Riley, Edward P. ''et al''. (ed.) [https://books.google.com/books?id=TiSL4txuYN0C&pg=PA112 Fetal Alcoholspectrum Disorder Fasd: Management and Policy Perspectives] {{Webarchive|url=https://web.archive.org/web/20170228175446/https://books.google.com/books?id=TiSL4txuYN0C&pg=PA112 |date=28 February 2017}}, Wiley-VCH, 2010, {{ISBN|3-527-32839-4}} p. 112</ref> In addition, when excess {{chem2|H2O2}} accumulates in the cell, catalase converts it to {{chem2|H2O}} through this reaction:
: {{chem2|H2O2 -> 0.5 O2 + H2O}}
[[Glutathione peroxidase]], a [[selenoenzyme]], also catalyzes the disproportionation of hydrogen peroxide.

===Fenton reaction===
The reaction of [[Ferrous|{{chem2|Fe(2+)}}]] and hydrogen peroxide is the basis of the [[Fenton reaction]], which generates [[hydroxyl radical]]s, which are of significance in biology:
:{{chem2|Fe(II) + H2O2 -> Fe(III)OH + HO*}}

The Fenton reaction explains the toxicity of hydrogen peroxides because the hydroxyl radicals rapidly and irreversibly oxidize all organic compounds, including [[protein]]s, [[membrane lipid]]s, and [[DNA]].<ref>Löffler G. and Petrides, P. E. ''Physiologische Chemie''. 4 ed., p. 288, Springer, Berlin 1988, {{ISBN|3-540-18163-6}} (in German)</ref> Hydrogen peroxide is a significant source of [[DNA damage (naturally occurring)|oxidative DNA damage]] in living cells. DNA damage includes formation of [[8-Oxo-2'-deoxyguanosine]] among many other altered bases, as well as strand breaks, inter-strand crosslinks, and deoxyribose damage.<ref name="Halliwell2021" /> By interacting with Cl<sup>−</sup>, hydrogen peroxide also leads to chlorinated DNA bases.<ref name="Halliwell2021">{{cite journal |vauthors=Halliwell B, Adhikary A, Dingfelder M, Dizdaroglu M |title=Hydroxyl radical is a significant player in oxidative DNA damage in vivo |journal=Chem Soc Rev |volume=50 |issue=15 |pages=8355–60 |date=August 2021 |pmid=34128512 |pmc=8328964 |doi=10.1039/d1cs00044f }}</ref> Hydroxyl radicals readily damage vital cellular components, especially those of the [[mitochondria]].<ref>{{cite journal |vauthors = Giorgio M, Trinei M, Migliaccio E, Pelicci PG |title = Hydrogen peroxide: a metabolic by-product or a common mediator of ageing signals? |journal = Nature Reviews. Molecular Cell Biology |volume = 8 |issue = 9 |pages = 722–8 |date = September 2007 |pmid = 17700625 |doi = 10.1038/nrm2240 |s2cid = 6407526 }}</ref><ref>{{cite journal |vauthors = Gonzalez D, Bejarano I, Barriga C, Rodriguez AB, Pariente JA |year = 2010 |title = Oxidative Stress-Induced Caspases are Regulated in Human Myeloid HL-60 Cells by Calcium Signal |journal = Current Signal Transduction Therapy |volume = 5 |issue = 2| pages = 181–6 |doi = 10.2174/157436210791112172}}</ref><ref>{{cite journal |vauthors = Bejarano I, Espino J, González-Flores D, Casado JG, Redondo PC, Rosado JA, Barriga C, Pariente JA, Rodríguez AB |display-authors = 6 |title = Role of Calcium Signals on Hydrogen Peroxide-Induced Apoptosis in Human Myeloid HL-60 Cells |journal = International Journal of Biomedical Science |volume = 5 |issue = 3 |pages = 246–256 |date = September 2009 |doi = 10.59566/IJBS.2009.5246 |pmid = 23675144 |pmc = 3614781}}</ref> The compound is a major factor implicated in the [[free-radical theory of aging]], based on its ready conversion into a [[hydroxyl radical]].

===Function===
[[File:Pheropsophus verticalis 01 Pengo.jpg|thumb|130px|Australian [[bombardier beetle]]]]Eggs of [[sea urchin]], shortly after fertilization by a sperm, produce hydrogen peroxide. It is then converted to [[hydroxyl radical]]s (HO•), which initiate [[radical polymerization]], which surrounds the eggs with a protective layer of [[polymer]].

The [[bombardier beetle]] combines [[hydroquinone]] and hydrogen peroxide, leading to a violent [[exothermic]] [[chemical reaction]] to produce boiling, foul-smelling liquid that partially becomes a [[gas]] ([[flash evaporation]]) and is expelled through an outlet valve with a loud popping sound.<ref>{{cite journal| vauthors = Schildknecht H, Holoubek K |title=The bombardier beetle and its chemical explosion|journal=Angewandte Chemie|volume=73|pages=1–7|year=1961|doi=10.1002/ange.19610730102}}</ref><ref name="ncse">{{cite journal |vauthors = Weber CG |title=The Bombardier Beetle Myth Exploded |journal=Creation/Evolution |volume=2 |issue=1 |pages=1–5 |date=Winter 1981 |url=https://ncse.com/cej/2/1/bombardier-beetle-myth-exploded |access-date=12 November 2017 |archive-url=https://web.archive.org/web/20170929125624/https://ncse.com/cej/2/1/bombardier-beetle-myth-exploded |archive-date=29 September 2017 |url-status=live}}</ref><ref name="to">{{cite web |vauthors = Isaak M |date=30 May 2003 |title=Bombardier Beetles and the Argument of Design |website=[[TalkOrigins Archive]] |url=https://www.talkorigins.org/faqs/bombardier.html |access-date=12 November 2017 |archive-url=https://web.archive.org/web/20171116235917/https://www.talkorigins.org/faqs/bombardier.html |archive-date=16 November 2017 |url-status=live}}</ref>

As a proposed [[signaling molecule]], hydrogen peroxide may regulate a wide variety of biological processes.<ref>{{cite journal |vauthors = Veal EA, Day AM, Morgan BA |title = Hydrogen peroxide sensing and signaling |journal = Molecular Cell |volume = 26 |issue = 1 |pages = 1–14 |date = April 2007 |pmid = 17434122 |doi = 10.1016/j.molcel.2007.03.016 |doi-access = free}}</ref><ref>{{Cite web|title=Wie Pflanzen sich schützen, Helmholtz-Institute of Biochemical Plant Pathology (in German)|url=https://www.helmholtz-muenchen.de/biop/printversionen/pdf/aktuelles/pflanzenschuetzen_no.pdf|url-status=dead|archive-url=https://web.archive.org/web/20110723120528/https://www.helmholtz-muenchen.de/biop/printversionen/pdf/aktuelles/pflanzenschuetzen_no.pdf|archive-date=23 July 2011|access-date=14 February 2022|publisher=Helmholtz-Institute of Biochemical Plant Pathology|language=de}}</ref> At least one study has tried to link hydrogen peroxide production to cancer.<ref>{{cite journal |vauthors = López-Lázaro M |title = Dual role of hydrogen peroxide in cancer: possible relevance to cancer chemoprevention and therapy |journal = Cancer Letters |volume = 252 |issue = 1 |pages = 1–8 |date = July 2007 |pmid = 17150302 |doi = 10.1016/j.canlet.2006.10.029}}</ref>