Editing Demethylation (section)

== In biochemistry ==
:[[File:DicambaDeMeth.svg|thumb|left|Dicamba, a widely used herbicide, biodegrades by demethylation to give 3,6-[[dichlorosalicylic acid]], catalyzed by a [[dioxygenase]] [[enzyme]].<ref>{{cite journal |doi=10.1016/j.jmb.2009.07.021 |title=Crystal Structure of Dicamba Monooxygenase: A Rieske Nonheme Oxygenase that Catalyzes Oxidative Demethylation |date=2009 |last1=Dumitru |first1=Razvan |last2=Jiang |first2=Wen Zhi |last3=Weeks |first3=Donald P. |last4=Wilson |first4=Mark A. |journal=Journal of Molecular Biology |volume=392 |issue=2 |pages=498–510 |pmid=19616011 |pmc=3109874 }}</ref> |422px]]

Demethylation is relevant to [[epigenetic]]s.  Demethylation of DNA is [[catalyst|catalyzed]] by [[demethylase]]s.  These enzymes [[oxidize]] N-methyl groups, which occur in [[histone]]s, in lysine derivatives, and in some forms of DNA.<ref name="Ped">{{cite journal | vauthors = Pedersen MT, Helin K | title = Histone demethylases in development and disease | journal = Trends in Cell Biology | volume = 20 | issue = 11 | pages = 662–71 | date = Nov 2010 | pmid = 20863703 | doi = 10.1016/j.tcb.2010.08.011 }}</ref>  
:R<sub>2</sub>N-CH<sub>3</sub>  +  O   →   R<sub>2</sub>N-H   +  CH<sub>2</sub>O
One family of such oxidative enzymes is the [[cytochrome P450]].<ref name="isbn0-470-01672-8">{{cite book |author1=Roland Sigel |author2=Sigel, Astrid |author3=Sigel, Helmut | title = The Ubiquitous Roles of Cytochrome P450 Proteins: Metal Ions in Life Sciences | publisher = Wiley | location = New York | year = 2007 | isbn = 978-0-470-01672-5 }}</ref> [[Alpha-ketoglutarate-dependent hydroxylase]]s are also active for demethylation of DNA, operating by a similar stoichiometry.<ref name="pmid24153300">{{cite journal |vauthors=Kohli RM, Zhang Y |title=TET enzymes, TDG and the dynamics of DNA demethylation |journal=Nature |volume=502 |issue=7472 |pages=472–9 |date=October 2013 |pmid=24153300 |pmc=4046508 |doi=10.1038/nature12750 |bibcode=2013Natur.502..472K }}</ref>  These reactions, which proceed via [[hydroxylation]], exploit the slightly weakened [[Carbon–hydrogen bond|C-H bond]]s of [[methylamine]]s and [[methyl ether]]s.

Demethylation of some [[sterol]]s are steps in the biosynthesis of [[testosterone]] and [[cholesterol]].  Methyl groups are lost as [[formate]].<ref>{{cite journal |doi=10.1016/j.molmet.2019.05.012|title=Formate Metabolism in Health and Disease |year=2020 |last1=Pietzke |first1=Matthias |last2=Meiser |first2=Johannes |last3=Vazquez |first3=Alexei |journal=Molecular Metabolism |volume=33 |pages=23–37 |pmid=31402327 |pmc=7056922 }}</ref>