Editing Methanol (section)

===Biosynthesis===
The catalytic conversion of methane to methanol is effected by enzymes including [[methane monooxygenase]]s. These enzymes are mixed-function oxygenases, i.e. oxygenation is coupled with production of water<ref>{{cite journal|title=Mechanistic Studies on the Hydroxylation of Methane by Methane Monooxygenase|author=Mu-Hyun Baik |author2=Martin Newcomb |author3=Richard A. Friesner |author4=Stephen J. Lippard |journal=Chem. Rev.|year=2003|volume=103|issue=6|pages=2385–2420|doi=10.1021/cr950244f|pmid=12797835}}</ref> and [[Nicotinamide adenine dinucleotide|{{chem2|NAD+}}]]:<ref name=":0" />

:{{chem2 | CH4 + O2 + NADPH + H+ -> CH3OH + H2O + NAD+ }}

Both Fe- and Cu-dependent enzymes have been characterized.<ref name=":0">{{cite journal|author1=Lawton, T. J. |author2=Rosenzweig, A. C. |title=Biocatalysts for methane conversion: big progress on breaking a small substrate|journal=Curr. Opin. Chem. Biol.|year=2016|volume=35|pages=142–149|doi=10.1016/j.cbpa.2016.10.001|pmid=27768948|pmc=5161620}}</ref> Intense but largely fruitless efforts have been undertaken to emulate this reactivity.<ref name="Alayon">{{Cite journal|last1=Alayon|first1=E. M. C.|last2=Nachtegaal|first2=M.|last3=Ranocchiari|first3=M.|last4=Van Bokhoven|first4=J. A.|title=Catalytic Conversion of Methane to Methanol Using Cu-Zeolites|doi=10.2533/chimia.2012.668|journal=CHIMIA International Journal for Chemistry|volume=66|issue=9|pages=668–674|year=2012|pmid=23211724|url=https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A20913|doi-access=free|access-date=10 May 2021|archive-date=26 May 2021|archive-url=https://web.archive.org/web/20210526070248/https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A20913|url-status=live}}</ref><ref name="Catalytic and Mechanic Insights">{{Cite journal|doi=10.1002/chem.201202802|pmid=23150452|title=Catalytic and Mechanistic Insights of the Low-Temperature Selective Oxidation of Methane over Cu-Promoted Fe-ZSM-5|journal=Chemistry: A European Journal|volume=18|issue=49|pages=15735–45|year=2012|last1=Hammond|first1=C.|last2=Jenkins|first2=R. L.|last3=Dimitratos|first3=N.|last4=Lopez-Sanchez|first4=J. A.|last5=Ab Rahim|first5=M. H.|last6=Forde|first6=M.M.|last7=Thetford|first7=A.|last8=Murphy|first8=D.M.|last9=Hagen|first9=H.|last10=Stangland|first10=E.E.|last11=Moulijn|first11=J.M.|last12=Taylor|first12=S. H.|last13=Willock|first13=D. J.|last14=Hutchings|first14=G.J.}}</ref> Methanol is more easily oxidized than is the feedstock methane, so the reactions tend not to be selective. Some strategies exist to circumvent this problem. Examples include [[Shilov system]]s and Fe- and Cu-containing zeolites.<ref>{{Cite journal|last1=Snyder|first1=Benjamin E. R.|last2=Bols|first2=Max L.|last3=Schoonheydt|first3=Robert A.|last4=Sels|first4=Bert F.|last5=Solomon|first5=Edward I.|date=19 December 2017|title=Iron and Copper Active Sites in Zeolites and Their Correlation to Metalloenzymes|journal=Chemical Reviews|volume=118|issue=5|pages=2718–2768|doi=10.1021/acs.chemrev.7b00344|pmid=29256242|url=https://limo.libis.be/primo-explore/fulldisplay?docid=LIRIAS1644877&context=L&vid=Lirias&search_scope=Lirias&tab=default_tab&lang=en_US&fromSitemap=1|access-date=25 September 2021|archive-date=26 May 2021|archive-url=https://web.archive.org/web/20210526075141/https://limo.libis.be/primo-explore/fulldisplay?docid=LIRIAS1644877&context=L&vid=Lirias&search_scope=Lirias&tab=default_tab&lang=en_US&fromSitemap=1|url-status=live}}</ref> These systems do not necessarily mimic the mechanisms employed by [[metalloenzymes]], but draw some inspiration from them. Active sites can vary substantially from those known in the enzymes. For example, a dinuclear active site is proposed in the [[Methane monooxygenase|sMMO]] enzyme, whereas a mononuclear iron ([[alpha-Oxygen|alpha-oxygen]]) is proposed in the Fe-zeolite.<ref>{{Cite journal|last1=Snyder|first1=Benjamin E. R.|last2=Vanelderen|first2=Pieter|last3=Bols|first3=Max L.|last4=Hallaert|first4=Simon D.|last5=Böttger|first5=Lars H.|last6=Ungur|first6=Liviu|last7=Pierloot|first7=Kristine|last8=Schoonheydt|first8=Robert A.|last9=Sels|first9=Bert F.|s2cid=4467834|title=The active site of low-temperature methane hydroxylation in iron-containing zeolites|journal=Nature|volume=536|issue=7616|pages=317–321|doi=10.1038/nature19059|pmid=27535535|bibcode=2016Natur.536..317S|year=2016}}</ref>

Global emissions of methanol by plants are estimated at between 180 and 250 million tons per year.<ref>{{Cite journal |last1=Stavrakou |first1=T. |last2=Guenther |first2=A. |last3=Razavi |first3=A. |last4=Clarisse |first4=L. |last5=Clerbaux |first5=C. |last6=Coheur |first6=P.-F. |last7=Hurtmans |first7=D. |last8=Karagulian |first8=F. |last9=De Mazière |first9=M. |last10=Vigouroux |first10=C. |last11=Amelynck |first11=C. |last12=Schoon |first12=N. |last13=Laffineur |first13=Q. |last14=Heinesch |first14=B. |last15=Aubinet |first15=M. |date=25 May 2011 |title=First space-based derivation of the global atmospheric methanol emission fluxes |url=https://acp.copernicus.org/articles/11/4873/2011/ |journal=Atmospheric Chemistry and Physics |language=en |volume=11 |issue=10 |pages=4873–4898 |doi=10.5194/acp-11-4873-2011 |bibcode=2011ACP....11.4873S |s2cid=54685577 |issn=1680-7324 |doi-access=free |access-date=26 September 2022 |archive-date=26 September 2022 |archive-url=https://web.archive.org/web/20220926161749/https://acp.copernicus.org/articles/11/4873/2011/ |url-status=live}}</ref> This is between two and three times larger than man-made industrial production of methanol.