Editing Ethanol (section)

=== Recreational drug ===
{{Main|Alcohol (drug)}}
As a [[central nervous system]] [[depressant]], ethanol is one of the most commonly consumed [[psychoactive drug]]s.<ref>{{Cite web | title=Alcohol use and safe drinking: MedlinePlus Medical Encyclopedia | url=https://medlineplus.gov/ency/article/001944.htm | access-date=2023-03-11 | website=medlineplus.gov | language=en}}</ref> Despite alcohol's psychoactive, addictive, and [[Alcohol and cancer|carcinogenic]] properties,{{citation needed|date=April 2025}} it is readily available and legal for sale in many countries. There are laws regulating the sale, exportation/importation, taxation, manufacturing, consumption, and possession of alcoholic beverages. The most common regulation is prohibition for minors.

In mammals, ethanol is primarily [[metabolized]] in the [[liver]] and [[stomach]] by ADH enzymes.<ref name="Farrés">{{cite journal | vauthors=Farrés J, Moreno A, Crosas B, Peralba JM, Allali-Hassani A, Hjelmqvist L, Jörnvall H, Parés X | display-authors=6 | title=Alcohol dehydrogenase of class IV (σσ-ADH) from human stomach. cDNA sequence and structure/function relationships | journal=European Journal of Biochemistry | volume=224 | issue=2 | pages=549–557 | date=September 1994 | pmid=7925371 | doi=10.1111/j.1432-1033.1994.00549.x | doi-access=free}}</ref> These enzymes catalyze the [[oxidation]] of ethanol into [[acetaldehyde]] (ethanal):<ref>{{cite journal | vauthors=Edenberg HJ, McClintick JN | title=Alcohol Dehydrogenases, Aldehyde Dehydrogenases, and Alcohol Use Disorders: A Critical Review | journal=Alcoholism: Clinical and Experimental Research | volume=42 | issue=12 | pages=2281–2297 | date=December 2018 | pmid=30320893 | doi=10.1111/acer.13904 | pmc=6286250}}</ref>

:CH<sub>3</sub>CH<sub>2</sub>OH + NAD<sup>+</sup> → CH<sub>3</sub>CHO + [[NADH]] + H<sup>+</sup>

When present in significant concentrations, this metabolism of ethanol is additionally aided by the [[cytochrome P450]] enzyme [[CYP2E1]] in humans, while trace amounts are also metabolized by [[catalase]].<ref>{{cite book | author1=Heit, C. | author2=Dong, H. | author3=Chen, Y. | author4=Thompson, D.C. | author5=Dietrich, R.A. | author6=Vasiliou, V.K. | title=Cytochrome P450 2E1: Its Role in Disease and Drug Metabolism | chapter=The Role of CYP2E1 in Alcohol Metabolism and Sensitivity in the Central Nervous System | series=Subcellular Biochemistry | date=2013 | volume=67 | pages=235–237 | doi=10.1007/978-94-007-5881-0_8 | pmid=23400924 | pmc=4314297 | isbn=978-94-007-5880-3}}</ref> The resulting intermediate, acetaldehyde, is a known carcinogen, and poses significantly greater toxicity in humans than ethanol itself. Many of the symptoms typically associated with alcohol intoxication—as well as many of the health hazards typically associated with the long-term consumption of ethanol—can be attributed to acetaldehyde toxicity in humans.<ref>{{cite web | title=Alcohol Metabolism: An Update | url=https://pubs.niaaa.nih.gov/publications/aa72/aa72.htm | website=NIAA Publications | publisher=National Institute of Health | access-date=10 March 2021 | archive-date=28 February 2021 | archive-url=https://web.archive.org/web/20210228215303/https://pubs.niaaa.nih.gov/publications/AA72/AA72.htm | url-status=dead}}</ref>

The subsequent oxidation of acetaldehyde into [[acetate]] is performed by [[aldehyde dehydrogenase]] (ALDH) enzymes. A mutation in the ALDH2 gene that encodes for an inactive or dysfunctional form of this enzyme affects roughly 50% of east Asian populations, contributing to the characteristic [[alcohol flush reaction]] that can cause temporary reddening of the skin as well as a number of related, and often unpleasant, symptoms of acetaldehyde toxicity.<ref name="Eng et al.">{{cite journal | vauthors=Eng MY, Luczak SE, Wall TL | date=2007 | title=ALDH2, ADH1B, and ADH1C genotypes in Asians: a literature review | journal=Alcohol Research & Health | volume=30 | issue=1 | pages=22–27 | pmc=3860439 | pmid=17718397}}</ref> This mutation is typically accompanied by another mutation in the ADH enzyme [[ADH1B]] in roughly 80% of east Asians, which improves the catalytic efficiency of converting ethanol into acetaldehyde.<ref name="Eng et al." />