Alcohol dehydrogenase#Human

Genetic evidence from comparisons of multiple organisms showed that a glutathione-dependent formaldehyde dehydrogenase, identical to a class III alcohol dehydrogenase (ADH-3/ADH5), is presumed to be the ancestral enzyme for the entire ADH family.{{cite journal | vauthors = Gutheil WG, Holmquist B, Vallee BL | title = Purification, characterization, and partial sequence of the glutathione-dependent formaldehyde dehydrogenase from Escherichia coli: a class III alcohol dehydrogenase | journal = Biochemistry | volume = 31 | issue = 2 | pages = 475–81 | date = January 1992 | pmid = 1731906 | doi = 10.1021/bi00117a025 }}{{cite journal | vauthors = Danielsson O, Jörnvall H | title = "Enzymogenesis": classical liver alcohol dehydrogenase origin from the glutathione-dependent formaldehyde dehydrogenase line | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 89 | issue = 19 | pages = 9247–51 | date = October 1992 | pmid = 1409630 | pmc = 50103 | doi = 10.1073/pnas.89.19.9247 | bibcode = 1992PNAS...89.9247D | doi-access = free }}{{cite journal | vauthors = Persson B, Hedlund J, Jörnvall H | title = Medium- and short-chain dehydrogenase/reductase gene and protein families : the MDR superfamily | journal = Cellular and Molecular Life Sciences | volume = 65 | issue = 24 | pages = 3879–94 | date = December 2008 | pmid = 19011751 | pmc = 2792335 | doi = 10.1007/s00018-008-8587-z }} Early on in evolution, an effective method for eliminating both endogenous and exogenous formaldehyde was important and this capacity has conserved the ancestral ADH-3 through time. Gene duplication of ADH-3, followed by series of mutations, led to the evolution of other ADHs.

The ability to produce ethanol from sugar (which is the basis of how alcoholic beverages are made) is believed to have initially evolved in yeast. Though this feature is not adaptive from an energy point of view, by making alcohol in such high concentrations so that they would be toxic to other organisms, yeast cells could effectively eliminate their competition. Since rotting fruit can contain more than 4% of ethanol, animals eating the fruit needed a system to metabolize exogenous ethanol. This was thought to explain the conservation of ethanol active ADH in species other than yeast, though ADH-3 is now known to also have a major role in nitric oxide signaling.{{cite journal | vauthors = Staab CA, Hellgren M, Höög JO | title = Medium- and short-chain dehydrogenase/reductase gene and protein families : Dual functions of alcohol dehydrogenase 3: implications with focus on formaldehyde dehydrogenase and S-nitrosoglutathione reductase activities | journal = Cellular and Molecular Life Sciences | volume = 65 | issue = 24 | pages = 3950–60 | date = December 2008 | pmid = 19011746 | doi = 10.1007/s00018-008-8592-2 | s2cid = 8574022 | pmc = 11131861 }}{{cite journal | vauthors = Godoy L, Gonzàlez-Duarte R, Albalat R | title = S-Nitrosogluthathione reductase activity of amphioxus ADH3: insights into the nitric oxide metabolism | journal = International Journal of Biological Sciences | volume = 2 | issue = 3 | pages = 117–24 | year = 2006 | pmid = 16763671 | pmc = 1458435 | doi = 10.7150/ijbs.2.117 }}

In humans, sequencing of the ADH1B gene (responsible for production of an alcohol dehydrogenase polypeptide) shows several functional variants. In one, there is a SNP (single nucleotide polymorphism) that leads to either a Histidine or an Arginine residue at position 47 in the mature polypeptide. In the Histidine variant, the enzyme is much more effective at the aforementioned conversion.{{cite journal|vauthors=Whitfield, John B |title=ADH and ALDH genotypes in relation to alcohol metabolic rate and sensitivity |journal=Alcohol and Alcoholism |volume=2 |pages=59–65 |url=http://152.98.160.29/contents/p/staff/JW058.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://152.98.160.29/contents/p/staff/JW058.pdf |archive-date=2022-10-09 |url-status=live |pmid=8974317 |year=1994 }}{{dead link|date=June 2017 |bot=InternetArchiveBot |fix-attempted=yes }} The enzyme responsible for the conversion of acetaldehyde to acetate, however, remains unaffected, which leads to differential rates of substrate catalysis and causes a buildup of toxic acetaldehyde, causing cell damage. This provides some protection against excessive alcohol consumption and alcohol dependence (alcoholism).{{cite journal | vauthors = Thomasson HR, Edenberg HJ, Crabb DW, Mai XL, Jerome RE, Li TK, Wang SP, Lin YT, Lu RB, Yin SJ | title = Alcohol and aldehyde dehydrogenase genotypes and alcoholism in Chinese men | journal = American Journal of Human Genetics | volume = 48 | issue = 4 | pages = 677–81 | date = April 1991 | pmid = 2014795 | pmc = 1682953 }}{{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 = October 2018 | pmid = 30320893 | pmc = 6286250 | doi = 10.1111/acer.13904 }}{{cite journal | vauthors = Hurley TD, Edenberg HJ | title = Genes encoding enzymes involved in ethanol metabolism | journal = Alcohol Research | volume = 34 | issue = 3 | pages = 339–44 | date = 2012 | pmid = 23134050 | pmc = 3756590 }}{{cite journal | vauthors = Walters RK, Polimanti R, Johnson EC, McClintick JN, Adams MJ, Adkins AE, etal | title = Transancestral GWAS of alcohol dependence reveals common genetic underpinnings with psychiatric disorders | journal = Nature Neuroscience | volume = 21 | issue = 12 | pages = 1656–1669 | date = December 2018 | pmid = 30482948 | pmc = 6430207 | doi = 10.1038/s41593-018-0275-1 }} Various haplotypes arising from this mutation are more concentrated in regions near Eastern China, a region also known for its low alcohol tolerance and dependence.

A study was conducted in order to find a correlation between allelic distribution and alcoholism, and the results suggest that the allelic distribution arose along with rice cultivation in the region between 12,000 and 6,000 years ago.{{cite journal | vauthors = Peng Y, Shi H, Qi XB, Xiao CJ, Zhong H, Ma RL, Su B | title = The ADH1B Arg47His polymorphism in east Asian populations and expansion of rice domestication in history | journal = BMC Evolutionary Biology | volume = 10 | pages = 15 | date = January 2010 | issue = 1 | pmid = 20089146 | pmc = 2823730 | doi = 10.1186/1471-2148-10-15 | bibcode = 2010BMCEE..10...15P | doi-access = free }} In regions where rice was cultivated, rice was also fermented into ethanol. This led to speculation that increased alcohol availability led to alcoholism and abuse, resulting in lower reproductive fitness. Those with the variant allele have little tolerance for alcohol, thus lowering chance of dependence and abuse. The hypothesis posits that those individuals with the Histidine variant enzyme were sensitive enough to the effects of alcohol that differential reproductive success arose and the corresponding alleles were passed through the generations. Classical Darwinian evolution would act to select against the detrimental form of the enzyme (Arg variant) because of the lowered reproductive success of individuals carrying the allele. The result would be a higher frequency of the allele responsible for the His-variant enzyme in regions that had been under selective pressure the longest. The distribution and frequency of the His variant follows the spread of rice cultivation to inland regions of Asia, with higher frequencies of the His variant in regions that have cultivated rice the longest. The geographic distribution of the alleles seems to therefore be a result of natural selection against individuals with lower reproductive success, namely, those who carried the Arg variant allele and were more susceptible to alcoholism.{{cite journal| vauthors = Eng MY |title=Alcohol Research and Health|journal=Alcohol Health & Research World |date=2007-01-01|publisher=U.S. Government Printing Office|issn=1535-7414}} However, the persistence of the Arg variant in other populations argues that the effect could not be strong.{{citation needed|date=February 2024}}

Image:ladh.jpg

The first-ever isolated alcohol dehydrogenase (ADH) was purified in 1937 from Saccharomyces cerevisiae (brewer's yeast).{{cite journal |title=Diphosphopyridinproteid ackohol, acetaldehyd|vauthors = Negelein E, Wulff HJ | journal = Biochem. Z. | year = 1937 | volume = 293 | page = 351 }} Many aspects of the catalytic mechanism for the horse liver ADH enzyme were investigated by Hugo Theorell and coworkers.{{cite journal | vauthors = Theorell H, McKEE JS | title = Mechanism of action of liver alcohol dehydrogenase | journal = Nature | volume = 192 | issue = 4797 | pages = 47–50 | date = October 1961 | pmid = 13920552 | doi = 10.1038/192047a0 | bibcode = 1961Natur.192...47T | s2cid = 19199733 }} ADH was also one of the first oligomeric enzymes that had its amino acid sequence and three-dimensional structure determined.{{cite journal | vauthors = Jörnvall H, Harris JI | title = Horse liver alcohol dehydrogenase. On the primary structure of the ethanol-active isoenzyme | journal = European Journal of Biochemistry | volume = 13 | issue = 3 | pages = 565–76 | date = April 1970 | pmid = 5462776 | doi = 10.1111/j.1432-1033.1970.tb00962.x | doi-access = }}{{cite journal | vauthors = Brändén CI, Eklund H, Nordström B, Boiwe T, Söderlund G, Zeppezauer E, Ohlsson I, Akeson A | title = Structure of liver alcohol dehydrogenase at 2.9-angstrom resolution | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 70 | issue = 8 | pages = 2439–42 | date = August 1973 | pmid = 4365379 | pmc = 433752 | doi = 10.1073/pnas.70.8.2439 | bibcode = 1973PNAS...70.2439B | doi-access = free }}{{cite book | vauthors = Hellgren M | title = Enzymatic studies of alcohol dehydrogenase by a combination of in vitro and in silico methods, PhD thesis | publisher = Karolinska Institutet | location = Stockholm, Sweden | year = 2009 | page = 70 | isbn = 978-91-7409-567-8 | url = http://diss.kib.ki.se/2009/978-91-7409-567-8/thesis.pdf }}

In early 1960, the alcohol dehydrogenase (ADH) gene was discovered in fruit flies of the genus Drosophila melanogaster.{{cite journal | vauthors = Sofer W, Martin PF | title = Analysis of alcohol dehydrogenase gene expression in Drosophila | journal = Annual Review of Genetics | volume = 21 | pages = 203–25 | year = 1987 | pmid = 3327463 | doi = 10.1146/annurev.ge.21.120187.001223 }} Flies that are mutant for ADH cannot breakdown alcohols into aldehydes and ketones.{{cite journal | vauthors = Winberg JO, McKinley-McKee JS | title = Drosophila melanogaster alcohol dehydrogenase: mechanism of aldehyde oxidation and dismutation | journal = The Biochemical Journal | volume = 329 | issue = Pt 3 | pages = 561–70 | date = February 1998 | pmid = 9445383 | pmc = 1219077 | doi = 10.1042/bj3290561 }} While ethanol produced by decaying fruit is a natural food source and location for oviposit for Drosophila at low concentrations (<4%), high concentrations of ethanol can induce oxidative stress and alcohol intoxication.{{cite journal | vauthors = Ogueta M, Cibik O, Eltrop R, Schneider A, Scholz H | title = The influence of Adh function on ethanol preference and tolerance in adult Drosophila melanogaster | journal = Chemical Senses | volume = 35 | issue = 9 | pages = 813–22 | date = November 2010 | pmid = 20739429 | doi = 10.1093/chemse/bjq084 | doi-access = free }} Drosophila's fitness is elevated by consuming the low concentration of ethanol. Initial exposure to ethanol causes hyperactivity, followed by incoordination and sedation.{{cite journal | vauthors = Park A, Ghezzi A, Wijesekera TP, Atkinson NS | title = Genetics and genomics of alcohol responses in Drosophila | journal = Neuropharmacology | volume = 122 | pages = 22–35 | date = August 2017 | pmid = 28161376 | pmc = 5479727 | doi = 10.1016/j.neuropharm.2017.01.032 }} Further research has shown that the antioxidant alpha-ketoglutarate may be beneficial in reducing the oxidative stress produced by alcohol consumption. A 2016 study concluded that food supplementation with 10-mM alpha-ketoglutarate decreased Drosophila alcohol sensitivity over time.{{cite journal | vauthors = Bayliak MM, Shmihel HV, Lylyk MP, Storey KB, Lushchak VI | title = Alpha-ketoglutarate reduces ethanol toxicity in Drosophila melanogaster by enhancing alcohol dehydrogenase activity and antioxidant capacity | journal = Alcohol | volume = 55 | pages = 23–33 | date = September 2016 | pmid = 27788775 | doi = 10.1016/j.alcohol.2016.07.009 }} For the gene that codes for ADH, there are 194 known classic and insertion alleles.{{Cite web|url=http://flybase.org/reports/FBgn0000055#alleles_main_sub|title=FlyBase Gene Report: Dmel\Adh|website=flybase.org|access-date=2019-03-26}} Two alleles that are commonly used for experimentation involving ethanol toxicity and response are ADH^s (slow) and ADH^F (fast). Numerous experiments have concluded that the two alleles account for the differences in enzymatic activity for each. In comparing Adh-F homozygotes (wild-type) and Adh- nulls (homozygous null), research has shown that Adh- nulls have a lower level of tolerance for ethanol, starting the process of intoxication earlier than its counter partner. Other experiments have also concluded that the Adh allele is haplosufficient. Haplosuffiency means that having one functioning allele will be adequate in producing the needed phenotypes for survival. That means that flies that were heterozygous for the Adh allele (one copy of the Adh null allele and one copy of the Adh Wild type allele) gave very similar phenotypical alcohol tolerance as the homozygous dominant flies (two copies of the wild type Adh allele). Regardless of genotype, Drosophila show a negative response to exposure to samples with an ethanol content above 5%, which render any tolerance inadequate, resulting in a lethal dosage and a mortality rate of around 70%.{{Cite journal| vauthors = Gao HH, Zhai YF, Chen H, Wang YM, Liu Q, Hu QL, Ren FS, Yu Y |date=September 2018|title=Ecological Niche Difference Associated with Varied Ethanol Tolerance between Drosophila suzukii and Drosophila melanogaster (Diptera: Drosophilidae)|journal=Florida Entomologist|volume=101|issue=3|pages=498–504|doi=10.1653/024.101.0308|issn=0015-4040|doi-access=free}} Drosophila show many of the same ethanol responses as humans do. Low doses of ethanol produce hyperactivity, moderate doses incoordination, and high doses sedation''.{{cite journal | vauthors = Parsch J, Russell JA, Beerman I, Hartl DL, Stephan W | title = Deletion of a conserved regulatory element in the Drosophila Adh gene leads to increased alcohol dehydrogenase activity but also delays development | journal = Genetics | volume = 156 | issue = 1 | pages = 219–27 | date = September 2000 | doi = 10.1093/genetics/156.1.219 | pmid = 10978287 | pmc = 1461225 | url = http://www.genetics.org/content/156/1/219 }}

The alcohol dehydrogenases comprise a group of several isozymes that catalyse the oxidation of primary and secondary alcohols to aldehydes and ketones, respectively, and also can catalyse the reverse reaction. In mammals this is a redox (reduction/oxidation) reaction involving the coenzyme nicotinamide adenine dinucleotide (NAD⁺).{{citation needed|date=June 2024}}

1. Binding of the coenzyme NAD⁺
2. Binding of the alcohol substrate by coordination to zinc(II) ion
3. Deprotonation of His-51
4. Deprotonation of nicotinamide ribose
5. Deprotonation of Thr-48
6. Deprotonation of the alcohol
7. Hydride transfer from the alkoxide ion to NAD⁺, leading to NADH and a zinc-bound aldehyde or ketone
8. Release of aldehyde.

The mechanism in yeast and bacteria is the reverse of this reaction. These steps are supported through kinetic studies.{{cite journal | vauthors = Hammes-Schiffer S, Benkovic SJ | title = Relating protein motion to catalysis | journal = Annual Review of Biochemistry | volume = 75 | pages = 519–41 | year = 2006 | pmid = 16756501 | doi = 10.1146/annurev.biochem.75.103004.142800 }}

The substrate is coordinated to the zinc and this enzyme has two zinc atoms per subunit. One is the active site, which is involved in catalysis. In the active site, the ligands are Cys-46, Cys-174, His-67, and one water molecule. The other subunit is involved with structure. In this mechanism, the hydride from the alcohol goes to NAD⁺. Crystal structures indicate that the His-51 deprotonates the nicotinamide ribose, which deprotonates Ser-48. Finally, Ser-48 deprotonates the alcohol, making it an aldehyde. From a mechanistic perspective, if the enzyme adds hydride to the re face of NAD⁺, the resulting hydrogen is incorporated into the pro-R position. Enzymes that add hydride to the re face are deemed Class A dehydrogenases.{{citation needed|date=June 2024}}

Image:active site3.jpg

The active site of human ADH1 (PDB:1HSO) consists of a zinc atom, His-67, Cys-174, Cys-46, Thr-48, His-51, Ile-269, Val-292, Ala-317, and Phe-319. In the commonly studied horse liver isoform, Thr-48 is a Ser, and Leu-319 is a Phe. The zinc coordinates the substrate (alcohol). The zinc is coordinated by Cys-46, Cys-174, and His-67. Leu-319, Ala-317, His-51, Ile-269 and Val-292 stabilize NAD⁺ by forming hydrogen bonds. His-51 and Ile-269 form hydrogen bonds with the alcohols on nicotinamide ribose. Phe-319, Ala-317 and Val-292 form hydrogen bonds with the amide on NAD⁺.

Image:Zinc interaction Cysteine.jpg

Mammalian alcohol dehydrogenases also have a structural zinc site. This Zn ion plays a structural role and is crucial for protein stability. The structures of the catalytic and structural zinc sites in horse liver alcohol dehydrogenase (HLADH) as revealed in crystallographic structures, which has been studied computationally with quantum chemistry as well as with classical molecular dynamics methods. The structural zinc site is composed of four closely spaced cysteine ligands (Cys97, Cys100, Cys103, and Cys111 in the amino acid sequence) positioned in an almost symmetric tetrahedron around the Zn ion. A recent study showed that the interaction between zinc and cysteine is governed by primarily an electrostatic contribution with an additional covalent contribution to the binding.{{cite journal | vauthors = Brandt EG, Hellgren M, Brinck T, Bergman T, Edholm O | title = Molecular dynamics study of zinc binding to cysteines in a peptide mimic of the alcohol dehydrogenase structural zinc site | journal = Physical Chemistry Chemical Physics | volume = 11 | issue = 6 | pages = 975–83 | date = February 2009 | pmid = 19177216 | doi = 10.1039/b815482a | url = https://zenodo.org/record/996012 | bibcode = 2009PCCP...11..975B }}

In humans, ADH exists in multiple forms as a dimer and is encoded by at least seven genes. Among the five classes (I-V) of alcohol dehydrogenase, the hepatic forms that are used primarily in humans are class 1. Class 1 consists of α, β, and γ subunits that are encoded by the genes ADH1A, ADH1B, and ADH1C.{{cite journal | vauthors = Sultatos LG, Pastino GM, Rosenfeld CA, Flynn EJ | title = Incorporation of the genetic control of alcohol dehydrogenase into a physiologically based pharmacokinetic model for ethanol in humans | journal = Toxicological Sciences | volume = 78 | issue = 1 | pages = 20–31 | date = March 2004 | pmid = 14718645 | doi = 10.1093/toxsci/kfh057 | doi-access = }}{{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 }} The enzyme is present at high levels in the liver and the lining of the stomach.{{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 (sigma sigma-ADH) from human stomach. cDNA sequence and structure/function relationships | journal = European Journal of Biochemistry | volume = 224 | issue = 2 | pages = 549–57 | date = September 1994 | pmid = 7925371 | doi = 10.1111/j.1432-1033.1994.00549.x | doi-access = }} It catalyzes the oxidation of ethanol to acetaldehyde (ethanal):

:CH₃CH₂OH + NAD⁺ → CH₃CHO + NADH + H⁺

This allows the consumption of alcoholic beverages, but its evolutionary purpose is probably the breakdown of alcohols naturally contained in foods or produced by bacteria in the digestive tract.{{cite web | url = http://www.medicinenet.com/alcohol_and_nutrition/article.htm | title = Alcohol and Nutrition | vauthors = Kovacs B, Stöppler MC | publisher = MedicineNet, Inc. | access-date = 2011-06-07 | archive-url = https://web.archive.org/web/20110623122224/http://www.medicinenet.com/alcohol_and_nutrition/article.htm | archive-date = 23 June 2011 | url-status = dead }}

Another evolutionary purpose is reversible metabolism of retinol (vitamin A), an alcohol, to retinaldehyde, also known as retinal, which is then irreversibly converted into retinoic acid, which regulates expression of hundreds of genes.{{cite journal | vauthors = Duester G | title = Retinoic acid synthesis and signaling during early organogenesis | journal = Cell | volume = 134 | issue = 6 | pages = 921–31 | date = September 2008 | pmid = 18805086 | pmc = 2632951 | doi = 10.1016/j.cell.2008.09.002 }}{{cite journal | vauthors = Hellgren M, Strömberg P, Gallego O, Martras S, Farrés J, Persson B, Parés X, Höög JO | title = Alcohol dehydrogenase 2 is a major hepatic enzyme for human retinol metabolism | journal = Cellular and Molecular Life Sciences | volume = 64 | issue = 4 | pages = 498–505 | date = February 2007 | pmid = 17279314 | doi = 10.1007/s00018-007-6449-8 | s2cid = 21612648 | pmc = 11138474 }}{{cite book |vauthors=Blaner WS |title = Present Knowledge in Nutrition, Eleventh Edition |chapter = Vitamin A | veditors = Marriott BP, Birt DF, Stallings VA, Yates AA |publisher = Academic Press (Elsevier) |year=2020 |location = London, United Kingdom |pages = 73–92 |isbn=978-0-323-66162-1}}

Alcohol dehydrogenase is also involved in the toxicity of other types of alcohol: For instance, it oxidizes methanol to produce formaldehyde and ultimately formic acid.{{cite book | vauthors = Ashurst JV, Nappe TM | chapter = Methanol Toxicity |date=2020 | chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK482121/| title = StatPearls |place= Treasure Island (FL)|publisher=StatPearls Publishing|pmid=29489213|access-date=2020-11-06}} Humans have at least six slightly different alcohol dehydrogenases. Each is a dimer (i.e., consists of two polypeptides), with each dimer containing two zinc ions Zn²⁺. One of those ions is crucial for the operation of the enzyme: It is located at the catalytic site and holds the hydroxyl group of the alcohol in place. {{Citation needed|date=February 2022}}

Alcohol dehydrogenase activity varies between men and women, between young and old, and among populations from different areas of the world. For example, young women are unable to process alcohol at the same rate as young men because they do not express the alcohol dehydrogenase as highly, although the inverse is true among the middle-aged.{{cite journal | vauthors = Parlesak A, Billinger MH, Bode C, Bode JC | title = Gastric alcohol dehydrogenase activity in man: influence of gender, age, alcohol consumption and smoking in a caucasian population | journal = Alcohol and Alcoholism | volume = 37 | issue = 4 | pages = 388–93 | year = 2002 | pmid = 12107043 | doi = 10.1093/alcalc/37.4.388 | doi-access = free }} The level of activity may not be dependent only on level of expression but also on allelic diversity among the population.

The human genes that encode class II, III, IV, and V alcohol dehydrogenases are ADH4, ADH5, ADH7, and ADH6, respectively.

Unlike humans, yeast and bacteria (except lactic acid bacteria, and E. coli in certain conditions) do not ferment glucose to lactate. Instead, they ferment it to ethanol and {{co2}}. The overall reaction can be seen below:

: Glucose + 2 ADP + 2 Pi → 2 ethanol + 2 CO₂ + 2 ATP + 2 H₂O{{cite book | vauthors = Cox M, Nelson DR, Lehninger AL | title = Lehninger Principles of Biochemistry | publisher = W. H. Freeman | location = San Francisco | year = 2005 | page = [https://archive.org/details/lehningerprincip00lehn_0/page/180 180] | isbn = 978-0-7167-4339-2 | url = https://archive.org/details/lehningerprincip00lehn_0/page/180 | url-access = registration }}

Image:AlcoholDehydrogenase-1A4U.png

In yeast{{cite journal | vauthors = Leskovac V, Trivić S, Pericin D | title = The three zinc-containing alcohol dehydrogenases from baker's yeast, Saccharomyces cerevisiae | journal = FEMS Yeast Research | volume = 2 | issue = 4 | pages = 481–94 | date = December 2002 | pmid = 12702265 | doi = 10.1111/j.1567-1364.2002.tb00116.x | doi-access = free }} and many bacteria, alcohol dehydrogenase plays an important part in fermentation: Pyruvate resulting from glycolysis is converted to acetaldehyde and carbon dioxide, and the acetaldehyde is then reduced to ethanol by an alcohol dehydrogenase called ADH1. The purpose of this latter step is the regeneration of NAD⁺, so that the energy-generating glycolysis can continue. Humans exploit this process to produce alcoholic beverages, by letting yeast ferment various fruits or grains. Yeast can produce and consume their own alcohol.

The main alcohol dehydrogenase in yeast is larger than the human one, consisting of four rather than just two subunits. It also contains zinc at its catalytic site. Together with the zinc-containing alcohol dehydrogenases of animals and humans, these enzymes from yeasts and many bacteria form the family of "long-chain"-alcohol dehydrogenases.{{citation needed|date=June 2024}}

Brewer's yeast also has another alcohol dehydrogenase, ADH2, which evolved out of a duplicate version of the chromosome containing the [https://www.yeastgenome.org/locus/adh1 ADH1] gene. [https://www.yeastgenome.org/locus/adh2 ADH2] is used by the yeast to convert ethanol back into acetaldehyde, and it is expressed only when sugar concentration is low. Having these two enzymes allows yeast to produce alcohol when sugar is plentiful (and this alcohol then kills off competing microbes), and then continue with the oxidation of the alcohol once the sugar, and competition, is gone.{{cite magazine | url = https://www.newscientist.com/channel/life/mg19225831.100-festive-special-the-brewers-tale.html | title = Festive special: The brewer's tale – life | vauthors = Coghlan A | date = 23 December 2006 | magazine = New Scientist | access-date = 2009-04-27| archive-url= https://web.archive.org/web/20080915051831/http://www.newscientist.com/channel/life/mg19225831.100-festive-special-the-brewers-tale.html| archive-date=15 September 2008| url-status= live}}

In plants, ADH catalyses the same reaction as in yeast and bacteria to ensure that there is a constant supply of NAD⁺. Maize has two versions of ADH – ADH1 and ADH2, Arabidopsis thaliana contains only one ADH gene. The structure of Arabidopsis ADH is 47%-conserved, relative to ADH from horse liver. Structurally and functionally important residues, such as the seven residues that provide ligands for the catalytic and noncatalytic zinc atoms, however, are conserved, suggesting that the enzymes have a similar structure.{{cite journal | vauthors = Chang C, Meyerowitz EM | title = Molecular cloning and DNA sequence of the Arabidopsis thaliana alcohol dehydrogenase gene | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 83 | issue = 5 | pages = 1408–12 | date = March 1986 | pmid = 2937058 | pmc = 323085 | doi = 10.1073/pnas.83.5.1408 | bibcode = 1986PNAS...83.1408C | doi-access = free }} ADH is constitutively expressed at low levels in the roots of young plants grown on agar. If the roots lack oxygen, the expression of ADH increases significantly.{{cite journal | vauthors = Chung HJ, Ferl RJ | title = Arabidopsis alcohol dehydrogenase expression in both shoots and roots is conditioned by root growth environment | journal = Plant Physiology | volume = 121 | issue = 2 | pages = 429–36 | date = October 1999 | pmid = 10517834 | pmc = 59405 | doi = 10.1104/pp.121.2.429 }} Its expression is also increased in response to dehydration, to low temperatures, and to abscisic acid, and it plays an important role in fruit ripening, seedlings development, and pollen development.{{cite journal | vauthors = Thompson CE, Fernandes CL, de Souza ON, de Freitas LB, Salzano FM | title = Evaluation of the impact of functional diversification on Poaceae, Brassicaceae, Fabaceae, and Pinaceae alcohol dehydrogenase enzymes | journal = Journal of Molecular Modeling | volume = 16 | issue = 5 | pages = 919–28 | date = May 2010 | pmid = 19834749 | doi = 10.1007/s00894-009-0576-0 | s2cid = 24730389 }} Differences in the sequences of ADH in different species have been used to create phylogenies showing how closely related different species of plants are.{{cite journal | vauthors = Järvinen P, Palmé A, Orlando Morales L, Lännenpää M, Keinänen M, Sopanen T, Lascoux M | title = Phylogenetic relationships of Betula species (Betulaceae) based on nuclear ADH and chloroplast matK sequences | journal = American Journal of Botany | volume = 91 | issue = 11 | pages = 1834–45 | date = November 2004 | pmid = 21652331 | doi = 10.3732/ajb.91.11.1834 }} It is an ideal gene to use due to its convenient size (2–3 kb in length with a ≈1000 nucleotide coding sequence) and low copy number.

{{Infobox protein family

| Symbol = Fe-ADH

| Name = Iron-containing alcohol dehydrogenase

| image = PDB 1jqa EBI.jpg

| width =

| caption = bacillus stearothermophilus glycerol dehydrogenase complex with glycerol

| Pfam = PF00465

| Pfam_clan = CL0224

| InterPro = IPR001670

| SMART =

| PROSITE = PDOC00059

| MEROPS =

| SCOP = 1jqa

| TCDB =

| =

| OPM protein =

| CAZy =

| CDD =

}}

A third family of alcohol dehydrogenases, unrelated to the above two, are iron-containing ones. They occur in bacteria and fungi. In comparison to enzymes the above families, these enzymes are oxygen-sensitive.{{Citation needed|date=August 2011}}

Members of the iron-containing alcohol dehydrogenase family include:

• Saccharomyces cerevisiae alcohol dehydrogenase 4 (gene ADH4){{cite journal | vauthors = Williamson VM, Paquin CE | title = Homology of Saccharomyces cerevisiae ADH4 to an iron-activated alcohol dehydrogenase from Zymomonas mobilis | journal = Molecular & General Genetics | volume = 209 | issue = 2 | pages = 374–81 | date = September 1987 | pmid = 2823079 | doi = 10.1007/bf00329668 | s2cid = 22397371 }}
• Zymomonas mobilis alcohol dehydrogenase 2 (gene adhB){{cite journal | vauthors = Conway T, Sewell GW, Osman YA, Ingram LO | title = Cloning and sequencing of the alcohol dehydrogenase II gene from Zymomonas mobilis | journal = Journal of Bacteriology | volume = 169 | issue = 6 | pages = 2591–7 | date = June 1987 | pmid = 3584063 | pmc = 212129 | doi = 10.1128/jb.169.6.2591-2597.1987}}
• Escherichia coli propanediol oxidoreductase {{EC number|1.1.1.77}} (gene fucO),{{cite journal | vauthors = Conway T, Ingram LO | title = Similarity of Escherichia coli propanediol oxidoreductase (fucO product) and an unusual alcohol dehydrogenase from Zymomonas mobilis and Saccharomyces cerevisiae | journal = Journal of Bacteriology | volume = 171 | issue = 7 | pages = 3754–9 | date = July 1989 | pmid = 2661535 | pmc = 210121 | doi = 10.1128/jb.171.7.3754-3759.1989}} an enzyme involved in the metabolism of fucose and which also seems to contain ferrous ion(s).
• Clostridium acetobutylicum NADPH- and NADH-dependent butanol dehydrogenases {{EC number|1.1.1.-}} (genes adh1, bdhA and bdhB),{{cite journal | vauthors = Walter KA, Bennett GN, Papoutsakis ET | title = Molecular characterization of two Clostridium acetobutylicum ATCC 824 butanol dehydrogenase isozyme genes | journal = Journal of Bacteriology | volume = 174 | issue = 22 | pages = 7149–58 | date = November 1992 | pmid = 1385386 | pmc = 207405 | doi = 10.1128/jb.174.22.7149-7158.1992}} enzymes that have activity using butanol and ethanol as substrates.
• E. coli adhE,{{cite journal | vauthors = Kessler D, Leibrecht I, Knappe J | title = Pyruvate-formate-lyase-deactivase and acetyl-CoA reductase activities of Escherichia coli reside on a polymeric protein particle encoded by adhE | journal = FEBS Letters | volume = 281 | issue = 1–2 | pages = 59–63 | date = April 1991 | pmid = 2015910 | doi = 10.1016/0014-5793(91)80358-A | s2cid = 22541869 | doi-access = | bibcode = 1991FEBSL.281...59K }} an iron-dependent enzyme that harbours three different activities: alcohol dehydrogenase, acetaldehyde dehydrogenase (acetylating) {{EC number|1.2.1.10}} and pyruvate-formate-lyase deactivase.
• Bacterial glycerol dehydrogenase {{EC number|1.1.1.6}} (gene gldA or dhaD).{{cite journal | vauthors = Truniger V, Boos W | title = Mapping and cloning of gldA, the structural gene of the Escherichia coli glycerol dehydrogenase | journal = Journal of Bacteriology | volume = 176 | issue = 6 | pages = 1796–800 | date = March 1994 | pmid = 8132480 | pmc = 205274 | doi = 10.1128/jb.176.6.1796-1800.1994}}
• Clostridium kluyveri NAD-dependent 4-hydroxybutyrate dehydrogenase (4hbd) {{EC number|1.1.1.61}}
• Citrobacter freundii and Klebsiella pneumoniae 1,3-propanediol dehydrogenase {{EC number|1.1.1.202}} (gene dhaT)
• Bacillus methanolicus NAD-dependent methanol dehydrogenase {{EC number|1.1.1.244}}{{cite journal | vauthors = de Vries GE, Arfman N, Terpstra P, Dijkhuizen L | title = Cloning, expression, and sequence analysis of the Bacillus methanolicus C1 methanol dehydrogenase gene | journal = Journal of Bacteriology | volume = 174 | issue = 16 | pages = 5346–53 | date = August 1992 | pmid = 1644761 | pmc = 206372 | doi = 10.1128/jb.174.16.5346-5353.1992}}
• E. coli and Salmonella typhimurium ethanolamine utilization protein eutG.
• E. coli hypothetical protein yiaY.

A further class of alcohol dehydrogenases belongs to quinoenzymes and requires quinoid cofactors (e.g., pyrroloquinoline quinone, PQQ) as enzyme-bound electron acceptors. A typical example for this type of enzyme is methanol dehydrogenase of methylotrophic bacteria.

Alcohol dehydrogenases are often used for the synthesis of enantiomerically pure stereoisomers of chiral alcohols. Often, high chemo- and enantioselectivity can be achieved. One example is the alcohol dehydrogenase from Lactobacillus brevis (LbADH), which is described to be a versatile biocatalyst.{{cite journal|vauthors=Leuchs S, Greiner L |title=Alcohol dehydrogenase from Lactobacillus brevis: A versatile catalyst for enenatioselective reduction |journal=CABEQ |pages=267–281 |year=2011 |url=http://www.hdki.hr/cabeq/pdf/25_2_2011/Cabeq_2011_02_13.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.hdki.hr/cabeq/pdf/25_2_2011/Cabeq_2011_02_13.pdf |archive-date=2022-10-09 |url-status=live }}{{dead link|date=June 2017 |bot=InternetArchiveBot |fix-attempted=yes }} The high chemospecificity has been confirmed also in the case of substrates presenting two potential redox sites. For instance cinnamaldehyde presents both aliphatic double bond and aldehyde function. Unlike conventional catalysts, alcohol dehydrogenases are able to selectively act only on the latter, yielding exclusively cinnamyl alcohol.{{cite journal | vauthors = Zucca P, Littarru M, Rescigno A, Sanjust E | title = Cofactor recycling for selective enzymatic biotransformation of cinnamaldehyde to cinnamyl alcohol | journal = Bioscience, Biotechnology, and Biochemistry | volume = 73 | issue = 5 | pages = 1224–6 | date = May 2009 | pmid = 19420690 | doi = 10.1271/bbb.90025 | s2cid = 28741979 | doi-access = free }}

In fuel cells, alcohol dehydrogenases can be used to catalyze the breakdown of fuel for an ethanol fuel cell. Scientists at Saint Louis University have used carbon-supported alcohol dehydrogenase with poly(methylene green) as an anode, with a nafion membrane, to achieve about 50 μA/cm².{{cite journal | vauthors = Moore CM, Minteer SD, Martin RS | title = Microchip-based ethanol/oxygen biofuel cell | journal = Lab on a Chip | volume = 5 | issue = 2 | pages = 218–25 | date = February 2005 | pmid = 15672138 | doi = 10.1039/b412719f }}

In 1949, E. Racker defined one unit of alcohol dehydrogenase activity as the amount that causes a change in optical density of 0.001 per minute under the standard conditions of assay.{{cite journal | vauthors = Racker E | title = Crystalline alcohol dehydrogenase from baker's yeast | journal = The Journal of Biological Chemistry | volume = 184 | issue = 1 | pages = 313–9 | date = May 1950 | doi = 10.1016/S0021-9258(19)51151-6 | pmid = 15443900 | doi-access = free }} Recently, the international definition of enzymatic unit (E.U.) has been more common: one unit of Alcohol Dehydrogenase will convert 1.0 μmole of ethanol to acetaldehyde per minute at pH 8.8 at 25 °C.{{cite web | title = Enzymatic Assay of Alcohol Dehydrogenase (EC 1.1.1.1) | url = http://www.sigmaaldrich.com/technical-documents/protocols/biology/enzymatic-assay-of-alcohol-dehydrogenase.html | publisher = Sigma Aldrich | access-date = 13 July 2015 }}

There have been studies showing that variations in ADH that influence ethanol metabolism have an impact on the risk of alcohol dependence.{{cite journal | vauthors = Sanchez-Roige S, Palmer AA, Fontanillas P, Elson SL, Adams MJ, Howard DM, Edenberg HJ, Davies G, Crist RC, Deary IJ, McIntosh AM, Clarke TK | display-authors = 6 | title = Genome-Wide Association Study Meta-Analysis of the Alcohol Use Disorders Identification Test (AUDIT) in Two Population-Based Cohorts | journal = The American Journal of Psychiatry | volume = 176 | issue = 2 | pages = 107–118 | date = February 2019 | pmid = 30336701 | pmc = 6365681 | doi = 10.1176/appi.ajp.2018.18040369 }} The strongest effect is due to variations in ADH1B that increase the rate at which alcohol is converted to acetaldehyde. One such variant is most common in individuals from East Asia and the Middle East, another is most common in individuals from Africa. Both variants reduce the risk for alcoholism, but individuals can become alcoholic despite that. Researchers have tentatively detected a few other genes to be associated with alcoholism, and know that there must be many more remaining to be found.{{cite journal | vauthors = Kranzler HR, Zhou H, Kember RL, Vickers Smith R, Justice AC, Damrauer S, Tsao PS, Klarin D, Baras A, Reid J, Overton J, Rader DJ, Cheng Z, Tate JP, Becker WC, Concato J, Xu K, Polimanti R, Zhao H, Gelernter J | display-authors = 6 | title = Genome-wide association study of alcohol consumption and use disorder in 274,424 individuals from multiple populations | journal = Nature Communications | volume = 10 | issue = 1 | pages = 1499 | date = April 2019 | pmid = 30940813 | pmc = 6445072 | doi = 10.1038/s41467-019-09480-8 | bibcode = 2019NatCo..10.1499K }} Research continues in order to identify the genes and their influence on alcoholism.{{citation needed|date=June 2024}}

Drug dependence is another problem associated with ADH, which researchers think might be linked to alcoholism. One particular study suggests that drug dependence has seven ADH genes associated with it, however, more research is necessary.{{cite journal | vauthors = Luo X, Kranzler HR, Zuo L, Wang S, Schork NJ, Gelernter J | title = Multiple ADH genes modulate risk for drug dependence in both African- and European-Americans | journal = Human Molecular Genetics | volume = 16 | issue = 4 | pages = 380–90 | date = February 2007 | pmid = 17185388 | pmc = 1853246 | doi = 10.1093/hmg/ddl460 }} Alcohol dependence and other drug dependence may share some risk factors, but because alcohol dependence is often comorbid with other drug dependences, the association of ADH with the other drug dependencies may not be causal.{{citation needed|date=June 2024}}

Fomepizole, a drug that competitively inhibits alcohol dehydrogenase, can be used in the setting of acute methanolInternational Programme on Chemical Safety (IPCS): Methanol (PIM 335), [http://www.inchem.org/documents/pims/chemical/pim335.htm#10.%20MANAGEMENT], retrieved on 1 March 2008 or ethylene glycol{{cite journal | vauthors = Velez LI, Shepherd G, Lee YC, Keyes DC | title = Ethylene glycol ingestion treated only with fomepizole | journal = Journal of Medical Toxicology | volume = 3 | issue = 3 | pages = 125–8 | date = September 2007 | pmid = 18072148 | pmc = 3550067 | doi = 10.1007/BF03160922 }} toxicity. This prevents the conversion of the methanol or ethylene glycol to its toxic metabolites (such as formic acid, formaldehyde, or glycolate). The same effect is also sometimes achieved with ethanol, again by competitive inhibition of ADH.{{citation needed|date=June 2024}}

The drug hydroxyzine is broken into its active metabolite cetirizine by alcohol dehydrogenase. Other drugs with alcohol groups may be metabolized in a similar way as long as steric hindrance does not prevent the alcohol from reaching the active site.{{cite book| vauthors = Nelson W | chapter = Chapter 36: Nonsteroidal anti-inflammatory drugs | veditors = Foye WO, Lemke TL, Williams DA |title=Foye's Principles of Medicinal Chemistry | edition = 7th |year= 2013 |isbn=978-1-60913-345-0 | location = Philadelphia | publisher = Wolters Kluwer Health/Lippincott Williams & Wilkins }}

• Alcohol dehydrogenase (NAD(P)+)
• Aldehyde dehydrogenase
• Oxidoreductase
• Blood alcohol content for rates of metabolism
• Alcoholic beverage

{{InterPro content|IPR001670}}

{{reflist|33em}}

{{commons category}}

• [https://web.archive.org/web/20080517055711/http://www.biochem.ucl.ac.uk/bsm/enzymes/ec1/ec01/ec01/ec0001/index.html PDBsum] has links to three-dimensional structures of various alcohol dehydrogenases contained in the Protein Data Bank
• [http://www.expasy.org/cgi-bin/nicezyme.pl?1.1.1.1 ExPASy] contains links to the alcohol dehydrogenase sequences in Swiss-Prot, to a Medline literature search about the enzyme, and to entries in other databases.
• [https://www.ebi.ac.uk/pdbe/pdbe-kb/proteins/P07327 PDBe-KB] provides an overview of all the structure information available in the PDB for Alcohol dehydrogenase 1A.
• [https://www.ebi.ac.uk/pdbe/pdbe-kb/proteins/P00325 PDBe-KB] provides an overview of all the structure information available in the PDB for Alcohol dehydrogenase 1B.
• [https://www.ebi.ac.uk/pdbe/pdbe-kb/proteins/P00326 PDBe-KB] provides an overview of all the structure information available in the PDB for Alcohol dehydrogenase 1C.
• [https://www.ebi.ac.uk/pdbe/pdbe-kb/proteins/P08319 PDBe-KB] provides an overview of all the structure information available in the PDB for Alcohol dehydrogenase 4.
• [https://www.ebi.ac.uk/pdbe/pdbe-kb/proteins/P11766 PDBe-KB] provides an overview of all the structure information available in the PDB for Alcohol dehydrogenase class-3.

{{Alcohol oxidoreductases}}

{{enzymes}}

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{{DEFAULTSORT:Alcohol Dehydrogenase}}

Category:Protein families

Category:EC 1.1.1

Category:NADH-dependent enzymes

Category:Iron enzymes

Category:Zinc enzymes

Category:Alcohol and health