Editing Monoamine oxidase (section)

== Substrates and specificities ==
Monoamine oxidases are well known [[enzymes]] in [[pharmacology]], since they are the target for the action of a number of [[monoamine oxidase inhibitor]] [[drugs]].  MAO-A is particularly important in the [[catabolism]] of monoamines ingested in food. Both MAOs are also vital to the inactivation of [[monoamine neurotransmitter]]s, for which they display different [[Enzyme#Specificity|specificities]].{{medical citation needed|date=May 2024}}
* [[Serotonin]], [[norepinephrine]], and [[epinephrine]] are mainly broken down by MAO-A.{{medical citation needed|date=May 2024}}
* [[Phenethylamine]] and [[benzylamine]] are mainly broken down by MAO-B.{{medical citation needed|date=May 2024}}
* Both forms metabolize [[dopamine]], [[tyramine]], and [[tryptamine]];<ref name="pmid11559028">{{cite journal | vauthors = Kalgutkar AS, Dalvie DK, Castagnoli N, Taylor TJ | title = Interactions of nitrogen-containing xenobiotics with monoamine oxidase (MAO) isozymes A and B: SAR studies on MAO substrates and inhibitors | journal = Chemical Research in Toxicology | volume = 14 | issue = 9 | pages = 1139–62 | date = September 2001 | pmid = 11559028 | doi = 10.1021/tx010073b }}</ref> however, some evidence suggests MAO-B may not be responsible for a significant amount of dopamine degradation.<ref name="pmid34244591">{{cite journal | vauthors = Cho HU, Kim S, Sim J, Yang S, An H, Nam MH, Jang DP, Lee CJ | title = Redefining differential roles of MAO-A in dopamine degradation and MAO-B in tonic GABA synthesis | journal = Exp Mol Med | volume = 53 | issue = 7 | pages = 1148–1158 | date = July 2021 | pmid = 34244591 | pmc = 8333267 | doi = 10.1038/s12276-021-00646-3 }}</ref>

Specific reactions catalyzed by MAO include:<ref name="Tipton2018">{{cite journal | vauthors = Tipton KF | title = 90 years of monoamine oxidase: some progress and some confusion | journal = J Neural Transm (Vienna) | volume = 125 | issue = 11 | pages = 1519–1551 | date = November 2018 | pmid = 29637260 | doi = 10.1007/s00702-018-1881-5 | url = }}</ref><ref name="BortolatoShih2011">{{cite journal | vauthors = Bortolato M, Shih JC | title = Behavioral outcomes of monoamine oxidase deficiency: preclinical and clinical evidence | journal = Int Rev Neurobiol | series = International Review of Neurobiology | volume = 100 | issue = | pages = 13–42 | date = 2011 | pmid = 21971001 | pmc = 3371272 | doi = 10.1016/B978-0-12-386467-3.00002-9 | isbn = 978-0-12-386467-3 | url = }}</ref>
* [[Serotonin]] to [[5-Hydroxyindoleacetaldehyde|5-hydroxyindoleacetaldehyde]] (5-HIAL; 5-HIAAL; serotonin aldehyde)<ref name="BortolatoChenShih2010">{{cite book | last1=Bortolato | first1=Marco | last2=Chen | first2=Kevin | last3=Shih | first3=Jean C. | title=Handbook of Behavioral Neuroscience | chapter=The Degradation of Serotonin: Role of MAO | publisher=Elsevier | volume=21 | date=2010 | isbn=978-0-12-374634-4 | doi=10.1016/s1569-7339(10)70079-5 | pages=203–218}}</ref><ref name="MatthesMosienkoBashammakh2010">{{cite journal | vauthors = Matthes S, Mosienko V, Bashammakh S, Alenina N, Bader M | title = Tryptophan hydroxylase as novel target for the treatment of depressive disorders | journal = Pharmacology | volume = 85 | issue = 2 | pages = 95–109 | date = 2010 | pmid = 20130443 | doi = 10.1159/000279322 | url = }}</ref>
* [[5-Methoxytryptamine]] ([[melatonin]] metabolite) to [[5-methoxyindoleacetaldehyde]] (5-MIAL; 5-MIAAL)<ref name="SlominskiTobinZmijewski2008">{{cite journal | vauthors = Slominski A, Tobin DJ, Zmijewski MA, Wortsman J, Paus R | title = Melatonin in the skin: synthesis, metabolism and functions | journal = Trends Endocrinol Metab | volume = 19 | issue = 1 | pages = 17–24 | date = January 2008 | pmid = 18155917 | doi = 10.1016/j.tem.2007.10.007 | url = }}</ref>
* [[Tryptamine]] to [[indole-3-acetaldehyde|indoleacetaldehyde]] (IAAL; tryptamine aldehyde)<ref name="BortolatoShih2011" />
* [[Dopamine]] to [[3,4-dihydroxyphenylacetaldehyde]] (DOPAL; dopamine aldehyde)<ref name="MeiserWeindlHiller2013">{{cite journal | vauthors = Meiser J, Weindl D, Hiller K | title = Complexity of dopamine metabolism | journal = Cell Commun Signal | volume = 11 | issue = 1 | pages = 34 | date = May 2013 | pmid = 23683503 | pmc = 3693914 | doi = 10.1186/1478-811X-11-34 | doi-access = free | url = }}</ref>
* [[Norepinephrine]] to [[3,4-dihydroxymandelaldehyde]] (DHMAL; norepinephrine/epinephrine aldehyde)<ref name="KawamuraEisenhoferKopin2002">{{cite journal | vauthors = Kawamura M, Eisenhofer G, Kopin IJ, Kador PF, Lee YS, Fujisawa S, Sato S | title = Aldose reductase: an aldehyde scavenging enzyme in the intraneuronal metabolism of norepinephrine in human sympathetic ganglia | journal = Auton Neurosci | volume = 96 | issue = 2 | pages = 131–139 | date = March 2002 | pmid = 11958479 | doi = 10.1016/s1566-0702(01)00385-x | url = }}</ref>
* [[Epinephrine]] to [[3,4-dihydroxymandelaldehyde]] (DHMAL; norepinephrine/epinephrine aldehyde)<ref name="KawamuraEisenhoferKopin2002" />
* [[Normetanephrine]] to [[3-methoxy-4-hydroxymandelaldehyde]] (MHMAL; normetanephrine/metanephrine aldehyde)<ref name="KawamuraEisenhoferKopin2002" />
* [[Metanephrine]] to [[3-methoxy-4-hydroxymandelaldehyde]] (MHMAL; normetanephrine/metanephrine aldehyde)<ref name="KawamuraEisenhoferKopin2002" />
* [[3-Methoxytyramine]] to [[3-methoxy-4-hydroxyphenylacetaldehyde]] (HMPAL)<ref name="BandalaCárdenas-RodríguezMendoza-Torreblanca2023">{{cite journal | vauthors = Bandala C, Cárdenas-Rodríguez N, Mendoza-Torreblanca JG, Contreras-García IJ, Martínez-López V, Cruz-Hernández TR, Carro-Rodríguez J, Vargas-Hernández MA, Ignacio-Mejía I, Alfaro-Rodriguez A, Lara-Padilla E | title = Therapeutic Potential of Dopamine and Related Drugs as Anti-Inflammatories and Antioxidants in Neuronal and Non-Neuronal Pathologies | journal = Pharmaceutics | volume = 15 | issue = 2 | date = February 2023 | page = 693 | pmid = 36840015 | pmc = 9966027 | doi = 10.3390/pharmaceutics15020693 | doi-access = free | url = }}</ref>
* [[Phenethylamine]] to [[phenylacetaldehyde]] (PAAL)<ref name="DalvieDi2019">{{cite journal | vauthors = Dalvie D, Di L | title = Aldehyde oxidase and its role as a drug metabolizing enzyme | journal = Pharmacol Ther | volume = 201 | issue = | pages = 137–180 | date = September 2019 | pmid = 31128989 | doi = 10.1016/j.pharmthera.2019.05.011 | url = }}</ref>
* [[Tyramine]] to [[4-hydroxyphenylacetaldehyde]] (HPAL)<ref name="BortolatoShih2011" />
* [[Benzylamine]] to [[benzaldehyde]]<ref name="Holt2018">{{cite journal | vauthors = Holt A | title = On the practical aspects of characterising monoamine oxidase inhibition in vitro | journal = J Neural Transm (Vienna) | volume = 125 | issue = 11 | pages = 1685–1705 | date = November 2018 | pmid = 30374594 | doi = 10.1007/s00702-018-1943-8 | url = }}</ref>

Other endogenous substrates of MAO include [[telemethylhistamine]], a metabolite of [[histamine]], and [[N-acetylputrescine|''N''-acetylputrescine]], a metabolite of [[putrescine]] and a [[precursor (biochemistry)|precursor]] and [[metabolic intermediate]] in a minor [[metabolic pathway]] resulting in the synthesis of [[γ-aminobutyric acid]] (GABA).<ref name="BenedettiDostert1994" /><ref name="AmbroziakMaśliński1988">{{cite journal | vauthors = Ambroziak W, Maśliński C | title = Participation of aldehyde dehydrogenase in the oxidative deamination pathway of histamine and putrescine | journal = Agents Actions | volume = 23 | issue = 3–4 | pages = 311–313 | date = April 1988 | pmid = 3394581 | doi = 10.1007/BF02142573 | url = }}</ref><ref name="WatanabeMaemuraKanbara2002">{{cite book | vauthors = Watanabe M, Maemura K, Kanbara K, Tamayama T, Hayasaki H | chapter = GABA and GABA Receptors in the Central Nervous System and Other Organs | title = A Survey of Cell Biology | journal = Int Rev Cytol | series = International Review of Cytology | volume = 213 | issue = | pages = 1–47 | date = 2002 | pmid = 11837891 | doi = 10.1016/s0074-7696(02)13011-7 | isbn = 978-0-12-364617-0 | chapter-url = }}</ref><ref name="Seiler2004">{{cite journal | vauthors = Seiler N | title = Catabolism of polyamines | journal = Amino Acids | volume = 26 | issue = 3 | pages = 217–233 | date = June 2004 | pmid = | doi = 10.1007/s00726-004-0070-z | url = }}</ref><ref name="ChoKimSim2021">{{cite journal | vauthors = Cho HU, Kim S, Sim J, Yang S, An H, Nam MH, Jang DP, Lee CJ | title = Redefining differential roles of MAO-A in dopamine degradation and MAO-B in tonic GABA synthesis | journal = Exp Mol Med | volume = 53 | issue = 7 | pages = 1148–1158 | date = July 2021 | pmid = 34244591 | pmc = 8333267 | doi = 10.1038/s12276-021-00646-3 | url = }}</ref>

Besides [[endogenous]] compounds, a variety of [[exogenous]] compounds and [[drug]]s are substrates of the MAOs.<ref name="BenedettiDostert1994">{{cite journal | vauthors = Benedetti MS, Dostert P | title = Contribution of amine oxidases to the metabolism of xenobiotics | journal = Drug Metab Rev | volume = 26 | issue = 3 | pages = 507–535 | date = 1994 | pmid = 7924902 | doi = 10.3109/03602539408998316 | url = }}</ref><ref name="PangTangGuo2022">{{cite journal | vauthors = Pang X, Tang C, Guo R, Chen X | title = Non-cytochrome P450 enzymes involved in the oxidative metabolism of xenobiotics: Focus on the regulation of gene expression and enzyme activity | journal = Pharmacol Ther | volume = 233 | issue = | pages = 108020 | date = May 2022 | pmid = 34637840 | doi = 10.1016/j.pharmthera.2021.108020 | url = }}</ref><ref name="StrolinBenedettiDostertTipton1988">{{cite book | veditors = Gibson GG | vauthors = Strolin Benedetti M, Dostert P, Tipton KF | chapter = Contributions of monoamine oxidase to the metabolism of xenobiotics | title = Progress in Drug Metabolism | volume = 11 | pages = 149–174 | url = https://scholar.google.com/scholar?cluster=4712296110836164590}}</ref><ref name="Zetin2013">{{cite journal | last=Zetin | first=Mark | title=A Clinician's Guide to Monoamine Oxidase Inhibitors | journal=Current Psychiatry Reviews | volume=9 | issue=4 | date=2013-08-31 | issn=1573-4005 | doi=10.2174/15734005113096660013 | pages=353–364}}</ref> Examples include [[substituted phenethylamine]] [[sympathomimetic]]s and [[sympatholytic]]s like [[phenylephrine]], [[propranolol]], and [[pronethalol]], [[substituted tryptamine]] [[serotonergic drug|serotonergic agent]]s like [[dimethyltryptamine]] (DMT), [[5-MeO-DMT]], [[bufotenin]], [[almotriptan]], [[rizatriptan]], and [[sumatriptan]], and other compounds like [[bicifadine]], [[citalopram]], [[CP-409092]], [[KW-2449]], [[milacemide]], [[MPTP]], [[nomifensine]], [[primaquine]], [[rivaroxaban]], [[sertraline]], and [[ticlopidine]], among others.<ref name="BenedettiDostert1994" /><ref name="PangTangGuo2022" /><ref name="StrolinBenedettiDostertTipton1988" /><ref name="Zetin2013" /> [[Haloperidol]] is another possible substrate of MAO, which may contribute to formation of its [[monoaminergic neurotoxin|neurotoxic]] metabolite [[HPP+|HPP<sup>+</sup>]].<ref name="BenedettiDostert1994" />