Monoamine oxidase

Monoamine oxidases (singular abbreviation MAO) (EC 1.4.3.4) are enzymes that catalyze the oxidation of monoamines. They are found bound to the outer membrane of mitochondria in most cell types in the body. The enzyme was discovered by Mary Hare in the liver, and received the name of tyramine oxidase.^[1] Image File history File links Gen w/ Deepview from PDB:1GOS File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Gen w/ Deepview from PDB:1GOS File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The Entrez logo The Entrez Global Query Cross-Database Search System allows access to databases at the National Center for Biotechnology Information (NCBI) website. ... Look up Hugo in Wiktionary, the free dictionary. ... The Mendelian Inheritance in Man project is a database that catalogues all the known diseases with a genetic component, and - when possible - links them to the relevant genes in the human genome. ... The National Center for Biotechnology Information (NCBI) is part of the US National Library of Medicine (NLM), which is a branch of the US National Institutes of Health. ... Swiss-Prot is a curated biological database of protein sequences created in 1986 by Amos Bairoch during his PhD and developed by the Swiss Institute of Bioinformatics and the European Bioinformatics Institute. ... The Enzyme Commission number (EC number) is a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. ... Short and long arms Chromosome. ... The X chromosome is one of the two sex chromosomes in mammals (the other is the Y chromosome). ... The Entrez logo The Entrez Global Query Cross-Database Search System allows access to databases at the National Center for Biotechnology Information (NCBI) website. ... Look up Hugo in Wiktionary, the free dictionary. ... The Mendelian Inheritance in Man project is a database that catalogues all the known diseases with a genetic component, and - when possible - links them to the relevant genes in the human genome. ... The National Center for Biotechnology Information (NCBI) is part of the US National Library of Medicine (NLM), which is a branch of the US National Institutes of Health. ... Swiss-Prot is a curated biological database of protein sequences created in 1986 by Amos Bairoch during his PhD and developed by the Swiss Institute of Bioinformatics and the European Bioinformatics Institute. ... The Enzyme Commission number (EC number) is a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. ... Short and long arms Chromosome. ... The X chromosome is one of the two sex chromosomes in mammals (the other is the Y chromosome). ... The Enzyme Commission number (EC number) is a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... In chemistry and biology, catalysis is the acceleration (increase in rate) of a chemical reaction by means of a substance, called a catalyst, that is itself not consumed by the overall reaction. ... The most fundamental reactions in chemistry are the redox processes. ... In biochemistry, monoamines are a group of organic compounds containing only one amino group. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ...

Locations of MAO-A and MAO-B

In humans there are two types of MAO: MAO-A and MAO-B. Monoamine oxidase A is an isozyme of monoamine oxidase. ...

• Both are found in neurons and astroglia.
• Outside the central nervous system:
  • MAO-A is also found in the liver, gastrointestinal tract and placenta.
  • MAO-B is mostly found in blood platelets.

Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Astrocytes (also known collectively as astroglia) are characteristic star-shaped glial cells in the brain. ... A diagram showing the CNS: 1. ... The liver is an organ present in vertebrates and some other animals. ... Upper and Lower gastrointestinal tract The gastrointestinal tract (GI tract), also called the digestive tract, or the alimentary canal, is the system of organs within multicellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... The placenta is an ephemeral (temporary) organ present in female placental vertebrates during gestation (pregnancy), but a placenta has evolved independently also in other animals as well, for instance scorpions and velvet worms. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... A 250 ml bag of newly collected platelets. ...

Function

Monoamine oxidases catalyze the oxidative deamination of monoamines. Oxygen is used to remove an amine group from a molecule, resulting in the corresponding aldehyde and ammonia. The general form of the catalyzed reaction (with R denoting an arbitrary group) is Oxidative deamination is a form of deamination which generates oxoacids in the liver. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... An aldehyde. ... Ammonia is a compound with the formula NH3. ...

 H H R-C-NH2 + O2 + H2O → R-C=O + NH3 + H2O2 H 

Monoamine oxidase contains the covalently-bound cofactor FAD. A cofactor is any substance that needs to be present in addition to an enzyme to catalyze a certain reaction. ... In biochemistry, flavin adenine dinucleotide (FAD) is the precursor molecule to FADH2. ...

Subtype Specificities

MAO-A is particularly important in the catabolism of monoamines ingested in food. Both MAOs are also vital to the inactivation of monoaminergic neurotransmitters, for which they display different specificities. Chemical structure of D-aspartic acid, a common amino acid neurotransmitter. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ...

• Serotonin, norepinephrine (noradrenaline), and epinephrine (adrenaline) are mainly broken down by MAO-A.
• Phenethylamine is broken down by MAO-B.
• Both forms break down dopamine.

Serotonin (pronounced ) (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesized in serotonergic neurons in the central nervous system (CNS) and enterochromaffin cells in the gastrointestinal tract of animals including humans. ... Norepinephrine (INN)(abbr. ... Adrenaline redirects here. ... Phenethylamine, or β-Phenylethylamine, is an alkaloid and monoamine. ... Dopamine is a phenethylamine naturally produced by the human body. ...

Disorders resulting from MAO dysfunction

Because of the vital role that MAOs play in the inactivation of neurotransmitters, MAO dysfunction (too much/too little MAO activity) is thought to be responsible for a number of neurological disorders. For example, unusually high or low levels of MAOs in the body have been associated with depression, substance abuse, attention deficit disorder, and irregular sexual maturation. Monoamine oxidase inhibitors are one of the major classes of drug prescribed for the treatment of depression, although they are last line treatment due to risk of the drug's interaction with diet or other drugs. Excessive levels of catecholamines (epinephrine, norepinephrine, and dopamine) may lead to a hypertensive crisis, and excessive levels of serotonin may lead to serotonin syndrome. Clinical depression (also called major depressive disorder, or unipolar depression when compared to bipolar disorder) is a state of intense sadness, melancholia or despair that has advanced to the point of being disruptive to an individuals social functioning and/or activities of daily living. ... Substance abuse refers to the overindulgence in and dependence on a psychoactive leading to effects that are detrimental to the individuals physical health or mental health, or the welfare of others. ... DISCLAIMER Please remember that Wikipedia is offered for informational use only. ... Monoamine oxidase inhibitors (MAOIs) are a class of antidepressant drugs prescribed for the treatment of depression. ... tyrosine is the precursor of catecholamines epinephrine norepinephrine dopamine Synthesis Catecholamines are chemical compounds derived from the amino acid tyrosine containing catechol and amine groups. ... Adrenaline redirects here. ... Norepinephrine (INN)(abbr. ... Dopamine is a phenethylamine naturally produced by the human body. ... Serotonin (pronounced ) (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesized in serotonergic neurons in the central nervous system (CNS) and enterochromaffin cells in the gastrointestinal tract of animals including humans. ... Serotonin syndrome is a rare, but potentially life-threatening adverse drug reaction that results from intentional self-poisoning, therapeutic drug use, or inadvertent interactions between drugs. ...

Recent PET research has shown that MAO is also heavily depleted by tobacco use.^[2] Image of a typical positron emission tomography (PET) facility Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three-dimensional image or map of functional processes in the body. ... Shredded tobacco leaf for pipe smoking Tobacco can also be pressed into plugs and sliced into flakes Tobacco is an agricultural product processed from the fresh leaves of plants in genus Nicotiana. ...

Genetics

The genes encoding MAO-A and MAO-B are located side-by-side on the short arm of the X chromosome, and have about 70% sequence similarity. For a non-technical introduction to the topic, see Introduction to Genetics. ... ‹ The template below (Expand) is being considered for deletion. ...

A study reported in Science in August 2002 concluded that maltreated children with a low-activity polymorphism in the promoter region of the MAO-A gene were more likely to develop antisocial conduct disorders than maltreated children with the high-activity variant.^[3] The suggested mechanism for this effect is the decreased ability of those with low MAO-A activity to quickly degrade norepinephrine, the synaptic neurotransmitter involved in sympathetic arousal and rage. This is alleged to provide direct support for the idea that genetic susceptibility to disease is not determined at birth, but varies with exposure to environmental influences. Science is the journal of the American Association for the Advancement of Science (AAAS). ... A promoter is a regulatory region of DNA located upstream (towards the 5 region) of a gene, providing a control point for regulated gene transcription. ...

Research also uncovered a possible link between predisposition to novelty seeking and a genotype of the MAO-A gene.^[4] Neophilia is defined as a love of novelty and new things. ... This article does not cite any references or sources. ...

In 2006, a New Zealand researcher, Dr Rod Lea said that a particular variant (or genotype) was over-represented in Māori. This supported earlier studies finding different proportions of variants in different ethnic groups. This is the case for many genetic variants, with 33% White/Non-Hispanic, 61% Asian/Pacific Islanders having the low-activity MAO-A promoter variant.^[5] This article does not cite any references or sources. ... Languages Māori, English Religions Māori religion, Christianity Related ethnic groups other Polynesian peoples, Austronesian peoples The word Māori refers to the indigenous Polynesian peoples of New Zealand, and to their language. ... A promoter is a regulatory region of DNA located upstream (towards the 5 region) of a gene, providing a control point for regulated gene transcription. ...

See also

• Oxidase
• Genetics and violence
• Neophilia

An oxidase is any enzyme that catalyzes an oxidation/reduction reaction involving molecular oxygen (O2) as the electron acceptor. ... Scientific interest in the correlation between genetic factors and violence dates back to the eugenics movement of the 19th century. ... Neophilia is defined as a love of novelty and new things. ...

References

External links

• MAO-B Structure at eurekalert.org
• Calculated orientations of Monoamine oxidases in membrane
• Monoamine oxidase (MAO) at bmc.uu.se
• Slides showing the effects of tobacco smoking on MAO at nida.nih.gov
• Foods to avoid when taking MAO inhibitors at lycaeum.org