Monoamine oxidase
Monoamine oxidase (MAO), an integral mitochondrial flavoprotein, can be found anchored to the outer membrane of mitochondria in neurons, glia and other cells through a transmembrane helix located within the carboxyl-terminal domain (Siegel et al., 2015)Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title. It plays an important role in metabolising and thus inactivating monoamine neurotransmitters including serotonin (5-HT) as well as catecholamines such as noradrenaline (NA) and dopamine (DA). Two isoenzymes of MAO – MAOA and MAOB – have been identified in human, both having different substrate preference, inhibitor sensitivity and distribution in tissue and brain (Tong et al., 2015)Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title.
5-HT is preferably metabolised by MAOA whereas catecholamines are metabolised by MAOB. However, 5-HT and catecholamines that are stored in vesicles are be protected from action of MAO. Analyses and assays have also showed that more MAOB than MAOA are observed in human brain (Shih, Chen & Ridd, 1999; Siegel et al., 2015)Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive titleCite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title.
MAOA and MAOB are encoded by two independent genes that are located on the X-chromosome and they have 70% homology (Wu et al., 2009)Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title. Thus, MAOA and MAOB are not the same protein that are modified differently but made up of two different polypeptides (Shih, Chen & Ridd, 1999)Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title.