Monoamine Oxidases (MAO) catalyze the oxidation of monoamines such as dopamine, serotonin and adrenalin. They are found bound to the outer membrane of mitochondria in most cell types in the body. Two subtypes of monoamine oxidase have been identified: MAO-A and MAO-B. Both are found in neurons and astroglia, with MAO-A also found in the liver, gastrointestinal tract and placenta and MAO-B in blood platelets. Abnormal regulation of MAOs in the body has been associated with depression, substance abuse, attention deficit disorder, and irregular sexual maturation. Mutation of this gene results in Brunner syndrome. This gene has also been associated with a variety of other psychiatric disorders, including antisocial behavior. Alternatively spliced transcript variants encoding multiple isoforms have been observed.