Monoamine oxidase

Monoamine oxidase (MAO) is an enzyme that catalyzes the oxidation of monoamines. They are found bound to the outer membrane of mitochondria in most cell types in the body. The enzyme was originally discovered by Mary Bernheim in the liver and was named tyramine oxidase.

Function

Monoamine oxidases play a vital role in the breakdown of monoamines in neurotransmitters such as dopamine, norepinephrine, and serotonin. They also assist in the metabolism of many drugs and toxins. The activity of the monoamine oxidase enzyme is vital for maintaining proper mental and physical health.

Types

There are two types of MAO: MAO-A and MAO-B. Both are found in neurons and astroglia. Outside the central nervous system, both types of MAO are also found in the liver, intestinal mucosa, and placenta.

MAO-A

MAO-A primarily degrades serotonin, melatonin, norepinephrine, and epinephrine.

MAO-B

MAO-B primarily degrades phenethylamine and certain other trace amines. In humans, it is selectively inhibited by selegiline.

Clinical significance

Abnormalities in the function of MAO are linked to a variety of psychiatric and neurological disorders. For example, an excess of MAO-A activity is associated with depression and certain types of anxiety, while a deficiency is associated with aggression and attention deficit disorder.

Inhibitors

MAO inhibitors are used to treat depression, anxiety, and Parkinson's disease. They work by blocking the action of MAO, thereby increasing the availability of monoamine neurotransmitters in the brain.

See also

• Monoamine oxidase A
• Monoamine oxidase B
• Monoamine oxidase inhibitor

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  Structure of Monoamine Oxidase A
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  Structure of Monoamine Oxidase
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  Noradrenaline breakdown pathway