Monoamine oxidase

In biology, monoamine oxidase is "an enzyme that catalyzes the oxidative deamination of naturally occurring monoamines. It is a flavin-containing enzyme that is localized in mitochondrial membranes, whether in nerve terminals, the liver, or other organs. Monoamine oxidase is important in regulating the metabolic degradation of catecholamines and serotonin in neural or target tissues. Hepatic monoamine oxidase has a crucial defensive role in inactivating circulating monoamines or those, such as tyramine, that originate in the gut and are absorbed into the portal circulation.

Type A monoamine oxidase (MAO-A)
MAO-A deaminates norepinephrine and serotonin.

Type B monoamine oxidase (MAO-B)
MAO-B deminates phenylethylamines.

Pharmacology
Monoamine oxidase inhibitors are "a chemically heterogeneous group of drugs that have in common the ability to block oxidative deamination of naturally occurring monoamines." Reversible inhibitor of monoamine oxidase A (RIMA) Clorgyline selectivly inhibits MAO-A.

Deprenyl selectivly inhibits MAO-B. Rasagiline, used to treat Parkinson Disease, is an inhibitor of Type B monoamine oxidase.