Monoamine oxidase A is an isozyme of monoamine oxidase. It preferentially deaminates norepinephrine (noradrenaline), epinephrine (adrenaline), serotonin, and dopamine (dopamine is equally deaminated by MAO-A and MAO-B). It is inhibited by clorgiline and befloxatone.This gene encodes monoamine oxidase A, an enzyme that degrades amine neurotransmitters, such as dopamine, norepinephrine, and serotonin. The protein localizes to the outer mitochondrial membrane. The gene is adjacent to a related gene (MAOB) on the opposite strand of chromosome X. Mutation in this gene results in monoamine oxidase deficiency, or Brunner syndrome. MAO-A levels in the brain as measured using positron emission tomography are elevated by an average of 34 percent in patients with major depressive disorder.