Monoamine oxidase is an enzyme normally found in the CNS that can deaminate (break down) the transmitters adrenaline, norepinephrine, serotonin, dopamine and histamine. The enzyme exists in two forms: monoamine oxidase A (MAOA) and monoamine oxidase B (MAOB).
MAOA and its gene MAOA have attracted a lot of attention in connection with various mental conditions and psychiatric illnesses.
An increased amount of MAOAs in the brain is thought to be responsible for some forms of severe depression and suicidal tendencies.
A reduced amount of MAOAs in the brain is believed to be behind certain forms of violent criminal behaviour (assault, sexual molestation, etc.).