Catalyzes the oxidative deamination of biogenic and xenobiotic amines and has important functions in the metabolism of neuroactive and vasoactive amines in the central nervous system and peripheral tissues. MAOA preferentially oxidizes biogenic amines such as 5-hydroxytryptamine (5-HT), norepinephrine and epinephrine. Defects in MAOA are the cause of Brunner syndrome (BRUNS). Brunner syndrome is a form of X-linked non- dysmorphic mild mental retardation. Male patients are affected by a syndrome of borderline mental retardation and exhibit abnormal behavior, including disturbed regulation of impulsive aggression. Obligate female carriers have normal intelligence and behavior. Belongs to the flavin monoamine oxidase family. Note: This description may include information from UniProtKB.