Amine Oxidase [Flavin-Containing] A (MAOA)

Monoamine oxidase A (MAOA) is a flavin-dependent oxidoreductase that catalyzes the oxidative deamination of primary and secondary amines, including neurotransmitters (UniProt: P21397). It preferentially oxidizes serotonin and plays critical roles in the metabolism of neuroactive and vasoactive amines in the central nervous system and peripheral tissues, generating hydrogen peroxide as a byproduct. The enzyme is encoded on the X chromosome and contains 527 amino acids with a molecular weight of approximately 59.7 kDa.

MAOA variants are associated with Brunnel syndrome (OMIM: 300615), an X-linked intellectual disability characterized by borderline cognitive deficits and impulsive aggression in affected males (UniProt: P21397). The enzyme's role in monoamine metabolism positions it at the intersection of neurotransmitter homeostasis and oxidative stress pathways in the brain.

In Alzheimer's disease, MAOA protein levels are significantly elevated in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics). The mean log2 fold-change is +1.0349, indicating approximate two-fold upregulation. This increased abundance may reflect altered monoamine metabolism or contribute to oxidative stress pathology in AD pathogenesis.