Monoamine oxidase (MAO) (MAO)

Monoamine oxidase (MAO) is a critical flavin-containing enzyme anchored to the outer mitochondrial membrane, responsible for the oxidative deamination of biogenic and xenobiotic amines (UniProt P21397, P27338). It exists in two distinct functional isoforms, MAO-A and MAO-B, which exhibit different substrate preferences and anatomical distributions (StatPearls, "Monoamine Oxidase Inhibitors"). MAO-A primarily metabolizes serotonin, norepinephrine, and epinephrine, while MAO-B shows a preference for phenylethylamine; both isoforms are involved in the breakdown of dopamine (PubMed, PMID: 21114311). Therapeutically, MAO inhibitors (MAOIs) are utilized to treat major depressive disorder by increasing neurotransmitter availability and Parkinson's disease by preserving dopamine levels (NIH, "Monoamine Oxidase Inhibitors"). Despite their efficacy, MAOIs are associated with significant safety risks, most notably the "cheese effect," where the inhibition of intestinal MAO-A leads to a hypertensive crisis upon ingestion of tyramine-rich foods (PubMed, PMID: 16342366). Additionally, the risk of serotonin syndrome necessitates strict avoidance of concomitant serotonergic medications (StatPearls, "Serotonin Syndrome"). These enzymes also play a role in oxidative stress through the production of hydrogen peroxide as a byproduct of their catalytic cycle, which has implications for neurodegenerative progression (PubMed, PMID: 21114311).

Other names

Amine oxidase [flavin-containing]hMAOMonoamine oxidase AMonoamine oxidase B

Irreversible or reversible inhibition of MAO-A and/or MAO-B enzymes to prevent the breakdown of monoamine neurotransmitters.