Monoamine oxidase A (MAO-A)

Monoamine oxidase A is a mitochondrial outer membrane-bound enzyme that catalyzes the oxidative deamination of biogenic and dietary amines, including key neurotransmitters such as serotonin, norepinephrine, and dopamine. It uses flavin adenine dinucleotide (FAD) as a cofactor to facilitate the oxidation process. The enzyme plays a central role in regulating neurotransmitter levels in both the central nervous system and peripheral tissues. Beyond its classical neurological functions, recent research has identified roles for monoamine oxidase A in modulating immune responses within the tumor microenvironment—acting as an immune checkpoint that can suppress antitumor T cell immunity—making it a promising target for cancer immunotherapy strategies. Clinically, selective inhibition of this enzyme is used primarily in the treatment of depressive disorders but also has implications for neurodegenerative diseases and cancer therapy. Safety concerns include potential hypertensive crises from dietary amines during treatment with non-selective or irreversible inhibitors.[1][2][3][8][10]

Other names

MAOAMonoamine oxidase type AAmine oxidase (flavin-containing) A

Inhibition of enzymatic activity to increase synaptic levels of monoamines for antidepressant effect[6] Reversible or irreversible inhibition depending on drug class (RIMAs vs. classic MAOIs)[6]