MAO-B is a member of the flavin monoamine oxidase family. MAO-B（Monoamine oxidase B) is a flavin-containing mitochondrial enzyme that catalyzes the oxidative deamination of biogenic and xenobiotic monoamines. MAO-B controls the metabolic degradation of catecholamines and serotonin in neural and other target tissues. MAO-B is located in platelets and in dopamine-secreting neurons in the brain. MAOB and MAOA genes have an imperative function in dopamine degradation. Benzylamine and phenylethylamine are preferentially degraded by MAOB. The MAOB gene is linked to autistic traits， empathy and Asperger syndrome. Amplified levels of MAO B are identified in the brain of Alzheimer’s patients. High phenylethylamine levels in neonates as a result of low MAOB are consistent with phenylketonuria in newborns. Polymorphisms in MAO-B are connected to smoking behavior.
