Biochemistry, Tyramine

Excerpt

Tyramine is a trace monoamine with sympathomimetic properties. It is naturally found in foods, plants, and animals. By definition, all monoamines have an amine group separated from an aromatic ring by a 2-carbon chain. Dopamine, norepinephrine, and serotonin are monoamines. Trace monoamines were named for their relatively low frequency in mammalian tissues compared to their more abundant and discussed monoamine neurotransmitter counterparts: epinephrine, norepinephrine, dopamine, and serotonin.

Other trace amines include octopamine, phenethylamine, N-methylphenethylamine, and N-methyltyramine. Tyramine is degraded by several enzymes, most notably monoamine oxidase. Tyramine is often found in fermented, aged, cured, and spoiled foods where microbes with decarboxylase enzymes convert the amino acid tyrosine into tyramine. Ingestion of high tyrosine-containing foods in patients taking monoamine oxidase inhibitors produces headaches, blurry vision, chest pain, and palpitations associated with hypertension, intracranial hemorrhages, and myocardial injury. Tyramine has long been shown to cause cardiovascular effects when consumed in large, pathologic amounts. New evidence suggests endogenous tyramine and other trace amines in lower physiologic levels may have additional roles, including modulating the immune system.