Catecholamine

A catecholamine (CA) is an organic compound that has a catechol (benzene with two hydroxyl side groups) and a side-chain amine.

A catechol is a 3,4-dihydroxybenzene group. Catecholamines derive from the amino acid tyrosine. Catecholamines are water-soluble and are 50%-bound to plasma proteins, so they circulate in the bloodstream.

In the human body, the most abundant catecholamines are epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine, all of which are produced from phenylalanine and tyrosine. Release of the hormones epinephrine and norepinephrine from the adrenal medulla of the adrenal glands is part of the fight-or-flight response.

Tyrosine is created from phenylalanine by hydroxylation by the enzyme phenylalanine hydroxylase. Tyrosine is also ingested directly from dietary protein. It is then sent to catecholamine-secreting neurons. Here, several reactions serially convert tyrosine to L-DOPA, to dopamine, to norepinephrine, and eventually to epinephrine.

Various stimulant drugs are catecholamine analogues.