Catecholamines are sympathomimetic "fight-or-flight" hormones released by the adrenal glands in response to stress. They are part of the sympathetic nervous system.
They are called catecholamines because they contain a catechol or 3,4-dihydroxylphenyl group. They are derived from the amino acid tyrosine.
In the human body, the most abundant catecholamines are epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine, all of which are produced from phenylalanine and tyrosine. Various stimulant drugs are catecholamine analogs.
Catecholamines are water-soluble and are 50% bound to plasma proteins, so they circulate in the bloodstream.
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.
Catecholamines have the distinct structure of a benzene ring with two hydroxyl groups, an intermediate ethyl chain, and a terminal amine group. Phenylethanolamines such as norepinephrine have a hydroxyl group on the ethyl chain.
Production and degradation
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