Catecholamine

A catecholamine (/ˌkætəˈkoʊləmiːn/; abbreviated CA) is a monoamine neurotransmitter, an organic compound that has a catechol (benzene with two hydroxyl side groups next to each other) and a side-chain amine.

Catecholamines are produced mainly by the chromaffin cells of the adrenal medulla and the postganglionic fibers of the sympathetic nervous system.

The rate limiting step in catecholamine biosynthesis through the predominant metabolic pathway is the hydroxylation of L-tyrosine to L-DOPA.

Insufficient amounts of phenylalanine hydroxylase result in phenylketonuria, a metabolic disorder that leads to intellectual deficits unless treated by dietary manipulation.

The hydroxylation of L-tyrosine by TH results in the formation of the DA precursor L-DOPA, which is metabolized by aromatic L-amino acid decarboxylase (AADC; see Cooper et al., 2002[citation needed]) to the transmitter dopamine.

Catabolism of catecholamines is mediated by two main enzymes: catechol-O-methyltransferase (COMT) which is present in the synaptic cleft and cytosol of the cell and monoamine oxidase (MAO) which is located in the mitochondrial membrane.

[9] Two catecholamines, norepinephrine and dopamine, act as neuromodulators in the central nervous system and as hormones in the blood circulation.

Extremely high levels of catecholamine can also be caused by neuroendocrine tumors in the adrenal medulla, a treatable condition known as pheochromocytoma.

High levels of catecholamines can also be caused by monoamine oxidase A (MAO-A) deficiency, known as Brunner syndrome.

[13] Catecholamines cause general physiological changes that prepare the body for physical activity (the fight-or-flight response).

They are precursors of benzo[c]phenanthridine alkaloids, which are the active principal ingredients of many medicinal plant extracts.

They have been shown to promote plant tissue growth, somatic embryogenesis from in vitro cultures, and flowering.

The adrenal glands secrete certain catecholamines into the blood when the person is physically or mentally stressed and this is usually a healthy physiological response.

[citation needed] However, acute or chronic excess of circulating catecholamines can potentially increase blood pressure and heart rate to very high levels and eventually provoke dangerous effects.