Katecholaminy

Katecholaminy, also known as catecholamines, are a group of monoamine neurotransmitters and hormones derived from the amino acid tyrosine. They include dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), with related compounds such as tyramine and octopamine discussed for certain physiological contexts. All possess a catechol moiety, a benzene ring with two adjacent hydroxyl groups, and an amine side chain.

Biosynthesis begins with the enzyme tyrosine hydroxylase converting tyrosine to L-DOPA, the rate-limiting step. L-DOPA is decarboxylated to dopamine, which can be converted to norepinephrine by dopamine beta-hydroxylase; norepinephrine can be further converted to epinephrine by phenylethanolamine N-methyltransferase in the adrenal medulla and some neurons. Catecholamines are stored in synaptic vesicles via VMAT2 and released in a calcium-dependent manner upon neuronal activation.

Inactivation occurs mainly by reuptake into presynaptic terminals through transporters such as DAT, NET, and SERT, followed by enzymatic degradation by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). Metabolites such as metanephrines and vanillylmandelic acid (VMA) are excreted in urine and can be measured for diagnostic purposes, for example in pheochromocytoma.

Functions of catecholaminy span the central and peripheral nervous systems. Dopamine modulates reward, motivation, and movement control; norepinephrine and epinephrine drive sympathetic responses, including increased heart rate, blood pressure, pupil dilation, bronchodilation, and metabolic activation. Dysregulation of catecholamine signaling is implicated in conditions such as Parkinson’s disease, depression, and anxiety, and pharmacological strategies often target synthesis, storage, reuptake, or receptor activity.