Structures of catecholamine stress hormones, inotropes, and their metabolites. The figure shows the pathway of catecholamine synthesis; it should be noted that for clarity the various cofactors utilised in the pathway are not shown. In mammals, dopamine is synthesized from L-dopa, obtained from dietary sources (such as the amino acids tyrosine and phenylalanine) [15]. Synthesis of catecholamines is to a degree tissue specific; for example, phenylethanolamine N-methyltransferase, which is required for adrenaline synthesis, is not expressed in cells of the enteric nervous system [15, 16]. Catecholamine biosynthesis, TH: tyrosine hydroxylase, AAD: aromatic L-amino decarboxylase, DBH: dopamine β-hydroxylase, PMT: phenylethanolamine N-methyltransferase. Metabolic inactivation: MAO: monoamine oxidase, AR: aldehyde reductase, ADH: aldehyde dehydrogenase. This figure was adapted with permission from Freestone et al. (2008) [3].
