ACTH (18-39) (HUMAN)

The ACTH family of polypeptides consists of ACTH(1-39) (adrenocorticotropin), ACTH (1-13)amide (α-melanotropin;α-MSH); and ACTH (18-39) (corticotropinlike intermediate lobe peptide, CLIP). These polypeptides are derived from a common precursor, proopiomelanocortin. In corticotropic cells of the pars distalis, proopiomelanocortin (POMC) undergoes a series of proteolytic cleavage reactions to yield ACTH (1-39) as a major end product. However, in the melanotropic cells of the pars intermedia, an additional set of proteolytic reactions results in the conversion of ACTH (1-39) to ACTH (1-13) amide and ACTH (18-39). In several species of vertebrates, ACTH (1-13) amide undergoes end product modification to yield mono- and diacetylated forms ofα-MSH as major end products in the pars intermedia.