In humans the proopiomelanocortin (POMC) gene is located on the short arm of the chromosome 2 at the 23.3 position and encodes a 39kDa peptide with 241 amino acids. This peptide is the precursor of the proopiomelanocortin prohormone and it is produced in both the anterior and posterior lobes of the pituitary, as well as the arcuate nucleus of the hypothalamus.
Maturation of POMC involves glycosylation, acetylation, and selective, sequential and tissue specific processing events mediated by proprotein convertases PC-1/3 and PC-2. Proteolytic cleavage of POMC at 9 different locations produces a variety of hormones, including adrenocorticotrophin (ACTH), α-, β- and γ-melanocyte-stimulating hormones (α-MSH, β-MSH, γ-MSH), corticotrophin-like intermediate peptide (CLIP), β-lipotropin (β-LPH), and β-endorphin (Fig. 1.).