Prepro-opiomelanocortin

Progesterone Receptor. Prepro-opiomelanocortin (POMC) is a huge precursor... 

Prepro-opiomelanocortin Primary Hemostasis Primary Hyperparathyroidism Prodrug... 

Not only this heptapeptide but also the entire amino acid sequence of a-melanotropin is found within the sequence of corticotropin (Fig. 30-2), which has an additional 29 amino acids at the C-terminal end.25 The same heptapeptide was also found in the lipotropins. The explanation is, in part, that several of these hormones arise from a single 31-kDa precursor protein called prepro-opiomelanocortin.25 26 It contains an N-terminal signal sequence that is removed shortly after synthesis, as well as pairs of adjacent basic residues (Arg-Arg, Arg-Lys, Lys-Arg and Lys-Lys) at a number of places (Fig. 30-2). After removal of the... 

Figure 30-2 Schematic structure of prepro-opiomelanocortin and of some of the products of its processing by protolytic enzymes The abbreviations K and R are for lysine and arginine. a-MSH CLIP V-LPH P-endorphin...

Endogenous opioid peptides. Extensive processing is also involved in formation of analgesic opioid peptides, which are present naturally in the brain (see also Section B). Tire formation of (1-endorphin in the hypothalamus from prepro-opiomelanocortin (Fig. 30-2) has already been mentioned. Prior to the discovery of P-endorphin, the pentapeptides Met-enkephalin and Leu-enkephalin (Table 30-4) were discovered and were found to compete with opiate drugs for receptors in the brain. Tire larger P-endorphin, which contains the Met-enkephalin sequence at its N terminus, is a far more potent opiate antagonist than are the enkephalins. Since the Met-enkephalin sequence within P-endorphin is not flanked by basic residues, it apparently is normally not released. Two other recently discovered brain peptides are endomorphin-1 (YPWF-NH2) and endomorphin-2 (YPFF-NH2). They are also potent agonists for the opioid receptors, especially the p receptor (see Section B,10).,61a,61b... 

Endogenous opioid peptides. Extensive processing is also involved in formation of analgesic opioid peptides, which are present naturally in the brain (see also Section B). The formation of p-endorphin in the hypothalamus from prepro-opiomelanocortin (Fig. 30-... 

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