Veterinary Physiology-III

PRO-OPIOMELANOCORTIN

• Within the pituitary gland, ACTH is produced in a process that also generates several other hormones. A large precursor protein named pro-opiomelanocortin (POMC) is synthesized in the intermediate lobe and in the corticotropes of anterior pituitary and proteolytically chopped into several fragments. Not all of the cleavages occur in all species and some occur only in the intermediate lobe of the pituitary. In the corticotropes, POMC is cleaved to ACTH and β-LPH and a small amount of β-endorphin. In the intermediate lobe, it is hydrolysed to corticotrophin-like intermediate lobe peptide (CLIP), α-LPH and a large amount of β- endorphins plus α and β MSH
• The major attributes of the hormones other than ACTH that are produced in this process are
  • Lipotropin: Originally described as having weak lipolytic effects, its major importance is as the precursor to β-endorphin.
  • β-endorphin, Met-enkephalin: Opioid peptides with pain-alleviation and euphoric effects.
  • Melanocyte-stimulating hormone (MSH): Known to control melanin pigmentation in the skin of most vertebrates.