Guinea pig Anti-Human Gamma MSH polyclonal antibody for IHC. Pro-opiomelanocortin (POMC) is a precursor polypeptide with 241 amino acid residues. POMC is synthesized from the 285-amino acid long polypeptide precursor, pre-pro-opiomelanocortin (pre-POMC), by the removal of a 44-amino acid long signal peptide sequence during translation. The POMC gene is located on chromosome 2p23.3. The POMC gene is expressed in both the anterior and intermediate lobes of the pituitary gland. This gene encodes a 285-amino acid polypeptide hormone precursor that undergoes extensive, tissue-specific, post-translational processing via cleavage by subtilisin-like enzymes known as prohormone convertases. The encoded protein is synthesized mainly in corticotroph cells of the anterior pituitary where four cleavage sites are used; adrenocorticotrophin (ACTH), essential for normal steroidogenesis and the maintenance of normal adrenal weight, and ?-lipotropin are the major end products. However, there are at least eight potential cleavage sites within the polypeptide precursor and, depending on tissue type and the available convertases, processing may yield as many as ten biologically active peptides involved in diverse cellular functions.