Background：

This gene encodes a preproprotein that undergoes extensive， tissue-specific， post-translational processing via cleavage by subtilisin-like enzymes known as prohormone convertases. There are eight potential cleavage sites within the preproprotein and， depending on tissue type and the available convertases， processing may yield as many as ten biologically active peptides involved in diverse cellular functions. The encoded protein is synthesized mainly in corticotroph cells of the anterior pituitary where four cleavage sites are used; adrenocorticotrophin， essential for normal steroidogenesis and the maintenance of normal adrenal weight， and lipotropin beta are the major end products. In other tissues， including the hypothalamus， placenta， and epithelium， all cleavage sites may be used， giving rise to peptides with roles in pain and energy homeostasis， melanocyte stimulation， and immune modulation. These include several distinct melanotropins， lipotropins， and endorphins that are co