Endorphins and Enkephalins

Endorphins and enkephalins are derived from a 91 amino acid pituitary hormone called beta-lipotropin. On release it is cleaved to form three major active products: residue 61-65 is called met-enkephalin, residue 61-77 is called gamma-endorphin, and residue 61-91 is called beta-endorphin. Beta-endorphin is most active, and is about 20 times as potent as morphine. It can produce dependence and tolerance.