Enkephalin (ENK)

An enkephalin is a pentapeptide ending with either leucine ("leu") or methionine ("met"). Both are products of the proenkephalin gene. Enkephalins play many roles in regulating pain. Met-enkephalin is an endogenous opioid peptide neurotransmitter found naturally in many part of the animal and human's body. One of the primary locations is in segment II of the dorsal horn of the spinal cord. Also present in the CNS (central nervous system), it is one of the two forms of enkephalin; the other is leu-enkephalin. The tyrosine residue at position 1 is thought to be analogous to the 3-hydroxyl group on morphine. Leu-enkephalin is an endogenous opioid peptide neurotransmitter found naturally in the brains of many animals, including humans. It is one of the two forms of enkephalin; the other is met-enkephalin. The tyrosine residue at position 1 is thought to be analogous to the 3-hydroxyl group on morphine.