Met-enkephalin is a pentapeptide that appears to enhance immune function at low doses and suppresse at high doses. This molecule acts in the central nervous, neuroendocrine, and immune systems. Cells from these systems have receptors for met-enkephalin and are able to generate met enkephalin from its prohormone, proenkephalin A. Met-enkephalin may be capable of enhancing immune function in cancer or AIDS patients. It isknown to be an endogenous ligand for opioid receptors and acts to mediate analgesia at the spinal level. Met-enkaphalin. Plasma met enkaphalinlevelsaresignificantly higher in patients with type I diabetes and could play a role in glucose homeostasis. Cross-reactivity (%) Met5-Enkephalin100 , Leu5-Enkephalin 5. 8 , beta-Endorphin 0. 01 , beta-Lipotropin0. 01