 These enzymes are sometimes referred to as enkephalinases.Met-enkephalin is a potent agonist of the δ-opioid receptor, and to a lesser extent the μ-opioid receptor, with little to no effect on the κ-opioid receptor.It is through these receptors that met-enkephalin produces its opioid effects, such as analgesia and antidepressant-like effects.