Leu-enkephalins compete with and mimic the effects of opiate drugs. They play a role in a number of physiologic functions, including pain perception and responses to stress (By similarity). Dynorphin peptides differentially regulate the kappa opioid receptor. Dynorphin A(1-13) has a typical opiod activity, it is 700 times more potent than Leu-enkephalin. Leumorphin has a typical opiod activity and may have anti-apoptotic effect. The N-terminal domain contains 6 conserved cysteines thought to be involved in disulfide bonding and/or processing. Belongs to the opioid neuropeptide precursor family.