Enkephalinases, including Neutral Endopeptidase (NEP) and Aminopeptidase N (APN), are key peptidases involved in the metabolism of opioid peptides such as enkephalins. These enzymes are expressed in various cells and tissues, especially within the central nervous system, where they regulate pain perception, emotional balance, and the natural analgesic system. By degrading enkephalins, they influence the activity of neurotransmitters and signaling pathways. The levels of gene expression and genetic mutations significantly impact their activity, thereby affecting the body's response to pain and stress. This is associated with various disease states, including chronic pain, psychiatric disorders, and substance dependence.