Enkephalins
Overview
Enkephalins are small peptides that play a significant role in the body's response to pain and stress. They are one of the three major families of opioid peptides produced within the body, the other two being endorphins and dynorphins. Enkephalins are pentapeptides, meaning they are composed of five amino acid residues.
Structure and Synthesis
Enkephalins are derived from the precursor protein proenkephalin, which is encoded by the PENK gene. The synthesis of enkephalins involves a series of enzymatic processes, including the cleavage of the precursor protein and post-translational modifications. The two major forms of enkephalins are Met-enkephalin, with the amino acid sequence Tyr-Gly-Gly-Phe-Met, and Leu-enkephalin, with the sequence Tyr-Gly-Gly-Phe-Leu.
Function
Enkephalins function as neurotransmitters and neuromodulators in the central and peripheral nervous systems. They bind to opioid receptors, specifically the delta receptor, to mediate their effects. Their primary role is in the modulation of pain perception, but they also play roles in other physiological processes, such as mood regulation, immune response, and stress response.
Clinical Significance
Enkephalins have been implicated in a variety of clinical conditions, including chronic pain, depression, and addiction. They have also been studied for their potential therapeutic uses. For example, drugs that inhibit the enzymes that degrade enkephalins are being investigated for their potential use in pain management.