Met-enkephalin

Met-enkephalin, also known as metenkephalin (sometimes abbreviated as MENK or MEN), is a naturally occurring, endogenous opioid peptide that has potent painkilling effects in the body. It is a pentapeptide with the amino acid sequence Tyr-Gly-Gly-Phe-Met.

Structure and Function

Met-enkephalin is derived from the precursor protein preproenkephalin and is widely distributed in the central and peripheral nervous systems. It is one of the two forms of enkephalin, the other being leu-enkephalin. Both forms bind to opioid receptors in the brain, but met-enkephalin has a higher affinity for the delta opioid receptor while leu-enkephalin has a higher affinity for the mu opioid receptor.

The primary function of met-enkephalin is to modulate pain perception. It does this by binding to and activating opioid receptors, which inhibits the release of substance P, a neuropeptide involved in pain transmission. Met-enkephalin also has other effects in the body, including modulating immune function and affecting mood and behavior.

Clinical Significance

Due to its potent analgesic effects, met-enkephalin has been investigated for potential therapeutic use in the treatment of chronic pain conditions. However, its clinical use is limited by its short half-life and rapid degradation by enkephalinase, an enzyme that breaks down enkephalins.

Research is ongoing into the development of enkephalinase inhibitors, which could potentially extend the half-life of met-enkephalin and make it a more viable therapeutic option. Met-enkephalin is also of interest in the study of addiction, as it is thought to play a role in the rewarding effects of drugs of abuse.

See Also

• Opioid peptide
• Endorphin
• Dynorphin

References

• 
  Met-enkephalin Structure
• 
  Met-enkephalin Ball-and-Stick Model