Hemorphin-4

Hemorphin-4 is an endogenousopioid peptide of the hemorphin family which possesses antinociceptive properties and is derived from the β-chain of hemoglobin in the bloodstream. It contains a tetrapeptide core with the amino acid sequence Tyr-Pro-Trp-Thr. Hemorphin-4 serves as a opioid receptor ligand that has affinities for the μ-, δ-, and κ-opioid receptors in the same range as the structurally related β-casomorphins, although affinity to the κ-opioid receptor is markedly higher in comparison. It acts as an agonist at these sites. It presents high affinity for other receptors such as angiotensin IV, bombesin subtype 3 (hBRS-3), and the corticotropin releasing factor (CRF). Even though it exhibits lower binding affinity for opioid receptors relative to traditional opioid peptides such as endorphins and enkephalins; it may still influence opioid receptor systems due to its high tissue concentration.