Spinorphin belongs to the family of hemorphins, which are endogenous peptides belonging to the family of atypical opioid peptides released from hydrolyzed hemoglobin. Hemorphin-4 binds preferentially to mu- delta and kappa receptors. Spinorphin functions as an endogenous inhibitor of enkephalin-degrading enzymes such as DPP3, and as a selective antagonist of the P2RX3 receptor which is involved in pain signaling. These properties implicate it as a regulator of pain and inflammation.H-Leu-Val-Val-Tyr-Pro-Trp-Thr-OH or H-LVVYPWT-OH