Synthetic BmK-YA activates human opioid receptors in vitro, with highest activity on the delta-type/OPRD1 receptor (EC(50)=2.5 uM) and lower activity on mu-type/OPRM1 and kappa-type/OPRK1 receptors (EC(50)=17 uM and 30 uM, respectively). Venom gland. The measured ranges are 35-42, 101-108, 145-152, 189-196. Four additional, similar peptides (containing a substitution of Tyr-4 to His-4) are predicted from this sequence: however, there is no evidence that they exist in vivo and the synthetic peptide has no known function. Truncated N-terminus.