Immunohistological Detection of Leucine-Enkephalin in the Digestive System of the Scallop Chlamys farreri

BmK-YA, an enkephalin-like peptide in scorpion venom

By screening extracts of venom from the Asian scorpion Buthus martensii Karsch (BmK) for their abilities to activate opioid receptors, we have identified BmK-YA, an amidated peptide containing an enkephalin-like sequence. BmK-YA is encoded by a precursor that displays a signal sequence and contains four copies of BmK-YA sequences and four of His⁴-BmK-YA, all flanked by single amino acid residues. BmK-YA and His⁴-BmK-YA are amidated and thus fulfill the characteristics expected of bioactive peptides. BmK-YA can activate mammalian opioid receptors with selectivity for the δ subtype while His⁴-BmK-YA is inactive at opioid receptors. The discovery of BmK-YA suggests that scorpion venom may represent a novel source of bioactive molecules targeting G protein-coupled receptors (GPCRs) and reveal additional insights on the evolution of the opioid precursors.

Immunohistological detection of mu, delta and kappa opioid-like receptors in the gill, gonad, and hemocytes of the scallop Chlamys farreri

Endogenous opioid peptides and opioid receptors form a neuromodulatory system, which plays an important part in the control of physiological pathways. In addition, some opioid peptides can function as endogenous messengers of the immune system and participate in the regulation of the immune response. The present studies indicated that mu, delta, and kappa opioid-like receptors were present in the gill and gonad of the scallop Chlamys farreri. Furthermore, the significance of opioid peptides involvement with the immune system is ascertained from the presence of mu, delta, and kappa opioid-like receptors on hemocytes of the scallop. Our report constitutes the first characterization of mu, delta, and kappa opioid-like receptors in the gill and gonad of the scallop Chlamys farreri.