Effects of Livagen and Epitalon, New Peptide Bioregulators, on Enkephalin-Degrading Enzymes from Human Serum


The effects of new peptide bioregulators—Livagen (Lys-Glu-Asp-Ala) and Epitalon (Ala-Glu-Asp-Gly)—on the endogenous opioid system was studied. In particular, attention was focused on their ability to change the activity of enkephalin-degrading enzymes of blood serum and interact with opioid receptors of the brain membrane fraction. Enkephalinase activity was assayed in vitro by the rate of 3H-Leu-enkephalin hydrolysis in the presence of Livagen and Epitalon. These peptides inhibited enkephalin-degrading enzymes of human serum. Livagen proved to be more efficient than some well-known peptidase inhibitors, such as puromycin, leupeptin, and D-PAM. The dose–inhibitory effect curves for Livagen and Epitalon were plotted; their IC50 equaled 20 and 500 μM, respectively. The interaction between the peptides and opioid receptors was estimated using a radioreceptor method with [3H][D-Ala2, D-Leu5]-enkephalin. No interaction was observed between the peptides and μ- or δ-opioid receptors of the membrane fraction from the rat brain.

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Kost, N.V., Sokolov, O.Y., Gabaeva, M.V. et al. Effects of Livagen and Epitalon, New Peptide Bioregulators, on Enkephalin-Degrading Enzymes from Human Serum. Biology Bulletin 30, 351–353 (2003). https://doi.org/10.1023/A:1024809822681

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  • Peptide
  • Human Serum
  • Blood Serum
  • Opioid Receptor
  • Membrane Fraction