LEU-ENKEPHALIN-LYS LEU-ENKEPHALIN-LYS ACETATE SALT H-TYR-GLY-GLY-PHE-LEU-LYS-OH ACETATE SALT H-TYR-GLY-GLY-PHE-LEU-LYS-OH ACOH H-Tyr-Gly-Gly-Phe-Leu-Lys-OH leucine enkephalin-lys leucine enkephalin lysine Tyr-Gly-Gly-Phe-Leu-Lys Acetate salt