Pentapeptide-18 (Leuphasyl)

Pentapeptide-18 is a synthetic five-residue peptide with sequence Tyr-D-Ala-Gly-Phe-Leu, also called Leuphasyl or [D-Ala2]leucine-enkephalin. Replacing the second residue with D-alanine fixes the stereochemical identity and differentiates it from ordinary leucine-enkephalin, whose native sequence is Tyr-Gly-Gly-Phe-Leu; the substitution therefore sits at the first of the two glycine positions and is a long-standing device in enkephalin structure–activity work for slowing aminopeptidase cleavage. The molecule is cataloged under CAS 64963-01-5 with formula C29H39N5O7 and molecular weight 569.65 g/mol.

Cosmetic-peptide research has examined Pentapeptide-18 in neurotransmitter-release and contraction-associated model systems, often beside Argireline, SNAP-8, Syn-AKE or Vialox. Those materials act through different proposed steps, so a useful study compares them under the same cell, tissue and vehicle conditions rather than grouping them as interchangeable “expression peptides.” Unlike the palmitoylated actives it is frequently benchmarked against, Pentapeptide-18 carries no lipid modification and behaves as an ordinary water-soluble small peptide, which changes both its formulation requirements and what can reasonably be expected of it in a permeation experiment.