Pentapeptide-4 is a 5 amino acid length fragment (lysine-threonine-threonine-lysine-serine, KTTKS) of pro-collagen I protein, that stimulates dermal matrix components production by skin fibroblasts. Palmitoyl pentapeptide-4 is the palmitoyl derivative of this pentapeptide and is often used in anti-wrinkle cosmetics.