Pentapeptides

A pentapeptide is a molecule consisting of five amino acids linked by four peptide bonds. Like other peptides, they are composed of amino acid residues connected by amide bonds between the carboxylate of one residue and the amino group of the next. In nature, most peptides are composed of L-amino acids, but synthetic pentapeptides may include D-enantiomers or noncanonical residues.

Because the sequence is short, pentapeptides are generally flexible in solution and adopt multiple conformations; their properties—charge, hydrophobicity, and steric effects—are determined by the side chains at the five positions. The N- and C- termini are free unless modified.

Synthesis is typically by solid-phase peptide synthesis (SPPS) using Fmoc or BOC strategies; purification by high-performance liquid chromatography; and characterization by mass spectrometry.

In proteins, pentapeptides appear as short motifs in larger sequences and can act as recognition elements or linkers; they may modulate binding interactions in studies of protein domains.

Applications include research tools, peptide libraries, and certain cosmetic products. For example, palmitoyl pentapeptide-4 (Pal-KTTKS) is marketed as a cosmetic ingredient claimed to stimulate collagen synthesis; GRGDS is used as a cell adhesion motif in biomaterials.

Stability and modification: Peptides are susceptible to proteases; modifications such as N- or C-terminal acylation or amidation, cyclization, or inclusion of D-amino acids can improve stability.