oligopeptides

An oligopeptide is a short chain of amino acids linked by peptide bonds. By convention, oligopeptides contain a small number of residues, typically 2–20, though definitions vary; dipeptides and tripeptides are the simplest examples, while tetrapeptides and pentapeptides are also included. Oligopeptides can arise naturally as parts of larger proteins through proteolytic processing or be synthesized de novo in laboratory settings.

Each oligopeptide has an N-terminus with a free amino group and a C-terminus with a free carboxyl group. The sequence and composition of amino acids determine properties such as charge, hydrophobicity, and conformation. Many oligopeptides function as signaling molecules, hormones, neurotransmitters, or antimicrobial agents. Examples include the tripeptide thyrotropin-releasing hormone, the pentapeptides enkephalins, and the nonapeptides vasopressin and oxytocin. In cells, oligopeptides also arise from the breakdown of larger proteins.

In laboratory contexts, oligopeptides are synthesized using solid-phase peptide synthesis or similar methods; they may be modified to enhance stability or receptor specificity. Because of their small size, oligopeptides are often susceptible to rapid proteolysis and can have limited oral bioavailability, influencing how they are delivered as therapeutics. Oligopeptides are fundamental in biology and biotechnology, serving as research tools, substrates in enzymatic studies, and the basis for many peptide-based medicines.