Glossary
Tripeptide
Tripeptides are three amino acids joined through two peptide bonds. Profiles of GHK, KPV, glutathione and TRH, and how such a short chain affects handling.
A tripeptide is a chain of just three residues held together by two peptide bonds; such molecules and generally weigh 250-500 Da. Small as they are, the class contains several of the most intensively researched bioactive sequences in the catalogue.
Defining examples
GHK (Gly-His-Lys), which Loren Pickart isolated from human plasma in 1973, chelates copper(II) through the imidazole ring of histidine plus the free amino terminus to give GHK-Cu — and it is the copper complex, rather than the free peptide, that is responsible for the bulk of published effects. KPV (Lys-Pro-Val), the last three residues of alpha-MSH, keeps anti-inflammatory readouts while lacking the pigmentation effects mediated by melanocortin receptors. Glutathione is a tripeptide whose unusual gamma-glutamyl bond protects it from ordinary aminopeptidases. TRH (pGlu-His-Pro-NH2) illustrates how capping both the N- and C-terminus stabilises a hormone only three residues long.
Their size dictates handling: tripeptides are inexpensive and clean to make, produce simple HPLC traces, and are cleared quickly from the circulation unless modified. A palmitoyl group, as carried by Palmitoyl Tripeptide-1, is the standard method to make one sufficiently lipophilic for topical formulations.
Related terms and material
See also half-life, tetrapeptide and matrikine. In the shop you will find KPV, GHK-Cu and Palmitoyl Tripeptide-1; our GHK-Cu explainer goes further.