Glossary
Tripeptide
A tripeptide consists of three amino acids linked by two peptide bonds. GHK, KPV, glutathione and TRH explained, and why the short chain shapes handling.
Tripeptides are made up of three amino acid residues linked through two peptide bonds 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, binds copper(II) via its histidine imidazole and N-terminal amine to give GHK-Cu — and it is the copper complex, rather than the free peptide, that accounts for most of the reported activity. KPV (Lys-Pro-Val), the C-terminal tripeptide 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. Palmitoylation — as in Palmitoyl Tripeptide-1 — is the usual way to make one sufficiently lipophilic for topical formulations.
Related terms and material
tetrapeptide · half-life · matrikine. Reference material: GHK-Cu, KPV, Palmitoyl Tripeptide-1. Further reading: what is GHK-Cu.