Tripeptides explained: three amino acids, two amide bonds, and more distinct chemistry than their size suggests.
Last updated 27 October 2026 · Written by the SHLabz research team
A tripeptide is the smallest peptide with a middle. It has an N-terminal residue, a C-terminal residue and one residue between them. Even so, several tripeptides have long research histories of their own.
This article covers three tripeptides, explained one at a time, that appear in the SHLabz catalogue: GHK, KPV and glutathione. For each, we cover the sequence, what makes the structure unusual and the kinds of models the literature describes. None of it says anything about effects in people.
What Makes a Peptide a Tripeptide
First, the arithmetic. Each amide bond forms by condensation, so linking three amino acids releases two molecules of water. As a result, a tripeptide weighs the sum of its three amino acids minus about 36 daltons. GHK, for example, has the formula C14H24N6O4, which puts it near 340 Da.
Size also changes how the molecule behaves. With only three residues, a tripeptide has no room to fold into a helix or a sheet. Instead, its chemistry depends almost entirely on its side chains and its two ends. That is why a single histidine or cysteine can define the whole molecule.
Notation follows the usual rule. Sequences run from the free amino end on the left to the carboxyl end on the right, so GHK means glycine first and lysine last. With tripeptides explained in those terms, the three compounds below become easier to compare.
Three Tripeptides Explained
Although all three are short, each one earns its interest from a different feature. Put simply, GHK binds a metal, KPV is a fragment of a hormone, and glutathione uses an unusual bond.
GHK: The Copper-Binding Tripeptide
GHK stands for glycyl-L-histidyl-L-lysine. A 2018 review by Loren Pickart and Anna Margolina dates its discovery to 1973, when researchers isolated it from human plasma. The same review calls it “the human copper-binding peptide”, and that affinity for copper(II) ions is its defining chemistry. In addition, the review notes that the Gly-His-Lys sequence occurs within the alpha 2(I) chain of type I collagen.
Most of the GHK literature therefore studies the copper complex, GHK-Cu, in cell culture and animal models of tissue repair. Our GHK-Cu guide covers that body of work in more detail.
KPV: A Fragment of Alpha-MSH
KPV is Lys-Pro-Val, the C-terminal tripeptide of alpha-melanocyte-stimulating hormone (alpha-MSH). The parent hormone comes from proopiomelanocortin, a larger precursor protein. A 2008 review in Endocrine Reviews discusses KPV alongside alpha-MSH. Specifically, it presents the tripeptide as a fragment that research has examined in animal models of inflammation, partly because it lacks the pigmentary activity of the full hormone.
Glutathione: The Gamma Link
Glutathione is the odd one out. Its sequence reads γ-Glu-Cys-Gly, and the Greek letter matters. Rather than joining through glutamate’s main-chain carboxyl group, the first bond uses the side-chain, or gamma, carboxyl. According to a 2023 review in Molecules, this bond means ordinary cellular and serum peptidases cannot cleave the molecule. Breaking it down instead takes a dedicated enzyme, γ-glutamyl transpeptidase.
The cysteine in the middle carries a thiol group, which lets glutathione act as a reducing agent. When it does, two molecules pair up through a disulfide bond to form glutathione disulfide, or GSSG. Notably, cells build glutathione without a ribosome, through two ATP-dependent enzymes: glutamate-cysteine ligase and glutathione synthetase.
What the Differences Mean in the Lab
These structural differences carry practical consequences. A GHK-Cu solution looks blue, because the copper complex absorbs visible light near 606 nm. Glutathione’s free thiol, by contrast, makes it prone to oxidation once dissolved. KPV has neither a metal nor a thiol, so it behaves more like a typical short peptide.
Storage, however, follows the same rule for all three. Sealed lyophilised powder is stable at room temperature, kept dry and out of direct light. Cold storage is possible but not required, and repeated cold cycling risks condensation inside the vial. After reconstitution, refrigerate the solution at 2–8°C.
Where SHLabz Fits
SHLabz lists all three as lyophilised vials: GHK-Cu, KPV and glutathione. KPV also comes as a pre-mixed nasal spray, which holds a solution from filling, needs 2–8°C from arrival and ships within the UAE only. Sealed lyophilised powder does not require cold chain. SHLabz holds the whole range to it anyway, because it removes a variable and the handling difference is small.
Every batch is tested by an independent laboratory. The GHK-Cu certificate is on the lab results page, and certificates for the other compounds are published there as they are released. All batch figures are in the open SHLabz Purity Index.
The Short Version
In short, tripeptides are three residues joined by two amide bonds, light enough that one side chain can dominate their chemistry. GHK binds copper, KPV is the last three residues of alpha-MSH, and glutathione links through a gamma bond that common peptidases cannot cut.
Still, all three share the same storage logic. Sealed powder is stable at room temperature when kept dry and dark, while any solution belongs at 2–8°C.
Frequently Asked Questions
What is a tripeptide? It is a chain of three amino acids joined by two amide bonds. Forming those bonds releases two molecules of water, so the mass is the sum of the three amino acids minus about 36 Da.
Is glutathione a normal tripeptide? Not quite. Its first bond runs through the side-chain carboxyl of glutamate rather than the main-chain one, which is why reviews write it as γ-Glu-Cys-Gly.
Where does KPV come from? KPV matches the C-terminal three residues of alpha-MSH, a hormone derived from proopiomelanocortin. Research has studied it as a separate fragment in models of inflammation.
Why is GHK-Cu blue? Because the copper(II) complex absorbs visible light in the orange-red region, the solution looks blue. Plain GHK without copper does not show that colour.
Do tripeptide vials need a fridge? Not while sealed. Lyophilised powder is stable at room temperature when kept dry and out of direct light, but once reconstituted, a solution should go to 2–8°C.
References
- Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data — Pickart and Margolina, International Journal of Molecular Sciences, 2018. GHK discovery in 1973, plasma origin, copper binding and the collagen sequence.
- Glycyl-L-histidyl-L-lysine (CID 73587) — PubChem, US National Library of Medicine. Identity and molecular formula of GHK.
- Alpha-melanocyte-stimulating hormone and related tripeptides — Endocrine Reviews, 2008. KPV as a fragment of alpha-MSH and the models it has appeared in.
- Glutathione-Related Enzymes and Proteins: A Review — Vašková and colleagues, Molecules, 2023. The γ-Glu-Cys-Gly structure, peptidase resistance and two-enzyme synthesis.
- Ternary Cu(II) Complex with GHK Peptide and Cis-Urocanic Acid as a Potential Physiologically Functional Copper Chelate — Bossak-Ahmad and colleagues, International Journal of Molecular Sciences, 2020. The visible absorption band of Cu(GHK).
These references describe published research. They say nothing about what any compound does for anybody, and nothing here should read as a claim that it does.
Finally, to see the three tripeptides side by side with the rest of the range, browse the catalogue.
This article is provided for general research and educational purposes only. All SHLabz products are sold strictly for laboratory research use and are not intended for human or veterinary consumption, diagnosis, treatment, or prevention of any disease. Nothing in this article constitutes medical advice. Always consult a qualified professional and comply with applicable local regulations regarding the handling and use of research compounds.
