GHK-Cu and AHK-Cu look almost identical on paper. Both are tripeptides that carry a copper ion, and their names differ by a single letter. That similarity leads to them being treated as interchangeable, which the published literature does not support – the difference in evidence volume between the two is large.
- GHK-Cu
- Glycyl-histidyl-lysyl copper
- AHK-Cu
- Alanyl-histidyl-lysyl copper
- Difference
- One amino acid in position 1
- Evidence gap
- Substantial – see below
The short answer
GHK-Cu and AHK-Cu are both copper-carrying tripeptides, but with different amino-acid sequences: GHK-Cu begins with glycine, AHK-Cu with alanine. That single substitution changes the molecule. More importantly for a researcher, GHK-Cu has a decades-long published literature, while the direct research on AHK-Cu specifically is thin – a much smaller body of work, weighted toward in-vitro studies.
| GHK-Cu | AHK-Cu | |
|---|---|---|
| Sequence | Glycine – histidine – lysine | Alanine – histidine – lysine |
| Copper-carrying | Yes | Yes |
| Published literature | Extensive, spanning decades | Limited |
| Dominant study type | In-vitro and in-vivo | Largely in-vitro |
| Supplied as | Lyophilized powder | Lyophilized powder |
Why the single amino acid matters
A tripeptide is three amino acids. Changing one of the three is a change to a third of the molecule, not a rounding error. The histidine and lysine residues that both share are involved in copper coordination, but the first-position residue differs, and published work does not establish that the two behave equivalently on that basis.
The evidence gap is the headline
GHK-Cu has been studied since the 1970s and appears across a broad published literature covering cell-model and animal work. The evidence for AHK-Cu specifically is thin by comparison, with a much smaller number of direct studies and a heavier weighting toward in-vitro models.
This is worth stating directly because sequence similarity invites an assumption of equivalent evidence. It is not equivalent. A researcher selecting AHK-Cu on the strength of the GHK-Cu literature is extrapolating across a gap the published work does not bridge.
Laboratory handling
Both are supplied as lyophilized powders and reconstituted with bacteriostatic water. Copper peptides carry a characteristic blue colouration in solution from the coordinated copper ion. Both are stored cold and dark and protected from freeze-thaw cycling.
All compounds referenced here are supplied as analytical-grade reference materials for in-vitro and laboratory research only. Nothing on this page is a recommendation for human or veterinary use, and no comparison below should be read as ranking these materials for any personal outcome.
Studies cited
- GHK-Cu tripeptide in liposomes — cosmetic study (Pharmaceutics, 2023)
- GHK-Cu microsphere filler — anti-inflammatory study (Colloids and surfaces. B, Biointerfaces, 2025)
- GHK-Cu skin permeation in liposomes (Molecules (Basel, Switzerland), 2025)
- The effect of tripeptide-copper complex on human hair growth in vitro (Archives of pharmacal research, 2007)
- The human tri-peptide GHK and tissue remodeling (Journal of biomaterials science. Polymer edition, 2008)
Questions
What is the difference between GHK-Cu and AHK-Cu?
GHK-Cu and AHK-Cu are both copper-carrying tripeptides, but with different amino-acid sequences – GHK-Cu begins with glycine and AHK-Cu with alanine. They also differ enormously in evidence volume: GHK-Cu has a literature spanning decades, while direct research on AHK-Cu is limited.
Can AHK-Cu be substituted for GHK-Cu in research?
The published literature does not establish that AHK-Cu and GHK-Cu behave equivalently. They differ by one of three amino acids, and the research bases behind them are very different in size, so substituting one for the other is an extrapolation the evidence does not support.
Why are copper peptides blue in solution?
Copper peptides such as GHK-Cu and AHK-Cu coordinate a copper ion, and that coordinated copper gives the reconstituted solution its characteristic blue colouration.
How strong is the evidence for AHK-Cu?
The evidence for AHK-Cu specifically is thin. The direct published research is a small body of work weighted toward in-vitro studies, which is a very different position from the decades-long literature behind GHK-Cu.
For laboratory research and educational purposes only. Not medical advice. The materials discussed are not for human or animal consumption and have not been evaluated by the FDA.