GHK-Cu vs AHK-Cu: Two Copper Tripeptides, Very Different Evidence

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.

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.