GHK-Cu or AHK-Cu: What Are the Differences, According to Chemistry and the Literature?
A single amino acid separates them: glycine versus alanine. Structure, copper binding and volume of literature: what really distinguishes the two copper tripeptides.
Contents
GHK-Cu and AHK-Cu are often mentioned together: two tripeptides, both associated with a copper ion, both blue. They differ by only one amino acid, but not by the volume of work published on them. Here is what sets them apart.
One letter of difference
- GHK-Cu: Gly-His-Lys + Cu²⁺.
- AHK-Cu: Ala-His-Lys + Cu²⁺.
Glycine is the smallest amino acid: its side chain is just a hydrogen atom. Alanine carries a methyl group (–CH₃) instead. The difference seems minor, but it concerns precisely the start of the chain, which takes part in binding the copper.
Chemical consequences
- A slightly higher molar mass for AHK.
- A slightly less flexible start of the chain, which can change the fine geometry of the copper complex.
- A shared histidine-lysine motif, and a shared blue colour, which comes from copper(II) (see why GHK-Cu is blue).
In peptide chemistry, this kind of substitution is often used to study the effect of a single sequence change on stability or affinity.
Natural or synthetic
GHK is described as a peptide naturally present in certain biological fluids, notably plasma, which explains how long it has been studied. AHK-Cu is presented as a synthetic analogue designed on the same model.
A large gap in the literature
This is the clearest difference:
- GHK-Cu has been studied for several decades, with an abundant body of *in vitro* and preclinical work (see what the literature documents about GHK-Cu);
- AHK-Cu has a much smaller body of work, often focused on cell models (see our article on AHK-Cu).
A smaller literature does not mean a less interesting compound: it means the possible conclusions are more limited, and studies should be cited with caution.
How to choose for a protocol
The choice depends on the research question: comparing the two analogues, relying on an abundant body of work (GHK-Cu) or exploring a less-studied variant (AHK-Cu). In all cases, the lot's certificate of analysis remains the reference for purity and identity.
To learn more
Research Use Only (RUO). This article compares two laboratory reagents based on the published literature. It constitutes neither a recommendation for use in humans or animals nor a therapeutic claim.
