AHK-Cu vs GHK-Cu: Copper Tripeptides Compared

AHK-Cu and GHK-Cu are copper(II) complexes of two tripeptides that differ in a single residue. GHK (Gly-His-Lys) is a natural plasma peptide; AHK (Ala-His-Lys) replaces the glycine with alanine. Both keep the amine–histidine arrangement that holds copper. The bigger difference is in the evidence base: GHK-Cu has been studied extensively, while AHK-Cu has only a few published reports.

For laboratory research use only. The compounds discussed are not approved for human or veterinary use and are not drugs, foods or cosmetics. This article summarises published research and is not medical advice.

Key points

One-residue difference: Ala (AHK) vs Gly (GHK) at position 1.
AHK is 14 Da heavier (354.4 vs 340.4 g/mol for the free peptide) and slightly more hydrophobic.
Both share the N-terminal amine + His motif involved in copper binding.
GHK-Cu: structural, cell, gene-expression and formulation data. AHK-Cu: limited hair-follicle and cell data.
Both are blue copper complexes and handled similarly in the lab.

Side-by-side comparison

	AHK-Cu	GHK-Cu
Peptide sequence	Ala-His-Lys	Gly-His-Lys
Free peptide formula	C₁₅H₂₆N₆O₄	C₁₄H₂₄N₆O₄
Free peptide mass	354.4 g/mol	340.4 g/mol
Origin	Synthetic analogue	Endogenous plasma peptide
Copper-binding motif	N-terminal NH₂, amide N, His imidazole (assumed by analogy)	N-terminal NH₂, amide N, His imidazole (shown by X-ray and spectroscopy)
Main published research	Hair follicle and dermal papilla cells	Fibroblasts, matrix remodelling, gene expression, formulation
Appearance	Blue to violet-blue powder and solution

Both are available for laboratory research: AHK-Cu and GHK-Cu, each in 50 mg and 100 mg vials.

What the single residue changes

Glycine has no side chain; alanine has a methyl group. At the N-terminus, which is one of the copper ligands, this adds a little steric bulk and hydrophobicity next to the binding site. In GHK, structural studies show copper bound by the N-terminal amine, a deprotonated amide nitrogen and the histidine imidazole, and the complex exchanges copper rapidly (Hureau et al., 2011). Whether the extra methyl group in AHK changes copper affinity or exchange rate measurably has not, to our knowledge, been reported in a comparable structural study. Any claim that one binds copper “better” should be treated with caution.

A small hydrophobicity increase may matter for formulation. GHK-Cu is highly hydrophilic, with log D around −2.4 (Badenhorst et al., 2016). AHK-Cu is expected to be slightly less hydrophilic, but still very water-soluble.

Research on GHK-Cu

GHK-Cu studies include dermal fibroblast cultures in which the complex increased MMP-2 together with its inhibitors TIMP-1 and TIMP-2 (Siméon et al., 2000), and gene-expression analyses linking GHK to many tissue-remodelling pathways (Pickart and Margolina, 2018). See what is GHK-Cu? for the full profile.

Research on AHK-Cu

The main peer-reviewed study tested AHK-Cu on human hair follicles ex vivo and on cultured dermal papilla cells. At 10⁻¹² to 10⁻⁹ M, AHK-Cu stimulated follicle elongation and dermal papilla cell proliferation. At 10⁻⁹ M it raised the Bcl-2/Bax ratio and reduced cleaved caspase-3 and PARP, although the reduction in apoptotic cells did not reach statistical significance (Pyo et al., 2007). The same paper notes that tripeptide-copper complexes stimulate fibroblast proliferation and VEGF production. These are in vitro findings from a single group.

Evidence compared

Evidence type	AHK-Cu	GHK-Cu
Structural (X-ray, spectroscopy)	Not found	Yes
Cell culture	Dermal papilla cells, follicles ex vivo	Fibroblasts and many other cell types
Gene expression	Not found	Yes
Formulation / stability	Not found	Yes

Handling

Handle both the same way: store powder sealed at −20 °C and protected from light; dissolve in water to a clear blue solution; avoid chelators, high pH and oxidants. Plan concentrations for the large 50–100 mg vials with the peptide reconstitution calculator. Colour-based quality checks are described in GHK-Cu powder: colour and quality.

Open questions

Does the alanine methyl group change copper affinity, exchange rate or redox behaviour compared with GHK? No head-to-head structural or thermodynamic study has been published.
Is AHK-Cu, like GHK, able to form ternary complexes with albumin?
Do the hair-follicle findings for AHK-Cu replicate in independent laboratories?
How do the two complexes compare in solution stability under the same stress conditions?

Until these are answered, the two peptides should be treated as related but not interchangeable in experimental design.

Related research

Frequently asked questions

What is the difference between AHK-Cu and GHK-Cu?

The first amino acid. AHK-Cu is Ala-His-Lys bound to copper; GHK-Cu is Gly-His-Lys bound to copper. Alanine adds a methyl group, so AHK is 14 Da heavier and slightly more hydrophobic.

Is AHK-Cu natural like GHK-Cu?

GHK is a naturally occurring plasma tripeptide. AHK-Cu is generally described as a synthetic analogue designed around the same copper-binding motif.

What has AHK-Cu been studied for?

Published work is limited. One study reported that AHK-Cu at picomolar to nanomolar concentrations stimulated elongation of human hair follicles ex vivo and proliferation of dermal papilla cells in vitro.

Do AHK-Cu and GHK-Cu bind copper the same way?

Both share an N-terminal amine followed by histidine, the motif that binds copper in GHK. Detailed structural studies have been published for Cu-GHK; equivalent data for AHK-Cu are scarce, so close similarity is assumed rather than demonstrated.

Which copper peptide has more research?

GHK-Cu, by a wide margin. It has structural, cell, gene-expression and formulation studies, whereas AHK-Cu has only a few published reports.

References

Pyo HK, et al. The effect of tripeptide-copper complex on human hair growth in vitro. Arch Pharm Res. 2007. PMID: 17703734 https://pubmed.ncbi.nlm.nih.gov/17703734/
Hureau C, et al. X-ray and solution structures of Cu(II) GHK and Cu(II) DAHK complexes: influence on their redox properties. Chemistry. 2011. PMID: 21780203 https://pubmed.ncbi.nlm.nih.gov/21780203/
Pickart L, et al. Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. Int J Mol Sci. 2018. PMID: 29986520 https://pubmed.ncbi.nlm.nih.gov/29986520/
Siméon A, et al. The tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+ stimulates matrix metalloproteinase-2 expression by fibroblast cultures. Life Sci. 2000. PMID: 11045606 https://pubmed.ncbi.nlm.nih.gov/11045606/
Badenhorst T, et al. Physicochemical characterization of native glycyl-l-histidyl-l-lysine tripeptide for wound healing and anti-aging: a preformulation study for dermal delivery. Pharm Dev Technol. 2016. PMID: 25384620 https://pubmed.ncbi.nlm.nih.gov/25384620/