GHK-Cu vs AHK-Cu
Research Comparison

Research Overview

GHK-Cu and AHK-Cu are two closely related copper(II)-binding tripeptide complexes studied in cell and animal research. Both share a His-Lys copper-coordination core, and both chelate a single Cu(II) ion. The only structural difference between them is the N-terminal residue: GHK begins with glycine (Gly, which has a hydrogen side chain), while AHK begins with alanine (Ala, which carries a methyl side chain). That single substitution makes AHK exactly one CH2 group, about 14 g/mol, heavier than GHK.

The two compounds are often grouped together as copper peptides, but their research literatures diverge. GHK-Cu is a naturally occurring human plasma copper peptide with a decades-deep body of in-vitro and preclinical work centered on wound healing and dermal-matrix remodeling. AHK-Cu is a synthetic analog created by the alanine-for-glycine swap, and its published research is thinner and focused primarily on hair-follicle and dermal-papilla cell studies.

This page compares the two on structure, identity data, copper-binding chemistry, and reported research context to help a research team decide which scaffold matches a given study design. All statements below describe in-vitro, ex-vivo, animal-model, or preclinical research context only. Nothing here describes or implies any human use, therapeutic benefit, or efficacy.

Structure and Class

Both GHK-Cu and AHK-Cu belong to the class of copper(II)-binding tripeptide metal complexes, sometimes described as small metallopeptides or cosmetic copper peptides. Each is a three-residue peptide that chelates one Cu(II) ion through a histidine-anchored coordination site. The central L-histidine provides an imidazole nitrogen that, together with backbone nitrogen atoms, forms a high-affinity Cu(II) binding pocket. This arrangement is frequently described as analogous to the copper-transport site at the N-terminus of human serum albumin.

The sequences differ by a single residue. GHK is glycyl-L-histidyl-L-lysine (Gly-His-Lys); AHK is L-alanyl-L-histidyl-L-lysine (Ala-His-Lys). Both retain the same central L-histidine and C-terminal L-lysine. Because glycine has only a hydrogen side chain and alanine carries a methyl group, AHK is exactly one CH2 unit heavier. This is reflected directly in the reported PubChem identity data: the free GHK peptide is C14H24N6O4 at approximately 340.38 g/mol (CID 73587), while free AHK is C15H26N6O4 at approximately 354.41 g/mol (CID 7408502), a difference of about 14 g/mol.

The copper complex molecular weight depends on stoichiometry and counterion. GHK-Cu is represented in PubChem both as a 1:1 anionic complex (C14H21CuN6O4-, approximately 400.90 g/mol, CID 139035031) and as a 2:1 bis-prezatide copper complex (C28H46CuN12O8, approximately 742.3 g/mol, CID 9831891). AHK-Cu appears as a monohydrochloride complex (C15H24ClCuN6O4-, approximately 451.39 g/mol, CID 168431292). The exact stoichiometry, salt form, and complex molecular weight of any specific catalog lot should be confirmed against the batch COA.

Copper-Binding Chemistry

The defining shared feature of these two peptides is their copper-carrying chemistry. Both use the same His-anchored Cu(II) coordination modeled on the albumin copper-transport site, so both function as copper-delivery peptides in research settings. In the foundational GHK review by Pickart (J Biomater Sci Polym Ed 2008, DOI 10.1163/156856208784909435), GHK and GHK-Cu are described in vitro and in animal models as copper-delivery and tissue-remodeling signals.

Because AHK differs only at the N-terminal residue, it shares this His-Lys copper motif. The methyl side chain of alanine sits away from the coordinating imidazole, so the copper-binding pocket itself is closely conserved between the two peptides. The practical consequence for research is that both are studied as vehicles that present Cu(II) to cells, with the sequence difference primarily influencing which research contexts each has been characterized in rather than the fundamental coordination chemistry.

A GHK-Cu preformulation study (Badenhorst et al., Pharm Dev Technol 2014, DOI 10.3109/10837450.2014.979944) reported GHK-Cu as highly hydrophilic (log D between -2.38 and -2.49 across pH 4.5 to 7.4) and susceptible to hydrolytic cleavage under basic and oxidative stress, with free histidine identified as one degradation product. Handling parameters for AHK-Cu are less characterized in the primary literature and should be treated conservatively; confirm against batch COA.

Research Context

GHK-Cu carries the far larger literature. It has been studied as a modulator of cutaneous wound healing in rodent models, including reported acceleration of ischemic open-wound closure with a topical tripeptide-copper complex (Canapp et al., Vet Surg 2003, DOI 10.1111/j.1532-950x.2003.00515.x), and open-wound healing and neovascularization in a rabbit model versus zinc oxide (Cangul et al., Vet Dermatol 2006, DOI 10.1111/j.1365-3164.2006.00551.x). In a rat wound model, GHK-Cu was reported to selectively modulate matrix metalloproteinase-2 and -9 expression during wound remodeling (Simeon et al., J Invest Dermatol 1999, DOI 10.1046/j.1523-1747.1999.00606.x). In normal human dermal fibroblasts, GHK and GHK-Cu were reported to decrease IGF-2-dependent TGF-beta-1 secretion (Gruchlik et al., Acta Pol Pharm 2014, PMID 25745767). GHK-Cu is also the subject of an interventional Phase 2, vehicle-controlled split-wound study of a topical gel for re-epithelialization of standardized acute skin wounds (ClinicalTrials.gov NCT07437586, recruiting, sponsor Hudson Biotech); this trial is recruiting and not yet reporting results.

AHK-Cu has a much thinner and more specialized literature. Its distinguishing reported activity is in hair-follicle biology. In Pyo et al. (Arch Pharm Res 2007, DOI 10.1007/BF02978833), AHK-Cu at picomolar-to-nanomolar concentrations was reported to stimulate elongation of human hair follicles ex vivo and proliferation of dermal papilla cells in vitro, with an anti-apoptotic signature in those cells (raised Bcl-2/Bax ratio, reduced cleaved caspase-3 and PARP). Beyond this hair-focused work and general cosmetic-ingredient use as a GHK-Cu analog, broader mechanistic detail for AHK-Cu could not be confirmed from primary sources this run.

One point of catalog hygiene: the DAHK and D-DAHK copper-binding tetrapeptides (albumin N-terminus analogs) are a separate compound family and should not be conflated with the AHK-Cu tripeptide.

Which Should a Study Use?

The choice follows the intended research context rather than any efficacy ranking, since no comparative human efficacy data exists for either compound. A study modeling cutaneous wound healing, dermal-matrix remodeling (collagen, elastin, MMP endpoints), or general copper-delivery signaling in skin has the deepest existing literature to reference with GHK-Cu, including animal models and a recruiting Phase 2 wound trial.

A study specifically probing hair-follicle elongation or dermal papilla cell proliferation has a directly relevant reference point in AHK-Cu via the Pyo 2007 work, where an alanine-for-glycine substitution is the deliberate structural variable of interest. Researchers comparing the two side by side often use AHK-Cu precisely because it isolates the effect of the N-terminal residue against the well-characterized GHK-Cu baseline.

For either choice, confirm the exact identity of the supplied material against the batch COA before designing quantitative work, because the copper complex molecular weight depends on stoichiometry and salt form, and because GHK-Cu is marketed under two different CAS numbers (see FAQ). Storage and reconstitution should follow the Lyophilized Storage Guide and the Reconstitution Calculator, using the molecular weight confirmed on the COA.