GHK-Cu vs AHK-Cu
Research Comparison

Research Overview

GHK-Cu and AHK-Cu differ by one residue and by the size of their literatures. The GHK-Cu research peptide is the copper(II) complex of glycyl-L-histidyl-L-lysine (Gly-His-Lys), a tripeptide isolated from human plasma (Pickart et al., 1980; Maquart et al., 1988). The AHK-Cu research peptide is the copper(II) complex of L-alanyl-L-histidyl-L-lysine (Ala-His-Lys), a synthetic analog with alanine in place of the N-terminal glycine (Pyo et al., 2007; Mateescu et al., 2026).

Both start with the same copper-binding motif, so their chemistry should be close; their evidence is not. A PubMed search on 9 October 2026 for GHK, GHK-Cu and their chemical names returned close to 300 records from many groups. A matching search for AHK-Cu found one primary study, from one laboratory, plus reviews that mention it.

Structure and Class

Both are copper-binding tripeptides holding one Cu(II) ion. They share the central histidine and the C-terminal lysine and differ only at the first residue: glycine, whose side chain is a hydrogen, in GHK, and alanine, which carries a methyl group, in AHK. That adds one CH2 unit, about 14 g/mol: free GHK is C14H24N6O4, 340.38 g/mol (PubChem CID 73587), and free AHK is C15H26N6O4, 354.41 g/mol (CID 7408502). The pair is also written without hyphens, GHK Cu vs AHK Cu.

Peptides that begin NH2-Xxx-His hold Cu(II) with three peptide nitrogens plus an outside ligand, the 3N form; those that begin NH2-Xxx-Zzz-His, such as Asp-Ala-His-Lys at the N-terminus of human serum albumin, use four (Gonzalez et al., 2017). GHK is the canonical 3N peptide: in solution its copper is held by the N-terminal amine, one backbone amide nitrogen and the histidine imidazole, with a labile fourth position (Hureau et al., 2011). AHK begins NH2-Ala-His, the same pattern, and PubChem's AHK-Cu record (CID 168431292) names the same three donor nitrogens.

The listed complex weights are different species. The GHK-Cu product page lists C14H22CuN6O4, 401.91 g/mol; the AHK-Cu product page lists C15H24ClCuN6O4⁻, 451.39 g/mol, which PubChem names as a monohydrochloride complex. Of the 49.5 g/mol gap, about 14 is the extra CH2 and 35.45 is chlorine. By these weights, 1 mg holds about 2.49 µmol of GHK-Cu but 2.22 µmol of AHK-Cu, about 11 percent fewer moles.

Side by Side

Research Context: GHK-Cu

During its isolation from plasma, GHK co-purified with roughly equimolar copper. It readily formed copper(II) complexes and raised copper uptake into cultured hepatoma cells, and several tripeptides with a histidyl-lysyl linkage, unnamed in the abstract, were nearly as active (Pickart et al., 1980).

In fibroblast cultures, GHK-Cu stimulated collagen synthesis starting between 10⁻¹² and 10⁻¹¹ M and peaking at 10⁻⁹ M, independent of cell number (Maquart et al., 1988). In rat wound chambers it produced concentration-dependent increases in dry weight, DNA, protein, collagen and glycosaminoglycans, while a control tripeptide had no significant effect (Maquart et al., 1993).

No single group dominates: the most frequent author appears on 17 of the 287 records in that search. A 2026 evidence-mapping review uses GHK-Cu as the reference copper peptide, with the best-characterized coordination and broadest dataset, and finds its clinical evidence sparse (Mateescu et al., 2026).

Research Context: AHK-Cu

The one primary study came from a dermatology group at Seoul National University. Human hair follicles cultured ex vivo and cultured dermal papilla cells, the specialized fibroblasts of the follicle, were exposed to AHK-Cu at 10⁻¹² to 10⁻⁹ M, and the authors reported follicle elongation and papilla cell proliferation. At 10⁻⁹ M the Bcl-2/Bax ratio rose and cleaved caspase-3 and PARP fell, while the drop in apoptotic cells was not statistically significant (Pyo et al., 2007).

That is the whole primary record: we found no animal or human study, no replication and no AHK-Cu measurement of collagen, matrix or angiogenesis endpoints in PubMed. A 2026 review of short peptides in hair follicle research lists the AHK-Cu data as experimental ex vivo evidence whose mechanism is less well characterized than that of GHK-Cu (Fan et al., 2026), and the 2026 evidence map judges its evidence base thin and poorly characterized (Mateescu et al., 2026).

Whether the alanine swap changes activity is untested. An analog study of GHK concluded that copper complex formation driven by the first residue appeared necessary for growth-factor activity in cell culture, and that the free lysine side chain was of fundamental importance (Conato et al., 2001). AHK keeps the lysine and changes exactly that first residue.

Choosing Between Them for a Research Question

Pick by question first. Questions on copper coordination, copper uptake into cells, collagen synthesis in fibroblast culture or matrix accumulation in rat wound chambers have direct precedent with GHK-Cu, the one of the pair with a measured binding constant.

AHK-Cu fits two kinds of question. One is follow-up of the single-laboratory follicle and dermal papilla findings (Pyo et al., 2007). The other is structure-activity work: run beside GHK-Cu in one assay, it changes a single methyl group at the residue the analog study tied to complex formation (Conato et al., 2001).

Match moles, not milligrams, using each lot's measured content and named species. Add free GHK, free AHK and copper-salt arms, since the 2026 review argues for separating free peptide, intact complex and free copper before an effect is assigned (Mateescu et al., 2026), and confirm AHK copper loading in the study buffer. Both reported active ranges are picomolar to low nanomolar (Maquart et al., 1988; Pyo et al., 2007), but in different cells and endpoints, so they say nothing about relative potency.

Handling and Storage

Both product pages list the same storage: -20°C for the lyophilized powder as shipped and 2 to 8°C after reconstitution, protected from light, with freeze/thaw cycles avoided. Let the sealed vial reach room temperature before opening so moisture does not condense on the cake, add diluent slowly down the vial wall, and swirl rather than shake.

Measured stability data exist only for GHK-Cu: it stayed stable in water and pH 4.5 to 7.4 buffers for at least two weeks at 60°C, while basic and oxidative stress drove hydrolytic cleavage (Badenhorst et al., 2016). Cu(II)GHK also exchanges copper quickly and forms ternary complexes with glycine or histidine (Hureau et al., 2011), so chelators such as EDTA and amino-acid buffers can change what is in solution. AHK-Cu has no stability study in PubMed; the same conditions are a reasonable default for it.

For both, split stock into single-use aliquots, record the lot number, and calculate molarity from the certificate in the COA portal. The copper peptides overview covers reductants and color checks.

Questions Researchers Ask

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

One residue and a large evidence gap. AHK-Cu has alanine where GHK-Cu has glycine; both keep the His-Lys pair that anchors the copper. GHK was isolated from human plasma (Pickart et al., 1980; Maquart et al., 1988) and appears in close to 300 PubMed records; AHK-Cu is synthetic, with one primary study (Pyo et al., 2007). The GHK-Cu research guide and the AHK-Cu research guide cover each.

AHK-Cu vs GHK-Cu: do they bind copper the same way?

By sequence they should, but only GHK has been measured: calorimetry gave a conditional dissociation constant of about 7.0 × 10⁻¹⁴ M at pH 7.4 (Trapaidze et al., 2012). We found no structure or binding constant for copper-bound AHK in PubMed.

Has GHK-Cu or AHK-Cu been studied in animals or people?

GHK-Cu has rodent work, such as the rat wound-chamber study (Maquart et al., 1993), and a 2026 review calls its clinical evidence sparse (Mateescu et al., 2026). For AHK-Cu we found no animal or human study in PubMed; its data come from follicles ex vivo and cultured cells (Pyo et al., 2007).

Is GHK-Cu or AHK-Cu FDA approved?

No. Drugs@FDA lists no product containing either (openFDA search, October 2026). An FDA page on bulk drug substances for compounding that may present significant safety risks, current as of April 2026, lists GHK-Cu for injectable routes among former category 2 substances whose nominations were withdrawn, citing possible immunogenicity and limited human data. AHK-Cu is not on that page.

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