AHK-Cu (Copper Tripeptide-3) vs GHK-Cu (Copper Tripeptide-1)

AHK-Cu (Copper Tripeptide-3)

AHK-Cu is a copper(II) complex of the synthetic tripeptide alanyl-histidyl-lysine, a close relative of the naturally occurring GHK-Cu. The two differ only in the first residue: alanine here, glycine in GHK. GHK is found in human plasma and has a long history in the literature as a copper-binding peptide; AHK is a synthetic variant with the histidine in the same position. Published work on AHK-Cu is small and mostly in vitro, using cultured human dermal papilla cells and fibroblasts, and isolated hair follicles kept alive in organ culture. Controlled human studies are scarce, and much of the wider discussion of the compound borrows from GHK-Cu rather than from data on AHK-Cu itself.

GHK-Cu (Copper Tripeptide-1)

GHK-Cu is the copper(II) complex of glycyl-L-histidyl-L-lysine, a tripeptide first isolated from human plasma. The free peptide binds copper with high affinity, and the complex is also known by the ingredient name copper tripeptide-1. Published work falls into three groups: cell-culture studies with fibroblasts and other skin-derived cells, wound and tissue models in animals, and a smaller number of studies of topical preparations in human volunteers. The human studies are mostly small and come from cosmetic research rather than controlled clinical trials. Reports that it alters the expression of large numbers of genes rest largely on reanalysis of gene-expression data from cultured cell lines, which shows association rather than a demonstrated effect in tissue.

How AHK-Cu (Copper Tripeptide-3) acts

In GHK-Cu, the copper ion is held by the N-terminal amine, the deprotonated amide nitrogen between the first two residues and a nitrogen of the histidine imidazole ring. AHK is thought to bind copper in the same way, since its histidine sits in the same position. Copper-peptide complexes of this kind have been studied as carriers that deliver copper, a cofactor for enzymes such as lysyl oxidase and superoxide dismutase, to cells. In cultured human dermal papilla cells, AHK-Cu has been reported to affect cell proliferation and markers of apoptosis, including the balance of Bcl-2 and Bax. Which receptors or transporters mediate these observations has not been established.

How GHK-Cu (Copper Tripeptide-1) acts

GHK holds copper(II) through the amino nitrogen of glycine, a deprotonated backbone nitrogen and the imidazole ring of histidine, giving a complex that is stable at neutral pH. One proposed role is as a carrier that moves copper between plasma proteins and cells. Copper is a cofactor for lysyl oxidase, the enzyme that cross-links collagen and elastin, and fibroblast culture studies have reported changes in collagen and glycosaminoglycan synthesis on exposure to the complex. Animal wound studies have also looked at blood-vessel formation and inflammatory markers. How much of the reported activity belongs to the peptide and how much to the copper it carries has not been settled.

The records side by side

• Type: AHK-Cu (Copper Tripeptide-3), Copper tripeptide complex; GHK-Cu (Copper Tripeptide-1), Copper tripeptide complex
• Length: AHK-Cu (Copper Tripeptide-3), 3 amino acids; GHK-Cu (Copper Tripeptide-1), 3 amino acids
• Molecular weight: AHK-Cu (Copper Tripeptide-3), 451.39 g/mol; GHK-Cu (Copper Tripeptide-1), 400.90 g/mol
• Molecular formula: AHK-Cu (Copper Tripeptide-3), C15H24ClCuN6O4-; GHK-Cu (Copper Tripeptide-1), C14H21CuN6O4-

Reading a comparison

A comparison places two records side by side; it does not merge them. Each description above is drawn from that compound's own record, and the two were not necessarily characterised by the same methods, at the same time, or to the same level of detail. Before comparing any attribute, it is worth establishing that both records describe the substance you think they describe — names are not identifiers, and two entries sharing a name can differ in salt form, stereochemistry or the convention used to state a mass. Where a figure carries no method beside it, the comparison is between two reported numbers rather than between two measurements.