GHK-Cu vs AHK-Cu: Copper Peptides Compared

GHK-Cu and AHK-Cu are both tripeptide-copper complexes, and they differ by a single amino acid. GHK-Cu is glycyl-histidyl-lysine bound to copper(II); AHK-Cu replaces the glycine with alanine. GHK occurs naturally in human plasma and has a literature going back to the 1970s [1]. AHK is a synthetic analog studied in a much smaller body of work, chiefly on hair follicle cells in culture [2].

How do the two structures differ?

The only change is at the first position. Glycine has a hydrogen as its side chain; alanine has a methyl group. That adds one carbon and two hydrogens to the peptide: GHK has an average molecular weight of about 340.4 Da and AHK about 354.4 Da. In both, copper is held mainly by the histidine imidazole, the N-terminal amine and adjacent backbone nitrogen atoms.

Why do copper-complex formulas differ between catalogs?

When copper binds, the peptide gives up protons, and different sources count those protons differently. That is why one catalog lists AHK-Cu as C15H24CuN6O4 at about 415.9 Da and another lists a hydrochloride salt with a different formula and a different CAS number. The same applies to GHK-Cu. When comparing listings, the peptide sequence and the presence of copper are the stable facts; the exact formula weight depends on the form described.

What has each been studied for?

GHK-Cu has been studied in cell culture and animal models of skin and connective tissue, and in gene-expression analyses summarized in review articles [1]. AHK-Cu has been studied mainly for effects on dermal papilla cells and hair follicles in vitro [2]. Neither body of work describes a use in humans, and results from one compound should not be assumed for the other.

How are they identified in the laboratory?

Mass spectrometry of copper complexes often shows both the free peptide and the copper-bound species, so a report may list either mass. Color is a quick visual cue: copper peptides are typically supplied as blue to violet powders, while the copper-free peptides are white.

Frequently asked questions

Is AHK-Cu the same as copper tripeptide-3?

Yes. Copper tripeptide-3 is a common name for AHK-Cu. GHK-Cu is often called copper tripeptide-1.

Does FLASK list both?

FLASK lists GHK-Cu (50 mg) and AHK-Cu (100 mg) as separate materials, each with its formula and CAS number on the product page.