GHK-Cu Copper Peptide: Structure and Research

Copper peptides are short peptides that bind a copper(II) ion tightly enough to exist as a defined complex, and GHK-Cu is the best-characterized of them. It is the copper complex of the tripeptide glycyl-L-histidyl-L-lysine (Gly-His-Lys), a molecule first isolated from human plasma by Loren Pickart and Martin Thaler in 1973. The peptide holds copper through three nitrogen atoms, with a conditional dissociation constant near 10⁻¹⁴ M at pH 7.4, which is why it is studied as a model copper carrier as much as a signaling molecule.

This profile covers the chemistry first: identifiers, the coordination geometry, and how the complex behaves in solution. It then turns to the history of the molecule, the systems it has been studied in, its regulatory position in the United States, and the practical points that matter when it arrives in a lab as a blue lyophilized powder.

What "copper peptide" means

The term is used loosely in commerce, but chemically it refers to a peptide whose side chains and backbone form a stable coordination complex with Cu²⁺. Not every peptide does this. Copper(II) prefers nitrogen donors arranged in a square plane, and a small number of short sequences present those donors in exactly the right positions.

Two such motifs occur naturally in human blood:

• The Xaa-His motif, where histidine sits at position 2. GHK is the example. The free N-terminal amine, the backbone amide nitrogen between residues 1 and 2, and the histidine imidazole together form a three-nitrogen binding site.
• The ATCUN motif (amino-terminal copper and nickel binding), where histidine sits at position 3. The N-terminus of human serum albumin, Asp-Ala-His-Lys (DAHK), is the classic case, and it binds copper through four nitrogens.

Most synthetic copper peptides sold as cosmetic ingredients or research reagents are variations on the first motif. AHK-Cu, for instance, swaps the glycine of GHK for alanine but keeps histidine at position 2, so it presents the same kind of binding site. The differences between the two are covered in detail in the comparison post on GHK-Cu and AHK-Cu.

Identity at a glance

PubChem holds separate records for the free tripeptide and for its copper complexes, which is worth knowing before comparing a certificate of analysis with a database entry. The table below lists both.

Two cautions apply. First, PubChem also lists a 2:1 complex, bis-prezatide copper (CID 9831891, C28H46CuN12O8), in which one copper ion is shared by two peptide molecules. That species is real in solution when the peptide is in excess, so it is not a database error. Second, commercial GHK-Cu is often supplied as a salt, commonly an acetate, and the counter-ion changes the formula weight. The certificate of analysis for a given lot should state which form is in the vial.

How GHK binds copper

The coordination chemistry has been worked out by X-ray crystallography and a range of spectroscopies. In their 2011 study, Hureau and colleagues confirmed that in solution the Cu(II)-GHK complex is monomeric and that copper is held by three nitrogen ligands: the N-terminal amine of glycine, the deprotonated amide nitrogen of the Gly-His peptide bond, and a nitrogen of the histidine imidazole ring. The fourth equatorial position is not fixed by the peptide. In the crystal it is filled by a carboxylate oxygen from a neighboring molecule, and in solution it is open to water or to another ligand, such as a second GHK molecule, glycine or histidine.

That open fourth site explains two practical observations. GHK-Cu exchanges copper quickly with other ligands, unlike the albumin-type DAHK complex, whose copper exchange is very slow. And the complex can hand copper to another binder, which is the basis of the long-standing hypothesis that GHK acts as a copper transporter.

Affinity has been measured directly. Trapaidze and colleagues used isothermal titration calorimetry with glycine as a competing ligand and reported a conditional dissociation constant of 7.0 × 10⁻¹⁴ M for Cu(II)-GHK at pH 7.4, against 2.6 × 10⁻¹⁴ M for DAHK. In other words, the tripeptide binds copper almost as tightly as the albumin N-terminus does, despite using one fewer nitrogen.

Redox behavior matters for anyone using the complex in cell culture. Hureau's group found both complexes inert under moderate redox potentials, so neither shuttles readily between Cu(II) and Cu(I) in ordinary conditions. Cu(II)-GHK could be reduced only at around −0.62 V versus Ag/AgCl, and reduction released the copper ion. The practical reading is that GHK-Cu is not a free-copper source under normal buffer conditions, but strong reductants will change that.

The complex is also useful outside biology. A 2020 paper by Mehr and colleagues fused GHK to the N-terminus of test proteins and used the bound copper as a crystallization aid and as an anomalous scatterer for phasing X-ray data, which is a neat demonstration of how well defined the binding site is.

Discovery in human plasma

GHK was isolated from human plasma by Pickart and Thaler, who reported in 1973 a tripeptide in human serum that prolonged the survival of normal liver cells and stimulated the growth of hepatoma cells in culture. The work came out of Pickart's doctoral research at the University of California, San Francisco. The starting observation, as later summarized by Pickart and Margolina, was that plasma from younger donors changed the protein synthesis pattern of liver tissue from older donors.

A 1980 paper by the same pair connected the peptide to metals. They reported that GHK is complexed with copper and iron in plasma, that at physiological pH it associates with copper, cobalt, iron, nickel, zinc and several other transition metals, and that it has no affinity for calcium, potassium or sodium. In hepatoma cultures, GHK acted together with copper or iron at nanomolar concentrations, and those two metals were the most active partners.

Pickart and Margolina's 2018 review gives the plasma level of GHK as about 200 ng/mL (roughly 10⁻⁷ M) at age 20, falling to about 80 ng/mL by age 60. That age-related decline is a descriptive observation from human plasma samples. It is not evidence about what adding the peptide does.

Research models and published work

Most of the literature on GHK-Cu comes from a relatively small group of laboratories, and much of it was reviewed by Pickart and colleagues between 2012 and 2018. The experimental systems fall into four groups:

• Cell culture. Fibroblasts, keratinocytes, hepatoma lines and neuroblastoma cells have been used to study effects on proliferation, gene expression and extracellular matrix synthesis.
• Animal models. Rats, mice, rabbits and pigs appear in the wound and tissue-remodeling models summarized in the reviews.
• Gene-expression data mining. The 2018 review draws on the Broad Institute's Connectivity Map, a database of expression profiles from cultured human cell lines exposed to small molecules. Pickart and Margolina report that GHK changed the expression of a large share of the genes profiled, by 50 percent or more. Connectivity Map data describe transcript changes in cell lines, not effects in a whole organism.
• Metal-transport chemistry. Electron spin resonance studies from the late 1980s examined how copper moves between GHK, histidine and cultured tumor cells, consistent with the copper-shuttle idea above.

Two limits deserve plain statement. Controlled studies in people are few and small, and the gene-expression work establishes association with transcript changes, not mechanism. When a claim about GHK-Cu reaches beyond cell and animal models, it is worth checking which of these categories it actually rests on.

Regulatory position

GHK-Cu is not the active ingredient of any drug approved by the FDA. In cosmetics, the European Commission's CosIng inventory lists Copper Tripeptide-1, described as a copper complex of Tripeptide-1, with the function recorded as skin conditioning. That listing is an ingredient-nomenclature entry, not an evaluation of any effect.

For compounding in the United States, FDA's page on bulk drug substances that may present significant safety risks (last updated April 22, 2026) lists GHK-Cu among 503B nominations that were later withdrawn by their nominators. FDA's note on that entry says compounded injectable drugs containing GHK-Cu may pose a risk of immunogenicity because of possible aggregation and peptide-related impurities, and that human data are limited. For the research laboratory, the relevant point is simpler: GHK-Cu is supplied as a chemical reagent for in-vitro and laboratory research, and Anhydrolabs supplies it on that basis.

Handling GHK-Cu in the lab

The copper complex behaves differently from a colorless peptide, and a few points follow from the chemistry above.

• Color is expected. Cu(II)-peptide complexes absorb in the visible range, so the lyophilized powder and its solutions are blue to violet. A shift to green or a cloudy solution is worth recording and checking against the certificate.
• Solvent. GHK-Cu dissolves readily in water. For in-vitro stock solutions, sterile water or a simple buffer is the usual starting point; the general procedure is in the guide on how to reconstitute peptides.
• Watch the buffer. Because the fourth coordination site is labile, strong chelators such as EDTA or high concentrations of free amino acids like histidine compete for the copper. Strong reducing agents can reduce Cu(II) to Cu(I) and release it. Neither is a reason to avoid common media, but both should be noted when designing controls, including a free-peptide and a copper-salt control.
• Storage. Keep the lyophilized powder sealed, cold, dry and away from light, and let the vial reach room temperature before opening. Once dissolved, divide the stock into single-use aliquots and freeze them. The site's storage and handling page and the post on how to store peptides cover temperatures and freeze-thaw in more detail.
• Identity and purity. Mass spectrometry of a copper complex can show both the free peptide and the copper-bound ion, and HPLC purity is normally reported for the peptide component. The post on peptide purity explains how that number is derived.

Anhydrolabs supplies GHK-Cu as a lyophilized powder in vacuum-sealed vials, with each lot's certificate on the product page, and also as 10-vial kits. The related copper tripeptide AHK-Cu is listed separately, as are the multi-peptide GLOW and KLOW blends, whose composition is stated on their own product pages. For a refresher on how three residues and two peptide bonds make up a molecule like this, see what peptides are.