GHK-Cu Copper Peptide: Coordination Chemistry and Extracellular Matrix Research

GHK is a linear tripeptide, Gly-His-Lys, with the sequence written H-Gly-His-Lys-OH. It occurs naturally in plasma, saliva and urine. In solution GHK forms a stable complex with Cu(II), and the research material is supplied as this preformed copper complex, typically as a blue lyophilized powder.

Early work proposed that the plasma tripeptide enhanced cellular copper uptake, which framed GHK as a copper-carrying peptide rather than a classical receptor ligand. That framing still shapes how GHK-Cu is studied: as a metal complex whose activity depends on its coordination chemistry and on copper delivery to cells.

X-ray crystallography, EPR spectroscopy, X-ray absorption spectroscopy and proton magnetic resonance have been used to define how GHK binds copper. In the 1:1 complex, Cu(II) is coordinated by three nitrogen donors from the peptide:

• the α-amino nitrogen of glycine,
• the deprotonated amide nitrogen of the Gly–His peptide bond, and
• the imidazole nitrogen of histidine.

The remaining coordination positions are filled by other ligands, such as a carboxylate from a neighboring GHK molecule in the solid state, or water and other donors in solution. At physiological pH, GHK can also form ternary complexes, for example with free histidine or with the copper-binding site of serum albumin.

Because its copper affinity is close to that of albumin, GHK can compete for Cu(II) in plasma-like conditions. Coordination by GHK also suppresses the redox activity of the bound copper, limiting copper-catalyzed formation of reactive oxygen species in solution, a property relevant to how the complex is handled in cell culture.

The best-known body of GHK-Cu work comes from cultured dermal fibroblasts. Studies by Maquart, Wegrowski, Siméon and colleagues reported that adding the copper complex to fibroblast cultures increased the synthesis of collagen and of sulfated glycosaminoglycans, with activity observed at low nanomolar concentrations (roughly 1–10 nM).

Those experiments typically measured incorporation of radiolabelled proline or sulfate into newly synthesized matrix molecules, alongside quantification of specific proteoglycans such as decorin, dermatan sulfate and chondroitin sulfate. McCormack and colleagues later reported that GHK-Cu increased growth factor release from fibroblasts maintained in serum-free culture.

ECM turnover depends on the balance between matrix metalloproteinases (MMPs), which degrade matrix proteins, and tissue inhibitors of metalloproteinases (TIMPs). Siméon and colleagues reported that GHK-Cu increased MMP-2 expression in fibroblast cultures while also affecting TIMP levels, which led to the description of GHK-Cu as a modulator of both matrix synthesis and matrix breakdown rather than a one-directional stimulator.

Common readouts in this research area include zymography for MMP activity, ELISA or western blot for TIMP-1 and TIMP-2, and qPCR for MMP and collagen transcripts.

GHK has been examined with genome-wide expression tools. Using the Broad Institute Connectivity Map, investigators identified GHK as a compound whose expression signature runs opposite to particular tissue-remodeling signatures, and reported that it altered the expression of a large number of genes (on the order of thousands) in cultured human cell lines.

Campbell and colleagues (2012) followed up in cultured lung fibroblasts and reported that GHK increased collagen gel contraction and integrin β1 expression and engaged TGF-β pathway gene expression. Gruchlik and colleagues measured cytokine output and reported lower IL-6 secretion after TNF-α stimulation in cultures exposed to GHK or GHK-Cu. These studies are used as starting points for mechanistic work on how a small copper peptide can influence matrix-related transcription.

Short peptides are rapidly degraded by proteases, which complicates long incubations in protease-rich media. Researchers have described mixed copper peptide complexes, in which Cu(II) is bound by GHK together with other peptide fragments, and reported greater resistance to proteolytic breakdown than GHK-Cu alone. For in vitro work, stability of the complex in the chosen medium is worth verifying by HPLC or LC-MS over the incubation period.

A research lot of GHK-Cu is documented with:

• HPLC purity, reported as percent peak area of the main component.
• Mass spectrometry to confirm identity. The copper complex (CAS 89030-95-5) has the formula C₁₄H₂₂CuN₆O₄ and a molecular weight of 401.9 g/mol; the free GHK peptide is C₁₄H₂₄N₆O₄ (340.4 g/mol).
• Appearance of the lyophilized cake or powder; the copper complex is characteristically blue.
• Lot number and analysis date, so results can be traced to a specific batch.

NuRev publishes lot documentation on its Certificates of Analysis page; GHK-Cu is listed as GHK-Cu 100mg.

Keep lyophilized GHK-Cu sealed, dry and cold, protected from light. Allow the vial to reach room temperature before opening to avoid moisture condensation. Once dissolved for an experiment, aliquot and freeze to limit repeated freeze–thaw, and avoid strongly chelating buffers or reducing agents that would compete for or reduce the bound Cu(II) unless that is part of the experimental design.

NuRev supplies GHK-Cu for laboratory research use only; it is not for human or veterinary use.