GHK-Cu

GHK-Cu is a copper-binding tripeptide complex: the sequence glycyl-L-histidyl-L-lysine (GHK) coordinated to a copper(II) ion. Unlike most research peptides, which are studied as the peptide alone, GHK is studied as a metal complex — the imidazole nitrogen of the histidine residue, the terminal amine of the glycine, and the intervening amide nitrogen together form the coordination site that holds Cu(II). That geometry is the compound; the free peptide and the copper-loaded complex are treated as distinct species in the literature and are not interchangeable in an experimental design.

The tripeptide was first isolated from human plasma fractions in the 1970s during work on factors that differed between plasma from younger and older donors, and the copper-binding behaviour was characterised shortly afterwards. That origin — an endogenous sequence identified by fractionation rather than a designed analogue — is why GHK-Cu is usually described in reviews as a naturally occurring copper carrier rather than as a synthetic mimetic, and why much of the primary literature concerns copper coordination chemistry as much as peptide biology.

Research interest centres on copper-transport and copper-handling pathways, and on extracellular-matrix biology. GHK-Cu appears in in-vitro studies examining copper exchange with albumin and other plasma copper-binding proteins, in fibroblast culture models where matrix protein and matrix-metalloproteinase gene expression are read out, and in transcriptomic screens that profile broad expression changes in cultured cells. Reported observations in these areas belong to the primary studies that generated them; they are not use, safety, or outcome claims made by Gals.

Analytical characterisation matters in a specific way for a metal complex. HPLC establishes peptide purity and the absence of related sequence impurities, while identity confirmation by mass spectrometry reflects the copper-bound species, whose isotope pattern differs from the free peptide because of the natural 63Cu/65Cu distribution. Copper stoichiometry and residual free copper are the variables most likely to confound a matrix-signalling experiment, so batch-level characterisation data — rather than nominal labelling — is the reasonable basis for evaluating material intended for reproducible work.

Within the copper-peptide class, GHK-Cu is the reference point against which other copper-coordinating sequences are compared, and it is the compound most often used to define what a "copper peptide" means in a methods section. It sits apart from the synthetic sequences elsewhere in this catalogue: it is a three-residue endogenous fragment rather than an engineered analogue such as melanotan 2, and its research questions are coordination-chemistry and matrix questions rather than receptor-agonism questions.