glycyl-L-histidyl-L-lysine
tripeptide-1, GHK, Gly-His-Lys, prezatide (as the copper complex, prezatide copper acetate)
Tripeptide-1 is the INCI name for copper-free glycyl-histidyl-lysine, the tripeptide that becomes copper tripeptide-1 or GHK-Cu when complexed with copper(II). It occurs naturally in human plasma and is found within collagen and SPARC sequences. Almost every reported biological effect of this molecule was measured with copper attached, which makes the copper-free ingredient a weaker proposition than its reputation suggests.
Mechanism
GHK is a physiological copper carrier. Lau and Sarkar showed in 1981 that it binds copper(II) with high affinity and can exchange copper with albumin, and Freedman and colleagues resolved the square-planar co-ordination geometry of the complex the following year. That chemistry is the foundation of everything else: the imidazole nitrogen of histidine, the alpha-amino group of glycine and the deprotonated peptide nitrogen together form a tight, biologically exchangeable copper-binding site. Copper is an obligatory cofactor for lysyl oxidase, the enzyme that cross-links collagen and elastin, and for superoxide dismutase, so a peptide that delivers copper into tissue has a plausible route to influencing matrix maturation and redox status without needing a dedicated receptor.
In fibroblast culture the copper complex increases synthesis of sulfated glycosaminoglycans, raises matrix metalloproteinase-2 expression, and alters cytokine output. Gruchlik and colleagues compared GHK, the related tripeptide GGH, and their copper complexes on TNF-alpha-dependent interleukin-6 secretion and found the free peptides and copper complexes behaved differently. That last point is the crux for anyone reading a cosmetic label. Tripeptide-1 as supplied is the copper-free peptide. In a finished formulation it may chelate copper already present, or it may not; its behaviour depends on formulation pH, on competing chelators such as EDTA, and on whether any copper is available. The published bioactivity data cannot simply be transferred from GHK-Cu to tripeptide-1, and no study has established equivalence between them.
What the research shows
The chemistry is settled. Lau and Sarkar characterised the copper(II)-GHK interaction and its relationship to albumin in the Biochemical Journal in 1981; Freedman and colleagues determined the complex's solution structure by EPR and ENDOR spectroscopy in 1982. This work is old, independent and uncontested, and it is why GHK is described as a physiological copper transport peptide.
The biology is real but almost always copper-dependent. Wegrowski and colleagues reported that GHK-Cu stimulated sulfated glycosaminoglycan synthesis in fibroblasts. Siméon and colleagues found that GHK-Cu upregulated matrix metalloproteinase-2, which argues the peptide promotes matrix turnover rather than pure accumulation, a nuance cosmetic marketing generally omits. Gruchlik and colleagues directly compared free tripeptides with their copper complexes on TNF-alpha-dependent fibroblast interleukin-6 secretion and found the two forms are not interchangeable. Pickart's reviews assemble a much wider range of claimed transcriptomic and regenerative effects; these should be read as a bibliography rather than as an independent evidence assessment, since the author has been the principal advocate of the molecule for five decades. GHK also appears as a scaffold in Park and colleagues' D-tyrosine work, where it is described as an anti-inflammatory peptide.
What is conspicuously absent is human trial data. PubMed returns reviews, animal models and mechanistic cell work, but no randomised controlled trial of topical GHK or GHK-Cu with objective wrinkle, elasticity or barrier endpoints. The frequently cited facial-cream studies from the early 2000s were conference abstracts and industry reports, not indexed peer-reviewed trials.
Evidence assessment
Preclinical only
There is no published randomised controlled trial of topical copper-free GHK and no controlled human study of tripeptide-1 as a single agent. The in vitro literature is genuine but nearly all of it uses the copper complex; the copper-free peptide is typically the weaker comparator rather than the compound of interest. Much of the enthusiastic review literature comes from a single long-standing proponent rather than from independent systematic assessment. Solid co-ordination chemistry and real cell-culture data for a related complex, with no clinical evidence for the ingredient itself, is a preclinical picture.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
The interaction of copper(II) and glycyl-L-histidyl-L-lysine, a growth-modulating tripeptide from plasma Preclinical only
Defined the copper(II)-GHK binding equilibrium and its relationship to albumin, establishing GHK as a physiological copper transport peptide.
Structure of the Glycyl-L-histidyl-L-lysine--copper(II) complex in solution Preclinical only
Resolved the square-planar copper co-ordination geometry, the structural basis for GHK's copper-carrier function.
Stimulation of sulfated glycosaminoglycan synthesis by the tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+ Preclinical only
The copper complex increased sulfated glycosaminoglycan synthesis, a core finding behind matrix-support claims.
The tripeptide-copper complex glycyl-L-histidyl-L-lysine-Cu2+ stimulates matrix metalloproteinase-2 expression by fibroblast cultures Preclinical only
GHK-Cu upregulated MMP-2, indicating the peptide drives matrix remodelling with both synthetic and degradative arms.
Effect of Gly-Gly-His, Gly-His-Lys and their copper complexes on TNF-alpha-dependent IL-6 secretion in normal human dermal fibroblasts Preclinical only
Compared free tripeptides with their copper complexes on TNF-alpha-dependent interleukin-6 secretion and found the two forms behave differently, showing that copper-free and copper-complexed GHK are not pharmacologically interchangeable.
Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data Preclinical only
Collates reported gene-expression and tissue-remodelling actions of GHK-Cu; an index of the literature rather than an independent assessment, authored by the molecule's principal proponent.
D-tyrosine adds an anti-melanogenic effect to cosmetic peptides Preclinical only
Adding D-tyrosine to GHK conferred anti-melanogenic activity without altering the peptide's intrinsic effects, in which GHK is characterised as an anti-inflammatory cosmetic peptide.
Safety
No safety signal has been reported for topical use of GHK or its copper complex at cosmetic concentrations. GHK is an endogenous plasma constituent, so systemic novelty is not the concern. Two practical points are worth noting. Copper-containing peptide products can stain fabric and, at higher concentrations, impart a blue-green tint to the skin; this is cosmetic rather than toxicological. Formulation incompatibility is a genuine and under-discussed issue: strong chelators, high concentrations of ascorbic acid and certain acids can compete for or reduce copper and change what the peptide is doing, and there are no published stability or compatibility data covering common regimen combinations. There are no reproductive, developmental, pregnancy or lactation data. This is a topical cosmetic ingredient; injectable GHK preparations sold through research-chemical channels have no safety evaluation, no pharmacopoeial standard and no legitimate clinical basis.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | Permitted as a cosmetic ingredient under the UK Cosmetics Regulation (retained Regulation (EC) No 1223/2009); not listed in any prohibited or restricted annex. Requires a Cosmetic Product Safety Report and responsible person. No MHRA medicines authorisation, and no licensed injectable preparation exists in the UK. |
| United States | Not an FDA-approved drug and not covered by an OTC drug monograph; marketed as a cosmetic ingredient under the FD&C Act as amended by the Modernization of Cosmetics Regulation Act 2022. The copper complex was investigated as a wound-healing drug candidate under the generic name prezatide copper acetate but never obtained marketing authorisation. |
| WADA (sport) | Not named on the WADA Prohibited List. Topical cosmetic use raises no anti-doping issue. |
Questions
No. Tripeptide-1 is the copper-free tripeptide glycyl-histidyl-lysine. Copper tripeptide-1, usually written GHK-Cu, is its copper(II) complex. Nearly all the published bioactivity data were generated with copper attached, and at least one study comparing the free peptides with their copper complexes found the two forms behave differently, so the data do not transfer automatically.
Not in the indexed literature. PubMed returns mechanistic cell work, animal models and reviews, but no randomised controlled trial of topical GHK or GHK-Cu with objective wrinkle, elasticity or barrier endpoints. The facial-cream results often cited were conference abstracts and industry reports.
Because copper is the point. GHK's defining property is high-affinity, exchangeable copper(II) binding, and copper is an obligatory cofactor for lysyl oxidase, which cross-links collagen and elastin, and for superoxide dismutase. A copper-free peptide in a formulation may or may not acquire copper depending on pH, available copper and competing chelators such as EDTA, none of which is disclosed on a label.
There is no licensed injectable GHK preparation in the UK or the US. The copper complex was investigated as a wound-healing drug candidate under the generic name prezatide copper acetate and never obtained marketing authorisation. Material sold through research-chemical channels has no pharmacopoeial standard, no sterility assurance and no safety evaluation.