reviewed april 2026|next review october 2026|88 physicians psi has verified|150717 published studies
Palmitoyl Tripeptide-5
Tripeptide-1 is the unmodified GHK tripeptide sequence (glycyl-histidyl-lysine) without copper binding or palmitoylation, the base signal peptide from which both GHK-Cu and palmitoyl tripeptide-1 are derived.
Evidence landscape: 150717 published studies
150,717 published items (very broad query). 5 human studies and 123 animal studies.
- 5 Human
- 123 Animal
- 72 Reviews
- 150517 Other research
Tripeptide-1 is the International Nomenclature of Cosmetic Ingredients (INCI) name for the GHK sequence. Same three amino acids (Gly-His-Lys), different naming convention.
The unmodified GHK tripeptide without copper binding (GHK-Cu) or fatty acid conjugation (palmitoyl tripeptide-1). Retains matrikine signaling but lacks the copper delivery and lipid penetration mechanisms.
The published research overwhelmingly involves the copper-bound form (GHK-Cu, 186 studies). Clinical data specific to the unmodified, copper-free tripeptide is minimal.
PSI Assessment
Tripeptide-1 is the INCI cosmetic name for the GHK sequence, the same three amino acids that form the backbone of GHK-Cu. Without copper, the peptide retains matrikine signaling activity but loses the copper delivery mechanism that drives much of GHK-Cu's documented effects across 4,000+ genes. Without palmitoylation, it also lacks the enhanced skin penetration of palmitoyl tripeptide-1. The research literature is dominated by the copper-bound form. Clinical data specific to the unmodified tripeptide is minimal.
Same three amino acids as GHK-Cu. Without copper, purely a signal peptide. Without palmitoylation, limited skin penetration.
Tripeptide-1 is the INCI (International Nomenclature of Cosmetic Ingredients) name for GHK (glycyl-histidyl-lysine), the base tripeptide sequence first identified by Pickart in 1973 as a factor in human plasma that stimulated liver cell growth. Without copper, GHK functions purely as a matrikine signal peptide, mimicking collagen breakdown fragments to stimulate fibroblast activity. Without palmitoylation, it has limited ability to penetrate the stratum corneum for topical applications. The published research overwhelmingly involves the copper-bound form (GHK-Cu). Whether the unmodified sequence retains meaningful biological activity without copper in vivo remains an open question.
What the evidence supports
The GHK tripeptide sequence retains matrikine signaling activity independent of copper binding. GHK mimics collagen breakdown fragments and stimulates fibroblast migration in cell culture. The sequence was originally identified by Pickart (1973) in human plasma.
What is not yet established
Whether GHK without copper delivers meaningful biological effects independent of copper delivery in vivo. The published research overwhelmingly involves the copper-bound form (GHK-Cu). Whether the unmodified tripeptide penetrates skin adequately for topical cosmetic use. Clinical efficacy data specific to the unmodified peptide.
Research Evidence
The findings below cover the GHK identity, the copper-independent activity question, and the evidence inheritance from GHK-Cu.
Evidence by condition
Evidence dimensions for tripeptide-1. All evidence is inherited from GHK-Cu research. Dedicated studies for the copper-free form are minimal.
| Condition | Mechanism | Animal evidence | Human evidence | Replication |
|---|---|---|---|---|
| Collagen Stimulation | ||||
| Skin Signal Peptide |
GHK was first identified by Pickart in 1973 as a growth factor in human plasma. The tripeptide is naturally (the body's own) released during collagen degradation and functions as a matrikine signal.
The discovery established GHK as a biologically active signal peptide. Subsequent research focused overwhelmingly on the copper-bound form.
Cell culture studies show GHK retains some biological activity independent of copper binding, including stimulation of fibroblast migration and collagen synthesis signaling.
Whether copper-independent activity translates to meaningful effects in vivo is not established. The relative contribution of matrikine signaling versus copper delivery to GHK-Cu's documented effects is not quantified.
The published research base is dominated by GHK-Cu (186 studies). Clinical data specific to the unmodified, copper-free GHK tripeptide is minimal.
Tripeptide-1 in cosmetic products inherits its scientific reputation from GHK-Cu research. Whether the copper-free form delivers equivalent or meaningful effects is not supported by dedicated evidence.
5 Human|123 Animal|72 Reviews
View all 150717 indexed studiesHow Palmitoyl Tripeptide-5 Works
Tripeptide-1 (GHK) is the unmodified glycyl-histidyl-lysine sequence that functions as a matrikine signal peptide, mimicking collagen breakdown fragments to stimulate fibroblast activity without the copper delivery mechanism of GHK-Cu.
Signals skin to produce more collagen. Same molecule as GHK.
For a more detailed view of the biology, here is what researchers have observed at the molecular level.
Gly-His-Lys tripeptide. Same as GHK. INCI name for cosmetic formulations.
What is Palmitoyl Tripeptide-5 being studied for?
Researchers are studying Palmitoyl Tripeptide-5 across several health conditions. Each condition below is labeled with the strength of evidence that exists for that specific use, not for Palmitoyl Tripeptide-5 overall. This means a compound can have human studies for one condition but only animal data for another.
Collagen Stimulation
·Animal StudiesThe GHK sequence stimulates collagen production in fibroblast cultures through matrikine signaling. The mechanism is established for the GHK backbone regardless of copper binding status.
Limitations: Whether the copper-free form produces clinically meaningful collagen stimulation in vivo is not established. The published evidence base is overwhelmingly for GHK-Cu.
Skin Signal Peptide
·PreclinicalGHK is naturally (the body's own) released during collagen degradation. The matrikine signaling function is characterized at the molecular level.
Limitations: No dedicated clinical studies for the copper-free form. Without palmitoylation, skin penetration is limited for topical applications.
Safety and Regulatory Status
FDA Status: Not a regulated pharmaceutical. Marketed as a cosmetic ingredient under the INCI name tripeptide-1.
Availability: Available in over-the-counter skincare products. Often formulated as part of multi-peptide complexes.
Class context: Base signal peptide of the copper peptide family. Same sequence as GHK and the backbone of GHK-Cu. More commonly used in palmitoylated form (palmitoyl tripeptide-1) for improved skin penetration.
Naturally occurring (the body's own) peptide with excellent safety profile. Present in human plasma. No safety concerns from topical application.
Peptide Structure
Technical molecular data for researchers and clinicians.
Questions and Comparisons
Questions the evidence raises for a Palmitoyl Tripeptide-5 discussion.
Comparison and Related Research
Tripeptide-1 is most often compared with GHK-Cu (copper-bound, full mechanism), palmitoyl tripeptide-1 (palmitoylated for enhanced penetration), and Matrixyl (different matrikine sequence).
Related compounds
Frequently Asked Questions
References
Each citation links to the original study on PubMed, the U.S. National Library of Medicine database.
- 1.Review of GHK biological activities and copper-binding properties. The paper covered the original 1973 discovery of GHK in human plasma, its matrikine signaling function, and the relationship between the copper-free peptide and the copper-bound GHK-Cu complex.Pickart L, 2008 in J Biomater Sci Polym Ed. View on PubMed
- 2.Review of GHK-Cu's role in tissue protection and repair, including analysis of the GHK tripeptide sequence's biological properties independent of copper binding.Pickart L et al., 2012 in Oxid Med Cell Longev. View on PubMed
Medical Disclaimer
This content is for educational and informational purposes only and does not constitute medical advice. The information presented reflects published research as indexed by PSI and should not be used to make treatment decisions. Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment.