Compound monograph
KTTKS (Pentapeptide-4)
KTTKS is the unmodified pentapeptide from type I procollagen that forms the peptide backbone of the palmitoylated cosmetic ingredient Matrixyl.
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Identity & nomenclature
KTTKS is the unmodified pentapeptide from type I procollagen that forms the peptide backbone of the palmitoylated cosmetic ingredient Matrixyl.
KTTKS is not Matrixyl. Matrixyl is the palmitoylated derivative, Pal-KTTKS, and N-palmitoylation adds C16H30O — 238.2297 Da — changing both the covalent structure and the physicochemical behaviour. 'Pentapeptide-4' alone does not distinguish them, which is why the sequence should always accompany the name. GSRS UNII 69B8BD4H9G identifies unmodified, all-L, free-terminal KTTKS and includes CAS 149128-48-3 and PubChem CID 9959565.
Canonical name: KTTKS.
Declared aliases and development codes: Pentapeptide-4, Collagen pentapeptide.
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Molecular properties
| Molecular formula | C23H45N7O9 |
|---|---|
| Molecular mass | 563.65 Da |
| CAS Registry Number | 149128-48-3 |
| PubChem CID | 9959565 |
| UNII | 69B8BD4H9G |
| One-letter sequence | KTTKS |
| Three-letter sequence | Lys–Thr–Thr–Lys–Ser |
| Terminal groups | Free N-terminus; Free C-terminal carboxyl |
Five residues, all L, free at both termini. No palmitoylation, no ring, no metal.
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Structural characteristics
It was identified as residues 212 to 216 of the type I procollagen carboxyl-terminal propeptide, and as the minimum sequence within a larger propeptide subfragment that produced the reported matrix effect in fibroblasts. Two limits follow. Identifying an active synthetic five-residue segment does not establish that free KTTKS is routinely released as an endogenous product. And 'signal peptide' is a functional description, not identification of a receptor: no direct molecular target is established. Its relationship to GHK is shared matrix-derived provenance, not a shared precursor protein or receptor — the two come from different parent proteins.
Terminal features: Free N-terminus, Free C-terminal carboxyl.
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Molecular targets & mechanisms
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Analytical considerations
Tandem MS must distinguish KTTKS from sequence permutations, and the palmitoylated species should be tested for explicitly rather than accepting 'pentapeptide-4' as sufficient identity. Threonine stereochemistry is not resolved by intact mass. A collagen hydrolysate containing compatible amino acids is not evidence of a purified KTTKS molecule. A direct comparison of KTTKS and pal-KTTKS in hairless mouse skin found both degraded rapidly, the palmitoylated form more stable, and only the palmitoylated form detectable in skin layers. Neither compound was detected in the receptor solution under the experimental conditions, so retention in skin layers should not be read as full-thickness permeation.
Disagreements and mix-ups
Points where sources disagree about this compound's identity, or where a name or form is easily confused with another, as noted in this record. The discrepancy register quotes the passage for each one.
Often mixed up · Name or substance
Matrixyl (palmitoyl-KTTKS) vs unmodified KTTKSAlso noted in Matrixyl
What the studies reported
Each finding describes one cited study in its stated model. These observations are specific to that study and do not establish effects in other settings.
Cell and tissue studies
Mesenchymal cells in extracellular-matrix production assays
Katayama et al. identified KTTKS as the minimum propeptide-derived sequence that stimulated collagen and fibronectin production in mesenchymal cells.
Reference [1]Skin extracts and homogenates from male CrlOri:SKH1-hr hairless mice
Choi et al. measured rapid KTTKS degradation in skin extracts and homogenates from male CrlOri:SKH1-hr hairless mice using LC-MS/MS.
Reference [2]Full-thickness skin from male CrlOri:SKH1-hr hairless mice in Franz diffusion cells
Choi et al. detected no KTTKS in the receptor solution beneath full-thickness skin from male CrlOri:SKH1-hr hairless mice in Franz diffusion-cell experiments.
Reference [2]Skin layers from male CrlOri:SKH1-hr hairless mice
Choi et al. detected no KTTKS in the sampled skin layers from male CrlOri:SKH1-hr hairless mice by LC-MS/MS.
Reference [2]
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Verified bibliography
Cited studies by type
The 3 papers this record cites, counted by the kind of work each reports. A count is the size of this record's selection, not of the research that exists, and says nothing about results, safety, effectiveness or approval.
A paper can report more than one kind of work. Each count opens those papers in the bibliography. Compare every record on the Evidence Map.
Reference 1
A pentapeptide from type I procollagen promotes extracellular matrix production.Katayama K, Armendariz-Borunda J, Raghow R, Kang AH, Seyer JM
The Journal of biological chemistry · 1993-05-15 · Journal Article
currentReference 2
Dermal Stability and In Vitro Skin Permeation of Collagen Pentapeptides (KTTKS and palmitoyl-KTTKS).Choi YL, Park EJ, Kim E, Na DH, Shin YH
Biomolecules & therapeutics · 2014-07 · Journal Article
currentReference 3
Development of a LC-MS/MS method to monitor palmitoyl peptides content in anti-wrinkle cosmetics.Chirita RI, Chaimbault P, Archambault JC, Robert I, Elfakir C
Analytica chimica acta · 2009-03-20 · Journal Article
current
Study models of these references
What kind of experiment each cited paper reports, taken from its abstract unless marked. Not a summary of results.
| Reference | Study models |
|---|---|
| Katayama K et al. 1993 | Study models reported: in vitro · from the abstract |
| Choi YL et al. 2014 | Study models reported: in vitro · from the abstract |
| Chirita RI et al. 2009 | Chemical, structural or analytical study; no biological model reported |
Compare
Record history
Published 2026-09-13.
- : Sequence and structure
- : Sequence and structure
- : Identity and nomenclature
Each entry names the parts of this record that changed on that date. Changes to links between records and to catalogue links are not listed. This history covers the tracked record fields; study findings are not listed here.
Cite this record: Purely Peptides Research Library. KTTKS (Pentapeptide-4). Published 2026-09-13; updated 2026-10-15. https://purelypeptides.org/research/compounds/kttks/
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Methodology & citation verification
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