Palmitoyl Pentapeptide-4

1 Identity

Acylated cosmetic pentapeptide (lipopeptide conjugate). A synthetic pentapeptide Lys-Thr-Thr-Lys-Ser - a subsequence of the human pro-alpha-1 type I procollagen chain, residues 212-216 - bearing a single C16:0 palmitoyl group amide-bonded to the N-terminal alpha-amino group of Lys1. The acyl chain is a formulation modification, not a pharmacological one, and it is 29.7 percent of the molecular mass. Sold as a bulk cosmetic and laboratory raw material. and CAS 214047-00-4. 'Matrixyl' is a registered trade name for a proprietary dilution of this ingredient and is the property of its owner; it appears nowhere on our label. Not a synonym: 'Palmitoyl Oligopeptide', a loose designation that has been applied to more than one article.

Sequence

N-hexadecanoyl(palmitoyl)-L-Lys-L-Thr-L-Thr-L-Lys-L-Ser-OH (Pal-KTTKS). A single C16:0 palmitoyl group is amide-bonded to the alpha-amino group of Lys1; free C-terminal carboxylic acid on Ser5; no amidation, no cyclization, no disulfide; all five residues L and proteinogenic. Supplied as the acetate salt of the conjugate. The sequence statement is incomplete without the regiochemistry statement: the two lysine epsilon-amines are competing acylation sites, the attachment point is not carried in the mass, and the article is specifically the N-alpha-palmitoyl regioisomer. The supplier declares the acylation site in writing and the company confirms it analytically rather than accepting the declaration.

Molecular formula

C39H75N7O10 (the conjugate, and the only formula against which content is ever calculated), corroborated on three independent routes and reconstructed from the sequence. Free pentapeptide KTTKS C23H45N7O9. Myristoyl (C14:0) analogue C37H71N7O10. Di-palmitoylated over-acylation product C55H105N7O11. Palmitic acid, the acyl fragment released on hydrolysis, C16H32O2.

Average mass

802.068 Da (C39H75N7O10) on IUPAC 2021 abridged conventional atomic weights. Two reagent catalogs and other listings print 802.05; that is the same formula evaluated on the older CODATA/IUPAC weights and is not an error, but 802.07 is what IUPAC 2021 gives and is the figure this catalog carries for consistency with every other record. 238.42 Da of that mass - 29.7 percent - is non-peptide palmitoyl, which is why every content calculation runs against the conjugate formula and never against the free pentapeptide. A different formula and weight circulate widely for this ingredient and are wrong: C30H58N6O9 at approximately 646.8 Da. C30H58N6O9 computes to 646.82, is not this molecule, and is 155 Da light of it; a certificate carrying that formula has identified something else. Confusables: free KTTKS 563.65; myristoyl pentapeptide-4 774.01; di-palmitoyl KTTKS 1040.48; palmitic acid 256.42; palmitoyl tripeptide-1 578.80; palmitoyl tetrapeptide-7 694.92; palmitoyl tripeptide-5 611.91.

Monoisotopic mass

801.55754 Da neutral (C39H75N7O10); [M+H]+ 802.56482; [M+2H]2+ m/z 401.78605; [M-H]- 801.55026. Identity window on [M+H]+ at plus or minus 5 ppm is plus or minus 0.0040 Da. Confusables at monoisotopic resolution: free KTTKS 563.32791 neutral, [M+H]+ 564.33519; myristoyl pentapeptide-4 773.52624 neutral, [M+H]+ 774.53352, exactly 28.03 Da light; di-palmitoyl KTTKS 1039.78724 neutral, [M+H]+ 1040.79452; palmitoyl tripeptide-1 578.41557; palmitoyl tetrapeptide-7 694.47411; palmitoyl tripeptide-5 611.49862. Monoisotopic values are carried to five decimals because the N-epsilon-palmitoyl regioisomer is C39H75N7O10 at 801.55754 - identical to the article at every decimal place, and separable only by MS/MS fragmentation or co-elution against a qualified standard - and because the myristoyl analogue is only 28 Da away.

Salt / variant note

(1) palmitoyl tripeptide-1 (Pal-Gly-His-Lys), C30H54N6O5, 578.80 / 578.41557, [M+H]+ 579.42285 - the single most likely substitution, because the loose INCI designation 'Palmitoyl Oligopeptide' has been applied to both articles and a supplier can fill an order written that way with Pal-GHK in good faith. (2) palmitoyl tetrapeptide-7 (Pal-Gly-Gln-Pro-Arg), C34H62N8O7, 694.92 / 694.47411, [M+H]+ 695.48139 - confirmed live: the consumer channel lists it as a 200 mg topical article printing exactly C34H62N8O7 / 694.9, and it is the other component of the two-peptide cosmetic blends. (3) palmitoyl tripeptide-5 (Pal-Lys-Val-Lys), C33H65N5O5, 611.91 / 611.49862 - also stocked at 200 mg on shelves where palmitoyl pentapeptide-4 is not, so it is what a loosely written topical-peptide order actually gets filled with. (4) myristoyl pentapeptide-4, C37H71N7O10, 774.01 / 773.52624, [M+H]+ 774.53352 - the same pentapeptide with a C14 acyl instead of C16, exactly 28.05 Da light at average mass, a real INCI ingredient with its own supply chain, and a substitution that any identity test reporting 'approximately 800' will pass. (5) des-palmitoyl KTTKS, C23H45N7O9, 563.65 / 563.32791, [M+H]+ 564.33519 - the unacylated starting peptide, 238.42 Da light; blended with free palmitic acid (256.42) it gives a correct elemental analysis and a correct appearance while the mass spectrum shows two peaks and no conjugate. (6) DI-palmitoyl KTTKS from over-acylation at a lysine epsilon-amine, C55H105N7O11, 1040.48 / 1039.78724, [M+H]+ 1040.79452. (7) the regioisomer trap, which carries NO mass difference at all: N-epsilon-palmitoyl KTTKS is C39H75N7O10 at 802.07 / 801.55754, identical to the article, and only MS/MS fragmentation or co-elution against a qualified standard separates them. (8) salt axis: acetate (specified) versus trifluoroacetate (refused for this article, because it is a cosmetic formulation raw material). (9) palmitoyl tripeptide-38 (Pal-Lys-Met(O2)-Lys), C33H65N5O7S, 675.97 - the third peptide in the branded blends that trade under names close to this ingredient's, and a confusable on the same ingredient lists. (10) presentation axis, which is not a molecule but is where the trade-name substitution actually happens: the ingredient is sold both as neat conjugate powder and as parts-per-million dilutions in butylene glycol and water, and the related blend sold under a similar trade name contains palmitoyl tripeptide-1 and palmitoyl tetrapeptide-7 and no palmitoyl pentapeptide-4 at all. None of the fourteen peptide sellers tracked for this catalog carries this molecule, which is why an order placed into that channel comes back as something else.

2 Class & testing panel

Form

Single article

Testing panel

P2 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Published literature exists for this article and is the strongest in this cosmetic group. Human: one 12-week, double-blind, placebo-controlled, split-face, left-right randomized trial in 93 women aged 35-55 comparing a 3 ppm formulation with the same vehicle, with quantitative technical image analysis and expert grader image analysis as endpoints, authors affiliated with the product manufacturer (Robinson et al., Int J Cosmet Sci 2005;27(3):155-60, PMID 18492182). Additional human data exist only inside multi-ingredient product studies where an individual peptide's contribution cannot be isolated. No registry number is quoted for that trial because none has been verified. In vitro and EX vivo: dermal stability and skin permeation of KTTKS and pal-KTTKS in hairless mouse skin, with recovery figures of 4.2 plus or minus 0.7 microg/cm2 in stratum corneum, 2.8 plus or minus 0.5 in epidermis and 0.3 plus or minus 0.1 in dermis for the palmitoylated form and no detection of the free peptide in any layer, neither crossing into receptor fluid (Choi et al., Biomol Ther 2014, PMID 25143811); a narrative review of the topical literature noting the absence of penetration data and the scarcity of clinical studies (Abu Samah and Heard, Int J Cosmet Sci 2011, PMID 21535443); fibroblast collagen-lattice work with a non-monotonic concentration response, active at 0.1 microM and not significant at 0.5 microM (Park et al., Tissue Eng Regen Med 2017, PMID 30603464); a synthetic analogue series with no fibroblast cytotoxicity observed (Talalaj et al., 2019, PMID 31618846); liposome-encapsulated formulation work in a murine fibroblast line (Vitali et al., 2024, PMID 38399273); and nanocarrier and ionic-liquid delivery work documenting low solubility and poor permeability (PMID 39783908, PMID 35656937). Safety literature: tolerability across 12 weeks of twice-daily facial application in the 93-subject trial, with no tolerability signal reported (PMID 18492182). Known gaps, stated plainly: no human pharmacokinetic data, no human skin-penetration dataset comparable to the one that exists for acetyl hexapeptide-8, no data beyond 12 weeks, no carcinogenicity, tumor-promotion, immunogenicity or cardiovascular data, and no data of any kind on injected administration.

4 Storage & specification

Storage

Off-white to pale-tan lyophilized powder, acetate salt, packed in amber glass with a nitrogen headspace and a desiccant sachet. Laboratory and cosmetic raw-material presentation: non-sterile, no sterility claim, no stoppered-and-crimped injection format. Labeled condition 2-8 degrees C, protect from light and moisture; the material is hygroscopic and must be equilibrated to room temperature in the sealed jar before opening to prevent condensation onto the powder. Shipped ambient with a temperature-excursion indicator; excursions to 25 degrees C for up to 14 days cumulative are accepted against the stability protocol. The palmitoyl chain makes the conjugate markedly less water-soluble than the free pentapeptide - described in the retrieved literature as low solubility and poor permeability requiring specialized carriers (PMID 39783908) - so dissolution for assay uses a named co-solvent or carrier system, stated on the handling page, which says nothing about administration, route or vehicle.

Shelf life

Provisional 24-month retest interval at 2-8 degrees C, and provisional 36 months at -20 degrees C plus or minus 5 degrees C for the retained reference portion. Both figures are provisional placeholders for the company's own ICH Q1A-format study on three production lots, long-term at 5 degrees C plus or minus 3 degrees C and accelerated at 25 degrees C / 60 percent RH, which replaces them at the 12-month data point. The stability-indicating attributes are free palmitic acid and des-palmitoyl KTTKS rather than total assay: hydrolysis at the acyl amide regenerates the free pentapeptide and palmitic acid, and a slow drift there is invisible inside an unspecified-impurity bucket. Both peptides are additionally reported as rapidly degraded by skin proteases with the palmitoylated form the more stable of the two (PMID 25143811), which is an experimental-design note for ex-vivo users rather than a storage statement. A retest date is printed on every jar; first-expiry-first-out is enforced against that date and not against receipt date.