Lysyl-serine

KTTKS is a matrikine that originates from the proteolytic hydrolysis of collagen. This peptide stimulates ECM production and types I and III collagen expression in vitro. A more stable form of KTTKS is pal-KTTKS, known as Matrixyl® or palmitoyl pentapeptide-3. A series of novel pentapeptides, analogues of KTTKS with the general formula X-KTTKS-OH(NH2), where X = acetyl, lipoyl, palmitoyl residues, was designed and synthesized. Their effect on amidolytic activity of urokinase, thrombin, trypsin, plasmin, t-PA, and kallikrein were tested. Cytotoxic tests on fibroblasts, as well as collagen and DNA biosynthesis tests for selected peptides, were also carried out. The test results showed that the most active plasmin inhibitors were palmitoyl peptides, whether in acid or amide form. No biological effects of lysine modification to arginine in the synthesized peptides were found. None of the synthesized peptides was not cytotoxic on fibroblasts, and three of them showed cell growth. These three compounds showed no concentration-activity relationship in the collagen and DNA biosynthesis assays.

In this work, we report the synthesis of a peptide analogue of the KTTKS, termed Ac- Wahx-KTTKS and evaluate its cytotoxicity and role in biosynthesis of collagen for future application in skin aging. The peptide was obtained with purity higher than 97.5%. In the cytotoxicity assay, we observed non-toxic effects for Ac-WAhx-KTTKS at concentrations below 600 µM for HaCaT and 500 µM for HepG2 cells, respectively. After 24 and 48 h it was possible to observe significant changes in collagen synthesis in the groups treated with various concentrations of the peptide. In conclusion, the Ac-Wahx- KTTKS peptide increased collagen synthesis in fibroblasts by 80% and it is a promising candidate for improving skin aging.

Although collagen pentapeptide (Lys-Thr-Thr-Lys-Ser, KTTKS) has received a great deal of attention owing to its collagen biosynthesis-stimulating effects, its enzymatic instability in the skin is an obstacle to effective topical application. PEGylation is a useful approach for improving the chemical and biological stability of peptides. However, the polydispersity of poly(ethylene glycol) (PEG) produces conjugates with different molecular sizes, which may create difficulties in chemical characterization and purity control, and in variability of biological properties. To overcome these difficulties, monodisperse PEG was site-specifically conjugated to the N-terminal amine of KTTKS to produce a single molecular conjugate, enabling more complete chemical characterization and more exact product specifications. PEG-KTTKS conjugates prepared using monodisperse PEG with two different molecular weights, monodisperse PEG220 and PEG572, were characterized by mass spectrometry. These monodisperse PEG-KTTKS conjugates showed no cytotoxicity (1-100 μM) and stimulated collagen biosynthesis in human skin fibroblasts. They also had high stability against proteolytic enzymes in rat skin. This study demonstrates the usefulness of monodisperse PEG for preparing chemically defined conjugates and suggests that monodisperse PEG-KTTKS would be a good candidate for use as a collagen biosynthesis-stimulating agent.