Acetyl tetrapeptide-5  is a synthetic peptide formed from organic molecules in which the amino acids present are linked by peptide bonds.   

The name describes the structure of the molecule:

• Acetyl is a functional group with the chemical formula -C(O)CH3. It is derived from acetic acid by removal of a hydroxyl group.
• Tetrapeptide is a peptide, a type of molecule composed of amino acids linked together by peptide bonds. A tetrapeptide is a specific type of peptide composed of four amino acids.
• -5 is a designation used by the cosmetics industry to differentiate different types of tetrapeptides. Each type of tetrapeptide has a unique amino acid sequence, and the '-5' simply refers to the specific amino acid sequence of this particular tetrapeptide.

The synthesis process takes place in different steps:

• Solid phase peptide synthesis (SPPS). The first step starts with the attachment of the first amino acid to a solid support, often a resin bead. The amino group of the amino acid is protected by a temporary protective group, which prevents its premature reaction.
• Deprotection. The protective group of the amino acid is removed, allowing it to react with the next amino acid in the sequence. The next amino acid is also attached to the resin and has its protective group.
• Coupling. The deprotected amino group of the first amino acid is coupled to the carboxyl group of the next amino acid, forming a peptide bond. This process is repeated for each amino acid in the sequence.
• Cleavage. Once the entire peptide sequence is assembled, the peptide is cleaved from the resin and the side chain protecting groups are removed.
• Purification. The peptide is purified, often using a technique such as high-performance liquid chromatography (HPLC), to remove unreacted amino acids or other impurities.
• Acetylation. In the last step, the peptide is acetylated to form Acetyl Tetrapeptide-5 by reacting the peptide with acetic anhydride, which acetylates the N-terminus of the peptide.

It appears in the form of a white powder.

What it is used for and where

Cosmetics

Synthetic peptides were introduced to the cosmetics market in 1980 and serve as anti-ageing agents for skin care. They are short-chain, very stable peptides that aid immunity, pigmentation and synthesis of the extracellular matrix. The skin ages naturally and decreases in production, the proteins of the extracellular matrix are degraded and the condition of elastin and collagen is worsened. Acetyl tetrapeptide-5 acts on elastin and collagen.

Humectant. Hygroscopic compound used to minimise water loss in the skin and to prevent it from drying out by facilitating faster and greater absorption of water into the stratum corneum of the epidermis.  The epidermis is the most superficial of the three layers that make up human skin (epidermis, dermis and hypodermis) and is the layer that maintains hydration in all three layers. In turn, the epidermis is composed of five layers: horny, the most superficial, granular, spinous, shiny, and basal. Humectants have the ability to retain the water they attract from the air in the stratum corneum and have the function of moisturising the skin. They are best used before emollients, which are oil-based.

Acetyl tetrapeptide-5 has emerged as a promising agent for use in anti-aging and protective cosmetics (1).

Medical

Useful in dermatocalase, a pathology of the upper eyelids. Acetyl tetrapeptide-5 has been shown to reduce oedema by inhibiting glycation and cross-linking of collagen by a process that prevents abnormal cross-linking of collagen fibres.

Acetyl tetrapeptide-5 studies

Typical commercial product characteristics Acetyl Tetrapeptide-5

• Molecular Formula  C₂₀H₂₈N₈O₇
• Molecular Weight     492.5
• Exact Mass    492.208099
• CAS  820959-17-9
• UNII    Y1DFQ308G8
• EC Number   
• DSSTox Substance ID  DTXSID10231560
• IUPAC  (2S)-2-[[(2S)-2-[[(2S)-2-(3-acetamidopropanoylamino)-3-(1H-imidazol-5-yl)propanoyl]amino]-3-hydroxypropanoyl]amino]-3-(1H-imidazol-5-yl)propanoic acid
• InChI=1S/C20H28N8O7/c1-11(30)23-3-2-17(31)26-14(4-12-6-21-9-24-12)18(32)28-16(8-29)19(33)27-15(20(34)35)5-13-7-22-10-25-13/h6-7,9-10,14-16,29H,2-5,8H2,1H3,(H,21,24)(H,22,25)(H,23,30)(H,26,31)(H,27,33)(H,28,32)(H,34,35)/t14-,15-,16-/m0/s1 
• InChl Key      ROTFCACGLKOUGI-JYJNAYRXSA-N
• SMILES   CC(=O)NCCC(=O)NC(CC1=CN=CN1)C(=O)NC(CO)C(=O)NC(CC2=CN=CN2)C(=O)O
• MDL number  
• PubChem Substance ID    

Synonyms

• (2S)-2-[[(2S)-2-[[(2S)-2-(3-acetamidopropanoylamino)-3-(1H-imidazol-5-yl)propanoyl]amino]-3-hydroxypropanoyl]amino]-3-(1H-imidazol-5-yl)propanoic acid
• N-Acetyl-β-alanyl-L-histidyl-L-seryl-l-histidin
• Eyeseryl
• N-Acetyl-β-alanyl-L-histidyl-L-seryl-L-histidine
• L-Histidine, N-acetyl-β-alanyl-L-histidyl-L-seryl-

References_____________________________________________________________________

(1) Wu Y, Cao K, Zhang W, Zhang G, Zhou M. Protective and Anti-Aging Effects of 5 Cosmeceutical Peptide Mixtures on Hydrogen Peroxide-Induced Premature Senescence in Human Skin Fibroblasts. Skin Pharmacol Physiol. 2021;34(4):194-202. doi: 10.1159/000514496. Epub 2021 Apr 13. PMID: 33849044.