Amino acids of the stratum corneum

Amino acids in the stratum corneum constitute over half of the natural moisturizing factor (NMF), which also includes their derivatives such as pyrrolidone carboxylic acid (PCA) and urocanic acid[2][3][9]. These amino acids, produced primarily via the enzymatic breakdown of filaggrin and keratinocyte differentiation, localize mainly to the upper and central regions of the stratum corneum[3][9]. They are critical for maintaining skin hydration by attracting and retaining water, supporting acid-base balance, and helping preserve the skin's barrier function against mechanical and environmental assault[2][4]. Disruptions in their abundance are linked to skin dryness and several dermatologic conditions, including atopic dermatitis, ichthyosis, and psoriasis[5]. Topical applications of amino acids or NMF formulations can improve hydration and barrier integrity, evidencing their functional role in skin health but not as classic drug targets[2][3][4]. Because "stratum corneum amino acids" refers to a heterogeneous group of small molecules and not a discrete therapeutic target (e.g., receptor, enzyme, transporter), it is not appropriate to classify it as a molecular drug target. The term should be used as a descriptor for functionally important amino acids in the uppermost skin, but not as a structured therapeutic target.

Other names

Stratum corneum NMF amino acidsNatural moisturizing factor amino acidsFree amino acids in the stratum corneum

Topical supplementation enhances stratum corneum hydration by replenishing NMF amino acids[2][3] Chelation of Ca²⁺ by exogenous amino acids can disrupt corneocyte adhesion[1]