Thiol and amine groups in skin proteins and biomolecules (None)

Thiol and amine groups in skin proteins and biomolecules serve as the primary nucleophilic targets for electrophilic chemicals, a process central to the development of skin sensitization (OECD, 2012). These functional groups are predominantly found on cysteine and lysine residues within abundant skin proteins such as keratin and human serum albumin (Gerberick et al., 2007). The covalent modification of these groups by haptens—small, reactive molecules—forms immunogenic hapten-protein complexes, which is the first key event in the Adverse Outcome Pathway (AOP) for allergic contact dermatitis (Aptula et al., 2005). While these groups are not therapeutic targets in the conventional sense, their reactivity is a critical parameter in the safety evaluation of topical pharmaceuticals and cosmetic ingredients (Karlberg et al., 2008). Understanding the kinetics and specificity of these interactions is essential for predicting the allergenic potential of new chemical entities using in chemico methods like the Direct Peptide Reactivity Assay (DPRA) (Natsch et al., 2013). These interactions can lead to the activation of the innate immune system and the subsequent priming of T-cells, resulting in a delayed-type hypersensitivity reaction upon re-exposure. Monitoring the depletion of synthetic peptides containing these groups is a standard regulatory approach for assessing skin sensitization risk. Beyond toxicology, these groups are also involved in the structural integrity of the skin barrier through the formation of disulfide bonds in the cornified envelope.

Other names

Skin protein nucleophilesNucleophilic amino acid residuesCysteine and lysine residues in skin proteinsProtein-reactive functional groups

Covalent binding (haptenization) to nucleophilic sites on skin proteins, leading to the formation of complete antigens and subsequent T-cell mediated immune responses.