Global Profiling of Human Proteome Cysteine Residues via Lipoic Acid-Mediated Disulfide Exchange

Lipoic acid (LA), an endogenous small molecule, is widely utilized in metabolic regulation and disease intervention. While its mechanism of action has been largely attributed to protein lipoylation, the dynamic chemical properties of its five-membered cyclic disulfide moiety remain underexplored. Here, we designed and synthesized alkyne-functionalized lipoic acid-derived probes, LAN-yne and LAO-yne. Employing a chemoproteomic strategy, we systematically mapped the covalent targets of the LAN-yne across the cellular proteome and assessed their potential biological functions. Quantitative proteomic analysis identified 852 probe-modified proteins and 1,157 corresponding cysteine modification sites. This study demonstrates that LA's endocyclic disulfide bond can be mimicked to mediate specific protein modification via thiol-disulfide exchange, providing novel molecular insights and a technical platform for investigating LA's potential pharmacological mechanisms and structural derivatization efforts beyond lipoylation.