Protein and peptide sulfhydryl groups (Free thiols) (-SH)

Free thiols, primarily represented by the sulfhydryl (-SH) groups of cysteine residues in proteins and small peptides like glutathione, are fundamental to cellular redox homeostasis and signaling [1]. They act as critical antioxidants, scavenging reactive oxygen and nitrogen species to prevent oxidative damage to cellular components [2]. Beyond defense, free thiols are involved in the regulation of protein function through reversible post-translational modifications such as S-nitrosylation and disulfide bond formation, which are essential for proper protein folding and enzymatic activity [3]. In clinical contexts, free thiols are targeted by various pharmacological agents; for instance, N-acetylcysteine serves as a thiol donor to replenish glutathione levels, while certain chemotherapeutics and covalent inhibitors target specific reactive thiols to modulate disease pathways [4]. Dysregulation of thiol-disulfide balance is a hallmark of several pathological states, including neurodegenerative diseases, cardiovascular disorders, and cancer, where oxidative stress leads to the depletion of these protective groups [5]. Consequently, monitoring and therapeutic modulation of free thiol levels remain key strategies in managing oxidative stress-related conditions [6].

Other names

Sulfhydryl groupsThiol groupsCysteine thiolsMercapto groupsProtein thiols

Drugs targeting free thiols typically act as thiol donors to replenish antioxidant pools, as chelating agents that bind metal ions via sulfhydryl coordination, or as electrophiles that covalently modify reactive cysteine residues to inhibit enzyme function or modulate signaling pathways [1, 4].