Cellular Thiols: Cysteine and Glutathione (N/A)

Cellular thiols, primarily cysteine and glutathione, are small molecules containing a sulfhydryl (–SH) group. They play central roles in maintaining cellular redox homeostasis, detoxification, antioxidant defense, and regulation of protein function through reversible post-translational modifications. Cysteine is a sulfur-containing amino acid with a free thiol group. Glutathione (GSH) is a tripeptide composed of glutamate, cysteine, and glycine. They act as major cellular redox buffers and are critical for cell survival under oxidative stress. Glutathione is the principal intracellular antioxidant, neutralizing reactive oxygen species (ROS) directly or via enzymatic reactions. It also conjugates with electrophilic toxins to facilitate their removal from cells. Protein cysteines can undergo reversible oxidation/reduction cycles—such as S-glutathionylation—which modulate protein activity. Glutathione serves as a stable reservoir for cysteine and facilitates amino acid transport. These properties make them fundamental targets for research into cell biology, toxicology, pharmacology, aging processes, cancer therapy resistance mechanisms—and more broadly—for understanding how cells sense/respond to environmental challenges at the molecular level.

Other names

CysteineGlutathioneGSHSulfhydryl compoundsThiol-based antioxidants

Thiol groups donate electrons to reduce ROS/RNS or disulfides; Redox buffering; Post-translational modifications of cysteine residues on proteins; Conjugation with toxins for excretion.