Glutathione: The Cell's Built-In Antioxidant
A tripeptide, made on demand
Glutathione is the one item in this set that is technically a peptide, a tripeptide of glutamate, cysteine, and glycine, but it behaves nothing like the signaling peptides. Cells synthesize it continuously, and it is the most abundant small-molecule antioxidant inside most cells, present at millimolar concentrations.
Its chemistry comes down to a single sulfur atom. The cysteine residue carries a thiol (-SH) group, and that group is what does the work: it donates electrons to neutralize reactive oxygen species, and in doing so two glutathione molecules link into a disulfide (GSSG). The ratio of reduced glutathione (GSH) to its oxidized form (GSSG) is one of the cell's primary readouts of redox state, how oxidizing or reducing its internal environment currently is.
What the research examines
In the peer-reviewed literature, glutathione is studied as:
- A direct antioxidant, quenching free radicals and reactive oxygen species
- A cofactor for detoxification enzymes (the glutathione-S-transferases) that conjugate and clear reactive compounds
- A redox-signaling participant, where the GSH/GSSG balance influences pathways governing cell proliferation and apoptosis
The shift in how the field views it, from a passive radical-scavenger to an active participant in cell signaling, is the subject of a widely cited review (Aquilano et al., *Front Pharmacol* 2014), and the broader biochemistry is surveyed in a more recent overview (Averill-Bates, *Vitam Horm* 2023).
Scope of these notes
This overview is deliberately limited to oxidative-stress and redox biology, the antioxidant and detoxification research that defines the molecule. That is the entire scope of what's described here.
Supplied for laboratory research use only. Not for human consumption.