Glutathione and redox chemistry
What glutathione is
Glutathione is a tripeptide made of glutamate, cysteine and glycine. Its molecular weight is about 307 Da. It is unusual among peptides because the first bond is not a standard peptide bond: the glutamate is joined through its side-chain carboxyl group, giving the gamma-glutamyl linkage written as gamma-Glu-Cys-Gly. The linkage distinguishes its structure from a conventional linear peptide backbone.
Is glutathione a peptide? Yes, by structure. It is also an endogenous metabolite found widely in cells, made on demand by two enzymes rather than on a ribosome. Both facts are true at once, and the second is why it is studied as a redox molecule rather than as a signalling peptide.
Reduced and oxidised forms
The chemistry that matters is at the cysteine thiol.
| Form | Abbreviation | Description |
|---|---|---|
| Reduced glutathione | GSH | Free thiol group on cysteine |
| Oxidised glutathione | GSSG | Two molecules joined by a disulfide bond |
Inside a cell, the ratio of GSH to GSSG is used as a measure of redox state, and GSH acts as a substrate for glutathione peroxidases and glutathione S-transferases. These are the biochemical roles described in textbooks, and they are the reason research material is normally specified as the reduced form.
The thiol is also the stability problem. In solution, in air, GSH oxidises to GSSG at a rate that depends on pH, temperature, metal ions and other conditions. Solid lyophilised material is far more stable, which is why research material is supplied as powder and why a certificate measured on the solid does not describe a solution made from it later.
What the research literature covers
The glutathione literature is enormous because it is a core metabolite, and most of it is about the molecule made inside cells, not about added material. Studies that add glutathione to a system fall into three groups.
- Cell culture studies of oxidative stress models, where GSH or its precursors are added to the medium.
- Animal studies of depletion and repletion.
- Human studies, mostly of oral or intravenous pharmaceutical products, which concern those products and their formulations.
The search phrase "glutathione injection" refers to products administered in aesthetic clinics in several countries. That is a different product and use context from an in-vitro research reagent.
Analytical documentation
Glutathione is simple to characterise and awkward to keep characterised. Mass spectrometry confirms the expected mass for GSH. HPLC separates GSH from GSSG, so a purity figure for the reduced form should be read together with the method and the date, because storage and handling can affect the sample composition. A batch certificate for the material should show the method and the date, and how to read a peptide COA explains those fields. As with every material on this site, the certificate reports identity and purity of the sample tested and nothing about biological activity.
EPS documentation
Use the research catalogue to check the exact name, labelled amount and format. The COA library publishes the original Janoshik reports selected for EPS, retaining the original report client name and any missing batch fields. Literature findings and another supplier's analytical results are not evidence about an EPS batch.