Glutathione: The Tripeptide With an Unusual Bond
Present at millimolar concentrations, joined by a gamma-peptide bond, and best understood as a redox buffer rather than a signal.
Glutathione is the most abundant antioxidant inside the cell, present at millimolar concentrations where most signalling molecules operate at nanomolar. That difference in scale is the first thing to understand about it: it is not a signal, it is a buffer.
Everything below describes published preclinical and in-vitro research. It is not a therapeutic claim, not medical advice, and not a statement about effects in humans.
What it is
Glutathione is a tripeptide — glutamate, cysteine, glycine — with a molecular weight of about 307 Da. It has one structural oddity that matters enormously: the bond between glutamate and cysteine is a gamma-peptide bond, formed at the side-chain carboxyl rather than the backbone one.
That single unusual bond is why glutathione is not simply digested by the peptidases that break down ordinary tripeptides. It is also why it cannot be made by standard solid-phase synthesis in the way the rest of this catalog is.
Reported roles
- Redox buffering — glutathione cycles between a reduced form (GSH) and an oxidised dimer (GSSG), and the ratio between them is the standard laboratory measure of a cell’s redox state.
- Detoxification — glutathione S-transferases conjugate it to electrophilic compounds, which is the first step in the principal route by which cells clear reactive xenobiotics.
- Enzyme cofactor — required by glutathione peroxidases, which reduce hydrogen peroxide and lipid peroxides.
- Protein handling — reported roles in the formation and reshuffling of disulfide bonds.
Practical notes
| Sequence | Glu-Cys-Gly, gamma-linked |
|---|---|
| Length | 3 amino acids |
| Molecular weight | ~307 Da |
| Forms | GSH (reduced), GSSG (oxidised dimer) |
| Typical vial size | 600 mg |
Two handling points specific to this molecule. First, the free cysteine thiol oxidises readily in air — a reduced glutathione preparation left in an open vessel becomes progressively GSSG, and the ratio matters for most assays. Second, the vial size is 600 mg, far larger than anything else in the catalog, which changes every concentration figure you might have carried over from a peptide.
Reading this literature critically
- Glutathione is not an approved medicine in the European Union or anywhere else.
- Oral and systemic availability are heavily contested in the literature, and study designs differ enough that comparing across them is often not meaningful.
- Because it is endogenous and abundant, “glutathione levels” in a study may refer to total, reduced, or the GSH:GSSG ratio — three different measurements that are frequently conflated in secondary reporting.
- Antioxidant capacity in vitro has a long history of not predicting outcomes elsewhere, and this literature is not an exception to that pattern.
Handling
Supplied as lyophilised powder. Protect from air once reconstituted, keep it cold, and prepare fresh where an assay depends on the reduced form. Our storage notes cover oxidation and the reconstitution calculator the arithmetic for a 600 mg vial.
Every batch is analysed by an independent laboratory for purity and identity, with batch-matched certificates available on request. See the Glutathione 600mg product page, or the rest of longevity research.
All products and information referenced are for in-vitro research and laboratory use only. Nothing here is medical advice, and no therapeutic claim is made or implied.