Is glutathione a peptide?
Yes, with a twist. Glutathione is a tripeptide of glutamate, cysteine and glycine, but its first link runs through glutamate's side chain instead of the usual backbone carboxyl, so it is not a standard peptide. Here is its structure, why that bond matters, how cells make it and what it does.
Glutathione in one table.
| Full name | Gamma-L-glutamyl-L-cysteinylglycine |
|---|---|
| Amino acids | Glutamate, cysteine, glycine |
| Length | 3 amino acids, a tripeptide |
| Formula | C10H17N3O6S |
| Molecular weight | 307.33 g/mol (monoisotopic 307.0838) |
| CAS number | 70-18-8 |
| PubChem CID | 124886 |
Formula and masses from PubChem.
Not a standard peptide link.
In a standard peptide bond, the backbone (alpha) carboxyl of one amino acid joins the amino group of the next. In glutathione, glutamate joins cysteine through its side-chain (gamma) carboxyl instead. The second link, from cysteine to glycine, is an ordinary alpha peptide bond. That gamma link is why glutathione is called a gamma-glutamyl peptide, and it takes a dedicated enzyme, gamma-glutamyltransferase, to remove the gamma-glutamyl group.
The unusual bond does not change the atoms. The ordinary alpha-linked tripeptide Glu-Cys-Gly has the same formula, C10H17N3O6S, and the same monoisotopic mass, 307.0838, as you can check in Helion's peptide molecular weight calculator. A mass alone cannot tell the two apart; that takes fragmentation or chromatography against a standard.
Two enzymes, not the ribosome.
Proteins are built on the ribosome from a genetic template. Glutathione is assembled instead by two enzymes in the cytosol. Glutamate-cysteine ligase, also called gamma-glutamylcysteine synthetase, joins glutamate and cysteine in an ATP-dependent step that limits the rate of the whole pathway, and glutathione synthetase then adds glycine.
The cell's main small thiol.
Glutathione is the most abundant small, non-protein thiol in cells. Its cysteine thiol group makes it a key antioxidant in the cell's redox balance, and reviews of its protective roles, measurement and synthesis run back decades.
Where it sits.
By length, glutathione is a tripeptide like GHK, the peptide in GHK-Cu, and KPV. Peptide vs polypeptide vs protein covers the names for each length, and the amino acid chart lists the three building blocks.
Helion does not supply glutathione. Its tripeptide is GHK-Cu 50mg (CU50), tested by lot at ILS Laboratories, for laboratory research use only.
Specs and storage by compound.
Questions (7)
Is glutathione a peptide?
Yes. It is a tripeptide of glutamate, cysteine and glycine, with a non-standard gamma bond between glutamate and cysteine.
Is glutathione a protein?
No. With three amino acids it is a tripeptide, far too short to be a protein.
What is the molecular weight of glutathione?
307.33 g/mol (C10H17N3O6S), 307.0838 monoisotopic.
What amino acids make up glutathione?
Glutamate, cysteine and glycine.
What is the gamma-glutamyl bond in glutathione?
The link from glutamate's side-chain carboxyl to cysteine's amino group, in place of the usual backbone carboxyl. The cysteine-glycine link is a normal peptide bond.
Is glutathione made by ribosomes?
No. Two enzymes assemble it: glutamate-cysteine ligase joins glutamate and cysteine, and glutathione synthetase adds glycine.
Does Helion sell glutathione?
No. Helion's tripeptide is GHK-Cu 50mg (CU50), for laboratory research use only.
Published studies (4)
- Glutathione synthesis
- Glutathione: overview of its protective roles, measurement, and biosynthesis
- The Emerging Roles of γ-Glutamyl Peptides Produced by γ-Glutamyltransferase and the Glutathione Synthesis System
- The enzymes of glutathione synthesis: gamma-glutamylcysteine synthetase
Citations from PubMed for reference. They describe the compound in the literature, not any Helion lot, and nothing here is guidance on use.