Glutathione in its reduced form (GSH) is the tripeptide γ-L-glutamyl-L-cysteinylglycine, the principal low-molecular-weight thiol found in most cell types. It has the molecular formula C₁₀H₁₇N₃O₆S, a molecular weight of 307.33 g/mol and CAS number 70-18-8. Unlike a conventional peptide, its glutamate is joined to cysteine through the side-chain (γ) carboxyl rather than an α-peptide bond, so it is assembled by dedicated enzymes rather than on the ribosome. The free cysteine thiol makes it a redox buffer that cycles between reduced GSH and the disulfide-linked dimer GSSG, a distinct compound (C₂₀H₃₂N₆O₁₂S₂, 612.6 g/mol). Supplied in 500mg and 1000mg vials as a white to off-white crystalline powder, highly water-soluble, stored sealed and refrigerated at 2–8 °C.