L-Glutathione

L-Glutathione (GSH) is a tripeptide composed of glutamate, cysteine, and glycine, with an unusual γ-peptide bond between the glutamate and cysteine residues. It is an abundant low-molecular-weight thiol in animal cells (typically 1–10 mM intracellularly) and participates in cellular redox reactions and phase-II conjugation chemistry. Research investigations include redox biology, enzyme biochemistry, and cell-based laboratory assays.

Reduced glutathione (GSH) has a free cysteine thiol (–SH) and is the redox-active form that neutralizes oxidants. When GSH donates electrons, two molecules join via a disulfide bond to form oxidized glutathione (GSSG). The intracellular GSH:GSSG ratio is typically >100:1 in healthy cells and drops under oxidative stress, making it a standard biomarker in redox research. Glutathione reductase regenerates GSH from GSSG using NADPH.

N-acetylcysteine (NAC) is a precursor that supplies cysteine — the rate-limiting amino acid for GSH biosynthesis — but is not itself glutathione. Research has used NAC to elevate intracellular GSH levels indirectly, while reduced glutathione (GSH) provides the intact tripeptide directly. Both are common reagents in oxidative-stress research with distinct pharmacokinetic profiles.