Glutathione (GSH) — wholesale 10-vial kits

Research context

Glutathione is a tripeptide of glutamate, cysteine and glycine, and the single most abundant low-molecular-weight thiol in most cells. Its defining structural feature is that the first peptide bond is not a normal α-amide: the glutamate is joined to cysteine through its γ-carboxyl, making a γ-glutamyl isopeptide linkage that ordinary peptidases cannot cleave and that only γ-glutamyl transpeptidase acts on. The reduced form, GSH, carries a free sulfhydryl on the cysteine; two molecules joined through a disulfide give the oxidized form, GSSG. The chemistry of that thiol is the whole reason the molecule is studied. The classic reference account is Meister and Anderson's 1983 Annual Review of Biochemistry article, which laid out its synthesis, turnover and redox role.

In redox biology GSH is the cell's main small-molecule reductant. The ratio of reduced to oxidized glutathione, GSH/GSSG, is the standard index of a sample's redox poise, and measuring it accurately is a recurring bench problem because GSH oxidizes readily once a sample is disturbed. The workhorse method is the enzymatic recycling assay: 5,5′-dithiobis(2-nitrobenzoic acid), Ellman's reagent, reacts with GSH to form a yellow chromophore read at 412 nm, glutathione reductase regenerates GSH from GSSG using NADPH, and the rate of color formation scales with total glutathione. Tietze described the enzymic recycling determination of total and oxidized glutathione in 1969, and Rahman and colleagues gave a widely used microplate version in 2006. To read GSSG on its own, Griffith's 1980 method masks GSH with 2-vinylpyridine before recycling, which is why 2-vinylpyridine derivatization appears in so many glutathione assay descriptions.

Glutathione is also a defined substrate and cofactor for two enzyme families that are assayed constantly. The glutathione S-transferases, characterized by Habig, Pabst and Jakoby in 1974 as the first enzymatic step in mercapturic-acid formation, conjugate GSH to electrophiles; their activity is routinely followed spectrophotometrically with 1-chloro-2,4-dinitrobenzene as the model substrate, with GSH as the co-substrate. The selenium-dependent glutathione peroxidases use GSH to reduce peroxides, and their activity is measured through the same reductase/NADPH coupling. In both cases GSH supplied at known purity is the reagent that makes the assay quantitative.

Beyond enzymology, reduced glutathione is a standard additive in cell-culture and biochemical work as a defined thiol antioxidant and a reducing agent for protein refolding, and it serves as an analytical reference standard for LC-MS and HPLC methods that quantify endogenous GSH and GSSG in cells, tissues and biofluids. Because the molecule is small and its thiol is UV-silent, those methods usually rely on derivatization or mass detection rather than direct absorbance, so a well-characterized reference standard is central to method development.

This item is supplied as 600 mg of lyophilized reduced glutathione per vial. Regulatory position, stated factually: glutathione is an endogenous tripeptide and a long-established biochemical reagent; the material sold here is a research reference standard and is not offered as, or as a component of, any approved product. WholesalePeptide.us supplies it for laboratory research only.

Practical note for assay design: the free thiol oxidizes in air and in neutral-to-alkaline solution, so GSH stocks are made fresh, often in slightly acidic buffer, and kept cold and under minimal headspace. Identity and purity are confirmed on each lot COA, and the net peptide content matters because residual water or counter-ion changes the real amount of GSH weighed into an assay.

Research areas

• cellular redox biology and the GSH/GSSG ratio
• enzymatic recycling (DTNB) glutathione assays
• glutathione S-transferase activity assays
• glutathione peroxidase activity assays
• thiol antioxidant additive in cell-culture studies
• analytical reference standard for GSH/GSSG quantification

Handling and storage

• Store lyophilized vials at −20 °C, sealed, protected from light and moisture.
• Let the vial equilibrate to room temperature before opening to limit condensation.
• Reconstitute in an appropriate sterile buffer or solvent according to your laboratory SOP.
• Reduced glutathione oxidizes in air and in neutral or alkaline solution; prepare stocks fresh, keep them cold, and minimize headspace and freeze–thaw.