Glutathione 1500mg

What is Glutathione ?

Glutathione (GSH) is the tripeptide γ-L-glutamyl-L-cysteinyl-glycine, the most abundant non-protein thiol in mammalian cells. We supply reduced glutathione as 1500mg of lyophilised powder per vial, for redox and oxidative-stress research.

Its three residues are glutamate, cysteine and glycine. Glutamate joins cysteine through its gamma-carboxyl group, not the alpha-carboxyl of an ordinary peptide bond. The formula is C₁₀H₁₇N₃O₆S, the molecular weight 307.32 g/mol and the CAS number of the reduced form 70-18-8.

Cells make it in the cytosol in two ATP-dependent steps. Glutamate cysteine ligase is the rate-limiting enzyme, glutathione synthetase the second, and cysteine supply governs the rate (Lu, Biochim Biophys Acta, 2013). Tissue levels are millimolar, highest in the liver.

Glutathione Research Applications

Typical uses are oxidative-stress models with GSH depletion as the readout, glutathione peroxidase and glutathione S-transferase assays, and GSH:GSSG measurements. Work on GSH synthesis looks at glutamate cysteine ligase and its regulation by Nrf2 through the antioxidant response element, AP-1 and NF-κB (Lu, 2013).

Reduced glutathione (GSH) vs oxidised glutathione (GSSG)

GSH is the reduced form, with a free thiol on its cysteine. GSSG is the disulfide formed when two GSH molecules are oxidised together. Glutathione reductase converts GSSG back to GSH using NADPH. The GSH:GSSG ratio is one of the most widely measured redox parameters in cell biology. Dissolved GSH oxidises in air, so solutions for ratio work need protecting from oxygen.

Research Overview

Glutathione (gamma-L-glutamyl-L-cysteinyl-glycine; GSH) is the principal low-molecular-weight thiol antioxidant of mammalian cells, with the molecular formula C₁₀H₁₇N₃O₆S, a molecular weight of 307.32 g/mol and CAS number 70-18-8. It is a tripeptide in which cysteine is flanked by glutamate and glycine, and, unusually, glutamate is joined to cysteine through its gamma-carboxyl group rather than the alpha-carboxyl used in an ordinary peptide bond. That gamma-glutamyl linkage is functionally important: it makes GSH resistant to the peptidases that would otherwise degrade a normal tripeptide, so intracellular GSH is cleaved only by gamma-glutamyl transpeptidase on the extracellular face of the plasma membrane. Biosynthesis is a two-step, ATP-dependent pathway (Meister and Anderson, Annual Review of Biochemistry, 1983): glutamate-cysteine ligase condenses glutamate and cysteine to gamma-glutamylcysteine, and glutathione synthetase then adds glycine. Because the first enzyme is both feedback-inhibited by GSH and limited by cysteine supply, cysteine availability is the dominant control point for synthesis (Lu, Biochimica et Biophysica Acta, 2013). Glutathione functions as a cellular redox buffer: it cycles between the reduced thiol form (GSH) and the oxidised disulfide (GSSG) through NADPH-dependent glutathione reductase, and healthy cells maintain a GSH:GSSG ratio of roughly 100:1. It acts as a direct radical scavenger, as the obligate electron donor for the glutathione peroxidases that reduce hydrogen peroxide and lipid peroxides, and as a substrate for the glutathione S-transferases that conjugate electrophiles and xenobiotics for export (Forman, Zhang and Rinna, Molecular Aspects of Medicine, 2009). Sies (Free Radical Biology and Medicine, 1999) framed these combined roles as a general cellular defence system against oxidative challenge, and the same review literature documents a well-replicated decline in tissue GSH with age. For experimental work the key practical point is that reduced GSH is air-oxidisable: dissolved GSH dimerises to GSSG on exposure to oxygen, so any assay of the reduced form must protect the thiols, by acid precipitation, alkylation or a reducing environment, if the GSH:GSSG couple is the measurement of interest.

Storage and Reconstitution

Store glutathione powder at -20°C, away from light and moisture. Once reconstituted, keep it at 2-8°C and use it within 4 weeks. For GSH:GSSG work, make solutions fresh or aliquot and freeze them at once, and avoid repeated freeze-thaw cycles.

Vials are sold on their own, without bacteriostatic water for mixing or other supplies.

How to reconstitute and handle

Let the vial reach room temperature and swab the stopper with alcohol. Add bacteriostatic water slowly down the inside wall and swirl gently until the powder dissolves. Do not shake. Reconstitute only what you need and keep headspace small, because reduced glutathione oxidises in air.

• Reduced glutathione (GSH) is air-oxidisable: in solution it dimerises to glutathione disulfide (GSSG) on exposure to oxygen, most rapidly at neutral to alkaline pH. Keep dissolved GSH cold, minimise headspace and, where the GSH:GSSG ratio matters, prepare solutions fresh or work under inert atmosphere.
• GSH absorbs only weakly in the near-UV, so quantitative work normally relies on thiol derivatisation (for example DTNB, Ellman's reagent) or on HPLC with fluorescence detection, with acid precipitation used to preserve the reduced form before measurement.

For the full method, see the peptide reconstitution guide and the reconstitution calculator.

Research References

• Glutathione (Meister and Anderson, Annu Rev Biochem, 1983)
• Glutathione: overview of its protective roles, measurement and biosynthesis (Forman et al., Mol Aspects Med, 2009)
• Glutathione and its role in cellular functions (Sies, Free Radic Biol Med, 1999)
• Glutathione synthesis (Lu, Biochim Biophys Acta, 2013)

Published research on Glutathione is indexed on PubMed. See our full UK buyer's guide for Glutathione and UK buyer's guide for Glutathione CoA.