The short version of GSSG fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-07-26 and is reviewed periodically as new material appears.
Commercial glutathione is produced by microbial fermentation or chemical synthesis, then purified. Reduced and oxidized grades are offered separately, with purity specifications often exceeding 98 percent. The compound appears in foods such as fresh fruits, vegetables, and meats, although cooking and processing can lower amounts. Oral, topical, and inhaled forms are discussed in research and consumer contexts, but absorption and tissue delivery remain active areas of study. Regulatory status varies by country and intended use.
Glutathione is a small sulfur-containing peptide built from glutamic acid, cysteine, and glycine. Its distinctive feature is a gamma-glutamyl bond between glutamate's side-chain carboxyl group and cysteine's amino group. This linkage resists ordinary peptidases and helps the molecule remain stable inside cells. The reduced thiol form, often abbreviated GSH, is the dominant intracellular species. The oxidized disulfide dimer, GSSG, forms when two reduced molecules link through their cysteine sulfur atoms. The balance between these forms is a common redox indicator.
In living systems, glutathione occurs in millimolar concentrations in many cell types, while extracellular levels are generally much lower. The liver holds a substantial share of the body's total pool, and the molecule participates in reduction, detoxification, and amino acid transport. It also serves as a cofactor for enzymes such as glutathione peroxidase and glutathione S-transferase. Because the cysteine residue supplies a reactive thiol, glutathione can donate electrons and become oxidized. Cells regenerate reduced glutathione through glutathione reductase using NADPH.
Samples for glutathione analysis require careful handling because the compound oxidizes readily and can be consumed by enzymes after collection. Blood is often treated with acid or thiol-blocking agents soon after draw, and plasma should be separated quickly from red blood cells. Tissues are usually snap-frozen or extracted immediately. Aqueous solutions of glutathione are less stable than dry powder and degrade faster at neutral or alkaline pH, in light, or with dissolved oxygen. Repeated freeze-thaw cycles also reduce reliability.
Quality control for glutathione materials checks identity, assay, purity, water content, and disulfide content. Commercial products vary from research-grade powder to dietary supplements, and labels may not distinguish reduced from oxidized forms. In the United States, oral glutathione is commonly sold as a dietary supplement rather than an approved drug, while injectable forms fall under different rules and may require a prescription. Regulatory status differs by country. Analytical certificates, when available, help verify what a material contains, but independent testing remains important for interpretation.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C10H17N3O6S | Reduced glutathione (GSH) |
| Molar mass | 307.32 g/mol | Oxidized dimer GSSG is 612.63 g/mol |
| Appearance | White to off-white crystalline powder | Typical purified solid |
| Solubility | Freely soluble in water; practically insoluble in ethanol | Polarity reflects multiple ionizable groups |
| Common synonyms | GSH; L-glutathione; γ-glutamylcysteinylglycine | 'Reduced' distinguishes it from GSSG |
Measuring glutathione requires attention to sample preparation because the molecule oxidizes readily. Blood, tissue, and cell samples are often treated with acid to precipitate proteins and stabilize the thiol. Without such steps, GSH can convert to GSSG or form mixed disulfides during storage. Analytical methods include spectrophotometric assays, high-performance liquid chromatography, and mass spectrometry. Each approach has different sensitivity, specificity, and susceptibility to interference from related compounds in complex matrices.
For solid glutathione, storage conditions affect shelf life. The reduced form is typically kept cool, dry, and protected from air and light. Moisture can promote oxidation, while elevated temperatures accelerate degradation. Suppliers often specify storage at or below freezing, sometimes under inert gas. Solutions are less stable than powders and may require preparation shortly before use. Buffers and chelating agents can slow oxidation, but they do not eliminate it. Published stability data vary with matrix, pH, and container.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine, and it is the most abundant non-protein thiol in most living cells. The reduced form, GSH, carries a sulfhydryl group that can donate electrons, while the oxidized form, GSSG, forms when two GSH molecules link via a disulfide bond. The balance between these two forms helps define the cellular redox environment, and their ratio is often used as an indicator of oxidative stress. Because the sulfhydryl group is reactive, glutathione participates in many cellular processes, including detoxification and protein regulation.
Glutathione is synthesized in two ATP-dependent steps. First, gamma-glutamylcysteine synthetase links glutamate and cysteine; second, glutathione synthetase adds glycine to form the complete tripeptide. The pathway is feedback-inhibited by GSH itself, which helps maintain steady intracellular levels. Tissues vary widely in glutathione content, with the liver typically containing the highest concentrations, followed by the kidneys, lungs, and erythrocytes. Because cysteine is often limiting, its availability influences synthesis rates, and regulation of this pathway varies by cell type.
Glutathione serves as a cofactor for several enzymes, including glutathione peroxidase and glutathione S-transferase. These enzymes help reduce hydrogen peroxide and lipid peroxides, and they conjugate reactive electrophiles for excretion. The molecule also acts as a reservoir for cysteine, an amino acid that is prone to oxidation. In addition, glutathione participates in the metabolism of nitric oxide, leukotrienes, and prostaglandins. Its roles extend to cell signaling, apoptosis, and the regulation of protein function through S-glutathionylation.
Adenylyl-sulfate reductase (glutathione) (EC 1.8.4.9) is an enzyme that catalyzes the chemical reaction AMP + sulfite + glutathione disulfide ⇌ {\displaystyle \rightleftharpoons } adenylyl sulfate + 2 glutathione The 3 substrates of this enzyme are adenosine monophosphate, sulfite, and glutathione disulfide, whereas its two products are adenylyl sulfate and glutathione. This enzyme belongs to the family of oxidoreductases, specifically those acting on a sulfur group of donors with a disulfide as acceptor. The systematic name of this enzyme class is AMP,sulfite:glutathione-disulfide oxidoreductase (adenosine-5'-phosphosulfate-forming). Other names in common use include 5'-adenylylsulfate reductase (also used for, internal_xref(ec_num(1,8,99,2))), AMP,sulfite:oxidized-glutathione oxidoreductase, (adenosine-5'-phosphosulfate-forming), and plant-type 5'-adenylylsulfate reductase. In plants, APS is reduced by the plastidic enzyme APS reductase (APR; EC 1.8.4.9) in the presence of physiological concentrations of reduced glutathione (GSH), which acts as an electron donor.
C4H2N2O4 + GSH → C4H3N2O4• + GS• C4H3N2O4• + GSH → C4H4N2O4 + GS• C4H4N2O4 + O2 → C4H3N2O4• + O2•− + H+ C4H3N2O4• + O2 → C4H2N2O4 + O2•− + H+ Because it selectively kills the insulin-producing beta-cells found in the pancreas, alloxan is used to induce diabetes in laboratory animals. This occurs most likely because of selective uptake of the compound due to its structural similarity to glucose as well as the beta-cell's highly efficient uptake mechanism (GLUT2). In addition, alloxan has a high affinity to SH-containing cellular compounds and, as a result, reduces glutathione content. Furthermore, alloxan inhibits glucokinase, a SH-containing protein essential for insulin secretion induced by glucose. Most studies have shown that alloxan is not toxic to the human beta-cell, even in very high doses, probably because of differing glucose uptake mechanisms in humans and rodents. Alloxan is, however, toxic to the liver and the kidneys in high doses, as these are tissues where the GLUT2 transporter is expressed in humans. Streptozotocin
Acetylcysteine or N-acetylcysteine (NAC) is a mucolytic that is used to treat paracetamol (acetaminophen) overdose and to loosen thick mucus in individuals with chronic bronchopulmonary disorders, such as pneumonia and bronchitis. It has been used to treat lactobezoar in infants. It can be taken intravenously, orally (swallowed by mouth), or by inhalation by use of a nebulizer. It is also sometimes used as a dietary supplement. Common side effects include nausea and vomiting when taken orally. The skin may occasionally become red and itchy with any route of administration. A non-immune type of anaphylaxis may also occur. It appears to be safe in pregnancy. For paracetamol overdose, it works by increasing the level of glutathione, an antioxidant that can neutralize the toxic breakdown products of paracetamol. When inhaled, it acts as a mucolytic by decreasing the thickness of mucus. Acetylcysteine was initially patented in 1960 and came into medical use in 1968. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication.
Alcohol dehydrogenase class-3 is an enzyme that in humans is encoded by the ADH5 gene. This gene encodes glutathione-dependent formaldehyde dehydrogenase or the class III alcohol dehydrogenase chi subunit, which is a member of the alcohol dehydrogenase family. Members of this family metabolize a wide variety of substrates, including ethanol, retinol, other aliphatic alcohols, hydroxysteroids, and lipid peroxidation products. Class III alcohol dehydrogenase is a homodimer composed of 2 chi subunits. It has virtually no activity for ethanol oxidation, but exhibits high activity for oxidation of long-chain primary alcohols and for oxidation of S-hydroxymethyl-glutathione, a spontaneous adduct between formaldehyde and glutathione. This enzyme is an important component of cellular metabolism for the elimination of formaldehyde, a potent irritant and sensitizing agent that causes lacrymation, rhinitis, pharyngitis, and contact dermatitis.
Sources: en.wikipedia.org
Acetylcysteine or N-acetylcysteine (NAC) is a mucolytic that is used to treat paracetamol (acetaminophen) overdose and to loosen thick mucus in individuals with chronic bronchopulmonary disorders, such as pneumonia and bronchitis. It has been used to treat lactobezoar in infants. It can be taken intravenously, orally (swallowed by mouth), or by inhalation by use of a nebulizer. It is also sometimes used as a dietary supplement. Common side effects include nausea and vomiting when taken orally. The skin may occasionally become red and itchy with any route of administration. A non-immune type of anaphylaxis may also occur. It appears to be safe in pregnancy. For paracetamol overdose, it works by increasing the level of glutathione, an antioxidant that can neutralize the toxic breakdown products of paracetamol. When inhaled, it acts as a mucolytic by decreasing the thickness of mucus. Acetylcysteine was initially patented in 1960 and came into medical use in 1968. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication.
N-Acetylcysteine amide (abbrev. NACA, AD4 and also known as acetylcysteinamide) is an amide derivative of N-acetylcysteine (NAC) that appears to have better blood–brain barrier permeability and bioavailability possessing potential antioxidant and anti-inflammatory activity When administered, NACA increases glutathione levels. Glutathione neutralizes reactive oxygen species, reduces oxidative stress, and prevents induced cell damage and apoptosis. NACA has increased lipophilicity and membrane permeability compared to NAC. This compound belongs to a class of experimental compounds known as N-acyl-alpha-amino acids and their derivatives. These are compounds containing an alpha-amino acid (or its derivative) with an acyl group on the terminal nitrogen atom.
Alcohol dehydrogenase class-3 is an enzyme that in humans is encoded by the ADH5 gene. This gene encodes glutathione-dependent formaldehyde dehydrogenase or the class III alcohol dehydrogenase chi subunit, which is a member of the alcohol dehydrogenase family. Members of this family metabolize a wide variety of substrates, including ethanol, retinol, other aliphatic alcohols, hydroxysteroids, and lipid peroxidation products. Class III alcohol dehydrogenase is a homodimer composed of 2 chi subunits. It has virtually no activity for ethanol oxidation, but exhibits high activity for oxidation of long-chain primary alcohols and for oxidation of S-hydroxymethyl-glutathione, a spontaneous adduct between formaldehyde and glutathione. This enzyme is an important component of cellular metabolism for the elimination of formaldehyde, a potent irritant and sensitizing agent that causes lacrymation, rhinitis, pharyngitis, and contact dermatitis.
Sources: en.wikipedia.org
C4H2N2O4 + GSH → C4H3N2O4• + GS• C4H3N2O4• + GSH → C4H4N2O4 + GS• C4H4N2O4 + O2 → C4H3N2O4• + O2•− + H+ C4H3N2O4• + O2 → C4H2N2O4 + O2•− + H+ Because it selectively kills the insulin-producing beta-cells found in the pancreas, alloxan is used to induce diabetes in laboratory animals. This occurs most likely because of selective uptake of the compound due to its structural similarity to glucose as well as the beta-cell's highly efficient uptake mechanism (GLUT2). In addition, alloxan has a high affinity to SH-containing cellular compounds and, as a result, reduces glutathione content. Furthermore, alloxan inhibits glucokinase, a SH-containing protein essential for insulin secretion induced by glucose. Most studies have shown that alloxan is not toxic to the human beta-cell, even in very high doses, probably because of differing glucose uptake mechanisms in humans and rodents. Alloxan is, however, toxic to the liver and the kidneys in high doses, as these are tissues where the GLUT2 transporter is expressed in humans. Streptozotocin
Adenylyl-sulfate reductase (glutathione) (EC 1.8.4.9) is an enzyme that catalyzes the chemical reaction AMP + sulfite + glutathione disulfide ⇌ {\displaystyle \rightleftharpoons } adenylyl sulfate + 2 glutathione The 3 substrates of this enzyme are adenosine monophosphate, sulfite, and glutathione disulfide, whereas its two products are adenylyl sulfate and glutathione. This enzyme belongs to the family of oxidoreductases, specifically those acting on a sulfur group of donors with a disulfide as acceptor. The systematic name of this enzyme class is AMP,sulfite:glutathione-disulfide oxidoreductase (adenosine-5'-phosphosulfate-forming). Other names in common use include 5'-adenylylsulfate reductase (also used for, internal_xref(ec_num(1,8,99,2))), AMP,sulfite:oxidized-glutathione oxidoreductase, (adenosine-5'-phosphosulfate-forming), and plant-type 5'-adenylylsulfate reductase. In plants, APS is reduced by the plastidic enzyme APS reductase (APR; EC 1.8.4.9) in the presence of physiological concentrations of reduced glutathione (GSH), which acts as an electron donor.
The oral bioavailability of acetylcysteine is relatively low due to extensive first-pass metabolism in the gut wall and liver. It ranges between 6% and 10%. Intravenous administration of acetylcysteine bypasses the first-pass metabolism, resulting in higher bioavailability compared to oral administration. Intravenous administration of acetylcysteine ensures nearly 100% bioavailability as it directly enters the bloodstream. Acetylcysteine is extensively liver metabolized, CYP450 minimal. After a single IV administration, urine excretion is 30% at 0.11 L/hr/kg, with a half-life of 5.6 hours. Acetylcysteine is the N-acetyl derivative of the amino acid L-cysteine and is a precursor in the formation of the antioxidant glutathione in the body. The thiol (sulfhydryl) group confers antioxidant effects and is able to reduce free radicals. Nitroglycerin interacts moderately with NAC, possibly resulting in hypotension and nitroglycerin-induced headache. Intravenous NAC can cause rate-related anaphylactoid reaction, usually mild.
Sources: en.wikipedia.org
It is a tripeptide rather than a full protein. Proteins generally contain many amino acids joined by alpha-peptide bonds, while glutathione has three residues and an unusual gamma-glutamyl linkage. That structure affects how enzymes recognize and break it down.
GSH is the reduced form with a free thiol group. GSSG is the oxidized disulfide dimer formed when two GSH molecules react. The GSH-to-GSSG ratio is used in research as one indicator of cellular redox conditions.
Yes, it is present in many animal and plant tissues, including meats, some vegetables, and fruits. Heat, storage, and processing can reduce its content, so measured amounts vary widely.
Common approaches include enzymatic recycling assays, HPLC, and LC-MS/MS. Acid extraction and rapid processing limit oxidation before analysis.