thiol comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-12-22. Where a claim depends on a specific study, the study is described rather than over-claimed.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. Its cysteine residue carries a thiol group, which allows the molecule to participate in reduction and oxidation reactions. The compound exists in most living cells, where the reduced form, often abbreviated GSH, is usually more abundant than the oxidized disulfide form, GSSG. Intracellular concentrations are commonly in the millimolar range, while extracellular concentrations are much lower. This uneven distribution supports its role as a major cellular redox buffer.
Cells synthesize glutathione through two ATP-dependent enzymatic steps. The first step combines glutamate and cysteine to form gamma-glutamylcysteine, catalyzed by glutamate-cysteine ligase. The second step adds glycine, producing the complete tripeptide, catalyzed by glutathione synthetase. Glutathione itself can inhibit the first enzyme, providing negative feedback when levels are high. Because cysteine is often limiting, its availability influences how quickly the pathway proceeds. These reactions occur in the cytosol, and the resulting glutathione can be distributed to other compartments.
Biosynthesis occurs in two ATP-dependent steps. The enzyme glutamate-cysteine ligase joins glutamate and cysteine, forming gamma-glutamylcysteine; glutathione synthetase then adds glycine to produce the complete tripeptide. Because the peptide bond from glutamate uses the gamma-carboxyl group, glutathione resists digestion by many ordinary peptidases. Tissues vary in synthesis capacity, and the liver generally contains high concentrations relative to many other organs. This uneven distribution contributes to organ-specific differences in redox buffering and affects how experimental results are interpreted across tissue types.
Glutathione participates in detoxification reactions, amino acid transport, and the maintenance of protein thiols. It serves as a cofactor for several enzymes, including glutathione peroxidases and glutathione S-transferases. In research literature, altered glutathione status appears in studies of aging, infection, metabolic stress, and environmental exposure. Whether low glutathione is a cause, consequence, or marker of such conditions often remains unresolved. Direct measurement in blood or tissue provides a snapshot, but results depend on sample handling, timing, and the method used.
Glutathione is a small tripeptide made of glutamic acid, cysteine, and glycine. Its cysteine thiol group allows reversible oxidation and reduction, making it central to cellular redox chemistry. The reduced form, often abbreviated GSH, predominates inside most cells, while the oxidized disulfide form, GSSG, forms when two GSH molecules react. The ratio of GSH to GSSG is widely used as an indicator of oxidative stress in laboratory research, though it does not by itself diagnose a clinical condition.
| Property | Value | Notes |
|---|---|---|
| Chemical formula | C10H17N3O6S | Reduced glutathione (GSH) |
| Molar mass | 307.32 g/mol | Calculated for C10H17N3O6S |
| Appearance | White to off-white powder | Typical solid form |
| Solubility | Water-soluble | Polar tripeptide |
| Common synonyms | GSH; L-glutathione | Gamma-glutamylcysteinylglycine |
Within cells, glutathione serves as a cofactor for glutathione peroxidases and glutathione S-transferases. These enzymes reduce hydrogen peroxide and organic peroxides or conjugate electrophilic compounds to the thiol group. The resulting conjugates can be exported and processed through mercapturic acid pathways. Glutathione also contributes to protein thiol homeostasis and to recycling of other antioxidants such as ascorbate. Its precise roles vary by tissue, and many regulatory effects observed in laboratory systems remain difficult to quantify in whole organisms.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. It occurs in nearly all living cells, with highest concentrations in liver, kidney, and red blood cells, and exists in reduced (GSH) and oxidized disulfide (GSSG) forms. The cysteine thiol group enables reversible oxidation and reduction reactions. This property makes glutathione a central participant in cellular redox balance. The balance between these forms is often used as an indicator of oxidative stress.
Glutathione synthesis proceeds in two ATP-dependent steps catalyzed by glutamate-cysteine ligase and glutathione synthetase. The first step joins glutamate and cysteine to form gamma-glutamylcysteine and is generally rate-limiting. The second step adds glycine to complete the tripeptide. Cysteine availability, feedback inhibition by glutathione, and oxidative conditions influence flux through this pathway. The pathway is conserved across many organisms, and degradation by gamma-glutamyl transpeptidase and related peptidases recycles amino acids for new synthesis.
Glutathione supports detoxification by conjugating reactive electrophiles through glutathione S-transferases. The resulting conjugates are processed and exported, often after further metabolism. It also stores cysteine, transports amino acids across membranes through the gamma-glutamyl cycle, and assists in the maturation of iron-sulfur clusters and some prostaglandins. In plants, animals, and many microbes, the molecule appears in similar roles, but concentrations vary enormously between tissues. Liver, kidney, and red blood cells tend to contain high amounts, while blood plasma contains much less.
Glutathione is a small tripeptide built from glutamate, cysteine, and glycine. The peptide bond between glutamate and cysteine uses the gamma-carboxyl group, a linkage that resists ordinary peptidases. Cells make it in two ATP-dependent steps: gamma-glutamylcysteine synthetase joins glutamate and cysteine, then glutathione synthetase adds glycine. The pathway is feedback-inhibited by glutathione itself, so intracellular levels tend to stay within a narrow range. Because cysteine is often limiting, sulfur amino acid supply influences how much glutathione a cell can produce.
Glutathione supports several cellular processes beyond direct antioxidant action. It serves as a cofactor for glutathione peroxidase and glutathione S-transferase enzymes, which reduce peroxides and conjugate electrophiles, respectively. The molecule also acts as a reservoir of cysteine, an amino acid that can limit protein synthesis and redox signaling. In human nutrition, oral glutathione is sold as a supplement, but how much intact glutathione reaches tissues after ingestion remains an active research question. Clinical claims about supplementation are not uniformly supported by controlled trials.
Glutathione is a small tripeptide built from glutamic acid, cysteine, and glycine. Its peptide bond between glutamate and cysteine involves the gamma-carboxyl group rather than the usual alpha-carboxyl group. This structure gives the molecule a reactive thiol on the cysteine residue. The reduced form, often abbreviated GSH, is the predominant intracellular species in many cell types. Because the thiol can donate electrons, glutathione participates in redox chemistry and in the conjugation of reactive molecules.
Cells synthesize glutathione through two ATP-dependent steps: glutamate-cysteine ligase joins glutamate and cysteine, and glutathione synthetase adds glycine to form the complete tripeptide. Breakdown occurs through gamma-glutamyl transpeptidase and subsequent peptidase reactions, forming the gamma-glutamyl cycle. Within cells, glutathione also forms a disulfide-linked dimer called GSSG when two GSH molecules react. The balance between GSH and GSSG is widely used as an indicator of oxidative conditions, although the ratio can vary by compartment and tissue.
== History == In September 2005, Pfizer received a non-approvable letter from the U.S. Food and Drug Administration regarding lasofoxifene (trade name Oporia), a selective estrogen receptor modulator for the prevention of osteoporosis. In January 2008, Ligand Pharmaceuticals, through its marketing partner, Pfizer, submitted a New Drug Application for lasofoxifene, which is expected to be marketed under the tradename Fablyn. Lasofoxifene was approved in the EU under the brand name Fablyn by the EMEA in March 2009.
===== Fixed-dose combinations of antiretroviral medicines ===== Abacavir/dolutegravir/lamivudine (abacavir + dolutegravir + lamivudine) Abacavir/lamivudine (abacavir + lamivudine) Dolutegravir/lamivudine/tenofovir (dolutegravir + lamivudine + tenofovir) Efavirenz/emtricitabine/tenofovir Efavirenz/lamivudine/tenofovir (efavirenz + lamivudine + tenofovir) Emtricitabine/tenofovir (emtricitabine + tenofovir) Lamivudine/zidovudine (lamivudine + zidovudine)
== In other animals == Demyelinating diseases/disorders have been found worldwide in various animals. Some of these animals include mice, pigs, cattle, hamsters, rats, sheep, Siamese kittens, and a number of dog breeds (including Chow Chow, Springer Spaniel, Dalmatian, Samoyed, Golden Retriever, Lurcher, Bernese Mountain Dog, Vizsla, Weimaraner, Australian Silky Terrier, and mixed breeds). Ziggy Star, a female northern fur seal, was treated at the Marine Mammal Center beginning in March 2014 and was noted as the first reported case of a demyelinating disease in a marine mammal. She was later transported to Mystic Aquarium & Institute for Exploration for lifelong care as an ambassador to the public. In 2017, she was the first seal treated for hydrocephalus.
EC 1.14.14.5: alkanesulfonate monooxygenase EC 1.14.14.6: Now EC 1.14.13.111, methanesulfonate monooxygenase EC 1.14.14.7: transferred to EC 1.14.19.9, tryptophan 7-halogenase EC 1.14.14.8: anthranilate 3-monooxygenase (FAD) EC 1.14.14.9: 4-hydroxyphenylacetate 3-monooxygenase EC 1.14.14.10: nitrilotriacetate monooxygenase EC 1.14.14.11: styrene monooxygenase EC 1.14.14.12: 3-hydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione monooxygenase EC 1.14.14.13: 4-(γ-L-glutamylamino)butanoyl-[BtrI acyl-carrier protein] monooxygenase EC 1.14.14.14: aromatase EC 1.14.14.15: (3S)-3-amino-3-(3-chloro-4-hydroxyphenyl)propanoyl-[peptidyl-carrier protein SgcC2] monooxygenase EC 1.14.14.16: steroid 21-monooxygenase EC 1.14.14.17: squalene monooxygenase EC 1.14.14.18: heme oxygenase (biliverdin-producing) EC 1.14.14.19: steroid 17α-monooxygenase EC 1.14.14.20: phenol 2-monooxygenase (FADH2) EC 1.14.14.21: dibenzothiophene monooxygenase EC 1.14.14.22: dibenzothiophene sulfone monooxygenase EC 1.14.14.23: cholesterol 7α-monooxygenase EC 1.14.14.24: vitamin D 25-hydroxylase EC 1.14.14.25: cholesterol 24-hydroxylase EC 1.14.14.26: 24-hydroxycholesterol 7α-hydroxylase EC 1.14.14.27: resorcinol 4-hydroxylase (FADH2) EC 1.14.14.28: long-chain alkane monooxygenase EC 1.14.14.29: 25/26-hydroxycholesterol 7α-hydroxylase EC 1.14.14.30: isobutylamine N-monooxygenase EC 1.14.14.31: ipsdienol synthase EC 1.14.14.32: 17α-hydroxyprogesterone deacetylase EC 1.14.14.33: ethylenediaminetetraacetate monooxygenase EC 1.14.14.34: methanesulfonate monooxygenase (FMNH2) EC 1.14.14.35: dimethylsulfone monooxygenase EC 1.14.14.36: tyrosine N-monooxygenase EC 1.14.14.37: 4-hydroxyphenylacetaldehyde oxime monooxygenase EC 1.14.14.38: valine N-monooxygenase EC 1.14.14.39: isoleucine N-monooxygenase EC 1.14.14.40: phenylalanine N-monooxygenase EC 1.14.14.41: (E)-2-methylbutanal oxime monooxygenase EC 1.14.14.42: homomethionine N-monooxygenase EC 1.14.14.43: (methylsulfanyl)alkanaldoxime N-monooxygenase EC 1.14.14.44: phenylacetaldehyde oxime monooxygenase EC 1.14.14.45: aromatic aldoxime N-monooxygenase EC 1.14.14.46: pimeloyl-[acyl-carrier protein] synthase EC 1.14.14.47: nitric-oxide synthase (flavodoxin) EC 1.14.14.48: jasmonoyl-L-amino acid 12-hydroxylase EC 1.14.14.49: 12-hydroxyjasmonoyl-L-amino acid 12-hydroxylase EC 1.14.14.50: tabersonine 3-oxygenase EC 1.14.14.51: (S)-limonene 6-monooxygenase EC 1.14.14.52: (S)-limonene 7-monooxygenase EC 1.14.14.53: (R)-limonene 6-monooxygenase EC 1.14.14.54: phenylacetate 2-hydroxylase EC 1.14.14.55: quinine 3-monooxygenase EC 1.14.14.56: 1,8-cineole 2-exo-monooxygenase EC 1.14.14.57: taurochenodeoxycholate 6α-hydroxylase EC 1.14.14.58: trimethyltridecatetraene synthase EC 1.14.14.59: dimethylnonatriene synthase EC 1.14.14.60: ferruginol monooxygenase EC 1.14.14.61: carnosic acid synthase EC 1.14.14.62: salviol synthase EC 1.14.14.63: β-amyrin 16β-monooxygenase EC 1.14.14.64: β-amyrin 6β-monooxygenase EC 1.14.14.65: sugiol synthase EC 1.14.14.66: marmesin synthase EC 1.14.14.67: 11-hydroxysugiol 20-monooxygenase EC 1.14.14.68: syn-pimaradiene 3-monooxygenase EC 1.14.14.69: ent-cassadiene hydroxylase EC 1.14.14.70: ent-sandaracopimaradiene 3-hydroxylase EC 1.14.14.71: cucurbitadienol 11-hydroxylase EC 1.14.14.72: drimenol monooxygenase EC 1.14.14.73: albendazole monooxygenase (sulfoxide-forming) EC 1.14.14.74: albendazole monooxygenase (hydroxylating) EC 1.14.14.75: fenbendazole monooxygenase (4′-hydroxylating) EC 1.14.14.76: ent-isokaurene C2/C3-hydroxylase EC 1.14.14.77: phenylacetonitrile α-monooxygenase EC 1.14.14.78: phylloquinone ω-hydroxylase EC 1.14.14.79: docosahexaenoic acid ω-hydroxylase EC 1.14.14.80: long-chain fatty acid ω-monooxygenase EC 1.14.14.81: flavanoid 3′,5′-hydroxylase EC 1.14.14.82: flavonoid 3′-monooxygenase EC 1.14.14.83: geraniol 8-hydroxylase EC 1.14.14.84: linalool 8-monooxygenase EC 1.14.14.85: 7-deoxyloganate 7-hydroxylase EC 1.14.14.86: ent-kaurene monooxygenase EC 1.14.14.87: 2-hydroxyisoflavanone synthase EC 1.14.14.88: isoflavone 3′-hydroxylase EC 1.14.14.89: 4′-methoxyisoflavone 2′-hydroxylase EC 1.14.14.90: isoflavone 2′-hydroxylase EC 1.14.14.91: trans-cinnamate 4-monooxygenase EC 1.14.14.92: benzoate 4-monooxygenase EC 1.14.14.93: 3,9-dihydroxypterocarpan 6a-monooxygenase EC 1.14.14.94: leukotriene-B4 20-monooxygenase EC 1.14.14.95: germacrene A hydroxylase EC 1.14.14.96: 5-O-(4-coumaroyl)-D-quinate 3′-monooxygenase EC 1.14.14.97: methyltetrahydroprotoberberine 14-monooxygenase EC 1.14.14.98: protopine 6-monooxygenase EC 1.14.14.99: (S)-limonene 3-monooxygenase EC 1.14.14.100: dihydrosanguinarine 10-monooxygenase EC 1.14.14.101: dihydrochelirubine 12-monooxygenase EC 1.14.14.102: N-methylcoclaurine 3′-monooxygenase EC 1.14.14.103: tabersonine 16-hydroxylase EC 1.14.14.104: vinorine hydroxylase EC 1.14.14.105: taxane 10β-hydroxylase EC 1.14.14.106: taxane 13α-hydroxylase EC 1.14.14.107: ent-kaurenoic acid monooxygenase EC 1.14.14.108: 2,5-diketocamphane 1,2-monooxygenase EC 1.14.14.109: 3-hydroxyindolin-2-one monooxygenase EC 1.14.14.110: 2-hydroxy-1,4-benzoxazin-3-one monooxygenase EC 1.14.14.111: 9β-pimara-7,15-diene oxidase EC 1.14.14.112: ent-cassa-12,15-diene 11-hydroxylase EC 1.14.14.113: α-humulene 10-hydroxylase EC 1.14.14.114: amorpha-4,11-diene 12-monooxygenase EC 1.14.14.115: 11-oxo-β-amyrin 30-oxidase EC 1.14.14.116: averantin hydroxylase EC 1.14.14.117: aflatoxin B synthase EC 1.14.14.118: tryprostatin B 6-hydroxylase EC 1.14.14.119: fumitremorgin C monooxygenase EC 1.14.14.120: dammarenediol 12-hydroxylase EC 1.14.14.121: protopanaxadiol 6-hydroxylase EC 1.14.14.122: oryzalexin E synthase EC 1.14.14.123: oryzalexin D synthase EC 1.14.14.124: dihydromonacolin L hydroxylase EC 1.14.14.125: monacolin L hydroxylase EC 1.14.14.126: β-amyrin 28-monooxygenase EC 1.14.14.127: methyl farnesoate epoxidase EC 1.14.14.128: farnesoate epoxidase EC 1.14.14.129: long-chain acyl-CoA ω-monooxygenase EC 1.14.14.130: laurate 7-monooxygenase EC 1.14.14.131: bursehernin 5′-monooxygenase EC 1.14.14.132: (–)-4′-demethyl-deoxypodophyllotoxin 4-hydroxylase EC 1.14.14.133: 1,8-cineole 2-endo-monooxygenase EC 1.14.14.134: β-amyrin 24-hydroxylase EC 1.14.14.135: glyceollin synthase EC 1.14.14.136: deoxysarpagine hydroxylase EC 1.14.14.137: (+)-abscisic acid 8′-hydroxylase EC 1.14.14.138: lithocholate 6β-hydroxylase EC 1.14.14.139: 5β-cholestane-3α,7α-diol 12α-hydroxylase EC 1.14.14.140: Now included with EC 1.14.14.162 EC 1.14.14.162, flavanone 2-hydroxylase EC 1.14.14.141: psoralen synthase EC 1.14.14.142: 8-dimethylallylnaringenin 2′-hydroxylase EC 1.14.14.143: (+)-menthofuran synthase EC 1.14.14.144: abieta-7,13-diene hydroxylase EC 1.14.14.145: abieta-7,13-dien-18-ol hydroxylase EC 1.14.14.146: geranylgeraniol 18-hydroxylase EC 1.14.14.147: 3-epi-6-deoxocathasterone 23-monooxygenase EC 1.14.14.148: angelicin synthase EC 1.14.14.149: 5-epiaristolochene 1,3-dihydroxylase EC 1.14.14.150: costunolide synthase EC 1.14.14.151: premnaspirodiene oxygenase EC 1.14.14.152: β-amyrin 11-oxidase EC 1.14.14.153: indole-2-monooxygenase EC 1.14.14.154: sterol 14α-demethylase EC 1.14.14.155: 3,6-diketocamphane 1,2-monooxygenase EC 1.14.14.156: tryptophan N-monooxygenase EC 1.14.14.157: indolin-2-one monooxygenase EC 1.14.14.158: carotenoid ε hydroxylase EC 1.14.14.159: dolabradiene monooxygenase EC 1.14.14.160: zealexin A1 synthase EC 1.14.14.161: nepetalactol monooxygenase EC 1.14.14.162: flavanone 2-hydroxylase EC 1.14.14.163: (S)-1-hydroxy-N-methylcanadine 13-hydroxylase EC 1.14.14.164: fraxetin 5-hydroxylase EC 1.14.14.165: indole-3-carbonyl nitrile 4-hydroxylase EC 1.14.14.166: (S)-N-methylcanadine 1-hydroxylase EC 1.14.14.167: (13S,14R)-13-O-acetyl-1-hydroxy-N-methylcanadine 8-hydroxylase EC 1.14.14.168: germacrene A acid 8β-hydroxylase EC 1.14.14.169: eupatolide synthase EC 1.14.14.170: 8-epi-inunolide synthase EC 1.14.14.171: β-amyrin 16α-hydroxylase EC 1.14.14.172: 3,5,6-trichloropyridin-2-ol monooxygenase EC 1.14.14.173: 2,4,6-trichlorophenol monooxygenase EC 1.14.14.174: geranylhydroquinone 3′′-hydroxylase EC 1.14.14.175: ferruginol synthase EC 1.14.14.176: taxadiene 5α-hydroxylase EC 1.14.14.177: ultra-long-chain fatty acid ω-hydroxylase EC 1.14.14.182: taxoid 7beta-hydroxylase EC 1.14.14.197: progesterone 11alpha-monooxygenase
Sources: en.wikipedia.org
The MNHN has been called "the Louvre of the Natural Sciences". Its largest and best-known gallery is the Grand Gallery of Evolution, located at the end of the central alley facing the formal garden. It replaced an earlier Neoclassical gallery built next to the same by Buffon, opened in 1785, and demolished in 1935. It was proposed in 1872 and begun in 1877 by the architect Louis-Jules André, a teacher at the influential École des Beaux-Arts in Paris. It is a prominent example of Beaux Arts Architecture. It was opened in 1889 for the Paris Universal Exposition of 1889, which also presented the Eiffel Tower. It was never fully completed in its original design; it never received the neoclassical entrance planned for the side of the building away from the garden, facing Rue Geoffroy-Saint-Hilaire. The facade of the building was designed specifically as a backdrop for the garden. The facade facing the garden is divided into eleven traverses. Ten are decorated with sculpted medallions honouring prominent French scientists associated with the MNHN. The central traverse has a larger marble statue of a woman seated holding a book, in a pose similar to that of statue of Buffon facing the building. The statues are the work of Eugene Guillaume, a pupil of the sculptor Pradier. While the building exterior was neo-classical, the iron framework of the interior was extremely modern for the 19th century, like that of the Gare d'Orsay railroad station of the same period.
In April 1943, Enrico Fermi suggested to Robert Oppenheimer the possibility of using the radioactive byproducts from enrichment to contaminate the German food supply. The background was fear that the German atomic bomb project was already at an advanced stage, and Fermi was also skeptical at the time that an atomic bomb could be developed quickly enough. Oppenheimer discussed the proposal with Edward Teller, who suggested the use of 90Sr. James Bryant Conant and Leslie R. Groves were also briefed, but Oppenheimer wanted to proceed with the plan only if enough food could be contaminated with the weapon to kill half a million people.
=== Electrogenetics === Mammalian designer cells are engineered by humans to behave a specific way, such as an immune cell that expresses a synthetic receptor designed to combat a specific disease. Electrogenetics is an application of synthetic biology that involves utilizing electrical fields to stimulate a response in engineered cells. Controlling the designer cells can be done with relative ease through the use of common electronic devices, such as smartphones. Additionally, electrogenetics allows for the possibility of creating devices that are much smaller and compact than devices that use other stimulus through the use of microscopic electrodes. One example of how electrogenetics is used to benefit public health is through stimulating designer cells that are able to produce/deliver therapeutics. This was implemented in ElectroHEK cells, cells that contain voltage-gated calcium channels that are electrosensitive, meaning that the ion channel can be controlled by electrical conduction between electrodes and the ElectroHEK cells. The expression levels of the artificial gene that these ElectroHEK cells contained was shown to be able to be controlled by changing the voltage or electrical pulse length. Further studies have expanded on this robust system, one of which is a beta cell line system designed to control the release of insulin based on electric signals.
In White Women, Race Matters: The Social Construction of Whiteness, Frankenberg argues race shapes both the lives of the oppressor (white people, according to Frankenberg) as well as the oppressed. Frankenberg examined ways in which Ashkenazi Jewish women experience a sense of cultural belonging, but do not consider their Jewish faith to be classified a formal "race". Gillian Freeman (1929–2019) novelist and screenwriter; best known for her screenplays for The Leather Boys, I Want What I Want (film) and Only Lovers Left Alive (novel) Hadley Freeman (born 15 May 1978) American British journalist based in London; writes for the Jewish Chronicle, The Guardian and Vogue; of Austro-Hungarian and Polish Jewish ancestry. Anna Freud CBE (3 December 1895 – 9 October 1982); psychoanalyst of Austrian–Jewish descent; born in Vienna; youngest child of Sigmund Freud and Martha Bernays and followed path of father and contributed to field of psychoanalysis; alongside Hermine Hug-Hellmuth and Melanie Klein, is considered founder of psychoanalytic child psychology. Stephen Fry (born 24 August 1957) is an English actor, broadcaster, comedian, director, narrator and writer. He has written novels, non fiction, scripts and autobiography.
=== Skin grafts and artificial skin === Two layers of skin created from animal sources as a skin graft is useful in venous leg ulcers. Artificial skin, made of collagen and cultured skin cells, is also used to cover venous ulcers and excrete growth factors to help them heal. A systematic review found that bilayer artificial skin with compression bandaging is useful in the healing of venous ulcers when compared to simple dressings.
Sources: en.wikipedia.org
Glutathione is built from three amino acids: glutamate, cysteine, and glycine. The linkage involves the gamma-carboxyl group of glutamate rather than the alpha-carboxyl group, which is unusual for peptides. This structure protects the bond from some common peptidases.
It is present in nearly all cells, with notable amounts in the liver, kidneys, and red blood cells. The highest intracellular concentrations are usually in the millimolar range. Levels differ by tissue, age, and physiological state.
It is not classified as an essential nutrient because cells can synthesize it from amino acids. Dietary sources exist, but their contribution to tissue pools is not fully established. The body's production depends on enzyme activity and precursor availability.
GSH is the reduced form of glutathione, with a free thiol group on cysteine. GSSG is the oxidized disulfide form, created when two GSH molecules become linked. The two forms exist together, and their balance is often reported as the GSH/GSSG ratio in laboratory studies.