If you have been reading about thiol and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-12-07. Where a claim depends on a specific study, the study is described rather than over-claimed.
Glutathione is a small tripeptide composed of glutamate, cysteine, and glycine, with the unusual gamma-glutamyl linkage between glutamate and cysteine. Its cysteine thiol group makes it a major non-enzymatic antioxidant in cells. The reduced form, GSH, predominates in most intracellular compartments, while the oxidized disulfide form, GSSG, is produced when GSH reduces reactive oxygen species. Intracellular concentrations often reach millimolar levels, whereas plasma concentrations are much lower, typically in the low micromolar range. This gradient reflects active synthesis, transport, and consumption rather than passive distribution.
Synthesis occurs in two ATP-dependent steps: glutamate-cysteine ligase joins glutamate and cysteine to form gamma-glutamylcysteine, and glutathione synthetase adds glycine to complete the tripeptide. The pathway is feedback-inhibited by GSH and limited by cysteine availability, so cysteine supply often constrains production. Once formed, GSH participates in redox buffering, xenobiotic conjugation, and protein glutathionylation. Glutathione peroxidase uses GSH to reduce hydrogen peroxide and lipid peroxides, yielding GSSG, while glutathione reductase regenerates GSH using NADPH. Glutathione S-transferases conjugate electrophiles to GSH, supporting detoxification and excretion.
In cells, glutathione helps maintain the reducing environment of the cytosol and supports enzymes that counteract reactive oxygen species. It acts as a cofactor for glutathione peroxidases, which reduce hydrogen peroxide and lipid peroxides, and for glutathione S-transferases, which conjugate electrophiles. The ratio of GSH to GSSG is often used as an indicator of oxidative stress, although the ratio can vary by compartment and cell type. Glutathione also stores cysteine, an amino acid that can be limiting for protein synthesis and antioxidant defense.
Synthesis occurs in two ATP-dependent steps. The enzyme glutamate-cysteine ligase joins glutamate and cysteine to form gamma-glutamylcysteine, and glutathione synthetase adds glycine. The first step is rate-limiting and is influenced by cysteine availability and feedback inhibition by GSH. Breakdown involves gamma-glutamyl transferase and subsequent peptidases, which release constituent amino acids for reuse. Because turnover differs among tissues, measurements from blood, plasma, and tissues are not directly interchangeable. Research continues to clarify how compartment-specific pools are regulated in health and disease.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. It contains an unusual gamma-glutamyl bond between glutamate and cysteine, which resists cleavage by many peptidases. The reduced form, GSH, carries a thiol group on cysteine and is the dominant intracellular form in most cells. Its structure allows it to participate in redox reactions and to serve as a sulfur donor. The oxidized form, GSSG, consists of two GSH molecules joined by a disulfide bond.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C10H17N3O6S | Tripeptide of glutamate, cysteine, and glycine. |
| Molar mass | 307.32 g/mol | Calculated from the molecular formula. |
| Appearance | White to off-white powder | Typically crystalline or lyophilized solid. |
| Solubility | Soluble in water; insoluble in ethanol | Aqueous solutions are acidic and prone to oxidation. |
| Typical storage | -20 °C, desiccated, protect from light | Reduce exposure to oxygen and moisture. |
Interpreting glutathione measurements requires attention to pre-analytical variables. The GSSG concentration in a sample can rise artificially during storage or processing, making the GSH/GSSG ratio unreliable if not controlled. Reference ranges vary by specimen type, assay, and population, so comparisons across studies are difficult. Plasma glutathione is low and sensitive to hemolysis, while whole blood reflects primarily erythrocyte content. Many studies measure total glutathione rather than the reduced and oxidized forms separately, which limits conclusions about redox status.
Accurate measurement of glutathione begins with careful sample handling. Because GSH oxidizes rapidly to GSSG, samples must be processed quickly or frozen immediately. Acid precipitation with metaphosphoric acid or perchloric acid is common; it lowers pH, precipitates proteins, and helps preserve the reduced form. Chelating agents such as EDTA can limit metal-catalyzed oxidation. For whole blood, hemolysis releases glutathione from erythrocytes, so plasma and serum values differ substantially from whole blood values.
Several analytical methods can quantify glutathione, including high-performance liquid chromatography (HPLC) with UV or fluorescence detection for separating GSH and GSSG. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) offers higher specificity and sensitivity, often detecting nanomolar concentrations. The enzymatic recycling assay, often called the Tietze method, measures total glutathione by coupling reduction of GSSG to a colorimetric or fluorometric readout. Capillary electrophoresis and electrochemical detection are also used in specialized laboratories. Each method has distinct advantages and limitations regarding throughput, cost, and susceptibility to interference.
Biosynthesis proceeds in two ATP-dependent steps. First, glutamate-cysteine ligase joins glutamate and cysteine. Second, glutathione synthetase adds glycine to the intermediate. The pathway is regulated by cysteine availability, enzyme expression, and feedback inhibition by glutathione itself. Liver tissue has a particularly high capacity for synthesis and export. Because the molecule is made inside cells, circulating glutathione reflects a balance of release, uptake, and breakdown rather than simple dietary supply.
Functionally, glutathione supports redox balance by donating electrons and becoming oxidized. It also serves as a cofactor for enzymes such as glutathione peroxidases and glutathione S-transferases. These enzymes participate in peroxide reduction and in conjugation reactions that help process reactive molecules. Separate from antioxidant roles, glutathione can modify protein cysteines through S-glutathionylation, influencing enzyme activity and signaling. Research continues to examine how these chemical roles translate into whole-organism effects.
Glutathione is present in most tissues, with especially high concentrations in the liver. It also serves as a cofactor for some enzymes and helps transport amino acids across cell membranes. In plants and microorganisms, glutathione contributes to stress responses and metal handling. The molecule is synthesized in two ATP-dependent steps, first producing gamma-glutamylcysteine and then adding glycine. Because cysteine availability often limits synthesis, dietary and metabolic factors can influence glutathione levels. Research continues to examine how these levels relate to health and disease.
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. The peptide bond between glutamate and cysteine uses the gamma-carboxyl group of glutamate rather than the alpha-carboxyl group. This unusual linkage protects the molecule from many common peptidases. The cysteine side chain carries a thiol group that can undergo reversible oxidation. Because of this thiol, glutathione participates in redox reactions and helps maintain the reducing environment inside most cells in living systems.
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Multivesicular bodies are endosomal compartments that sort ubiquitinated membrane proteins by incorporating them into vesicles. This process involves the sequential action of three multiprotein complexes, ESCRT I to III (ESCRT standing for 'endosomal sorting complexes required for transport'). Vps4p is a AAA-type ATPase involved in this MVB sorting pathway. It had originally been identified as a ”class E” vps (vacuolar protein sorting) mutant and was subsequently shown to catalyse the dissociation of ESCRT complexes. Vps4p is anchored via Vps46p to the endosomal membrane. Vps4p assembly is assisted by the conserved Vta1p protein, which regulates its oligomerization status and ATPase activity.
== History == Chlordiazepoxide (initially called methaminodiazepoxide) was the first benzodiazepine to be synthesized in the mid-1950s. The synthesis was derived from work on a class of dyes, quinazoline-3-oxides. It was discovered by accident when in 1957 tests revealed that the compound had hypnotic, anxiolytic, and muscle relaxant effects. "The story of the chemical development of Librium and Valium was told by Sternbach. The serendipity involved in the invention of this class of compounds was matched by the trials and errors of the pharmacologists in the discovery of the tranquilizing activity of the benzodiazepines. The discovery of Librium in 1957 was due largely to the dedicated work and observational ability of a gifted technician, Beryl Kappell. For some seven years she had been screening compounds by simple animal tests for muscle relaxant activity using Myanesin as a standard and then meprobamate and chlorpromazine when they became available. All compounds submitted by the chemical staff for central nervous activity were screened. It was this battery of tests that picked out RO 5-0690 (Librium, chlordiazepoxide) as being similar but more potent than meprobamate." Three years later chlordiazepoxide was marketed as a therapeutic benzodiazepine medication under the brand name Librium. Following chlordiazepoxide, in 1963 diazepam hit the market under the brand name Valium—and was followed by many further benzodiazepine compounds over the subsequent years and decades. In 1959 it was used by over 2,000 physicians and more than 20,000 patients.
== Combination drugs == Some DPP-4 inhibitor drugs have received approval from the FDA to be used with metformin concomitantly with additive effect to increase the level of glucagon-like peptide 1 (GLP-1) which also decreases hepatic glucose production.
Sources: en.wikipedia.org
Blood alcohol content (BAC), also known as blood alcohol concentration or blood alcohol level, is the concentration of alcohol in a person's blood, measured for legal or medical purposes. BAC is expressed as the mass of alcohol per unit volume of blood. In the United States and many other countries, it is commonly reported as a percentage, such as 0.08% (equivalent to 0.8 g/L). Legal limits for driving vary by country, ranging from zero tolerance policies to 0.08%. Levels above 0.40% (4 g/L) may be fatal.
==== Arguments against a vent setting ==== Hyperthermophily could have been a result of convergent evolution in bacteria and archaea; a mesophilic environment has been called more likely. Production of prebiotic organic compounds at hydrothermal vents is estimated to be 108 kg/yr. Key prebiotic compounds, such as methane are in far lower concentrations at vents than in a Miller-Urey Experiment environment. Some organic compounds are now understood to have been formed by other geological processes and inherited by vents. Methane, for example, more likely comes from leached fluid inclusions formed deeper in oceanic crust from magmatic carbon. Vents do not concentrate prebiotic materials, due to strong dilution by seawater. This open system cycles compounds through vent minerals, leaving little residence time to accumulate. All modern cells rely on phosphates for nucleotide backbone and potassium for protein formation, making it likely that the first life forms shared these functions. These elements were not available in high quantities in the Archaean oceans. However, phosphate can be concentrated in lakes, as in the modern Last Chance Lake. Submarine hydrothermal vents are not conducive to condensation reactions to polymerise macromolecules. An older argument was that key polymers were encapsulated in vesicles after condensation, which supposedly would not happen in saltwater.
Prolidase is involved in the degradation of certain iminodipeptides (those containing C-terminal proline or hydroxyproline) formed during the breakdown of collagen, recycling the constituent amino acids (proline and hydroxyproline) and making them available for the cell to reuse – not least in the synthesis of new collagen. This recycling by prolidase, seen in the image above, is essential for maintaining proline-based systems in the cell, such as the collagen-rich extracellular matrix (ECM), which serves to physically support the structure of internal organs and connective tissues. Inadequate recycling due to a dysfunctional prolidase enzyme, caused by an appropriate mutation in the pertinent gene, leads to the deterioration of that support structure and therefore the connective tissue of the skin, capillaries, and the lymphatic tissue, as is the case in PD. In particular, it has been proposed that the buildup of non-degraded dipeptides might induce programmed cell-death (apoptosis), whereafter the cell's contents would be expelled into the neighbouring tissue potentially resulting in inflammation and giving rise to the dermatological problems seen in PD. Similarly, a dysfunctional collagen metabolism will likely interfere with physiological remodelling processes of the extracellular matrix (which require collagen to be dynamically degraded and rebuilt), which might cause problems with the skin, as well.
Cone snails, or cones, are highly venomous sea snails that constitute the family Conidae. Conidae is a taxonomic family (previously subfamily) of predatory marine gastropod molluscs in the superfamily Conoidea. As of 2014, cone snails are the only member of the superfamily Conoidea. Some previous classifications grouped the cone snails in a subfamily, Coninae. As of March 2015 Conidae contained over 800 recognized species, varying widely in size from lengths of 1.3 cm to 21.6 cm. Working in 18th-century Europe, Carl Linnaeus knew of only 30 species that are still considered valid. Fossils of cone snails have been found from the Eocene to the Holocene epochs. Cone snail species have shells that are roughly conical in shape. Many species have colorful patterning on the shell surface. Cone snails are almost exclusively tropical in distribution. All cone snails are venomous and capable of stinging. Cone snails use a modified radula tooth and a venom gland to attack and paralyze their prey before engulfing it. The tooth, which is likened to a dart or a harpoon, is barbed and can be extended some distance out from the head of the snail at the end of the proboscis. Cone snail venoms are mainly peptide-based, and contain many different toxins that vary in their effects. The sting of several larger species of cone snails can be serious, and even fatal to humans. Cone snail venom also shows promise for medical use.
==== Variants ==== In May 2021, a study by researchers of the National University of Córdoba, Argentina, found that the vaccine produced antibodies capable of neutralizing the Gamma variant. A study in Argentina found that neutralization is maintained against Alpha and Lambda and reduced against Gamma. The degree of reduction, however, does not necessarily imply reduced protection. A small study of 12 serum samples found that antibodies from the vaccine effectively neutralize the Alpha variant, with moderately reduced neutralization against the E484K substitution (median 2.8 fold reduction). However, neutralization of the Beta variant was markedly reduced (median 6.1 fold reduction).
Sources: en.wikipedia.org
Besides the above traditional types, hydrolyzed vegetable protein and other flavor enhancers may be mixed with brewed soy sauce to produce cheaper substitutes. This type is known as "blended soy sauce" (Chinese: 配製醬油) in China until 2019, when a Chinese 2018 standard that removed this type from the definition of soy sauce went into effect. The 2018 Chinese standard defines soy sauce as "liquid condiments with special color, aroma and taste made from soybeans and/or defatted soybeans, wheat and/or wheat flour and/or wheat bran as main raw materials through microbial fermentation." It still allows food additives to be used "following the definitions of GB 2760", which does not restrict the use of MSG and disodium ribonucleotides. (Hydrolyzed vegetable protein is not listed as a food additive in GB 2760 and is therefore unacceptable in products labelled as "soy sauce".)
A familiar example of the opposite, a shear thinning fluid, or pseudoplastic fluid, is wall paint: The paint should flow readily off the brush when it is being applied to a surface but not drip excessively. Note that all thixotropic fluids are extremely shear thinning, but they are significantly time dependent, whereas the colloidal "shear thinning" fluids respond instantaneously to changes in shear rate. Thus, to avoid confusion, the latter classification is more clearly termed pseudoplastic. Another example of a shear thinning fluid is blood. This application is highly favoured within the body, as it allows the viscosity of blood to decrease with increased shear strain rate.
== Synthesis == The original synthesis of prostaglandins F2α and E2 is shown below. It involves a Diels–Alder reaction which establishes the relative stereochemistry of three contiguous stereocenters on the prostaglandin cyclopentane core.
The NHS prescription fee was increased to £9.90 for each item in England in May 2024; prescriptions are free of charge if prescribed and dispensed in Scotland, Wales and Northern Ireland, and for some patients in England, such as inpatients, children, those over 60s or with certain medical conditions, and claimants of certain benefits. The pharmacy charges the NHS the actual cost of the medicine, which may vary from a few pence to hundreds of pounds. A patient can consolidate prescription charges by using a prescription payment certificate (informally a "season ticket"), effectively capping costs at £31.25 a quarter or £111.60 for a year. Outside the NHS, private prescriptions are issued by private medical practitioner and sometimes under the NHS for medicines that are not covered by the NHS. A patient pays the pharmacy the normal price for medicine prescribed outside the NHS. Survey results published by Ipsos MORI in 2008 found that around 800,000 people in England were not collecting prescriptions or getting them dispensed because of the cost, the same as in 2001.
Sources: en.wikipedia.org
GSH is the reduced, thiol-containing form of glutathione, while GSSG is the oxidized disulfide dimer formed when two GSH molecules react. Cells maintain a high GSH-to-GSSG ratio under normal conditions. A shift toward GSSG is often interpreted as oxidative stress, though sample handling can affect the measured ratio.
No. It is a tripeptide made from three amino acids: glutamate, cysteine, and glycine. The gamma-glutamyl bond is unusual and distinguishes it from typical peptide linkages.
Most ingested glutathione is broken down in the gastrointestinal tract into its constituent amino acids. Some formulations may protect it from digestion, but intact absorption and delivery to specific tissues remain uncertain. Research continues on precursors and delivery methods.
GSH is the reduced form with a free thiol group, while GSSG is the oxidized disulfide-linked dimer. Most assays distinguish the two because their balance reflects redox conditions. The names are not interchangeable.