thiol group raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-05-22. Anything still debated is marked as such rather than presented as settled.
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.
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. 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.
| Property | Value | Notes |
|---|---|---|
| Common name | Glutathione | Reduced form is abbreviated GSH |
| Chemical class | Tripeptide | Composed of glutamate, cysteine, and glycine |
| Molar mass | 307.32 g/mol | For reduced glutathione |
| CAS Registry Number | 70-18-8 | For reduced L-glutathione |
| Appearance | White crystalline powder | Typical solid reference material |
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.
In its reduced form, glutathione carries a sulfhydryl group that can donate electrons. This property lets it act as a major cellular antioxidant and redox buffer. Glutathione peroxidase uses it to reduce hydrogen peroxide and lipid peroxides, while glutathione reductase regenerates the reduced form using NADPH. The ratio of reduced glutathione to glutathione disulfide is widely used as an indicator of oxidative stress, though the ratio changes with compartment, cell type, and sample handling. Oxidized glutathione can also form mixed disulfides with proteins, affecting their activity.
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 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.
The fundamental process in photoionization is the absorption of a high-energy photon by the molecule and subsequent ejection of an electron. In direct APPI, this process occurs for the analyte molecule, forming the molecular radical cation M•+. The analyte radical cation can be detected as M•+ or it can react with surrounding molecules and be detected as another ion. The most common reaction is the abstraction of a hydrogen atom from the abundant solvent to form the stable [M+H]+ cation, which is usually the observed ion. In dopant-APPI (or photoionization-induced APCI), a quantity of photoionizable molecules (e.g., toluene or acetone) is introduced into the sample stream to create a source of charge carriers. Use of a photoionizable solvent can also achieve the same effect. The dopant or solvent ions can then react with neutral analyte molecules via proton transfer or charge exchange reactions. The above table simplifies the dopant process. In fact, there may be extensive ion-molecule chemistry between dopant and solvent before the analyte becomes ionized. APPI can also produce negative ions by creating a high abundance of thermal electrons from dopant or solvent ionization or by photons striking metal surfaces in the ionization source. The cascade of reactions that can lead to M− or dissociative negative ions [M-X]− often involve O2 as an electron charge carrier. Examples of negative ionization mechanisms include: Direct or dopant-assisted negative ion APPI
The comeback is the largest in NBA Finals history, surpassing the 24-point comeback from the Boston Celtics in Game 4 of the 2008 NBA Finals. The Florida Supreme Court declines to block a new Republican-drawn congressional map from being used in the midterm elections. The map could enable Republicans to gain as many as four additional seats in the U.S. House.
Affinity chromatography can be used in a number of applications, including nucleic acid purification, protein purification from cell free extracts, and purification from blood. By using affinity chromatography, one can separate proteins that bind to a certain fragment from proteins that do not bind that specific fragment. Because this technique of purification relies on the biological properties of the protein needed, it is a useful technique and proteins can be purified many folds in one step.
Sources: en.wikipedia.org
Only when the South Ossetians opened up with artillery on Georgian villages, did the offensive to take Tskhinvali begin." The cable also says, "All evidence available to the country team supports Saakashvili's statement that this fight was not Georgia's original intention. Key Georgian officials, who would have had responsibility for an attack on South Ossetia have been on leave, and the Georgians only began mobilizing August 7 once the attack was well underway." The cable reported, "Fighting had continued throughout the night of August 7, resuming four hours after President Saakashvili unilaterally declared a cease-fire at 1900." The cable noted, "Although most in the Georgian government believed that the fighting had started as a ploy of de facto leader Kokoity, Saakashvili was now concerned that this might have been a Russian pretext and a further attack could be expected." The cable also reported that "The Georgians believe the South Ossetians are targeting the Russians to provoke a bigger Georgian-Russian conflict" and named the person responsible for the escalation of the conflict, "One plausible explanation for all this is that de facto leader Kokoity decided to roll the dice and stimulate a conflict with the Georgians in hopes of bringing in the Russians and thereby saving himself or enhancing his position." The cable reported that Russia had launched 4 ballistic missiles against Tskhinvali. The cable reported that the Georgians were fighting with unidentified Russian combatants north of Tskhinvali.
Since the 1999 publication of Good Manufacturing Practice for Active Pharmaceutical Ingredients, by the International Conference on Harmonization (ICH), GMPs now apply in those countries and trade groupings that are signatories to ICH (the EU, Japan and the U.S.), and applies in other countries (e.g., Australia, Canada, Singapore) which adopt ICH guidelines for the manufacture and testing of active raw materials.
==== Aerobic ==== In aerobic cells with sufficient oxygen, as in most human cells, the pyruvate is further metabolized. It is irreversibly converted to acetyl-CoA, giving off one carbon atom as the waste product carbon dioxide, generating another reducing equivalent as NADH. The two molecules acetyl-CoA (from one molecule of glucose) then enter the citric acid cycle, producing two molecules of ATP, six more NADH molecules and two reduced (ubi)quinones (via FADH2 as enzyme-bound cofactor), and releasing the remaining carbon atoms as carbon dioxide. The produced NADH and quinol molecules then feed into the enzyme complexes of the respiratory chain, an electron transport system transferring the electrons ultimately to oxygen and conserving the released energy in the form of a proton gradient over a membrane (inner mitochondrial membrane in eukaryotes). Thus, oxygen is reduced to water and the original electron acceptors NAD+ and quinone are regenerated. This is why humans breathe in oxygen and breathe out carbon dioxide. The energy released from transferring the electrons from high-energy states in NADH and quinol is conserved first as proton gradient and converted to ATP via ATP synthase. This generates an additional 28 molecules of ATP (24 from the 8 NADH + 4 from the 2 quinols), totaling to 32 molecules of ATP conserved per degraded glucose (two from glycolysis + two from the citrate cycle).
Sources: en.wikipedia.org
=== Cardiac-valvular === Cardiac-valvular EDS (cvEDS) is characterized by three major criteria: severe progressive cardiac-valvular problems (affecting aortic and mitral valves), skin problems such as hyperextensibility, atrophic scarring, thin skin, and easy bruising, and joint hypermobility (generalized or restricted to small joints). Four minor criteria may aid in the diagnosis of cvEDS. cvEDS is an autosomal recessive disorder, inherited through variation in both alleles of the gene COL1A2.
=== Polymorphonuclear neutrophils === Within an hour of wounding, polymorphonuclear neutrophils (PMNs) arrive at the wound site and become the predominant cells in the wound for the first two days after the injury occurs, with especially high numbers on the second day. They are attracted to the site by fibronectin, growth factors, and substances such as kinins. Neutrophils phagocytise debris and kill bacteria by releasing free radicals in what is called a respiratory burst. They also cleanse the wound by secreting proteases that break down damaged tissue. Functional neutrophils at the wound site only have life-spans of around two days, so they usually undergo apoptosis once they have completed their tasks and are engulfed and degraded by macrophages. Other leukocytes to enter the area include helper T cells, which secrete cytokines to cause more T cells to divide and to increase inflammation and enhance vasodilation and vessel permeability. T cells also increase the activity of macrophages.
== Discoidin domain receptors == Discoidin domain receptors form a subgroup of receptor tyrosine kinases. Receptor activation happens when collagen binds into preformed DDR dimers on cell membrane, when collagen is bound, a conformational change probably occurs, which causes cytosolic kinases to rotate to face each other, and their autophosphorylation. The exact way of receptor activation is unknown so far. Unlike other tyrosine-kinase receptors, maximal activation of receptors occurs 18 hours after collagen stimulation. They function as receptors for different collagen types, they recognize many fibrillar collagens and they are capable of binding some nonfibrillar collagens as well. Nevertheless, the native conformation of collagen is a requirement for receptor binding, denatured collagen is not bound. DDRs are expressed widely already during development and level of expression is high in adults as well. DDR1 is a homodimer. Its ectodomain consists of a collagen-binding discoidin domain followed by ~200 residues of unknown structure. It binds fibril-forming collagens and primarily type IV collagen, but also collagen of types I, VI, VIII. It is expressed mainly in epithelial cells and leukocytes and expression rate changes due to cell cycle phase. Functions include: mammary gland development; arterial wound repair; regulation of cell proliferation, cell adhesion and MMP expression; kidney function, differentiation and function of leukocytes. DDR2 structure as above. Binds fibril-forming collagens, collagen of types I, II, III and X.
An atrophic scar takes the form of a sunken recess in the skin, which has a pitted appearance. These are caused when underlying structures supporting the skin, such as fat or muscle, are lost. This type of scarring is often associated with acne, chickenpox, other diseases (especially Staphylococcus infection), surgery, certain insect and spider bites, or accidents. It can also be caused by a genetic connective tissue disorder, such as Ehlers–Danlos syndrome.
Sources: en.wikipedia.org
GSH is the reduced thiol form, while GSSG is the disulfide-linked oxidized dimer. The GSH:GSSG ratio is used as a redox indicator, though the ratio can vary with sample handling and cell type.
Glutathione is present in many foods, including meats, poultry, fish, some vegetables, and fruits. Cooking, storage, and digestion affect the amounts available for absorption.
Yes, both enzymatic steps in glutathione synthesis consume ATP. The first step, catalyzed by glutamate-cysteine ligase, is usually rate-limiting.
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.