The short version of thiol fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-10-03. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common analytical method | LC-MS/MS or HPLC | Separation of GSH and GSSG |
| Limit of detection | Nanomolar range | Method dependent |
| Typical sample storage | -80 °C | For biological matrices |
| Common reducing agent | TCEP or DTT | Prevents oxidation during processing |
| Common synonym | Gamma-glutamylcysteinylglycine | Systematic name |
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. Its glutamate-cysteine linkage uses the gamma-carboxyl group of glutamate, a feature that resists standard peptidases. The cysteine residue provides a thiol group, which gives the molecule its reducing character. In cells, glutathione is often the most abundant small-molecule thiol, with concentrations varying widely by tissue and compartment. It exists mainly in a reduced form called GSH, while oxidation produces a disulfide-linked dimer called GSSG.
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 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.
In cells, glutathione exists mainly in a reduced form called GSH. When two GSH molecules react, they form oxidized glutathione, or GSSG, which contains a disulfide bond. The ratio of GSH to GSSG is often used as an indicator of oxidative stress. Enzymes such as glutathione peroxidase and glutathione reductase help cycle the molecule between these two states. This cycling supports antioxidant defense, detoxification of reactive molecules, and regulation of certain signaling pathways.
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 functions in redox balance, detoxification, and sulfur amino acid storage. It participates in reactions that help maintain ascorbate and protein thiol status. The molecule serves as a cofactor for several enzymes, including glutathione peroxidases and glutathione S-transferases. These enzymes reduce peroxides and conjugate electrophiles, respectively. Glutathione also contributes to the metabolism of xenobiotics and to the transport of cysteine between tissues. How interorgan transport and tissue-specific regulation shape whole-body pools remains an active area of study.
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.
The larval brain and nerve cord consist of 3,016 neurons and 548,000 synapses. The Drosophila adult central nervous system (brain plus ventral nerve cord) has been reconstructed in both the male and the female and contains around 160,000 neurons and over 200 million synapses. These datasets allow scientists to generate testable hypotheses about how the brain processes information and gives rise to behavior.
Pseudomonas syringae pv. tabaci, the causal agent of the wildfire of tobacco P. syringae pv. coronafaciens P. syringae pv. garcae P. syringae BR2, which causes a disease of bean (Phaseolus vulgaris) similar to tobacco wildfire. This organism is closely related to P. syringae pv. tabaci but cannot be classified in the pathovar tabaci because it is not pathogenic on tobacco. Tabtoxin is a dipeptide precursor to the biologically active form of TBL, differing by having an extra threonine attached by a peptide bond to the C terminus. Tabtoxin is required by BR2(R) for both chlorosis and lesion formation on bean. All mutations that affected tabtoxin production, whether spontaneous deletion or transposon-induced, also affected lesion formation, and in all cases, restoration of tabtoxin production also restored pathogenic symptoms. Other factors may be required for BR2 to be pathogenic on bean, but apparently these are in addition to tabtoxin production. This toxin is a irreversible inhibitor of glutamine synthetase.
== Sources == Topographic maps and Geologic Folios of the United States Geological Survey Goodge, J. W.; Vervoort, J. D.; Fanning, C. M.; Brecke, D. M.; Farmer, G. L.; Williams, I. S.; Myrow, P. M.; DePaolo, D. J. (2008). "A positive test of East Antarctica–Laurentia juxtaposition within the Rodinia supercontinent" (PDF). Science. 321 (5886): 235–240. Bibcode:2008Sci...321..235G. doi:10.1126/science.1159189. ISSN 0036-8075. PMID 18621666. S2CID 11799613. Retrieved February 4, 2016. Loewy, S. L.; Dalziel, I. W. D.; Pisarevsky, S.; Connelly, J. N.; Tait, J.; Hanson, R. E.; Bullen, D. (2011). "Coats Land crustal block, East Antarctica: A tectonic tracer for Laurentia?". Geology. 39 (9): 859–862. Bibcode:2011Geo....39..859L. doi:10.1130/G32029.1. Retrieved January 24, 2016.
Sources: en.wikipedia.org
=== Enzymatic method for RNA oligonucleotide synthesis === One approach under investigation for overcoming length limitations in oligonucleotide synthesis involves the use of engineered enzymes to construct RNA sequences, rather than relying solely on traditional chemical methods. A key enzyme studied in this context is CID1 poly(U) polymerase (PUP), which naturally catalyzes the addition of nucleotides to the 3′ end of an RNA strand. In its native form, PUP functions as a template-independent polymerase, typically adding repeated sequence nucleotide tails to RNA molecules. To enable controlled sequence synthesis, enzymatic RNA synthesis has been adapted into a cyclic two-step process consisting of nucleotide extension and deblocking. During the extension step, a single nucleotide is enzymatically added, while the deblocking step removes a protecting group to allow subsequent incorporation. One investigated method involves the use of nucleoside triphosphates modified with a 3′-O-allyl blocking group. These modified nucleotides are synthesized and purified using techniques such as ion-exchange chromatography and preparative high-performance liquid chromatography (HPLC). Upon incorporation by PUP, the 3′-O-allyl group prevents further extension, thereby enabling single-nucleotide addition per cycle. Chemical removal of the blocking group then permits the next round of extension. Studies have shown that wild-type PUP exhibits limited efficiency when incorporating modified nucleotides.
== Medical uses == Oxazepam is an intermediate-acting benzodiazepine with a slow onset of action, so it is usually prescribed to individuals who have trouble staying asleep, rather than falling asleep. It is commonly prescribed for anxiety disorders with associated tension, irritability, and agitation. It is also prescribed for drug and alcohol withdrawal, and for anxiety associated with depression. Oxazepam is sometimes prescribed off-label to treat social phobia, post-traumatic stress disorder, insomnia, premenstrual syndrome, and other conditions.
Pegylated interferon alfa-2b is a drug used to treat melanoma, as an adjuvant therapy to surgery. Also used to treat hepatitis C (typically, in combination with ribavirin), it is no longer recommended due to poor efficacy and adverse side-effects. Subcutaneous injection is the preferred delivery method. Belonging to the alpha interferon family of medications, the molecule is PEGylated to prevent breakdown. Approval for medical use in the United States was granted in 2001. It is on the World Health Organization's List of Essential Medicines as a therapy for chronic hepatitis C.
Sources: en.wikipedia.org
Glutathione oxidizes quickly when cells are disrupted or when samples sit at room temperature. Rapid processing or immediate freezing minimizes the conversion of GSH to GSSG. This step helps ensure that the measured ratio reflects the original biological state.
The Tietze assay is an enzymatic recycling method that measures total glutathione. It uses glutathione reductase to reduce GSSG back to GSH, which then reacts with a chromogen or fluorophore. The reaction cycles repeatedly, amplifying the signal for detection.
Yes, but the choice of blood fraction matters. Plasma or serum contains low glutathione levels and is easily affected by hemolysis. Whole blood mainly reflects the high glutathione content of erythrocytes, so results from different fractions are not directly comparable.
It is a tripeptide of glutamic acid, cysteine, and glycine. The linkage between glutamate and cysteine uses the gamma-carboxyl group, which is unusual for peptides.