A practical reference on thiol: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-12-06. Anything still debated is marked as such rather than presented as settled.
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.
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. 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.
| 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 |
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.
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.
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.
== Oligomerization == Glutathione S-transferases form homodimers, but in eukaryotes can also form heterodimers of the A1 and A2 or YC1 and YC2 subunits. The homodimeric enzymes display a conserved structural fold. Each monomer is composed of a distinct N-terminal sub-domain, which adopts the thioredoxin fold, and a C-terminal all-helical sub-domain. This entry is the C-terminal domain.
== Function == Enzyme-generated isopeptide bonds have two main biological purposes: signaling and structure. Biosignaling influences protein function, chromatin condensation, and protein-half life. The biostructural roles of isopeptide bonds include blood clotting (for wound healing), extracellular matrix upkeep, the apoptosis pathway, modifying micro-tubules, and forming pathogenic pili in bacteria. Isopeptide bonds contribute to the pathogenicity of Vibrio cholerae because the actin cross-linking domain (ACD) forms an intermolecular bond between the γ-carboxyl group of glutamate and the ε-amino group of lysine in actin. This process stops actin polymerization in the host cell.
=== Removal of additives === In 2011, food blogger and activist Vani Hari noted that Chick-fil-A sandwiches contained nearly 100 ingredients, including peanut oil preserved with tert-butylhydroquinone (TBHQ), made from butane. In October 2012, Chick-fil-A invited Hari to meet with company executives at its headquarters. In December 2013, Chick-fil-A said that it was removing high-fructose corn syrup and artificial dyes, and was testing a new peanut oil. Like other companies, Chick-fil-A does not publicly announce such changes unless already in the news, because it focuses on these ingredients.
Sources: en.wikipedia.org
=== Phosphite triester synthesis === In the 1970s, substantially more reactive P(III) derivatives of nucleosides, 3'-O-chlorophosphites, were successfully used for the formation of internucleosidic linkages. This led to the discovery of the phosphite triester methodology. The group led by M. Caruthers took the advantage of less aggressive and more selective 1H-tetrazolidophosphites and implemented the method on solid phase. Very shortly after, the workers from the same group further improved the method by using more stable nucleoside phosphoramidites as building blocks. The use of 2-cyanoethyl phosphite-protecting group in place of a less user-friendly methyl group led to the nucleoside phosphoramidites currently used in oligonucleotide synthesis (see Phosphoramidite building blocks below). Many later improvements to the manufacturing of building blocks, oligonucleotide synthesizers, and synthetic protocols made the phosphoramidite chemistry a very reliable and expedient method of choice for the preparation of synthetic oligonucleotides.
=== Recreational use === The alkaloid has been rising in popularity as a recreational drug known as 7-OH, particularly in the United States. 7-OH-MIT containing tablets are sold in an unregulated manner over the counter in gas stations and smoke shops, with little to no information provided to consumers about the risk of addiction or adverse effects. According to the United States Poison Control Center, the number of cases relating to kratom-based products such as 7-OH-MIT have increased from under 200 in 2014 to 1600 in 2024, with approximately 40% of 7-OH-MIT reports coming from individuals who were abusing the drug.
=== Names === In 2013, trastuzumab emtansine was approved in the United States with the generic name "ado-trastuzumab emtansine", rather than the original United States Adopted Name (USAN) issued in 2009, "trastuzumab emtansine". Trastuzumab is the anti-HER2 antibody; emtansine refers to the linker-drug (SMCC-DM1). The "ado-" prefix was added at the request of the FDA to help prevent dispensing errors. During preclinical development and clinical trials, the drug was also known as trastuzumab-DM1 or trastuzumab-MCC-DM1 (after the codename for emtansine), both abbreviated T-DM1, and by the codename PRO132365.
Sources: en.wikipedia.org
Newsweek posted an article about Cheese, titled "Stopping a Kid Killer," in 2007. Jack Schafer, a columnist for Slate, criticized the Newsweek article; Schafer believes that the Newsweek article does not adequately explain the process of creating Cheese and did not use scientists as sources. Jane C. Maxwell, a senior research scientist of the Gulf Coast Addiction Technology Transfer Center at The University of Texas at Austin, stated in "“Cheese” Heroin: Status as of May 2, 2007" that she believes that the effect of Cheese could increase due to media reporting aspects such as "unsubstantiated numbers" and "sensationalistic emphasis" regarding "new highs" and "schoolboy drugs," leading to copycat outbreaks. In mid-2007, a number of area stores opted either to remove Tylenol PM and similar products from their shelves or to move them to shelves within a pharmacist's view or control. The manager of a Fiesta Mart supermarket in northwest Dallas explained his store's policy shift regarding various diphenhydramine-containing products by saying local youths were stealing these items, adding, "We didn't want to be part of the problem or anybody dying," implying that the store also pulled the products to curb abuse. The manager stated that theft decreased after removing the products, and various local Carnival supermarkets and Walgreens pharmacies also voluntarily shifted the products to pharmacist-controlled or -monitored shelves. The Dallas Morning News unofficially reported that arrests for Cheese in DISD decreased.
=== Pharmacodynamics === 1,2-Diarylethylamines primarily antagonize NMDA receptors, leading to dissociative effects like those of ketamine or phencyclidine (PCP). Many also interact with dopamine/norepinephrine transporters (DAT/NET) and sigma receptors, contributing to stimulant or hallucinogenic properties.
Complete androgen insensitivity syndrome (CAIS) is an AIS condition that results in the complete inability of the cell to respond to androgens. As such, the insensitivity to androgens is only clinically significant when it occurs in individuals who are exposed to significant amounts of testosterone at some point in their lives. The unresponsiveness of the cell to the presence of androgenic hormones prevents the masculinization of male genitalia in the developing fetus, as well as the development of male secondary sexual characteristics at puberty, but does allow, without significant impairment, female genital and sexual development in those with the condition. All human fetuses begin fetal development looking similar, with both the Müllerian duct system (female) and the Wolffian duct system (male) developing. Sex differentiation begins with the gonads, which in XX individuals become ovaries, and in XY individuals (including those with CAIS) typically become testicles due to the presence of the Y chromosome. It is at the seventh week of gestation that the bodies of non-CAIS individuals with the XY karyotype begin their masculinization: i.e., the Wolffian duct system is promoted and the Müllerian duct system is suppressed (the reverse happens with typically developing females). This process is triggered by androgens produced by the testicles.
==== Antimicrobial ==== Introduction of silver into bacterial cells induces a high degree of structural and morphological changes, which can lead to cell death. As the silver nanoparticles come in contact with the bacteria, they adhere to the cell wall and cell membrane. Once bound, some of the silver passes through to the inside, and interacts with phosphate-containing compounds like DNA and RNA, while another portion adheres to the sulfur-containing proteins on the membrane. The silver-sulfur interactions at the membrane cause the cell wall to undergo structural changes, like the formation of pits and pores. Through these pores, cellular components are released into the extracellular fluid, simply due to the osmotic difference. Within the cell, the integration of silver creates a low molecular weight region where the DNA then condenses. Having DNA in a condensed state inhibits the cell's replication proteins contact with the DNA. Thus the introduction of silver nanoparticles inhibits replication and is sufficient to cause the death of the cell. Further increasing their effect, when silver comes in contact with fluids, it tends to ionize which increases the nanoparticles' bactericidal activity. This has been correlated to the suppression of enzymes and inhibited expression of proteins that relate to the cell's ability to produce ATP.
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 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.