The short version of thiol fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. 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.
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. 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.
| 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 |
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 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.
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. 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.
== Clinical trials == Preclinical research showed that it elicits neutralizing antibodies in non-human primates against COVID-19 variants of concern, including the SARS-CoV-2 Alpha variant, Beta variant, Delta variant, and Gamma variant.
Around late November to early December, Liu Xiang's forces made plans to assault Renshou and Jianyang, both on the approaches to Chengdu. Several sources cite December as the end date of the Two-Liu War; however, fighting continued long into 1933.
=== Active control studies === In cases where giving a placebo to a person suffering from a disease may be unethical, "active comparator" (also known as "active control") trials may be conducted instead. In trials with an active control group, subjects are given either the experimental treatment or a previously approved treatment with known effectiveness. In other cases, sponsors may conduct an active comparator trial to establish an efficacy claim relative to the active comparator instead of the placebo in labeling.
An enzyme is a biological macromolecule, usually a protein, that acts as a biological catalyst, accelerating chemical reactions without being consumed in the process. The molecules on which enzymes act are called substrates, which are converted into products. Nearly all metabolic processes within a cell depend on enzyme catalysis to occur at biologically relevant rates. A metabolic pathway is typically composed of a series of enzyme-catalyzed steps. The study of enzymes is known as enzymology, and a related field focuses on pseudoenzymes—proteins that have lost catalytic activity but may retain regulatory or scaffolding functions, often indicated by alterations in their amino acid sequences or unusual 'pseudocatalytic' behavior. Enzymes are known to catalyze over 5,000 types of biochemical reactions. Other biological catalysts include catalytic RNA molecules, or ribozymes, which are sometimes classified as enzymes despite being composed of RNA rather than protein. More recently, biomolecular condensates have been recognized as a third category of biocatalysts, capable of catalyzing reactions by creating interfaces and gradients—such as ionic gradients—that drive biochemical processes, even when their component proteins are not intrinsically catalytic. Enzymes increase the reaction rate by lowering a reaction's activation energy, often by factors of millions. A striking example is orotidine 5′-phosphate decarboxylase, which accelerates a reaction that would otherwise take millions of years to occur in milliseconds.
=== Available forms === Phenibut is available as a medication in the form of 250 mg or 500 mg tablets for oral administration and as a solution at a concentration of 10 mg/mL for infusion. In the US, dietary supplements labeled as containing phenibut have been found to contain zero to greater than 1,100 mg of phenibut per serving.
Sources: en.wikipedia.org
Sexually active women of reproductive potential should use contraception while receiving azacitidine and for one week after the last dose, and sexually active men with female partners of reproductive potential should use contraception during treatment and for three months following the last dose. A study undertaken to evaluate the immediate and long-term effects of a single-day exposure to Azacytidine (5-AzaC) on neurobehavioral abnormalities in mice found, that the inhibition of DNA methylation by 5-AzaC treatment causes neurodegeneration and impairs extracellular signal-regulated kinase (ERK1/2) activation and the activity-regulated cytoskeleton-associated (Arc) protein expression in neonatal mice and induces behavioral abnormalities in adult mice, as DNA methylation-mediated mechanisms appear to be necessary for the proper maturation of synaptic circuits during development, and disruption of this process by 5-AzaC could lead to abnormal cognitive function. Azacitidine can also cause nausea, vomiting, fevers, diarrhea, redness at its injection sites, constipation, bruising, petechiae, rigors, weakness, abnormally low potassium levels in the bloodstream, and many other side effects, some of which can be severe or even fatal.
== Therapeutic effects == Serotonin, given orally at a dose of 100 mg, produced effects in humans including blood pressure changes, abdominal cramps, muscle aches, and a feeling of sedation. In contrast to psychedelic drugs like LSD, no hallucinogenic effects were reported. In other studies, serotonin, at low intravenous doses of 2 to 6 mg, had no effects on electroencephalogram (EEG) readings in humans. In accordance with the preceding findings, it has been stated that administration of serotonin in humans produces no psychoactive effects that cannot be attributed to anxiety by its profound peripheral adverse effects including circulatory disturbance, other autonomic effects, and vomiting. Intracerebroventricular injection of serotonin has been studied in patients with severe psychiatric conditions, but little information about its psychoactive effects is provided. It is thought that exogenous serotonin is too hydrophilic to cross the blood–brain barrier and has too poor of metabolic stability due to rapid metabolism by monoamine oxidase (MAO) such that it cannot produce drug-like central effects in humans with peripheral administration. However, close analogues of serotonin that are more lipophilic and metabolically stable, like bufotenin (N,N-dimethylserotonin), 5-MeO-DMT (N,N,O-trimethylserotonin), and 5-MeO-AMT (α,O-dimethylserotonin), among many others, are active and produce pronounced centrally mediated effects in humans.
== Regulation of TIMP expression == Transcription of this gene is highly inducible in response to many cytokines and hormones. In addition, the expression from some but not all inactive X chromosomes suggests that this gene inactivation is polymorphic in human females. This gene is located within intron 6 of the synapsin I gene and is transcribed in the opposite direction. In adrenocortical cells the trophic hormone ACTH induces expression of TIMP-1 and the increase in TIMP expression is also associated with decreased collagenase activity. Increased expression of TIMP1 has been found to be associated with worse prognosis of various tumors, such as laryngeal carcinoma or melanoma.
== Clinical significance == Recessive mutations in NADK2 cause NADK2 deficiency, an inherited metabolic disorder characterized by neurological symptoms including hypotonia, developmental delay, ataxia, and encephalopathy. Affected individuals also show metabolic abnormalities, including hyperlysinemia and impaired fat oxidation with elevated C10:2-carnitine levels, consistent with secondary 2,4-dienoyl-CoA reductase deficiency. Cancer cells are exposed to elevated oxidative stress and are consequently highly dependent on mitochondrial NADPH to maintain redox homeostasis. NADK2 is essential for mitochondrial NADPH production and has therefore been proposed as a potential target to increase oxidative stress and sensitize cancer cells to apoptosis. A lack of NADK2 additionally impairs proline biosynthesis, rendering cancer cells dependent on exogenous proline for proliferation. NADK2 has been linked to Alzheimer's disease. Tau oligomers upregulate NADK2 in human neurons, leading to increased mitochondrial NADPH production, which in turn increases LRP1 expression and promotes tau uptake, creating a self-reinforcing cycle.
Sources: en.wikipedia.org
According to this position, the electromagnetic properties of the mother's heart and its interaction with her own and the fetal nervous system ensure the balanced development of the embryo's nervous system and guarantee the development of the correct architecture of the nervous system with the necessary cognitive functions corresponding to the ecological context and the qualities that make human beings unique. Based on these results, the article suggested the hypothesis of the origin of neurostimulation during gestation. Although the exact mechanisms of neurostimulation remain unknown, the empirical effectiveness has resulted in the surge of its clinical application. Existing and emerging neuromodulation treatments also include application in medication-resistant epilepsy, chronic head pain conditions, and functional therapy ranging from bladder and bowel or respiratory control to improvement of sensory deficits, such as hearing (cochlear implants and auditory brainstem implants) and vision (retinal implants). Technical improvements include a trend toward minimally invasive (or noninvasive) systems, as well as smaller, more sophisticated devices that may have automated feedback control, and conditional compatibility with magnetic resonance imaging. Neuromodulation therapy has been investigated for other chronic conditions, such as Alzheimer's disease, depression, chronic pain, and as an adjunctive treatment in recovery from stroke.
== Discovery == Prohibitins are evolutionarily conserved genes that are ubiquitously expressed. The human prohibitin gene, located on the BRCA1 chromosome region 17q21, was originally thought to be a negative regulator of cell proliferation and a tumor suppressor. This anti-proliferative activity was later attributed to the 3' untranslated region of the PHB gene, and not to the actual protein. Mutations in human PHB have been linked to sporadic breast cancer. However, over-expression of PHB has been associated with a reduction in androgen receptor activity and a reduction in PSA gene expression resulting in a decrease of androgen-dependent growth of prostate cancer cells. Prohibitin is expressed as two transcripts with varying lengths of 3' untranslated region. The longer transcript is present at higher levels in proliferating tissues and cells, suggesting that this longer 3' untranslated region may function as a trans-acting regulatory RNA.
Ejaculation is the ejection of semen from the penis. It is usually accompanied by orgasm. A series of muscular contractions delivers semen, containing male gametes known as sperm cells or spermatozoa, from the penis. Ejaculation usually happens as the result of sexual stimulation, but it can be due to prostatic disease in rare cases. Ejaculation may occur spontaneously during sleep (known as a nocturnal emission). Anejaculation is the condition of being unable to ejaculate. Sperm are produced in the testicles and stored in the attached epididymides. During ejaculation, sperm are propelled up the vasa deferentia, two ducts that pass over and behind the bladder. Fluids are added by the seminal vesicles and the vasa deferentia turn into the ejaculatory ducts, which join the urethra inside the prostate. The prostate, as well as the bulbourethral glands, add further secretions (including pre-ejaculate), and the semen is expelled through the penis. Ejaculation has two phases: emission and ejaculation proper. The emission phase of the ejaculatory reflex is under control of the sympathetic nervous system, while the ejaculatory phase is under control of a spinal reflex at the level of the spinal nerves S2–4 via the pudendal nerve. A refractory period succeeds the ejaculation, and sexual stimulation precedes it. The ischiocavernosus muscle helps to stabilize the penis during erection by compressing the crus and slowing the return of blood through the veins. The bulbospongiosus muscle also contributes to erection along with the expulsion of urine and semen.
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.
Glutathione is a sulfur-containing tripeptide made from glutamate, cysteine, and glycine. It is found in most cells and participates in redox balance and detoxification reactions.