If you have been reading about redox 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.
Updated 2025-09-26. Numbers and descriptions here follow the published literature rather than marketing material.
Glutathione is a small tripeptide made of glutamic acid, cysteine, and glycine. Its cysteine thiol group allows reversible oxidation and reduction, making it central to cellular redox chemistry. The reduced form, often abbreviated GSH, predominates inside most cells, while the oxidized disulfide form, GSSG, forms when two GSH molecules react. The ratio of GSH to GSSG is widely used as an indicator of oxidative stress in laboratory research, though it does not by itself diagnose a clinical condition.
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 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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C10H17N3O6S | Reduced glutathione (GSH); oxidized form differs by disulfide linkage. |
| Molar mass | 307.32 g/mol | Calculated for the reduced tripeptide. |
| Appearance | White to off-white crystalline powder | Typical laboratory reagent description. |
| Solubility | Soluble in water | Aqueous solutions are acidic; solubility depends on pH and salt form. |
| CAS Registry Number | 70-18-8 | Refers to reduced L-glutathione; oxidized form has a different number. |
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.
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.
=== Engineering === MHD is related to engineering problems such as plasma confinement, liquid-metal cooling in nuclear reactors, and electromagnetic casting. A magnetohydrodynamic drive, or MHD propulsor, is a method for propelling seagoing vessels using only electric and magnetic fields, with no moving parts. The working principle involves electrifying the propellant (gas or water), which can then be directed by a magnetic field, thereby pushing the vehicle in the opposite direction. Although some working prototypes exist, MHD drives remain impractical. The first prototype of this type of propulsion was built and tested in 1965 by Steward Way, a professor of mechanical engineering at the University of California, Santa Barbara. While on leave from his job at Westinghouse Electric, Way assigned his senior-year undergraduate students to develop a submarine using this new propulsion system. In the early 1990s, the Ship & Ocean Foundation (Minato-ku, Tokyo) built an experimental boat, the Yamato-1, which used a magnetohydrodynamic drive incorporating a superconductor cooled by liquid helium and could travel at 15 km/h. MHD power generation fueled by potassium-seeded coal-combustion gas showed potential for more efficient energy conversion (the absence of solid moving parts allows operation at higher temperatures) but ultimately failed due to cost-prohibitive technical difficulties. One major engineering problem was the abrasion-induced failure of the wall of the primary-coal combustion chamber.
Russian-installed officials in occupied Ukraine claimed that 22 people were killed and 15 others were injured by Ukrainian shelling in Sadove, Kherson Oblast, while four people were killed and 57 others were injured in a Ukrainian missile strike in Luhansk. One person was claimed killed in a drone strike in Belgorod Oblast. One person was killed in a Russian missile attack near Poltava. Russia claimed to have taken the village of Paraskoviivka, 25 kilometers southwest of Donetsk. The Ukrainian military claimed to have "rendered unserviceable” a Ropucha-class landing ship that had been moved from the Black Sea to the Sea of Azov and was being used to ferry ammunition and other supplies to Russian forces in Mariupol. The HUR claimed that Hennadii Matsehora, the former mayor of Kupiansk who was wanted for collaboration with Russia, was critically injured in an assassination attempt in Stary Oskol, Belgorod Oblast. He subsequently died from his injuries on 11 June. Ukraine signed a contract for the supply of a second Ground Master 200 radar and command module from France that can be integrated with the SAMP/T system.
== Medical laboratory accreditation == Credibility of medical laboratories is paramount to the health and safety of the patients relying on the testing services provided by these labs. Credentialing agencies vary by country. The international standard in use today for the accreditation of medical laboratories is ISO 15189 - Medical laboratories - Requirements for quality and competence. In the United States, billions of dollars is spent on unaccredited lab tests, such as Laboratory developed tests which do not require accreditation or FDA approval; about a billion USD a year is spent on US autoimmune LDTs alone. Accreditation is performed by the Joint Commission, College of American Pathologists, AAB (American Association of Bioanalysts), and other state and federal agencies. Legislative guidelines are provided under CLIA 88 (Clinical Laboratory Improvement Amendments) which regulates Medical Laboratory testing and personnel. The accrediting body in Australia is NATA, where all laboratories must be NATA accredited to receive payment from Medicare. In France the accrediting body is the Comité français d'accréditation (COFRAC). In 2010, modification of legislation established ISO 15189 accreditation as an obligation for all clinical laboratories. In the United Arab Emirates, the Dubai Accreditation Department (DAC) is the accreditation body that is internationally recognised by the International Laboratory Accreditation Cooperation (ILAC) for many facilities and groups, including Medical Laboratories, Testing and Calibration Laboratories, and Inspection Bodies.
Sources: en.wikipedia.org
== External links == Gene Ontology: GO:0003720: telomerase activity Human telomerase reverse transcriptase (TERT) gene on genecards.org The Telomerase Database - A Web-based tool for telomerase research Archived 2021-04-19 at the Wayback Machine Three-dimensional model of telomerase at MUN Elizabeth Blackburn's Seminars: Telomeres and Telomerase Telomerase at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Overview of all the structural information available in the PDB for UniProt: O14746 (Human Telomerase reverse transcriptase) at the PDBe-KB. Overview of all the structural information available in the PDB for UniProt: Q0QHL8 (Tribolium castaneum Telomerase reverse transcriptase) at the PDBe-KB.
Several types of chocolate can be distinguished. Pure, unsweetened chocolate, often called "baking chocolate", contains primarily non-fat cocoa solids and cocoa butter in varying proportions. Much of the chocolate consumed today is in the form of sweet chocolate, which combines chocolate with sugar.
== Function == This gene encodes a precursor protein that is processed to produce oxytocin and neurophysin I. Oxytocin is a posterior pituitary hormone that is synthesized as an inactive precursor in the hypothalamus along with its carrier protein neurophysin I. Together with neurophysin, it is packaged into neurosecretory vesicles and transported axonally to the nerve endings in the neurohypophysis, where it is either stored or secreted into the bloodstream. The precursor seems to be activated while it is being transported along the axon to the posterior pituitary. This hormone contracts smooth muscle during parturition and lactation. It is also involved in cognition, tolerance, adaptation, and complex sexual and maternal behavior, as well as in the regulation of water excretion and cardiovascular functions. [provided by RefSeq, Dec 2013].
Sources: en.wikipedia.org
The calculation uses 8,033 years, the mean-life derived from Libby's half-life of 5,568 years, not 8,267 years, the mean-life derived from the more accurate modern value of 5,730 years. Libby's value for the half-life is used to maintain consistency with early radiocarbon testing results; calibration curves include a correction for this, so the accuracy of final reported calendar ages is not affected.
=== Initial analogue development (1996–2014) === The development of insulin analogues began with Humalog (insulin lispro), a short-acting insulin analogue developed by Eli Lilly, which was approved by the FDA in 1996. Humalog was designed to be absorbed more quickly than regular insulin, offering improved flexibility in meal timing and postprandial glucose control. In 2000, Lantus (insulin glargine) was approved by the FDA and the European Medicines Agency (EMA). Lantus is a long-acting insulin analogue designed to provide a steady basal level of insulin throughout the day, typically lasting up to 24 hours, thereby reducing the need for multiple daily injections. In 2004, Apidra (insulin glulisine), another short-acting insulin analog, was approved by Sanofi-Aventis to improve postprandial glucose control. In 2005, Levemir (insulin detemir), developed by Novo Nordisk, was approved for clinical use. Levemir is a long-acting insulin analogue similar to Lantus but with a slightly shorter duration of action. It provides stable basal insulin coverage with a reduced risk of hypoglycemia compared to older insulins.
Some people misinterpreted Rice's memoirs as admitting to Georgia's responsibility for starting the war. On 5 August 2012, a new documentary "A Lost Day" (Russian: "Потерянный день") was released on YouTube. The authors of the documentary were unknown. Several high-ranking military officials were featured. Yuri Baluyevsky, former Chief of the General Staff of Russia said that President Dmitry Medvedev didn't want to make a decision to go to war for some time. Baluyevsky said that it was Putin that had ordered to "retaliate" militarily against Georgia "after the first tensions", however "high-level officials" in Moscow had the fear of responsibility "until a kick in one place from Vladimir Vladimirovich in Beijing followed." Baluyevsky said after President Putin had decided to wage the war against Georgia prior to the May 2008 inauguration of Dmitry Medvedev as president of Russia, a military action was planned and explicit orders were issued in advance before August 2008. Russian researcher Andrey Illarionov later commented on the movie that the movie and the remarks of Putin confirmed the date of issue of the order by Medvedev to the Russian military to cross the border into Georgia was the night of 4-5 August. Russian Generals said in the movie that the plan intended that Russian troops would reach Tskhinvali on the morning of 8 August, but they actually reached Tskhinvali on the morning of 10 August. Illarionov attributed this delay of the Russian troops to the Georgian resistance.
== Determination == Death was historically believed to be an event that coincided with the onset of clinical death. It is now understood that death is a series of physical events, not a single one, and determination of permanent death is dependent on other factors beyond simple cessation of breathing and heartbeat. Clinical death that occurs unexpectedly is treated as a medical emergency. CPR is initiated. In a United States hospital, a Code Blue is declared and Advanced Cardiac Life Support procedures used to attempt to restart a normal heartbeat. This effort continues until either the heart is restarted, or a physician determines that continued efforts are useless and recovery is impossible. If this determination is made, the physician pronounces legal death and resuscitation efforts stop. If clinical death is expected due to terminal illness or withdrawal of supportive care, often a Do Not Resuscitate (DNR) or "no code" order is in place. This means that no resuscitation efforts are made, and a physician or nurse may pronounce legal death at the onset of clinical death. A patient with working heart and lungs who is determined to be brain dead can be pronounced legally dead without clinical death occurring. However, some courts have been reluctant to impose such a determination over the religious objections of family members, such as in the Jesse Koochin case. Similar issues were also raised by the case of Mordechai Dov Brody, but the child died before a court could resolve the matter.
Sources: en.wikipedia.org
GSH is the reduced form of glutathione, with a free thiol group on cysteine. GSSG is the oxidized disulfide form, created when two GSH molecules become linked. The two forms exist together, and their balance is often reported as the GSH/GSSG ratio in laboratory studies.
Glutathione is synthesized inside cells from amino acids rather than being classified as an essential dietary nutrient. Dietary sources can provide glutathione or its precursors, but digestion and absorption alter what reaches tissues. Research continues on how dietary intake relates to cellular glutathione levels.
The liver has high glutathione concentrations and uses the compound in conjugation and antioxidant reactions. These reactions are relevant to the processing of drugs, pollutants, and normal metabolic byproducts. Studies often examine liver glutathione as a marker of oxidative stress or detoxification capacity.
It is a tripeptide of glutamate, cysteine, and glycine. The glutamate-cysteine bond is unusual because it forms through the gamma-carboxyl group.