Redox buffer comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-09-22. Where a claim depends on a specific study, the study is described rather than over-claimed.
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 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.
| 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 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.
Glutathione supports detoxification by conjugating reactive electrophiles through glutathione S-transferases. The resulting conjugates are processed and exported, often after further metabolism. It also stores cysteine, transports amino acids across membranes through the gamma-glutamyl cycle, and assists in the maturation of iron-sulfur clusters and some prostaglandins. In plants, animals, and many microbes, the molecule appears in similar roles, but concentrations vary enormously between tissues. Liver, kidney, and red blood cells tend to contain high amounts, while blood plasma contains much less.
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.
== External links == "The Company Behind 'Female Viagra' Just Raised $20 Million in Funding". Fortune. 4 September 2019. "The Women's Libido Pill Is Back, and So Is the Controversy". Bloomberg. 13 June 2018.
=== 1971 === January 25: Idi Amin launches a successful coup d'état against Milton Obote in Uganda and declares himself President of Uganda. Under Amin, Uganda would switch allegiances to the Eastern Bloc and develop strong ties to the Soviet Union and East Germany. February 8: South Vietnamese forces enter Laos to briefly cut the Ho Chi Minh Trail. February 11: Seabed Arms Control Treaty is signed banning the placement of nuclear weapons outside of a country's 12-mile (22.2 km) coastal zone. March 10: Dominion of Ceylon declared under emergency conditions after communist People's Liberation Front attacks the American embassy. March 25 : Bangladeshi genocide From The West Pakistani Troops until 16 December March 26: Bangladeshi Declaration of Independence and Bangladesh Liberation War begin April 19: Salyut 1 is launched becoming the first space station. May 15: Anwar Sadat's Corrective Revolution purges Nasserist members of the government and security forces, and eventually expels the Soviet military from Egypt. May 28: Mars 3 is launched. May 30: Mariner 9 is launched. July 19–22: a communist-backed coup attempted unsuccessfully against Jaafar Nimeiry in Sudan. September: 105 Soviet officials expelled from Great Britain by Prime Minister Edward Heath in Operation FOOT. September 3: Four-Power Agreement on Berlin is signed by the United Kingdom, the Soviet Union, France, and the United States. October 11: Salyut 1 burns up in the atmosphere.
Tunable diode laser absorption spectroscopy (TDLAS, sometimes referred to as TDLS, TLS or TLAS) is a technique for measuring the concentration of certain species such as methane, water vapor and many more, in a gaseous mixture using tunable diode lasers and laser absorption spectrometry. The advantage of TDLAS over other techniques for concentration measurement is its ability to achieve very low detection limits (of the order of ppb). Apart from concentration, it is also possible to determine the temperature, pressure, velocity and mass flux of the gas under observation. TDLAS is by far the most common laser based absorption technique for quantitative assessments of species in gas phase.
Sources: en.wikipedia.org
Most countries have no legal definition for absinthe, whereas the method of production and content of spirits such as whisky, brandy, and gin are globally defined and regulated. Therefore, producers are at liberty to label a product as "absinthe" or "absinth" without regard to any specific legal definition or quality standards. Producers of legitimate absinthes employ one of two historically defined processes to create the finished spirit – distillation or cold mixing. In the sole country (Switzerland) that does possess a legal definition of absinthe, distillation is the only permitted method of production.
Historians have noted that Chinese scholars wrote these studies instead of "books of prescriptions or advice manuals." In their historical and environmental understanding, no two illnesses were alike, so the healing strategies of the practitioner were unique every time to the specific diagnosis of the patient. Medical case studies existed throughout Chinese history, but "individually authored and published case history" was a prominent creation of the Ming dynasty. An example of such case studies would be the literati physician, Cheng Congzhou, collection of 93 cases published in 1644.
Basil I (r. 867–886) continued Michael's policies. His armies campaigned with mixed results in Italy but defeated the Paulicians of Tephrike. His successor Leo VI (r. 886–912) sponsored, compiled, and issued a large body of written works. These included the Basilika, a Greek translation of Justinian I's legal corpus that incorporated Leo's new laws; the Tactica, a military treatise; and the Book of the Eparch, a manual on Constantinople's trading regulations. Outside these literary, legal, and administrative projects, Leo's reign was less successful: the empire was defeated by the Bulgarians and lost Taormina, its last outpost on Sicily. He also provoked theological scandal by marrying four times in an attempt to father a legitimate heir. The early reign of this heir, Constantine VII, was tumultuous, as his mother Zoe, his uncle Alexander, the patriarch Nicholas, members of leading aristocratic families, and the powerful external pressure of Simeon I of Bulgaria shaped the struggle for power. In 920, the admiral Romanos I used his fleet to secure power, crowning himself and demoting Constantine to the position of junior co-emperor. His reign, marked by the end of the war against Bulgaria and successes in the east under the general John Kourkouas, ended in 944 when his sons deposed him; Constantine then removed them and ruled as sole emperor. Constantine's politically limited sole rule is often associated with the Macedonian Renaissance, but many of the works compiled at his court were also intended to legitimise and glorify the Macedonian dynasty.
Sources: en.wikipedia.org
Sagan again argued that some of the effects of the smoke could be similar to the effects of a nuclear winter, with smoke lofting into the stratosphere, a region of the atmosphere beginning around 43,000 feet (13,000 m) above sea level at Kuwait, resulting in global effects and that he believed the net effects would be very similar to the explosion of the Indonesian volcano Tambora in 1815, which resulted in the year 1816 being known as the Year Without a Summer. He reported on initial modeling estimates that forecast impacts extending to south Asia, and perhaps to the northern hemisphere as well. Singer, on the other hand, said that calculations showed that the smoke would go to an altitude of about 3,000 feet (910 m) and then be rained out after about three to five days and thus the lifetime of the smoke would be limited. Both height estimates made by Singer and Sagan turned out to be wrong, albeit with Singer's narrative being closer to what transpired, with the comparatively minimal atmospheric effects remaining limited to the Persian Gulf region, with smoke plumes, in general, lofting to about 10,000 feet (3,000 m) and a few times as high as 20,000 feet (6,100 m). Along with Singer's televised critique, Richard D. Small criticized the initial Nature paper in a reply on March 7, 1991, arguing along similar lines as Singer.
The Mass Transit Railway (MTR) is an extensive passenger rail network, connecting 99 metro stations and 68 light-rail stops throughout the territory. With a daily ridership of almost five million, the system serves 41% of all public transit passengers in the city and has an on-time rate of 99.9%. The East Rail line offers metro services to Shenzhen. Its southern terminus is Admiralty. Connecting service to the national high-speed rail system is provided at West Kowloon railway station. Although public transport systems handle most passenger traffic, over 500,000 private vehicles are registered in Hong Kong. Unlike in mainland China, automobiles in Hong Kong drive on the left due to the historical influence of the British Empire. Vehicle traffic is extremely congested in urban areas, exacerbated by limited space to expand roads and an increasing number of vehicles. More than 18,000 taxicabs, easily identifiable by their bright colours and taxi lights, are licensed to carry riders in the territory. Unlicensed ride-hailing services such as Uber exist in Hong Kong as well, with some operating with licensed taxis to legitimise their business in ride-sharing. Unlicensed drivers have been targeted by the government and taxi drivers in the past, mainly due to the lack of third-party insurance for passengers, and because taxi drivers feared competition from drivers of these ride-hailing services.
=== Gene therapy === Gene therapy for hemoglobinopathies was first trialled in 2014 on a single patient with sickle cell disease (a fault in the beta globin gene), and followed by clinical trials in which a number of patients with either sickle cell or beta thalassemia were successfully treated. Gene therapies work by first harvesting the patient's HSCs, then using CRISPR gene editing to modify their DNA in the laboratory. In parallel with this, the person with thalassemia disease undergoes a myeloablation procedure (a form of chemotherapy) to destroy the remaining HSCs in their bone marrow. The laboratory treated cells are then infused back into the patient where they colonise the bone marrow and eventually commence production of healthy blood cells. There are fewer risks from this procedure than from HSCT, since the transplanted cells are autologous having originated from the patient herself/himself. There are two approved forms of gene therapy for beta thalassemia. Betibeglogene autotemcel, sold under the brand name Zynteglo, is a gene therapy for the treatment for beta thalassemia which adds a healthy beta-globin gene to the HSCs. It was approved for medical use in the United States in August 2022. The procedure involves collecting hematopoietic stem cells (HSCs) from the affected person's blood. In the laboratory, these HSCs then have a new gene for T87Q-globin (a modified beta-globin) introduced to them using a lentiviral vector.
anticodon A series of three consecutive nucleotides within a transfer RNA which complement the three nucleotides of a codon within an mRNA transcript. During translation, each tRNA recruited to the ribosome contains a single anticodon triplet that pairs with its complementary codon from the mRNA sequence, allowing each codon to specify a particular amino acid to be added to the growing peptide chain. Anticodons containing inosine in the first position are capable of pairing with more than one codon due to a phenomenon known as wobble base pairing.
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.
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.