This is a working overview of tripeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-08-21. Anything still debated is marked as such rather than presented as settled.
In cells, glutathione helps maintain the reducing environment of the cytosol and supports enzymes that counteract reactive oxygen species. It acts as a cofactor for glutathione peroxidases, which reduce hydrogen peroxide and lipid peroxides, and for glutathione S-transferases, which conjugate electrophiles. The ratio of GSH to GSSG is often used as an indicator of oxidative stress, although the ratio can vary by compartment and cell type. Glutathione also stores cysteine, an amino acid that can be limiting for protein synthesis and antioxidant defense.
Synthesis occurs in two ATP-dependent steps. The enzyme glutamate-cysteine ligase joins glutamate and cysteine to form gamma-glutamylcysteine, and glutathione synthetase adds glycine. The first step is rate-limiting and is influenced by cysteine availability and feedback inhibition by GSH. Breakdown involves gamma-glutamyl transferase and subsequent peptidases, which release constituent amino acids for reuse. Because turnover differs among tissues, measurements from blood, plasma, and tissues are not directly interchangeable. Research continues to clarify how compartment-specific pools are regulated in health and disease.
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 | For reduced glutathione; the oxidized dimer has two sulfur atoms. |
| Molar mass | 307.32 g/mol | Calculated for the reduced form. |
| Appearance | White to off-white crystalline powder | Typical for solid reagent; solutions are usually colorless. |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar organic solvents. |
| Typical storage | -20 °C, desiccated, protected from light | Limits oxidation, moisture uptake, and degradation. |
Glutathione is a tripeptide composed of glutamate, cysteine, and glycine. The peptide bond between glutamate and cysteine uses the gamma-carboxyl group of glutamate rather than the alpha-carboxyl group. This unusual linkage protects the molecule from many common peptidases. The cysteine side chain carries a thiol group that can undergo reversible oxidation. Because of this thiol, glutathione participates in redox reactions and helps maintain the reducing environment inside most cells in living systems.
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 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.
=== Deficiency === In humans methionine is an essential amino acid; cysteine is conditionally essential and may be synthesized from non-essential serine via sulfur salvaged from methionine. Sulfur deficiency is uncommon due to the ubiquity of cysteine and methionine in food. Isolated sulfite oxidase deficiency is a rare, fatal genetic disease caused by mutations to sulfite oxidase, which is needed to metabolize sulfites to sulfates.
Among unconfirmed and often contradictory news reports aired throughout the day, one of the most prevalent claimed a car bomb had been detonated at the U.S. State Department's headquarters in Washington, D.C., but the report was retracted. Another jet (Delta Air Lines Flight 1989) was suspected of having been hijacked, but the aircraft responded to controllers and landed safely in Cleveland, Ohio. Korean Air flight 085 diverted to Whitehorse, Yukon, Canada, surrounded by police snipers and Whitehorse airport and downtown evacuated after it responded to air traffic control to transmit a hijacking code but air traffic control interpreted it to mean an actual hijack and not merely a response to air traffic request. Prime Minister Jean Chretien of Canada had given the authorization to shoot down the Korean Air Boeing 747 if necessary. A single exception to the FAA's grounding order came on September 12, when a flight was authorized from Fort Lauderdale, to San Diego, and on to Miami to retrieve a rare antivenom for a professional snake handler who had been bitten by an inland taipan. In an April 2002 interview, Mohammed and bin al-Shibh, who are believed to have organized the attacks, said Flight 93's intended target was the United States Capitol, not the White House. During the planning stage of the attacks, Atta thought the White House might be too tough a target and sought an assessment from Hanjour.
In Table 5, the approximately $85 billion fine chemical market is subdivided into major applications according to their relevance: fine chemicals for pharmaceuticals, agrochemicals, and specialty chemicals outside life sciences. Furthermore, a distinction is made between captive (in-house) production and merchant market. Pharmaceutical fine chemicals (PFCs) account for two-thirds of the total. Out of the PFC value of $55 billion, about $23 billion (~40%) are traded, and $32 billion (~60%) are the production value of the pharma industry's in-house production. Within life science products, fine chemicals for agro and veterinary drugs follow in importance. The production value for fine chemicals used for specialty chemicals other than pharmaceuticals and agrochemicals is estimated at $15 billion. As the leading specialty chemical companies (Akzo Nobel, Dow, DuPont, Evonik, Chemtura and Mitsubishi) are backward-integrated, the share of in-house production is estimated at 75%, leaving a merchant market of approximately $5 billion.
Sources: en.wikipedia.org
=== 1990–1998: Early modeling and television roles === Larter began her modeling career at the age of 14 when a modeling scout discovered her on the street and asked her to star in a Philadelphia Phillies commercial. That led to a modeling contract with the prestigious Ford Modeling Agency in Manhattan, New York. Larter subsequently skipped her senior year to model in Australia, Italy, and Japan; Japan being a country she temporarily lived in at 17. While modeling in Italy, Larter met fellow model and aspiring actress Amy Smart and the two "became instant friends", according to Larter. In November 1996, Larter portrayed fictional actress Allegra Coleman in an Esquire magazine hoax. When speaking about the cover and her fame, Larter said, "When the door opens for you in Hollywood, you need to run with it. You know?" Larter is signed to IMG Models. She landed her first professional acting roles in 1997 when she appeared in several television programs. She appeared in "The Ways and Means", an episode of the NBC television series Suddenly Susan starring Brooke Shields, and the short-lived series Chicago Sons also on NBC. The roles were followed by a number of other appearances on Dawson's Creek on The WB, CBS' Chicago Hope, and Just Shoot Me! on NBC.
Natural iron (26Fe) consists of four stable isotopes: 5.85% 54Fe, 91.75% 56Fe, 2.12% 57Fe and 0.28% 58Fe. There are 28 known radioisotopes and 8 nuclear isomers, the most stable of which are 60Fe (half-life 2.62 million years) and 55Fe (half-life 2.7562 years). Much of the past work on measuring the isotopic composition of iron has centered on determining 60Fe variations due to processes accompanying nucleosynthesis (e.g., meteorite studies) and ore formation. In the last decade however, advances in mass spectrometry technology have allowed the detection and quantification of minute, naturally occurring variations in the ratios of the stable isotopes of iron. Much of this work has been driven by the Earth and planetary science communities, though applications to biological and industrial systems are beginning to emerge.
Tecemotide (INN; emepepimut-S (USAN); formerly known as BLP25 or EMD 531444) is a synthetic lipopeptide that is used as antigen in an investigational therapeutic cancer vaccine (formerly known as Stimuvax, L-BLP25, BLP25 liposomal vaccine, or BLP25 liposome vaccine). The investigational therapeutic cancer vaccine is designed to induce a cellular immune response to cancer cells that express MUC1, a glycoprotein antigen that is widely over-expressed on common cancers such as lung cancer, breast cancer, prostate cancer, and colorectal cancer. The cellular immune response may lead to a rejection of tumor tissue expressing the MUC1 antigen.
Sources: en.wikipedia.org
== Biological function == Enzymes serve a wide variety of functions inside living organisms. They are indispensable for signal transduction and cell regulation, often via kinases and phosphatases. They also generate movement, with myosin hydrolyzing adenosine triphosphate (ATP) to generate muscle contraction, and also transport cargo around the cell as part of the cytoskeleton. Other ATPases in the cell membrane are ion pumps involved in active transport. Enzymes are also involved in more exotic functions, such as luciferase generating light in fireflies. Viruses can also contain enzymes for infecting cells, such as the HIV integrase and reverse transcriptase, or for viral release from cells, like the influenza virus neuraminidase. An important function of enzymes is in the digestive systems of animals. Enzymes such as amylases and proteases break down large molecules (starch or proteins, respectively) into smaller ones, so they can be absorbed by the intestines. Starch molecules, for example, are too large to be absorbed from the intestine, but enzymes hydrolyze the starch chains into smaller molecules such as maltose and eventually glucose, which can then be absorbed. Different enzymes digest different food substances. In ruminants, which have herbivorous diets, microorganisms in the gut produce another enzyme, cellulase, to break down the cellulose cell walls of plant fiber.
=== Residual stress === In physiological state soft tissues usually present residual stress that may be released when the tissue is excised. Physiologists and histologists must be aware of this fact to avoid mistakes when analyzing excised tissues. This retraction usually causes a visual artifact.
=== Numbers and habitats of major phyla === The following table lists estimated numbers of described extant species for the major animal phyla, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. Species estimates shown here are based on numbers described scientifically; much larger estimates have been calculated based on various means of prediction, and these can vary wildly. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. Using patterns within the taxonomic hierarchy, the total number of animal species—including those not yet described—was calculated to be about 7.77 million in 2011.
Sources: en.wikipedia.org
GSH is the reduced form with a free thiol group, while GSSG is the oxidized disulfide-linked dimer. Most assays distinguish the two because their balance reflects redox conditions. The names are not interchangeable.
It is synthesized in the body from amino acids, so it is not classified as an essential dietary nutrient for most people. Dietary and supplemental forms are studied for their effects on tissue levels and health markers. Evidence varies by population and outcome.
The phrase highlights its high intracellular concentration and its role in several antioxidant and detoxification reactions. It is not the only antioxidant, and the term can oversimplify its functions. Scientific descriptions usually specify the pathway or enzyme involved.
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.