This is a working overview of gamma-glutamyl bond, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-12-31 and is reviewed periodically as new material appears.
Enzymatic recycling assays provide a complementary approach for total glutathione. In these methods, glutathione reductase reduces oxidized glutathione while a thiol-reactive reagent, such as 5,5'-dithiobis(2-nitrobenzoic acid), produces a colored product. The reaction cycles between reduced and oxidized forms, amplifying the signal. Spectrophotometric or fluorometric detection can then estimate concentration. Distinguishing reduced glutathione from glutathione disulfide often requires separate aliquots, masking agents, or chromatographic separation, and the choice affects reported values.
Storage conditions strongly influence glutathione stability. The solid reduced form is commonly kept desiccated at or below minus twenty degrees Celsius, protected from light and moisture. Aqueous solutions are less stable because the thiol group reacts with dissolved oxygen, and oxidation accelerates at neutral or alkaline pH. Acidic solutions and oxygen-free handling can slow degradation, but repeated freeze-thaw cycles should be avoided. Researchers often verify concentration before use, because apparent losses can arise from oxidation or water uptake.
Commercial glutathione is produced by microbial fermentation or chemical synthesis, then purified. Reduced and oxidized grades are offered separately, with purity specifications often exceeding 98 percent. The compound appears in foods such as fresh fruits, vegetables, and meats, although cooking and processing can lower amounts. Oral, topical, and inhaled forms are discussed in research and consumer contexts, but absorption and tissue delivery remain active areas of study. Regulatory status varies by country and intended use.
Glutathione is a small sulfur-containing peptide built from glutamic acid, cysteine, and glycine. Its distinctive feature is a gamma-glutamyl bond between glutamate's side-chain carboxyl group and cysteine's amino group. This linkage resists ordinary peptidases and helps the molecule remain stable inside cells. The reduced thiol form, often abbreviated GSH, is the dominant intracellular species. The oxidized disulfide dimer, GSSG, forms when two reduced molecules link through their cysteine sulfur atoms. The balance between these forms is a common redox indicator.
In living systems, glutathione occurs in millimolar concentrations in many cell types, while extracellular levels are generally much lower. The liver holds a substantial share of the body's total pool, and the molecule participates in reduction, detoxification, and amino acid transport. It also serves as a cofactor for enzymes such as glutathione peroxidase and glutathione S-transferase. Because the cysteine residue supplies a reactive thiol, glutathione can donate electrons and become oxidized. Cells regenerate reduced glutathione through glutathione reductase using NADPH.
| Property | Value | Notes |
|---|---|---|
| Solid storage temperature | -20 °C | Desiccated, protected from light |
| Solution stability | Hours to days at neutral pH | Acidic pH and low oxygen slow oxidation |
| Oxidized form | Glutathione disulfide (GSSG) | Formed by thiol oxidation |
| Typical analytical method | LC-MS/MS or enzymatic recycling | Choice depends on matrix and specificity |
| Thiol pKa | Approximately 9.2 | Influences reactivity at physiological pH |
=== 31 March === Seven people were killed by RSF shelling on the Abu Shouk camp. The RSF claimed to have taken Khor El Dalaib in South Kordofan following clashes that left 12 civilians dead. It also claimed to have killed 70 fighters of the Islamic Movement, and destroyed or captured 13 vehicles.
In Ethiopia and Zambia, elaborate scarification is often done on women at puberty, used to denote a willingness to be a mother. The markings show that she can stand the pain of childbirth, as well as being an indication of her emotional maturity.
=== Cellular localization === Several factors that regulate eIF4E functions also modulate the subcellular localization of eIF4E. For instance, overexpression of PRH/Hex leads to cytoplasmic retention of eIF4E, and thus loss of its mRNA export activity and suppression of transformation. PML overexpression leads to sequestration of eIF4E to nuclear bodies with PML and decrease of eIF4E nuclear bodies containing RNA, which correlates to repressed eIF4E dependent mRNA export and can be modulated by stress. Overexpression of LRPPRC reduces eIF4E's co-localization with PML in the nucleus and leads to increased mRNA export activity of eIF4E. As discussed above, Importin 8 brings eIF4E into the nucleus and its overexpression stimulates the RNA export and oncogenic transformation activities of eIF4E in cell lines. Transduction of primary AML cells with IkB-SR resulted not only in reduction of eIF4E mRNA levels, but also re-localization of eIF4E protein.
Detailed CIDRAP Smallpox overview Archived 6 May 2013 at the Wayback Machine Agent Fact Sheet: Smallpox, Center for Biosecurity Smallpox Images and Diagnosis Synopsis Archived 29 July 2008 at the Wayback Machine Virus Pathogen Database and Analysis Resource (ViPR): Poxviridae
The synthesis of glucose established the structure of organic material and consequently formed the first definitive validation of Jacobus Henricus van 't Hoff's theories of chemical kinetics and the arrangements of chemical bonds in carbon-bearing molecules. Between 1891 and 1894, Fischer established the stereochemical configuration of all the known sugars and correctly predicted the possible isomers, applying the Van 't Hoff equation of asymmetrical carbon atoms. The names initially referred to the natural substances. Their enantiomers were given the same name with the introduction of systematic nomenclatures, taking into account absolute stereochemistry (e.g. Fischer nomenclature, d/l nomenclature). For the discovery of the metabolism of glucose Otto Fritz Meyerhof received the Nobel Prize in Physiology or Medicine in 1922. Hans von Euler-Chelpin was awarded the Nobel Prize in Chemistry along with Arthur Harden in 1929 for their "research on the fermentation of sugar and their share of enzymes in this process". In 1947, Bernardo Houssay (for his discovery of the role of the pituitary gland in the metabolism of glucose and the derived carbohydrates) as well as Carl and Gerty Cori (for their discovery of the conversion of glycogen from glucose) received the Nobel Prize in Physiology or Medicine. In 1970, Luis Leloir was awarded the Nobel Prize in Chemistry for the discovery of glucose-derived sugar nucleotides in the biosynthesis of carbohydrates.
Sources: en.wikipedia.org
=== Buccal administration === Progesterone has been studied for use by buccal administration. The medication has been marketed in the form of buccal tablets under the brand names Progesterone Lingusorbs, Lutocylol, Membrettes, and Syngestrets, although these products are no longer available. The clinical dosage of buccal progesterone has been described as 10 to 50 mg/day relative to 5 to 60 mg/day in the case of intramuscular injection.
=== 30 March === The SAF and allied fighters repelled an RSF assault on El Fasher and attacked a supply convoy, destroying 16 vehicles and killing dozens of RSF fighters. Nine civilians were killed and 17 more were injured in RSF shelling.
=== Diagnosis === ESR can sometimes be useful in diagnosing diseases, such as multiple myeloma, temporal arteritis, polymyalgia rheumatica, various autoimmune diseases, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease and chronic kidney diseases. In many of these cases, the ESR may exceed 100 mm/hour. It is commonly used for a differential diagnosis for Kawasaki's disease (from Takayasu's arteritis; which would have a markedly elevated ESR) and it may be increased in some chronic infective conditions like tuberculosis and infective endocarditis. It is also elevated in subacute thyroiditis also known as DeQuervain's. In markedly increased ESR of over 100 mm/h, infection is the most common cause (33% of cases in an American study), followed by cancer (17%), kidney disease (17%) and noninfectious inflammatory disorders (14%). Yet, in pneumonia the ESR stays under 100. The usefulness of the ESR in current practice has been questioned by some, as it is a relatively imprecise and non-specific test compared to other available diagnostic tests. Current literature suggests that an ESR should be "obtained on all patients over the age of 50" who have an intense headache.
== Formation and structure == β-Endorphin is found in neurons of the hypothalamus, as well as the pituitary gland. It is derived from β-lipotropin, which is produced in the pituitary gland from a larger peptide precursor, proopiomelanocortin (POMC). POMC is cleaved into two neuropeptides, adrenocorticotropic hormone (ACTH) and β-lipotropin. The formation of β-endorphin is then the result of cleavage of the C-terminal region of β-lipotropin, producing a 31 amino acid-long neuropeptide with an alpha-helical secondary structure. However, POMC also gives rise to other peptide hormones, including α- and γ-melanocyte-stimulating hormone (MSH), resulting from intracellular processing by internal enzymes known as prohormone convertases. A significant factor that differentiates β-endorphin from other endogenous opioids is its high affinity for and lasting effect on μ-opioid receptors. The structure of β-endorphin in part accounts for this through its resistance to proteolytic enzymes, as its secondary structure makes it less vulnerable to degradation.
== External links == Clinical trial number NCT02861534 for "A Study of Vericiguat in Participants With Heart Failure With Reduced Ejection Fraction (HFrEF) (MK-1242-001) (VICTORIA)" at ClinicalTrials.gov
Sources: en.wikipedia.org
Chromatographic methods can separate the two forms before detection. Enzymatic assays often measure total glutathione first and then use a separate procedure to estimate the oxidized fraction. The difference between total and oxidized amounts provides an indirect estimate of the reduced form.
Acidification lowers pH and slows thiol oxidation during handling. It also helps precipitate proteins that could interfere with detection. Typical choices include metaphosphoric acid and sulfosalicylic acid.
Dissolved oxygen reacts with the thiol group, forming glutathione disulfide. Neutral and alkaline conditions generally increase the oxidation rate. Light, metal ions, and repeated freezing and thawing can also reduce stability.
It is a tripeptide rather than a full protein. Proteins generally contain many amino acids joined by alpha-peptide bonds, while glutathione has three residues and an unusual gamma-glutamyl linkage. That structure affects how enzymes recognize and break it down.