2-Hydroxybutyric acid, is a

hydroxybutyric acid Hydroxybutyric acid is a group of four-carbon organic compounds that have both hydroxyl and carboxylic acid functional groups. They can be viewed as derivatives of butyric acid. The carboxylate anion and the esters of hydroxybutyric acids are kn ...

with the

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

group on the carbon adjacent to the

carboxyl In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl group (e.g. ...

. It is a

chiral Chirality () is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek language, Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is dist ...

compound having two

enantiomers In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...

, D-2-hydroxybutyric acid and L-2-hydroxybutyric acid. Its

conjugate base A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid gives a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as it loses a hydrogen ion in the reve ...

is known as ''alpha''-hydroxybutyrate and α-hydroxybutyrate. (R)-2-Hydroxybutanic Acid Structural Formula V1.svg, -2-hydroxybutyric acid, alt=Molecular diagram of 2-hydroxybutyric acid, with the central alcohol carbon labeled "(R)" (S)-2-Hydroxybutanic Acid Structural Formula V1.svg, -2-hydroxybutyric acid, alt=Molecular diagram of 2-hydroxybutyric acid, with the central alcohol carbon labeled "(S)" 2-Hydroxybutyrate, the

of 2-hydroxybutyric acid, is produced in mammalian tissues (principally hepatic) that catabolize L-threonine or synthesize

glutathione Glutathione (GSH, ) is an organic compound with the chemical formula . It is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by sources ...

Oxidative stress Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. Disturbances in the normal ...

or detoxification demands can dramatically increase the rate of hepatic glutathione synthesis. Under such metabolic stress conditions, supplies of L-cysteine for glutathione synthesis become limiting, so

homocysteine Homocysteine (; symbol Hcy) is a non-proteinogenic α-amino acid. It is a homologous series, homologue of the amino acid cysteine, differing by an additional methylene bridge (). It is biosynthesized from methionine by the removal of its terminal ...

is diverted from the

transmethylation Transmethylation is a biologically important organic chemical reaction in which a methyl group is transferred from one compound to another. An example of transmethylation is the recovery of methionine from homocysteine. In order to sustain suffic ...

pathway forming methionine into the

transsulfuration The transsulfuration pathway is a metabolic pathway involving the interconversion of cysteine and homocysteine through the intermediate cystathionine. Two transsulfurylation pathways are known: the ''forward'' and the ''reverse''. The ''forward ...

pathway forming cystathionine. 2-Hydroxybutyrate is released as a byproduct when

cystathionine Cystathionine is an intermediate in the synthesis of cysteine from homocysteine. It is produced by the transsulfuration pathway and is converted into cysteine by cystathionine gamma-lyase (CTH). Biosynthetically, cystathionine is generated from h ...

is cleaved to cysteine that is incorporated into glutathione. Chronic shifts in the rate of glutathione synthesis may be reflected by urinary excretion of 2-hydroxybutyrate. α-hydroxybutyrate may be useful as an early indicator of

insulin resistance Insulin resistance (IR) is a pathological response in which cells in insulin-sensitive tissues in the body fail to respond normally to the hormone insulin or downregulate insulin receptors in response to hyperinsulinemia. Insulin is a horm ...

in non-diabetic subjects. Moreover, elevated serum α-hydroxybutyrate predicts worsening

glucose tolerance Prediabetes is a component of metabolic syndrome and is characterized by elevated blood sugar levels that fall below the threshold to diagnose diabetes mellitus. It usually does not cause symptoms, but people with prediabetes often have obesity ( ...

References

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