α-Ketobutyric acid is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula CH₃CH₂C(O)CO₂H. It is a colorless solid that melts just above room temperature. Its conjugate base α-ketobutyrate is the predominant form found in nature (near neutral pH). It results from the lysis of

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 ...

. It is also one of the degradation products of

threonine Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form when dissolved in water), a carboxyl group (which is in the deprotonated −COO− ...

, produced by the catabolism of the amino acid by threonine dehydratase. It is also produced by the degradation of

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 ...

and the metabolism of

methionine Methionine (symbol Met or M) () is an essential amino acid in humans. As the precursor of other non-essential amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine play ...

. α-Ketobutyrate is transported into the

mitochondrial matrix In the mitochondrion, the matrix is the space within the inner membrane. It can also be referred as the mitochondrial fluid. The word "matrix" stems from the fact that this space is viscous, compared to the relatively aqueous cytoplasm. The mitoc ...

, where it is converted to

propionyl-CoA Propionyl-CoA is a coenzyme A derivative of propionic acid. It is composed of a 24 total carbon chain (without the coenzyme, it is a 3 carbon structure) and its production and metabolic fate depend on which organism it is present in. Several diffe ...

branched-chain alpha-keto acid dehydrogenase complex The branched-chain α-ketoacid dehydrogenase complex (BCKDC or BCKDH complex) is a multi-subunit complex of enzymes that is found on the mitochondrial inner membrane. This enzyme complex catalyzes the oxidative decarboxylation of branched, short-c ...

. Further mitochondrial reactions produce

succinyl-CoA Succinyl-coenzyme A, abbreviated as succinyl-CoA () or SucCoA, is a thioester of succinic acid and coenzyme A. Sources It is an important intermediate in the citric acid cycle, where it is synthesized from Alpha-Ketoglutaric acid, α-ketoglutarate ...

. This is first through the enzyme mitochondria

propionyl-CoA carboxylase Propionyl-CoA carboxylase (, PCC) catalyses the carboxylation reaction of propionyl-CoA in the mitochondrial matrix. PCC has been classified both as a ligase and a lyase. The enzyme is biotin-dependent. The product of the reaction is (S)-methylmal ...

with

biotin Biotin (also known as vitamin B7 or vitamin H) is one of the B vitamins. It is involved in a wide range of metabolic processes, both in humans and in other organisms, primarily related to the utilization of fats, carbohydrates, and amino acids. ...

as a cofactor to produce (''S'')-

methylmalonyl-CoA Methylmalonyl-CoA is the thioester consisting of coenzyme A linked to methylmalonic acid. It is an important intermediate in the biosynthesis of succinyl-CoA, which plays an essential role in the tricarboxylic acid cycle (aka the Citric Acid Cycl ...

. This is subsequently converted to (''R'')-methylmalonyl-CoA by mitochondrial

methylmalonyl-CoA epimerase Methylmalonyl-CoA is the thioester consisting of coenzyme A linked to methylmalonic acid. It is an important intermediate in the biosynthesis of succinyl-CoA, which plays an essential role in the tricarboxylic acid cycle (aka the Citric Acid Cycle ...

. Finally, mitochondrial

methylmalonyl-CoA mutase Methylmalonyl-CoA mutase (, MCM), mitochondrial, also known as methylmalonyl-CoA isomerase, is a protein that in humans is encoded by the ''MUT'' gene. This vitamin B12-dependent enzyme catalyzes the isomerization of methylmalonyl-CoA to succin ...

with cofactor

adenosylcobalamin Adenosylcobalamin (AdoCbl), also known as coenzyme B12, cobamamide, and dibencozide, is one of the biologically active forms of vitamin B12. Adenosylcobalamin participates as a cofactor in radical-mediated 1,2-carbon skeleton rearrangements. T ...

produces succinyl-CoA which enters the

citric acid cycle The citric acid cycle—also known as the Krebs cycle, Szent–Györgyi–Krebs cycle, or TCA cycle (tricarboxylic acid cycle)—is a series of chemical reaction, biochemical reactions that release the energy stored in nutrients through acetyl-Co ...

Conversion in sotolon in French ''vin jaune''

Vin jaune is a special and characteristic type of white wine made in the Jura (wine), Jura region in eastern France. It is similar to dry fino Sherry and gets its character from being matured in a barrel under a film of yeast (wine), yeast, known as the ...

'' is marked by the formation of

sotolon Sotolon (also known as sotolone) is a butenolide lactone and an extremely potent aroma compound, with the typical smell of fenugreek or curry at high concentrations and maple syrup, caramel, or burnt sugar at lower concentrations. Sotolon is the m ...

from alpha-ketobutyric acid.

References

{{DEFAULTSORT:Ketobutyric acid, alpha- Alpha-keto acids

Conversion in sotolon in French ''vin jaune''

See also

References