Organic compounds with a –COOH group and a C=O group
Not to be confused with oxyacid.
Pyruvic acid (top), acetoacetic acid and levulinic acid (bottom)
In organic chemistry, keto acids or ketoacids (also called oxo acids or oxoacids) are organic compounds that contain a carboxylic acid group (−COOH) and a ketone group (>C=O).[1] In several cases, the keto group is hydrated. The alpha-keto acids are especially important in biology as they are involved in the Krebs citric acid cycle and in glycolysis.[2]
Common types of keto acids include:
Alpha-keto acids, alpha-ketoacids, or 2-oxoacids have the keto group adjacent to the carboxylic acid. They often arise by oxidative deamination of amino acids, and reciprocally, they are precursors to the same. Alpha-keto acids possesses extensive chemistry as acylation agents.[3] Furthermore, alpha-keto acids such as phenylpyruvic acid are endogenous sources for carbon monoxide (as a gasotransmitter) and pharmaceutical prodrug scaffold.[4] Important representatives:
pyruvic acid, pervasive intermediate in metabolism.
oxaloacetic acid, a component of the Krebs cycle.[5]
alpha-ketoglutarate, a 5-carbon ketoacid derived from glutamic acid. Alpha-ketoglutarate participates in cell signaling by functioning as a coenzyme.[6] It is commonly used in transamination reactions.
Beta-keto acids, beta-ketoacids, or 3-oxoacids, such as acetoacetic acid, have the ketone group at the second carbon from the carboxylic acid. They generally form by the Claisen condensation. The presence of the keto group at the beta position allows them to easily undergo thermal decarboxylation.[7]
Gamma-keto acids, Gamma-ketoacids, or 4-oxoacids have the ketone group at the third carbon from the carboxylic acid. Levulinic acid is an example.
Keto acids appear in a wide variety of anabolic pathways in metabolism. For instance, in plants (specifically, in hemlock, pitcher plants, and fool's parsley), 5-oxo-octanoic acid is converted in enzymatic and non-enzymatic steps into the cyclic class of coniine alkaloids.[8]
When ingested sugars and carbohydrate levels are low, stored fats and proteins are the primary source of energy production. Glucogenic amino acids from proteins and/or Glycerol from Triglycerides are converted to glucose. Ketogenic amino acids can be deaminated to produce alpha keto acids and ketone bodies.
Alpha keto acids are used primarily as energy for liver cells and in fatty acid synthesis, also in the liver.
^Franz Dietrich Klingler, Wolfgang Ebertz "Oxocarboxylic Acids" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a18_313
^Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
^Penteado, Filipe; Lopes, Eric F.; Alves, Diego; Perin, Gelson; Jacob, Raquel G.; Lenardão, Eder J. (16 April 2019). "α-Keto Acids: Acylating Agents in Organic Synthesis". Chemical Reviews. 119 (12): 7113–7278. doi:10.1021/acs.chemrev.8b00782. PMID 30990680. S2CID 119535331.
^Hopper, Christopher P.; De La Cruz, Ladie Kimberly; Lyles, Kristin V.; Wareham, Lauren K.; Gilbert, Jack A.; Eichenbaum, Zehava; Magierowski, Marcin; Poole, Robert K.; Wollborn, Jakob; Wang, Binghe (2020-12-23). "Role of Carbon Monoxide in Host–Gut Microbiome Communication". Chemical Reviews. 120 (24): 13273–13311. doi:10.1021/acs.chemrev.0c00586. ISSN 0009-2665. PMID 33089988. S2CID 224824871.
^Kerber, Robert C.; Fernando, Marian S. (October 2010). "α-Oxocarboxylic Acids". Journal of Chemical Education. 87 (10): 1079–1084. doi:10.1021/ed1003096.
^Hewitson, K.S.; McNeill, L.A.; Elkins, J.M.; Schofield, C.J. (1 June 2003). "The role of iron and 2-oxoglutarate oxygenases in signalling". Biochemical Society Transactions. 31 (3): 510–515. doi:10.1042/bst0310510. PMID 12773146.
^Smith, Michael B. (2017), "Functional Group Exchange Reactions", Organic Synthesis, Elsevier, p. 137, doi:10.1016/b978-0-12-800720-4.00003-9, ISBN 978-0-12-800720-4, retrieved 2022-06-01
^Leete, E.; Olson, J. O. (1970). "5-Oxo-octanoic acid and 5-oxo-octanal, precursors of coniine". Journal of the Chemical Society D: Chemical Communications (23): 1651–1652. doi:10.1039/C29700001651. ISSN 0577-6171.
organic chemistry, ketoacids or ketoacids (also called oxo acids or oxoacids) are organic compounds that contain a carboxylic acid group (−COOH) and a...
fatty acid synthesis mechanisms, including that which forms tuberculosteric acid. The branched-chain fatty acid synthesizing system uses α-ketoacids as...
transferred to the ketoacid acceptor, forming the amino acid product while regenerating the enzyme. The chirality of an amino acid is determined during...
−O2CC(O−)CHCO2− + H+, pKa = 13.03 The enol forms of oxaloacetic acid are particularly stable. Keto-enol tautomerization is catalyzed by the enzyme oxaloacetate...
Sialic acids are a class of alpha-ketoacid sugars with a nine-carbon backbone. The term "sialic acid" (from Greek σίαλον (síalon) 'saliva') was first...
acid and an α-ketoacid. They are important in the synthesis of amino acids, which form proteins. An amino acid contains an amino (NH2) group. A keto...
Pyruvic acid (IUPAC name: 2-oxopropanoic acid, also called acetoic acid) (CH3COCOOH) is the simplest of the alpha-ketoacids, with a carboxylic acid and a...
The other product of transamidation is a ketoacid that enters the citric acid cycle. Glucogenic amino acids can also be converted into glucose, through...
alpha-hydrogen, undergo keto-enol tautomerization; the tautomer is an enol. Tautomerization is catalyzed by both acids and bases. Usually, the keto form is more...
oxalosuccinates. Oxalosuccinic acid/oxalosuccinate is an unstable 6-carbon intermediate in the tricarboxylic acid cycle. It's a ketoacid, formed during the oxidative...
system, branched chain ketoacid dehydrogenase, and the α-oxo(keto)adipate dehydrogenase. The first two are critical to the citric acid cycle. The GCS regulates...
organic compound with the formula CH3COCH2COOH. It is the simplest beta-ketoacid, and like other members of this class, it is unstable. The methyl and...
one amino acid (making it an α-ketoacid) to another α-ketoacid (making it an amino acid). This is important in the biosynthesis of amino acids, as for...
amino acid becomes oxidized, resulting in an α-ketoacid. The alpha-ketoacid will then proceed into the TCA cycle, in order to produce energy. The acid can...
deaminated carbon skeleton in the form of a ketoacid. Several of these ketoacids are intermediates in the citric acid cycle, for example α-ketoglutarate formed...
Levulinic acid, or 4-oxopentanoic acid, is an organic compound with the formula CH3C(O)CH2CH2CO2H. It is classified as a ketoacid. This white crystalline...
symmetrical (dialdehydes, diketones, diesters, etc.) or unsymmetrical (keto-esters, keto-acids, etc.). The only 1,2-dialdehyde is glyoxal, (CHO)2. Like many alkyldialdehydes...
Examples of keto-enol tautomerism In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry...
Phenylpyruvic acid is the organic compound with the formula C6H5CH2C(O)CO2H. It is a ketoacid. The compound exists in equilibrium with its E- and Z-enol...
glucogenic amino acids involves these amino acids being converted to alpha ketoacids and then to glucose, with both processes occurring in the liver. This...
R2-α-ketoacid ⇌ R1-α-ketoacid + R2-amino acid A very common α-ketoacid is α-ketoglutarate, an intermediate in the citric acid cycle. Transamination of α-ketoglutarate...
Oxidative deamination is a form of deamination that generates α-ketoacids and other oxidized products from amine-containing compounds, and occurs primarily...
an alpha-ketoacid. Industrially, aspartate is produced by amination of fumarate catalyzed by L-aspartate ammonia-lyase. Racemic aspartic acid can be synthesized...
a coding gene that is part of the BCKD complex (branched-chain alpha-ketoacid dehydrogenase). BCKDHA was discovered by John Menkes in 1954. After he...
Phenylalanine undergoes biotransformation to form an alpha-ketoacid, phenylpyruvic acid, which can tautomerize to a reactive enol. The benzylic carbon...
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