beta-Hydroxybutyric acid

beta-Hydroxybutyric acid

Names
IUPAC name 3-Hydroxybutanoic acid
Identifiers
CAS Number	300-85-6 Y
ChEBI	CHEBI:20067 Y
ChEMBL	ChEMBL1162496 Y
ChemSpider	428 Y
IUPHAR/BPS	1593
Jmol 3D model	Interactive image Interactive image
MeSH	beta-Hydroxybutyrate
PubChem	441
InChI InChI=1S/C4H8O3/c1-3(5)2-4(6)7/h3,5H,2H2,1H3,(H,6,7) Y Key: WHBMMWSBFZVSSR-UHFFFAOYSA-N Y InChI=1/C4H8O3/c1-3(5)2-4(6)7/h3,5H,2H2,1H3,(H,6,7) Key: WHBMMWSBFZVSSR-UHFFFAOYAO
SMILES O=C(O)CC(O)C CC(CC(=O)O)O
Properties
Chemical formula	C4H8O3
Molar mass	104.11 g·mol−1
Appearance	white solid
Melting point	44-46
Related compounds
Other anions	hydroxybutyrate
Related carboxylic acids	propionic acid lactic acid 3-hydroxypropanoic acid malonic acid hydroxypentanoic acid butyric acid β-methylbutyric acid β-hydroxy β-methylbutyric acid
Related compounds	erythrose threose 1,2-butanediol 1,3-butanediol 2,3-butanediol 1,4-butanediol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references

β-Hydroxybutyric acid, also known as 3-hydroxybutyric acid, is an organic compound and a beta hydroxy acid with the formula CH₃CH(OH)CH₂CO₂H; its conjugate base is beta-hydroxybutyrate, also known as 3-hydroxybutyrate. β-Hydroxybutyric acid is a chiral compound having two enantiomers, D-β-hydroxybutyric acid and L-β-hydroxybutyric acid. Its oxidized and polymeric derivatives occur widely in nature.

Biosynthesis

In humans, D-3-hydroxybutyrate is synthesized in the liver from acetoacetate, the first ketone produced in the fasting state. The biosynthesis is catalyzed by the enzyme beta-hydroxybutyrate dehydrogenase.

In epilepsy patients on the ketogenic diet, blood beta-hydroxybutyrate levels correlate best with degree of seizure control. The threshold for optimal anticonvulsant effect appears to be approximately 4 mmol/L.

Although beta-hydroxybutyrate is not a ketone itself, its concentration, as with other ketone bodies, is raised in ketosis. This elevated beta-hydroxybutyrate level is naturally expected, as beta-hydroxybutyrate is formed from acetoacetate. The compound can be used as an energy source by the brain when blood glucose is low. Diabetic patients can have their ketone levels tested via urine or blood to indicate diabetic ketoacidosis. In alcoholic ketoacidosis, this ketone body is produced in greatest concentration. Ketogenesis occurs if oxaloacetate in the liver cells is depleted, a circumstance created by reduced carbohydrate intake (through diet or starvation), prolonged, excessive alcohol consumption, and/or insulin deficiency. Because oxaloacetate is crucial for entry of Acetyl-CoA into the TCA cycle, the rapid production of Acetyl-CoA from fatty acid oxidation in the absence of ample oxaloacetate overwhelms the decreased capacity of the TCA cycle, and the resultant excess of Acetyl-CoA is shunted towards ketone body production.

Laboratory and industrial chemistry

beta-Hydroxybutyric acid is the precursor to polyesters, which are biodegradable plastics. Known as poly(3-hydroxybutyrate), this polymer is also produced biologically by the bacteria Alcaligenes eutrophus.

beta-Hydroxybutyrate can be extracted from poly(3-hydroxybutyrate) by acid hydrolysis.

Blood beta-hydroxybutyrate levels are measured through a test that uses beta-hydroxybutyrate dehydrogenase, with NAD+ as an electron-accepting cofactor. The conversion of B-OHB to acetoacetate catalyzed by the enzyme reduces the NAD+ to NADH, generating an electrical change, the magnitude of which can then be used to extrapolate the amount of beta-hydroxybutyrate in the sample.

See also

• Hydroxybutyric acid
• Ketogenesis