Glucuronic acid (from Greek γλυκερός - "sweet") is a carboxylic acid. Its structure is similar to that of glucose. However, glucuronic acid's sixth carbon is oxidized to a carboxylic acid. Its formula is C₆H₁₀O₇.

The salts of glucuronic acid are known as glucuronates; the anion C₆H₉O₇⁻ is the glucuronate ion.

Glucuronic acid should not be confused with gluconic acid, a linear carboxylic acid resulting from the oxidation of a different carbon of glucose. Both glucuronic acid and gluconic acid are reported to be found in the fermented drink known as kombucha. Glucuronic acid has been attributed with the mildly-alcoholic effect that drinking the tea has for some.

Functions

Glucuronidation

Glucuronic acid is highly soluble in water. In the animal body, glucuronic acid is often linked to the xenobiotic metabolism of substances such as drugs, pollutants, bilirubin, androgens, estrogens, mineralocorticoids, glucocorticoids, fatty acid derivatives, retinoids, and bile acids. These linkages involve O-glycosidic bonds, and this linkage process is known as glucuronidation. Glucuronidation occurs mainly in the liver, although the enzyme responsible for its catalysis, UDP-glucuronyltransferase, has been found in all major body organs, e.g., heart, kidneys, adrenal gland, spleen, and thymus. UDP-glucuronic acid (glucuronic acid linked via a glycosidic bond to uridine diphosphate) is an intermediate in the process and is formed in the liver. The substances resulting from glucuronidation are known as glucuronides (or glucuronosides) and are typically much more water-soluble than the non-glucuronic acid-containing substance from which they were originally synthesised. The human body uses glucuronidation to make a large variety of substances more water-soluble, and, in this way, allow for their subsequent elimination from the body upon urination. Hormones may also be glucuronidated to allow for easier transport around the body. Pharmacists also commonly link drugs to glucuronic acid to allow for easier drug delivery.

Acyl glucuronidation

Acyl glucuronidation is an important metabolic pathway for fluoroquinolone antibiotics.

N-glucuronidation

Conformation

Unlike its C5 epimer iduronic acid, which may occur in a number of conformations, glucuronic acid occurs in predominantly the ⁴C₁ conformation.

Glucuronidases

Glucuronidases are those enzymes that hydrolyze the glycosidic bond between glucuronic acid and some other compound.

References

Further reading

• Chiu SH, Huskey SW (1998). "Species differences in N-glucuronidation". Drug Metab. Dispos. 26 (9): 838–47.
• Kuehl GE, Murphy SE (2003). "N-glucuronidation of nicotine and cotinine by human liver microsomes and heterologously expressed UDP-glucuronosyltransferases". Drug Metab. Dispos. 31 (11): 1361–8.
• Kuehl GE, Murphy SE (2003). "N-glucuronidation of trans-3'-hydroxycotinine by human liver microsomes". Chem. Res. Toxicol. 16 (12): 1502–6.
• Benowitz NL, Perez-Stable EJ, Fong I, Modin G, Herrera B, Jacob P (1999). "Ethnic differences in N-glucuronidation of nicotine and cotinine". J. Pharmacol. Exp. Ther. 291 (3): 1196–203.
• Mannfred A Hollinger, Introduction to Pharmacology, ISBN 0-415-28033-8
• Chang, K. M.; McManus, K.; Greene, J.; Byrd, G. D.; DeBethizy, J. D. Glucuronidation as a metabolic pathway for nicotine metabolism. 1991
• Coffman B.L., King C.D., Rios G.R. and Tephly T.R. The glucuronidation of opioids, other xenobiotics, and androgens by human