Glucuronic acid 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. Glucuronic acid is common in carbohydrate chains of proteoglycans. It is part of mucous animal secretions (such as saliva), cell glycocalyx, and intercellular matrix (for instance hyaluronan). 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 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., intestine, kidneys, brain, adrenal gland, spleen, and thymus.