- Urocanic acid
Section1= Chembox Identifiers
Section2= Chembox Properties
Section3= Chembox Hazards
Urocanic acid is an intermediate in the
catabolismof L- histidine.
It is formed from L-histidine through the action of
histidine ammonialyase(also known as histidase or histidinase) by elimination of ammonium.
In the liver, urocanic acid is transformed by
urocanate hydratase(or urocanase) to 4-imidazolone-5-propionic acidand subsequently to glutamic acid.
Inherited deficiency of urocanase leads to elevated levels of urocanic acid in the urine, a condition known as
Urocanic acid was detected in animal sweat and skin where, among other possible functions, it acts as an endogenous sunscreen or photoprotectant against
UVB-induced DNA damage. Urocanic acid is found predominantly in the stratum corneumof the skin and it is likely that most of it is derived from filaggrincatabolism (a histidine-rich protein). When exposed to UVB irradiation, trans-urocanic acid is converted "in vitro" and "in vivo" to the cis isomer. The cis form is known to activate suppressor T cells.
Urocanic acid was first isolated in 1874 by the chemist M. Jaffé from the urine of a dog, [Jaffé, M. (1874) Concerning a new constituent in the urine of dogs. "Ber. Deut. Chem. Ges." 7, 1669-1673.] hence the name (
Latin: "urina" = urine, and "canis" = dog).
Inborn error of metabolism
* [http://books.mcgraw-hill.com/getommbid.php?isbn=0071459960&template=ommbid&c=80 The Online Metabolic and Molecular Bases of Inherited Disease - Chapter 80] - An overview of disorders of histidine metabolism, including urocanic aciduria.
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