Urocanic acid

Urocanic acid

Names
Preferred IUPAC name (2E)-3-(1H-imidazol-4-yl)prop-2-enoic acid
Other names (E)-3-(1H-imidazol-4-yl)acrylic acid
Identifiers
CAS Number	104-98-3 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:30817 N
ChemSpider	643824 N
ECHA InfoCard	100.002.963
MeSH	Urocanic+acid
PubChem	1178
InChI InChI=1S/C6H6N2O2/c9-6(10)2-1-5-3-7-4-8-5/h1-4H,(H,7,8)(H,9,10)/b2-1+ N Key: LOIYMIARKYCTBW-OWOJBTEDSA-N N InChI=1/C6H6N2O2/c9-6(10)2-1-5-3-7-4-8-5/h1-4H,(H,7,8)(H,9,10)/b2-1+ Key: LOIYMIARKYCTBW-OWOJBTEDBA
SMILES c1c(nc[nH]1)/C=C/C(=O)O
Properties
Chemical formula	C6H6N2O2
Molar mass	138.124 g/mol
Melting point	225 °C (437 °F; 498 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Urocanic acid is an intermediate in the catabolism of 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 acid and subsequently to glutamic acid.

Inherited deficiency of urocanase leads to elevated levels of urocanic acid in the urine, a condition known as urocanic aciduria.

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 corneum of the skin and it is likely that most of it is derived from filaggrin catabolism (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 regulatory T cells.

Urocanic acid was first isolated in 1874 by the chemist Max Jaffé from the urine of a dog, hence the name (Latin: urina = urine, and canis = dog).