Urocanic acid

Urocanic acid
Names

IUPAC name (E)-3-(1H-imidazol-4-yl)prop-2-enoic acid
Identifiers
CAS Registry Number	104-98-3^Y
ChEBI	CHEBI:30817^N
ChemSpider	643824^N
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
Jmol-3D images	Image
MeSH	Urocanic+acid
PubChem	1178
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 noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
N verify (what is: Y/N?)
Infobox references

Urocanic acid is an intermediate in the catabolism of L-histidine.

Metabolism

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.

Clinical significance

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

Function

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.^[1] The cis form is known to activate regulatory T cells.^[2]

History

Urocanic acid was first isolated in 1874 by the chemist Max Jaffé from the urine of a dog,^[3]^[4]^[5] hence the name (Latin: urina = urine, and canis = dog).

References

↑ Egawa M, Nomura J, Iwaki H: The evaluation of the amount of cis- and trans-urocanic acid in the stratum corneum by Raman spectroscopy. Photochem. Photobiol. Sci., 2010, 9, 730-733.
↑ Schwarz T: Mechanisms of UV-induced immunosuppression. Keio J Med 2005;54(4):165-171.
↑ Jaffé, M. (1874). "Concerning a new constituent in the urine of dogs". Ber. Deut. Chem. Ges. 7: 1669–1673.
↑ M. Jaffe: Ueber die Urocaninsäure. In: Berichte der deutschen chemischen Gesellschaft. - Weinheim : Wiley-VCH, ISSN 0365-9496 Vol. 8 (1. 1875), p. 811-813.
↑ M. Jaffe: Ueber einen neuen Bestandtheil des Hundeharns. In: Berichte der deutschen chemischen Gesellschaft. - Weinheim : Wiley-VCH, ISSN 0365-9496 Vol. 7 (2. 1874), p. 1669-1673.

External links

The Online Metabolic and Molecular Bases of Inherited Disease - Chapter 80 - An overview of disorders of histidine metabolism, including urocanic aciduria.

Amino acid metabolism metabolic intermediates

K→acetyl-CoA

lysine→	Saccharopine Allysine α-Aminoadipic acid α-Ketoadipate Glutaryl-CoA Glutaconyl-CoA Crotonyl-CoA β-Hydroxybutyryl-CoA

leucine→	α-Ketoisocaproic acid Isovaleryl-CoA 3-Methylcrotonyl-CoA 3-Methylglutaconyl-CoA HMG-CoA

tryptophan→alanine→	N'-Formylkynurenine Kynurenine Anthranilic acid 3-Hydroxykynurenine 3-Hydroxyanthranilic acid 2-Amino-3-carboxymuconic semialdehyde 2-Aminomuconic semialdehyde 2-Aminomuconic acid Glutaryl-CoA

G→pyruvate→citrate

glycine→serine→	3-Phosphoglyceric acid glycine→creatine: Glycocyamine Phosphocreatine Creatinine

G→glutamate→
α-ketoglutarate

histidine→	Urocanic acid Imidazol-4-one-5-propionic acid Formiminoglutamic acid Glutamate-1-semialdehyde

proline→	1-Pyrroline-5-carboxylic acid

arginine→	Agmatine Ornithine Cadaverine Putrescine

other	cysteine+glutamate→glutathione: γ-Glutamylcysteine

G→propionyl-CoA→
succinyl-CoA

valine→	α-Ketoisovaleric acid Isobutyryl-CoA Methacrylyl-CoA 3-Hydroxyisobutyryl-CoA 3-Hydroxyisobutyric acid 2-Methyl-3-oxopropanoic acid

isoleucine→	2,3-Dihydroxy-3-methylpentanoic acid 2-Methylbutyryl-CoA Tiglyl-CoA 2-Methylacetoacetyl-CoA

methionine→	generation of homocysteine: S-Adenosyl methionine S-Adenosyl-L-homocysteine Homocysteine conversion to cysteine: Cystathionine alpha-Ketobutyric acid+Cysteine

threonine→	α-Ketobutyric acid

propionyl-CoA→	Methylmalonyl-CoA

G→fumarate

phenylalanine→tyrosine→	4-Hydroxyphenylpyruvic acid Homogentisic acid 4-Maleylacetoacetic acid

G→oxaloacetate

see urea cycle

Other

Cysteine metabolism	Cysteine sulfinic acid

Index of inborn errors of metabolism

Description	Metabolism Enzymes and pathways: citric acid cycle enzymes pentose phosphate intermediates glycoproteins enzymes glycosaminoglycans proteoglycan enzymes phospholipid metabolism cholesterol and steroid intermediates sphingolipids enzymes eicosanoids enzymes amino acid intermediates urea cycle enzymes nucleotide intermediates

Disorders	Citric acid cycle and electron transport chain Glycoprotein Proteoglycan Fatty-acid Phospholipid Cholesterol and steroid Eicosanoid Amino acid Purine-pyrimidine Heme metabolism Symptoms and signs

Treatment	Drugs other

Index of biochemical families

Carbohydrates	Alcohols Glycoproteins Glycosides

Lipids	Eicosanoids Fatty acids intermediates Glycerides Phospholipids Sphingolipids Steroids

Nucleic acids	Constituents intermediates

Proteins	Amino acids intermediates

Other	Tetrapyrroles intermediates