Urobilin
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| Names | |
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| IUPAC name
3,3′-[(4S,16S)-3,18-Diethyl-2,7,13,17-tetramethyl-1,19-dioxo-1,4,5,15,16,19,22,24-octahydro-21H-biline-8,12-diyl]dipropanoic acid
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| Systematic IUPAC name
3,3′-([12S,4(52)Z,72S]-13,74-Diethyl-14,33,54,73-tetramethyl-15,75-dioxo-12,15,72,75-tetrahydro-11H,31H,71H-1,7(2),3,5(2,5)-tetrapyrrolaheptaphan-4(52)-ene-34,53-diyl)dipropanoic acid | |
| Other names
Urochrome
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.015.870 |
| MeSH | Urobilin |
PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| C33H42N4O6 | |
| Molar mass | 590.721 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Urobilin or urochrome is the chemical primarily responsible for the yellow color of urine. It is a linear tetrapyrrole compound that, along with the related colorless compound urobilinogen, are degradation products of the cyclic tetrapyrrole heme.
Metabolism
[edit]Urobilin is generated from the degradation of heme, which is first degraded through biliverdin to bilirubin. Bilirubin is then excreted as bile, which is further degraded by microbes present in the large intestine to urobilinogen. The enzyme responsible for the degradation is bilirubin reductase, which was identified in 2024.[1][2] Some of this remains in the large intestine, and its conversion to stercobilin gives feces their brown color. Some is reabsorbed into the bloodstream and then delivered to the kidneys. When urobilinogen is exposed to air, it is oxidized to urobilin, which has a yellow color.[3]
Importance
[edit]Many urine tests (urinalysis) monitor the amount of urobilin in urine, as its levels can give insight on the effectiveness of urinary tract function. Normally, urine would appear as either light yellow or colorless. A lack of water intake, for example following sleep or dehydration, reduces the water content of urine, thereby concentrating urobilin and producing a darker color of urine. Obstructive jaundice reduces biliary bilirubin excretion, which is then excreted directly from the blood stream into the urine, giving a dark-colored urine but with a paradoxically low urobilin concentration, no urobilinogen, and usually with correspondingly pale faeces. Darker urine can also be due to other chemicals, such as various ingested dietary components or drugs, porphyrins in patients with porphyria, and homogentisate in patients with alkaptonuria.
See also
[edit]References
[edit]- ^ Hall, Brantley; Levy, Sophia; Dufault-Thompson, Keith; Arp, Gabriela; Zhong, Aoshu; Ndjite, Glory Minabou; Weiss, Ashley; Braccia, Domenick; Jenkins, Conor; Grant, Maggie R.; Abeysinghe, Stephenie; Yang, Yiyan; Jermain, Madison D.; Wu, Chih Hao; Ma, Bing (January 2024). "BilR is a gut microbial enzyme that reduces bilirubin to urobilinogen". Nature Microbiology. 9 (1): 173–184. doi:10.1038/s41564-023-01549-x. ISSN 2058-5276. PMC 10769871. PMID 38172624.
- ^ Rayne, Elizabeth (2024-01-27). "Gotta go? We've finally found out what makes urine yellow". Ars Technica. Retrieved 2024-01-28.
- ^ John E. Hall (2016). "The liver as an organ". Guyton and Hall Textbook of Medical Physiology, 13th edition. Elsevier. p. 885. ISBN 978-1455770052.
Further reading
[edit]- Bishop, Michael; Duben-Engelkirk, Janet L., and Fody, Edward P. (1992). "Chapter 19, Liver Function, Clinical Chemistry Principles, Procedures, Correlations, 2nd Ed." Philadelphia, J.B. Lippincott Company.
- Miyabara, Yuichi; Tabata, Masako; Suzuki, Junzo; Suzuki, Shizuo (1992). "Separation and sensitive determination of i-urobilin and 1-stercobilin by high-performance liquid chromatography with fluorimetric detection". Journal of Chromatography B: Biomedical Sciences and Applications. 574 (2): 261–265. doi:10.1016/0378-4347(92)80038-R. PMID 1618958.
- Miyabara, Y.; Sakata, Y.; Suzuki, J.; Suzuki, S. (1994). "Estimation of faecal pollution based on the amounts of urobilins in urban rivers". Environmental Pollution. 84 (2): 117–122. doi:10.1016/0269-7491(94)90093-0. PMID 15091706.
- Munson-Ringsrud, Karen and Jorgenson-Linné, Jean (1995). "Urinalysis and Body Fluids, a ColorText and Atlas." St. Louis, Mosby.
- Nelson, L.; David, Cox M.M. (2005). “Chapter 22 – Biosynthesis of Amino Acids, Nucleotides, and Related Molecules”, pp. 856, In Lehninger Principles of Biochemistry. Freeman, New York. pp. 856.
- Voet, Donald; Voet, Judith G.; Pratt, Charlotte W. (2018-01-23). Voet's Principles of Biochemistry, Global Edition, 5th Edition. Wiley. p. 1200. ISBN 978-1-119-45166-2. Retrieved 2024-02-01.