Chemistry:Hydroxymethylbilane
Hydroxymethylbilane, also known as preuroporphyrinogen, is an organic compound that occurs in living organisms during the synthesis of porphyrins, a group of critical substances that include haemoglobin, myoglobin, and chlorophyll. The name is often abbreviated as HMB.
Structure
The compound is a substituted bilane, a chain of four pyrrole rings interconnected by methylene bridges –CH
2–. The chain starts with a hydroxymethyl group –CH
2–OH and ends with a hydrogen, in place of the respective methylene bridges. The other two carbon atoms of each pyrrole cycle are connected to an acetic acid group –CH
2–COOH and a propionic acid group –CH
2–CH
2–COOH, in that order.[1]
Metabolism
HMB is generated from four molecules of porphobilinogen by the enzyme porphobilinogen deaminase in the overall reaction:[2][3]
The enzyme uroporphyrinogen III synthase catalyses the cyclisation reaction of hydroxymethylbilane into uroporphyrinogen III via a spiro intermediate which allows one of the pyrrole rings to convert its initial acetate to propionate configuration into a propionate-acetate one.[2][4][5]
Uroporphyrinogen III is a porphyrinogen, which is a class of compounds with the hexahydroporphine macrocycle. In the absence of the enzyme, the compound undergoes spontaneous cyclization and becomes uroporphyrinogen I.[6][7]
References
- ↑ Paul R. Ortiz de Montellano (2008). Wiley Encyclopedia of Chemical Biology. John Wiley & Sons. doi:10.1002/9780470048672.wecb221. ISBN 978-0470048672.
- ↑ 2.0 2.1 Voet, Donald; Voet, Judith G. (2011). Biochemistry (4. ed.). Hoboken, NJ: Wiley. ISBN 978-0-470-57095-1.
- ↑ Enzyme 2.5.1.61 at KEGG Pathway Database.
- ↑ Battersby, Alan R.; Fookes, Christopher J. R.; Matcham, George W.J.; McDonald, Edward (1980). "Biosynthesis of the pigments of life: formation of the macrocycle". Nature 285 (5759): 17–21. doi:10.1038/285017a0. PMID 6769048. Bibcode: 1980Natur.285...17B.
- ↑ Enzyme 4.2.1.75 at KEGG Pathway Database.
- ↑ Paul R. Ortiz de Montellano (2008). Wiley Encyclopedia of Chemical Biology. John Wiley & Sons. doi:10.1002/9780470048672.wecb221. ISBN 978-0470048672.
- ↑ Sassa, S.; Kappas, A. (2000). "Molecular aspects of the inherited porphyrias". Journal of Internal Medicine 247 (2): 169–178. doi:10.1046/j.1365-2796.2000.00618.x. PMID 10692079.
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