Xylulose_5-phosphate

Xylulose 5-phosphate

Xylulose 5-phosphate

Chemical compound

D-Xylulose 5-phosphate (D-xylulose-5-P) is an intermediate in the pentose phosphate pathway. It is a ketose sugar formed from ribulose-5-phosphate by ribulose-5-phosphate epimerase. In the non-oxidative branch of the pentose phosphate pathway, xylulose-5-phosphate acts as a donor of two-carbon ketone groups in transketolase reactions.[1]

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Xylulose-5-phosphate also plays a crucial role in the regulation of glycolysis through its interaction with the bifunctional enzyme PFK2/FBPase2. Specifically, it activates protein phosphatase, which then dephosphorylates PFK2/FBPase2. This inactivates the FBPase2 activity of the bifunctional enzyme and activates its PFK2 activity.[2] As a result, the production of fructose 2,6-bisphosphate increases, ultimately leading to an upregulation of glycolysis.[3]

Although previously thought of mainly as an intermediary in the pentose phosphate pathway, recent research reported that the sugar also has a role in gene expression, mainly by promoting the ChREBP transcription factor in the well-fed state.[4][5] However, more recent study showed that D-glucose-6-phosphate, rather than D-xylulose-5-phosphate, is essential for the activation of ChREBP in response to glucose.[6]

References

  1. [1]
    Stincone A, Prigione A, Cramer T, Wamelink MM, Campbell K, Cheung E, et al. (August 2015). "The return of metabolism: biochemistry and physiology of the pentose phosphate pathway". Biological Reviews of the Cambridge Philosophical Society. 90 (3): 927–963. doi:10.1111/brv.12140. PMC 4470864. PMID 25243985.
  2. [2]
    Nelson, David L.; Cox, Michael M.; Nelson, David L. (2013). Lehninger, Albert L. (ed.). Lehninger principles of biochemistry (6th ed.). Basingstoke: Macmillan Higher Education. p. 606. ISBN 978-1-4292-3414-6.
  3. [3]
    Uyeda K (June 2021). "Short- and Long-Term Adaptation to Altered Levels of Glucose: Fifty Years of Scientific Adventure". Annual Review of Biochemistry. 90 (1): 31–55. doi:10.1146/annurev-biochem-070820-125228. PMID 34153217.
  4. [4]
    Kabashima T, Kawaguchi T, Wadzinski BE, Uyeda K (April 2003). "Xylulose 5-phosphate mediates glucose-induced lipogenesis by xylulose 5-phosphate-activated protein phosphatase in rat liver". Proceedings of the National Academy of Sciences of the United States of America. 100 (9): 5107–5112. Bibcode:2003PNAS..100.5107K. doi:10.1073/pnas.0730817100. PMC 154306. PMID 12684532.
  5. [5]
    Iizuka K, Horikawa Y (August 2008). "ChREBP: a glucose-activated transcription factor involved in the development of metabolic syndrome". Endocrine Journal. 55 (4): 617–624. doi:10.1507/endocrj.k07e-110. PMID 18490833.
  6. [6]
    Dentin R, Tomas-Cobos L, Foufelle F, Leopold J, Girard J, Postic C, Ferré P (January 2012). "Glucose 6-phosphate, rather than xylulose 5-phosphate, is required for the activation of ChREBP in response to glucose in the liver". Journal of Hepatology. 56 (1): 199–209. doi:10.1016/j.jhep.2011.07.019. PMID 21835137.
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