D-Xylulose 5-phosphate (D-xylulose-5-P) is an intermediate in the

pentose phosphate pathway The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt or HMP shunt) is a metabolic pathway parallel to glycolysis. It generates NADPH and pentoses (five-carbon sugars) as well as ribose 5-ph ...

. It is a

ketose In organic chemistry, a ketose is a monosaccharide containing one ketone () group per molecule. The simplest ketose is dihydroxyacetone (), which has only three carbon atoms. It is the only ketose with no optical activity. All monosaccharide keto ...

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. 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. As a result, the production of fructose 2,6-bisphosphate increases, ultimately leading to an upregulation of glycolysis. 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 molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...

in the well-fed state. 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.

References

{{Pentose phosphate pathway intermediates Monosaccharide derivatives Organophosphates Pentose phosphate pathway