数据之源，洞见之始

Metabolite Card

Note

Xylulose 5-phosphate (Xu-5-P) is a metabolite of the hexose monophosphate pathway that activates protein phosphatase 2A to mediate the acute effects of carbohydrate feeding on the glycolytic pathway, as well as the coordinate long-term control of the enzymes required for fatty acid and triglyceride synthesis. Xu-5-P is the signal for the coordinated control of lipogenesis. Feeding carbohydrate causes levels of liver glucose, Glucose-6-phosphate (Glc-6-P), and Fructose-6-phosphate (Fru-6-P) to rise. Elevation of Fru-6-P leads to elevation of Xu-5-P in reactions catalyzed by the near-equilibrium isomerases of the nonoxidative portion of the hexose monophosphate pathway (ribulose 5-phosphate (Ru5P) epimerase [EC 5.1.3.1], ribose 5-phosphate (Rib5P) isomerase [EC 5.3.1.6], transaldolase [EC 2.2.1.2], and transketolase [EC 2.2.1.1]). The elevation of Xu-5-P is the coordinating signal that both acutely activates phosphofructokinase [PFK; EC 2.7.1.11] in glycolysis and promotes the action of the transcription factor carbohydrate responsive element binding protein (ChREBP) to increase transcription of the genes for the enzymes of lipogenesis, the hexose monophosphate shunt, and glycolysis, all of which are required for the de novo synthesis of fat. (PMID 12721358).