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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.
The systematic name of this enzyme class is pyruvate: d-glyceraldehyde-3-phosphate acetaldehydetransferase (decarboxylating). Other names in common use include 1-deoxy-d-xylulose-5-phosphate pyruvate-lyase (carboxylating), and DXP-synthase. This enzyme participates in biosynthesis of steroids.
The enzyme involved in making 1-deoxy-d-xylulose 5-phosphate (DXP) is DXP synthase. [2] The mechanism follows a catalysis of decarboxylative condensation of pyruvate and d-glyceraldehyde 3-phosphate to produce DXP. [2] [3] In addition, the molecule is involved in making thiamine (vitamin B 1) and pyridoxol (vitamin B 6). [2]
XR is reducing D-xylose to xylitol using NADH or NADPH. Xylitol is then oxidized to D-xylulose by XDH, using the cofactor NAD. In the last step D-xylulose is phosphorylated by an ATP utilising kinase, XK, to result in D-xylulose-5-phosphate which is an intermediate of the pentose phosphate pathway.
The mevalonate pathway (MVA pathway or HMG-CoA reductase pathway) and the MEP pathway are metabolic pathways for the biosynthesis of isoprenoid precursors: IPP and DMAPP. . Whereas plants use both MVA and MEP pathway, most organisms only use one of the pathways for the biosynthesis of isoprenoid precurs
The second reaction catalyzed by transketolase in the pentose phosphate pathway involves the same thiamine diphosphate-mediated transfer of a 2-carbon fragment from D-xylulose-5-P to the aldose erythrose-4-phosphate, affording fructose 6-phosphate and glyceraldehyde-3-P. Again, the same reaction occurs in the Calvin cycle but in the opposite ...
ATP + D-xylulose ⇌ ADP + D-xylulose 5-phosphate. Thus, the two substrates of this enzyme are ATP and D-xylulose, whereas its two products are ADP and D-xylulose 5-phosphate. This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing groups (phosphotransferases) with an alcohol group as acceptor.
In Arabidopsis thaliana 1-deoxy-D-xylulose 5-phosphate reductoisomerase is the first committed enzyme of the MEP pathway for isoprenoid precursor biosynthesis. The enzyme requires Mn 2+ , Co 2+ or Mg 2+ for activity, with Mn 2+ being most effective.