Disease relevance of xylulose-phosphate

• In Escherichia coli, RpiA catalyzes the interconversion of ribose-5-phosphate and ribulose-5-phosphate and is a key enzyme in the pentose phosphate pathway [1].
• Since the pentose shunt product, ribulose-5-phosphate, is converted to arabinose-5-phosphate as the first step in 3-keto-D-manno-octulosonic acid biosynthesis by gram-negative bacteria, such a conversion was then searched for in mycobacteria [2].
• The dod gene of Serratia marcescens was expressed in Pseudomonas stutzeri and was shown to code for D-ribulose-5-phosphate 3-epimerase [3].
• One of the major species detected in one of the resistant derivatives had an apparent denatured molecular mass of approximately 90 kDa, and was identified as xylulose-5-phosphate/fructose-6-phosphate phosphoketolase, the key enzyme of Bifidobacterium carbohydrate catabolism [4].
• Ribulose-5-phosphate kinase from Chromatium [5].

High impact information on xylulose-phosphate

• Addition of xylitol, a precursor of xylulose-5-phosphate, to primary rat hepatocytes increased FXR expression to a comparable level as D-glucose [6].
• Renal and hepatic microsomes also have detectable levels of these enzymes except ribulose-5-phosphate epimerase and ribose-5-phosphate isomerase [7].
• Stoichiometry of the reaction suggests that 2 mol of NAD+ are reduced per mol of ribulose-5-P generated [8].
• The extremely labile recombinant spinach (Spinacia oleracea L.) enzyme was stabilized by DL-alpha-glycerophosphate or ethanol and destabilized by D-ribulose-5-phosphate or 2-mercaptoethanol [9].
• Despite these changes, the activities of transaldolase (3.4 +/- 0.3 mumol/min per g), transketolase (7.8 +/- 0.2 mumol/min per g) and ribulose-5-P 3-epimerase (7.5 +/- 0.4 mumol/min per g) were not increased in meal-fed animals above those observed in starved animals (3.4 +/- 0.2, 7.1 +/- 0.3 and 8.6 +/- 0.4 mumol/min per g respectively) [10].

Chemical compound and disease context of xylulose-phosphate

• Tools for discovery of inhibitors of the 1-deoxy-D-xylulose 5-phosphate (DXP) synthase and DXP reductoisomerase: an approach with enzymes from the pathogenic bacterium Pseudomonas aeruginosa [11].

Biological context of xylulose-phosphate

• Treatment also increased hepatic concentrations of glycogen and xylulose-5-phosphate (X-5-P), a key stimulator of glycolysis [12].
• Evidence for a reactive cysteine at the nucleotide binding site of spinach ribulose-5-phosphate kinase [13].
• In this study, erythritol, xylitol, and arabitol were produced as carbon storage compounds when the flux through the PP pathway exceeded the need in ribulose-5-phosphate for the biomass synthesis [14].
• A broad-host-range expression vector series including a Ptac test plasmid and its application in the expression of the dod gene of Serratia marcescens (coding for ribulose-5-phosphate 3-epimerase) in Pseudomonas stutzeri [3].
• The gene encoding xylulose-5-phosphate/fructose-6-phosphate phosphoketolase (xfp) is conserved among Bifidobacterium species within a more variable region of the genome and both are useful for strain identification [15].

Anatomical context of xylulose-phosphate

• Effect of added xylulose-5-phosphate on the assay of erythrocyte transketolase [16].

Associations of xylulose-phosphate with other chemical compounds

• An affinity label for the regulatory dithiol of ribulose-5-phosphate kinase from maize (Zea mays) [17].
• The labeling of the D-ara-bino-3-hexulose-6-phosphate, as well as the other sugar-Ps, indicates that this hexose-6-phosphate was the precursor to ribulose-5-phosphate that in turn was converted into ribose-5-phosphate by ribose-5-phosphate isomerase [18].
• Ribose-5-phosphate isomerase and ribulose-5-phosphate kinase show apparent specificity for a specific ribulose 5-phosphate species [19].
• The last reaction step of the DOXP pathway is catalysed by the LytB enzyme which contains a [4Fe-4S] cluster [20].
• Additional work has demonstrated that ribulose-5-phosphate is derived by the loss of formaldehyde from D-arabino-3-hexulose-6-phosphate, catalyzed by the protein product of the MJ1447 gene [18].

Gene context of xylulose-phosphate

• We have cloned and characterized the two remaining unknown genes of the non-oxidative part of the pentose-phosphate pathway of Saccharomyces cerevisiae encoding the enzymes D-ribulose-5-phosphate 3-epimerase (Rpe1p) and D-ribose-5-phosphate ketol-isomerase (Rki1p) [21].
• In separate experiments, we have shown that the 24 kDa protein has d-ribulose-5-phosphate epimerase activity (similar to CbbE), and we call the gene rpe [22].
• However, ribulose-5-phosphate 3'-epimerase (EC 5.1.3.1) and transketolase (EC 2.2.1.1) activities were detectable only in procyclic forms [23].
• 0. Four nonoxidative pentose-biosynthetic enzymes were found (specific activity in milliunits per milligram of protein): transketolase, 12; transaldolase, 24; ribulose-5-phosphate-3-epimerase, 55; and ribulose-5-phosphate isomerase, 100 [24].
• The DOXP/MEP pathway leads to the formation of various phosphorylated intermediates, including DOXP, 4-hydroxy-3-methylbutenyl diphosphate (HMBPP), and finally IPP [25].

Analytical, diagnostic and therapeutic context of xylulose-phosphate

• An efficient purification procedure utilizing affinity chromatography is described for spinach ribulose-5-phosphate kinase, a light-regulated chloroplastic enzyme [26].

References