Disease relevance of xylose

• End-stage renal disease and diabetes catalyze the formation of a pentose-derived crosslink from aging human collagen [1].
• The cause of the abnormal pentose metabolism in these conditions is unknown but may relate to hemolysis, impaired pentose excretion, cellular stress, and accelerated breakdown of ribonucleotides [1].
• Body weight (P < 0.003), lean body mass (P < 0.006), D-xylose absorption (P < 0.02), insulin-like growth factor 1 (P < 0.002), and insulin-like growth factor binding protein 3 (P < 0.002) increased, whereas uptake of GH binding protein decreased (P < 0.01), without any major adverse effect [2].
• L-Xylose absorption and electrolyte movement were not altered in cystic fibrosis [3].
• Krebs cycle, pentose phosphate pathway, and glycolysis in the uninvolved gastric mucosa of peptic ulcer and gastric cancer patients [4].

Psychiatry related information on xylose

• Enzymatic activities in the heart indicated an increased rate of oxidative pentose phosphate pathway activity during sleep deprivation [5].
• Since previous studies have shown that casein and casein hydrolysate led to a decrease of small intestinal motor activity and transit, the aim was to evaluate the effect of these nutrients on small intestinal motility and D-Xylose absorption [6].
• Transketolase is a key enzyme in the pentose-phosphate pathway which has been implicated in the latent human genetic disease, Wernicke-Korsakoff syndrome [7].
• Effect of food deprivation on D-xylose absorption test results in mares [8].
• D-xylose concentrations in plasma in psychological stress mice were significantly higher than those in the control group (2.90+/-0.89 mmol/L vs 0.97+/-0.33 mmol/L, P<0.01) [9].

High impact information on xylose

• Pentose-phosphate-pathway-mediated inhibition of cell death was due to the inhibitory phosphorylation of caspase-2 by calcium/calmodulin-dependent protein kinase II (CaMKII) [10].
• We show that pentose-phosphate-pathway generation of NADPH is critical for oocyte survival and that the target of this regulation is caspase-2, previously shown to be required for oocyte death in mice [10].
• It lacks the pentose phosphate cycle and, more unexpectedly, ATP-synthase subunits, which are thought to be essential for life [11].
• Whatever the chemical determinants by which nature selected RNA as a genetic system, maximization of base-pairing strengths within the domain of pentose-derived oligonucleotide systems was not the critical selection criterion [12].
• In this study reported here the activity of glucose-6-phosphate dehydrogenase, the first and rate-limiting enzyme of the oxidative pentose phosphate shunt, was very low in the human heart and was of the same order of magnitude in the myocardium of various animal species [13].

Chemical compound and disease context of xylose

• Uninvolved gastric mucosa from duodenal ulcer, gastric ulcer, and gastric cancer patients was incubated with [1-14C]glucose and [6-14C]glucose in order to assess the relative contributions of the pentose phosphate pathway and Krebs cycle to glucose metabolism [4].
• The locations of Met-87, Thr-89, Val-134, and Glu-180, which contact the C-6-OH group of the substrate in the sorbitol-bound xylose isomerase from Arthrobacter [Collyer, C.A., Henrick, K. & Blow, D. M. (1990) J. Mol. Biol. 212, 211-235], are equivalent to those of Trp-139, Thr-141, Val-186, and Glu-232 in the thermophilic enzyme [14].
• Surprisingly, it does not inhibit transport of L-arabinose or D-xylose by the related E. coli AraE and XylE transporters, even though the amino acid sequences of their proteins are 30-64% identical to GalP and to the mammalian GLUT family [15].
• Absorptive capacity and intestinal permeability were assessed using 3-O-methyl-D-glucose, D-xylose, L-rhamnose, and lactulose in 88 HIV infected patients and the findings were correlated with the degree of immunosuppression (CD4 counts), diarrhoea, wasting, intestinal pathogen status, and histomorphometric analysis of jejunal biopsy samples [16].
• The structures of D-xylose isomerase from Arthrobacter strain B3728 containing the polyol inhibitors xylitol and D-sorbitol have been solved at 2.5 A and 2.3 A, respectively [17].

Biological context of xylose

• The importance of the pentose phosphate shunt pathway for energy metabolism in the stimulated lymphocyte was confirmed [18].
• The weight, basal metabolic rate, nutrient and electrolyte balance, serum insulin-like growth factor I levels, D-xylose absorption, morphology and DNA proliferation of small intestinal mucosa, and gastrointestinal transit were evaluated [19].
• That AdoMet controls a part of the pentose phosphate pathway sheds new light on mechanisms regulating the relative fluxes of carbon utilization through the pentose phosphate pathway and glycolysis [20].
• The cleft is an obvious suggestion for an active site, which has putative binding sites for at least four xylose residues [21].
• We conclude that G6PD activity is dispensable for pentose synthesis, but is essential to protect cells against even mild oxidative stress [22].

Anatomical context of xylose

• The metabolic basis for this effect is the low capacity of the oxidative pentose phosphate pathway in the myocardium [13].
• The metabolism of pentose-phosphate was investigated in Plasmodium falciparum-infected normal and glucose-6-phosphate dehydrogenase (G6PD)-deficient human red blood cells in vitro [23].
• 1alpha(OH)-D3 had no effect on unidirectional calcium flux into the lumen or on xylose and electrolyte absorption in either area of the small intestine [24].
• Relationship between transport of D-xylose and other monosaccharides in jejunal mucosa of children [25].
• The jejunum was anatomically and functionally intact in all subjects, as demonstrated by normal gastrointestinal radiology and xylose absorption, respectively [26].

Associations of xylose with other chemical compounds

• Small-intestinal function was assessed by xylose, fat and vitamin B12, lactose, and bile-acid absorption [27].
• First, the addition of comparable amounts of xylose or galactose to the perfusion medium neither released insulin nor potentiated the CCK-induced response [28].
• However, the addition of methylene blue, which accelerates the oxidative pentose shunt that produces ribose-5-phosphate, resulted in acceleration of PRPP generation and of purine synthesis only when PRPP synthetase was largely activated at high Pi concentration [29].
• These mice absorbed D-xylose normally, but there was virtually no absorption of retinol palmitate or cholesterol [30].
• The permeability ratio of L-xylose/urea was used to assess apparent permeability of the mucosa and to calculate the average pore radius of the aqueous pathway for passive diffusion [31].

Gene context of xylose

• We suggest that loss of GPT1 function results in disruption of the oxidative pentose phosphate cycle, which in turn affects fatty acid biosynthesis [32].
• The MUR3 gene was cloned positionally and shown to encode a xyloglucan galactosyltransferase that acts specifically on the third xylose residue within the XXXG core structure of xyloglucan [33].
• Hemolytic anemia in hereditary pyrimidine 5'-nucleotidase deficiency: nucleotide inhibition of G6PD and the pentose phosphate shunt [34].
• Here we report that these two sod1Delta phenotypes were specifically suppressed by elevated expression of the TKL1 gene, encoding transketolase of the pentose phosphate pathway [35].
• Our studies suggest that this defect results from the impaired redox status of aerobically grown sod1 and zwf1 mutants, implicating Sod1 and the pentose phosphate pathway as being critical for maintenance of the cellular redox state [35].

Analytical, diagnostic and therapeutic context of xylose

• The trophic effect of TSH can be assayed in vitro by measuring DNA-synthesis by Feulgen cytophotometry; elevated pentose-shunt oxidative activity correlates with DNA synthesis [36].
• The [14C]D-xylose breath test with 1 g of D-xylose has been useful in identifying malabsorption caused by bacterial overgrowth in the small intestine [37].
• Results: CVID patients with gastrointestinal symptoms differed from asymptomatic CVID patients by having significantly longer duration of disease and lower body mass index, D-xylose absorption, serum albumin, CD4/CD45RA cells, CD3/CD25 cells, and natural killer cells [38].
• We have shown that optimal discrimination between normal and impaired xylose absorption is achieved by measuring blood xylose levels 1 hr after oral administration and then correcting the results to a constant body surface area [39].
• Molecular cloning, DNA structure and expression of the Escherichia coli D-xylose isomerase [40].

References