Gene Symbol: xapA
Description: purine nucleoside phosphorylase 2; nicotinamide 1-beta-D-riboside synthase
Alias: ECK2401, JW2398, pndA
Species: Escherichia coli str. K-12 substr. MG1655

Top Publications

  1. Koszalka G, VanHooke J, Short S, Hall W. Purification and properties of inosine-guanosine phosphorylase from Escherichia coli K-12. J Bacteriol. 1988;170:3493-8 pubmed
  2. Dandanell G, Szczepanowski R, Kierdaszuk B, Shugar D, Bochtler M. Escherichia coli purine nucleoside phosphorylase II, the product of the xapA gene. J Mol Biol. 2005;348:113-25 pubmed
    ..Escherichia coli PNP-II, the product of the xapA gene, is similar to trimeric PNPs in sequence, but has been reported to migrate as a hexamer and to accept ..
  3. Seeger C, Poulsen C, Dandanell G. Identification and characterization of genes (xapA, xapB, and xapR) involved in xanthosine catabolism in Escherichia coli. J Bacteriol. 1995;177:5506-16 pubmed
    ..One of the genes (xapA) encodes xanthosine phosphorylase...
  4. Dong W, Sun C, Zhu G, Hu S, Xiang L, Shao J. New function for Escherichia coli xanthosine phophorylase (xapA): genetic and biochemical evidences on its participation in NAD(+) salvage from nicotinamide. BMC Microbiol. 2014;14:29 pubmed publisher
    ..We wanted to verify whether xanthosine phophorylase (xapA) contributed to a new NAD(+) salvage pathway from nicotinamide...
  5. Bezirdzhian K, Kocharian S, Akopian Z. [Hexameric purine nucleoside phosphorylase II from Escherichia coli K-12. Physico-chemical and catalytic properties and stabilization with substrates]. Biokhimiia. 1987;52:1624-31 pubmed
    ..Hypoxanthine, especially in combination with phosphate, afford the best protection against inactivation. ..
  6. Bezirdzhian K, Kocharian S, Akopian Z. [Isolation of the hexameric form of purine nucleoside phosphorylase from E. coli. Comparative study of trimeric and hexameric forms of the enzyme]. Biokhimiia. 1986;51:1085-92 pubmed
    ..85 X 10(-5) M. The isoelectric point for the both forms of the enzyme in the presence of 9 M urea is about 5.5. Both forms have a pH optimum of phosphorolytic activity between 6.5 and 7.0. ..
  7. Jørgensen C, Dandanell G. Isolation and characterization of mutations in the Escherichia coli regulatory protein XapR. J Bacteriol. 1999;181:4397-403 pubmed
    ..XapR regulates the expression of xanthosine phosphorylase (XapA), a purine nucleoside phosphorylase in Escherichia coli...
  8. Shimaoka M, Takenaka Y, Mihara Y, Kurahashi O, Kawasaki H, Matsui H. Effects of xapA and guaA disruption on inosine accumulation in Escherichia coli. Biosci Biotechnol Biochem. 2006;70:3069-72 pubmed
    A xapA-disrupted mutant was studied to minimize hypoxanthine production and to improve inosine productivity in mutants of Escherichia coli. The xapA-disrupted mutant accumulated 5...
  9. Brun Y, Breton R, Lanouette P, Lapointe J. Precise mapping and comparison of two evolutionarily related regions of the Escherichia coli K-12 chromosome. Evolution of valU and lysT from an ancestral tRNA operon. J Mol Biol. 1990;214:825-43 pubmed
    ..3 kb-(valU alpha-valU beta-valU gamma-lysV = supN) greater than xapR-xapA- less than lig-1 kb-cysK greater than -0.4 kb-ptsH greater than -0.05 kb-pstI greater than -0...

More Information


  1. Buxton R, Hammer Jespersen K, Valentin Hansen P. A second purine nucleoside phosphorylase in Escherichia coli K-12. I. Xanthosine phosphorylase regulatory mutants isolated as secondary-site revertants of a deoD mutant. Mol Gen Genet. 1980;179:331-40 pubmed
  2. Hammer Jespersen K, Buxton R, Hansen T. A second purine nucleoside phosphorylase in Escherichia coli K-12. II. Properties of xanthosine phosphorylase and its induction by xanthosine. Mol Gen Genet. 1980;179:341-8 pubmed
    ..No other known nucleoside catabolising enzyme was induced by xanthosine. The implications of non-linear induction kinetics of xanthosine phosphorylase is discussed. ..