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MetaCyc Pathway: xanthine and xanthosine salvage
Inferred from experiment

Pathway diagram: xanthine and xanthosine salvage

This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Superclasses: BiosynthesisNucleosides and Nucleotides BiosynthesisPurine Nucleotide BiosynthesisPurine Nucleotide Salvage

Some taxa known to possess this pathway include : Escherichia coli K-12 substr. MG1655

Expected Taxonomic Range: Archaea, Bacteria , Eukaryota

General Background

Purine bases consist of a six-membered and a five-membered nitrogen-containing rings fused together. There are four purine bases, namely adenine, guanine, hypoxanthine and xanthine. Purine nucleotides may be synthesized de novo from simpler precursors, or they may be derived from exogenous purine nucleosides and bases by the salvage pathways.

In Escherichia coli, the salvage pathways collect exogenous, preformed bases and nucleosides for nucleotide synthesis, reutilize bases and nucleosides produced endogenously from nucleotide turnover, and make available the pentose moieties of exogenous nucleosides as sources of carbon. When free bases or nucleosides present in the growth medium are salvaged, the contribution from the de novo pathways to nucleotide synthesis is greatly suppressed.

About This Pathway

Xanthosine is converted to xanthine by xanthosine phosphorylase, one of the two purine nucleoside phosphorylases (PNPs) in Escherichia coli, encoded by the xapA gene [Seeger95, Dandanell05]. This enzyme does not cleave or synthesize adenosine and deoxyadenosine but catalyzes the phosphorolysis of xanthosine, inosine and guanosine with comparable efficiency.

Xanthine is converted to XMP by xanthine-guanine phosphoribosyltransferase, a purine salvage enzyme which converts either xanthine or guanine to XMP or GMP, respectively [Liu83, Deo85].

Variants: purine deoxyribonucleosides salvage, superpathway of purine nucleotide salvage

Unification Links: EcoCyc:SALVPURINE2-PWY

Martha Arnaud on Tue Jan 21, 2003:
The pathways "salvage pathways of guanine, xanthine, and their nucleosides" and "salvage pathways of adenine, hypoxanthine, and their nucleotides" supersede the pathway formerly called "purine ribonucleotide/ribonucleoside metabolism."

Created 17-Dec-2002 by Arnaud M, SRI International
Revised 12-Feb-2010 by Sarker M
Revised 21-Sep-2010 by Caspi R, SRI International


Dandanell05: Dandanell G, Szczepanowski RH, Kierdaszuk B, Shugar D, Bochtler M (2005). "Escherichia coli purine nucleoside phosphorylase II, the product of the xapA gene." J Mol Biol 348(1);113-25. PMID: 15808857

Deo85: Deo SS, Tseng WC, Saini R, Coles RS, Athwal RS (1985). "Purification and characterization of Escherichia coli xanthine-guanine phosphoribosyltransferase produced by plasmid pSV2gpt." Biochim Biophys Acta 839(3);233-9. PMID: 3886014

Liu83: Liu SW, Milman G (1983). "Purification and characterization of Escherichia coli guanine-xanthine phosphoribosyltransferase produced by a high efficiency expression plasmid utilizing a lambda PL promoter and CI857 temperature-sensitive repressor." J Biol Chem 1983;258(12);7469-75. PMID: 6305942

Seeger95: Seeger C, Poulsen C, Dandanell G (1995). "Identification and characterization of genes (xapA, xapB, and xapR) involved in xanthosine catabolism in Escherichia coli." J Bacteriol 177(19);5506-16. PMID: 7559336

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Bezirdzhian86: Bezirdzhian KhO, Kocharian ShM, Akopian ZhI (1986). "[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(7);1085-92. PMID: 3089333

Bezirdzhian87: Bezirdzhian KhO, Kocharian ShM, Akopian ZhI (1987). "[Hexamere purine nucleoside phosphorylase from Escherichia coli K-12. Kinetic analysis and mechanism of reaction]." Biokhimiia 52(11);1770-6. PMID: 3125860

Bezirdzhian87a: Bezirdzhian KhO, Kocharian ShM, Akopian ZhI (1987). "[Hexameric purine nucleoside phosphorylase II from Escherichia coli K-12. Physico-chemical and catalytic properties and stabilization with substrates]." Biokhimiia 1987;52(10);1624-31. PMID: 3122852

Buxton80: Buxton RS, Hammer-Jespersen K, Valentin-Hansen P (1980). "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 179(2);331-40. PMID: 7007808

Bzowska00: Bzowska A, Kulikowska E, Shugar D (2000). "Purine nucleoside phosphorylases: properties, functions, and clinical aspects." Pharmacol Ther 88(3);349-425. PMID: 11337031

DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114

Dong14: Dong WR, Sun CC, Zhu G, Hu SH, Xiang LX, Shao JZ (2014). "New function for Escherichia coli xanthosine phophorylase (xapA): genetic and biochemical evidences on its participation in NAD(+) salvage from nicotinamide." BMC Microbiol 14;29. PMID: 24506841

Gaudet10: Gaudet P, Livstone M, Thomas P (2010). "Annotation inferences using phylogenetic trees." PMID: 19578431

GOA01: GOA, MGI (2001). "Gene Ontology annotation based on Enzyme Commission mapping." Genomics 74;121-128.

GOA01a: GOA, DDB, FB, MGI, ZFIN (2001). "Gene Ontology annotation through association of InterPro records with GO terms."

GOA06: GOA, SIB (2006). "Electronic Gene Ontology annotations created by transferring manual GO annotations between orthologous microbial proteins."

Guddat02: Guddat LW, Vos S, Martin JL, Keough DT, de Jersey J (2002). "Crystal structures of free, IMP-, and GMP-bound Escherichia coli hypoxanthine phosphoribosyltransferase." Protein Sci 11(7);1626-38. PMID: 12070315

HammerJespersen80: Hammer-Jespersen K, Buxton RS, Hansen TD (1980). "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(2);341-8. PMID: 7007809

Holden76: Holden JA, Harriman PD, Wall JD (1976). "Escherichia coli mutants deficient in guanine-xanthine phosphoribosyltransferase." J Bacteriol 126(3);1141-8. PMID: 820683

Ishihama08: Ishihama Y, Schmidt T, Rappsilber J, Mann M, Hartl FU, Kerner MJ, Frishman D (2008). "Protein abundance profiling of the Escherichia coli cytosol." BMC Genomics 9;102. PMID: 18304323

Jorgensen99: Jorgensen C, Dandanell G (1999). "Isolation and characterization of mutations in the Escherichia coli regulatory protein XapR." J Bacteriol 181(14);4397-403. PMID: 10400599

Khersonsky11: Khersonsky O, Malitsky S, Rogachev I, Tawfik DS (2011). "Role of chemistry versus substrate binding in recruiting promiscuous enzyme functions." Biochemistry 50(13);2683-90. PMID: 21332126

Kocharian86: Kocharian ShM, Melkumian MA (1986). "[Genetic analysis of Escherichia coli K-12 mutants defective for the structural and regulatory genes for second purine nucleoside phosphorylase]." Genetika 22(8);2055-65. PMID: 3095187

Konrad12: Konrad A, Piškur J, Liberles DA (2012). "The evolution of catalytic residues and enzyme mechanism within the bacterial nucleoside phosphorylase superfamily 1." Gene 510(2);154-61. PMID: 22967797

Koszalka88: Koszalka GW, Vanhooke J, Short SA, Hall WW (1988). "Purification and properties of inosine-guanosine phosphorylase from Escherichia coli K-12." J Bacteriol 170(8);3493-8. PMID: 3042752

Showing only 20 references. To show more, press the button "Show all references".

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by Pathway Tools version 19.5 (software by SRI International) on Sun May 1, 2016, biocyc13.