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:||Degradation/Utilization/Assimilation → Nucleosides and Nucleotides Degradation → Purine Nucleotides Degradation → Guanosine Nucleotides Degradation|
The distinction between nucleoside degradation and salvage is not always straight forward. A general rule is that degradation pathways start with the nucleotide forms and convert them to simpler forms, eventually leading to complete mineralization, while salvage pathways start with either the nucleoside or the free base form, and convert those to the nucleotide forms.
Nucleotide recycling is achieved by a combination of both types - a nucleotide is partially degraded via a degradation pathway, but the products are shuttled into a salvage pathway rather then towrds complete mineralization.
About This Pathway
This pathway of guanosine nucleotides degradation begins with the conversion of GMP to guanosine, which is then converted to the free base guanine by the enzyme purine nucleoside phosphorylase (EC 184.108.40.206). Guanine is converted to urate via xanthine by the enzymes guanine deaminase and xanthine oxidase [Hesberg04].
This pathway is very similar to a pathway that occurs in plants and fungi (guanosine nucleotides degradation II). However, in this pathway guanosine is converted to guanine by the enzyme purine nucleoside phosphorylase (EC 220.127.116.11) while in plants this conversion is catalyzed by the enzyme guanosine deaminase (EC 18.104.22.168) [Roberts03a].
Superpathways: purine nucleotides degradation II (aerobic)
Unification Links: EcoCyc:PWY-6608
Hesberg04: Hesberg C, Hansch R, Mendel RR, Bittner F (2004). "Tandem orientation of duplicated xanthine dehydrogenase genes from Arabidopsis thaliana: differential gene expression and enzyme activities." J Biol Chem 279(14);13547-54. PMID: 14726515
Silva03: Silva RG, Carvalho LP, Oliveira JS, Pinto CA, Mendes MA, Palma MS, Basso LA, Santos DS (2003). "Cloning, overexpression, and purification of functional human purine nucleoside phosphorylase." Protein Expr Purif 27(1);158-64. PMID: 12509998
Amaya02: Amaya Y, Kawamoto S, Kashima Y, Okamoto K, Nishino T (2002). "Purification and characterization of multiple forms of rat liver xanthine oxidoreductase expressed in baculovirus-insect cell system." J Biochem 132(4);597-606. PMID: 12359075
Asai07: Asai R, Matsumura T, Okamoto K, Igarashi K, Pai EF, Nishino T (2007). "Two mutations convert mammalian xanthine oxidoreductase to highly superoxide-productive xanthine oxidase." J Biochem 141(4);525-34. PMID: 17301076
Bennett03: Bennett EM, Li C, Allan PW, Parker WB, Ealick SE (2003). "Structural basis for substrate specificity of Escherichia coli purine nucleoside phosphorylase." J Biol Chem 278(47);47110-8. PMID: 12937174
Bennett03a: Bennett EM, Anand R, Allan PW, Hassan AE, Hong JS, Levasseur DN, McPherson DT, Parker WB, Secrist JA, Sorscher EJ, Townes TM, Waud WR, Ealick SE (2003). "Designer gene therapy using an Escherichia coli purine nucleoside phosphorylase/prodrug system." Chem Biol 10(12);1173-81. PMID: 14700625
Bertoša14: Bertosa B, Mikleusevic G, Wielgus-Kutrowska B, Narczyk M, Hajnic M, Lescic Asler I, Tomic S, Luic M, Bzowska A (2014). "Homooligomerization is needed for stability: a molecular modelling and solution study of Escherichia coli purine nucleoside phosphorylase." FEBS J 281(7);1860-71. PMID: 24785777
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
Borowiec06: Borowiec A, Lechward K, Tkacz-Stachowska K, Skladanowski AC (2006). "Adenosine as a metabolic regulator of tissue function: production of adenosine by cytoplasmic 5'-nucleotidases." Acta Biochim Pol 53(2);269-78. PMID: 16770441
Buxton75: Buxton RS (1975). "Genetic analysis of thymidine-resistant and low-thymine-requiring mutants of Escherichia coli K-12 induced by bacteriophage Mu-1." J Bacteriol 121(2);475-84. PMID: 1089630
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
Bzowska88: Bzowska A, Kulikowska E, Darzynkiewicz E, Shugar D (1988). "Purine nucleoside phosphorylase. Structure-activity relationships for substrate and inhibitor properties of N-1-, N-7-, and C-8-substituted analogues; differentiation of mammalian and bacterial enzymes with N-1-methylinosine and guanosine." J Biol Chem 263(19);9212-7. PMID: 3132457
Calderone04: Calderone V, Forleo C, Benvenuti M, Cristina Thaller M, Maria Rossolini G, Mangani S (2004). "The first structure of a bacterial class B Acid phosphatase reveals further structural heterogeneity among phosphatases of the haloacid dehalogenase fold." J Mol Biol 335(3);761-73. PMID: 14687572
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