Escherichia coli K-12 substr. MG1655 Reaction:

Superclasses: Reactions Classified By Conversion Type Simple Reactions Chemical Reactions
Reactions Classified By Substrate Small-Molecule Reactions

EC Number:

Enzymes and Genes:
xanthosine phosphorylase Inferred from experiment : xapA
purine nucleoside phosphorylase Inferred from experiment : deoD

In Pathway: guanine and guanosine salvage , guanosine nucleotides degradation III , purine ribonucleosides degradation

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

Mass balance status: Balanced.

Direct generic reaction:
a purine ribonucleoside + phosphate ↔ a purine base + α-D-ribose-1-phosphate (

Enzyme Commission Primary Name: guanosine phosphorylase

Enzyme Commission Summary:
This enzyme has been defined based on a single publication of an enzyme from rabbit bone marrow that appears to be highly specific for guanosine and deoxyguanosine [YAMADA61]. Most enzymes that are known to catalyze this reaction, such as the human purine nucleoside phosphorylase, can accept other purines as well, and thus were attributed to a specific case of the more general enzyme EC, (guanosine + phosphate ↔ guanine + α-D-ribose-1-phosphate).

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

Instance reactions of [a purine ribonucleoside + phosphate ↔ a purine base + α-D-ribose-1-phosphate] (
i1: adenosine + phosphate ↔ α-D-ribose-1-phosphate + adenine (

i2: guanosine + phosphate ↔ α-D-ribose-1-phosphate + guanine (
i3: inosine + phosphate ↔ α-D-ribose-1-phosphate + hypoxanthine (

Relationship Links: BRENDA:EC: , ENZYME:EC: , IUBMB-ExplorEnz:EC:


YAMADA61: YAMADA EW (1961). "The phosphorolysis of nucleosides by rabbit bone marrow." J Biol Chem 236;3043-6. PMID: 14008731

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
Page generated by SRI International Pathway Tools version 19.0 on Mon Apr 27, 2015, BIOCYC14B.