Escherichia coli K-12 substr. MG1655 Reaction:

Superclasses: Reactions Classified By Conversion TypeSimple ReactionsChemical Reactions
Reactions Classified By SubstrateSmall-Molecule Reactions

EC Number:

Enzymes and Genes:
xanthosine phosphorylaseInferred from experiment: xapA
purine nucleoside phosphorylaseInferred from experiment: deoD

In Pathway: adenosine nucleotides degradation II, adenine and adenosine salvage III, purine ribonucleosides degradation

Note that this reaction equation differs from the official Enzyme Commission reaction equation for this EC number, which can be found here .

The direction shown, i.e. which substrates are on the left and right sides, 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: purine-nucleoside phosphorylase

Enzyme Commission Synonyms: inosine phosphorylase, PNPase, PUNPI, PUNPII, inosine-guanosine phosphorylase, nucleotide phosphatase, purine deoxynucleoside phosphorylase, purine deoxyribonucleoside phosphorylase, purine nucleoside phosphorylase, purine ribonucleoside phosphorylase

Enzyme Commission Summary:
Specificity not completely determined. Can also catalyse ribosyltransferase reactions of the type catalysed by EC, nucleoside ribosyltransferase.

Citations: [Agarwal69 , Heppel52, Saunders69, Tsuboi57, Friedkin61, Kalckar47]

Gene-Reaction Schematic

Gene-Reaction Schematic

Instance reactions of [a purine ribonucleoside + phosphate ↔ a purine base + α-D-ribose-1-phosphate] (
i1: inosine + phosphate ↔ α-D-ribose-1-phosphate + hypoxanthine (
i2: guanosine + phosphate ↔ α-D-ribose-1-phosphate + guanine (

i3: adenosine + phosphate ↔ α-D-ribose-1-phosphate + adenine (

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


Agarwal69: Agarwal RP, Parks RE (1969). "Purine nucleoside phosphorylase from human erythrocytes. IV. Crystallization and some properties." J Biol Chem 244(4);644-7. PMID: 5768862

Friedkin61: Friedkin M, Kalckar H (1961). "Nucleoside phosphorylases." In: Boyer, P.D., Lardy, H. and Myrbäck, K. (Eds), The Enzymes, 2nd edn, vol. 5, Academic Press, New York, pp. 237-255.

Heppel52: Heppel LA, Hilmoe RJ (1952). "[Phosphorolysis and hydrolysis of purine ribosides by enzymes from yeast]." J Biol Chem 198(2);683-94. PMID: 12999785

Kalckar47: Kalckar HM (1947). "The enzymatic synthesis of purine ribosides." J. Biol. Chem. 167 477-486.

Saunders69: Saunders PP, Wilson BA, Saunders GF (1969). "Purification and comparative properties of a pyrimidine nucleoside phosphorylase from Bacillus stearothermophilus." J Biol Chem 244(13);3691-7. PMID: 4978445

Tsuboi57: Tsuboi KK, Hudson PB (1957). "Enzymes of the human erythrocyte. I. Purine nucleoside phosphorylase; isolation procedure." J Biol Chem 224(2);879-87. PMID: 13405917

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 Pathway Tools version 19.5 (software by SRI International) on Mon Nov 30, 2015, biocyc13.