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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1a69

E.C. namepurine-nucleoside phosphorylase
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz) 2.4.2.1
CSA Homologues of 1a69There are 44 Homologs
CSA Entries With UniProtID P0ABP8
CSA Entries With EC Number 2.4.2.1
PDBe Entry 1a69
PDBSum Entry 1a69
MACiE Entry 1a69

Literature Report

IntroductionPurine nucleoside phosphorylase is involved in purine metabolism, metabolising adenosine into adenine and guanosine into guanine, for example. These pathways allow the cell to produce nucleotide monophosphates when they cannot synthesise them de novo.
MechansimThe enzyme catalyses the reversible phosphorolytic cleavage of the glycosidic bond of purine nucleosides with the overall reaction:
beta-purine nucleoside + orthophosphate <-> purine base + alpha-D-pentose-1-phosphate
Catalytic action involves protonation of the purine base at position N7 by the side-chain of Asp204, which is initially in the acid form. The proton transfer is triggered by the Arg217 side-chain which is moved by the conformation change into hydrogen bond distance to Asp204. When the substrate is protonated, it can be attacked by the negatively charged orthophosphate group.
Reaction

Catalytic Sites for 1a69

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
AspA204205macie:sideChainTransfers a proton to the substrate, activating it for attack.
ArgA217218macie:sideChain Triggers proton transfer from Asp204 to the substrate.

Literature References

Notes:
Koellner G
Open and closed conformation of the E. coli purine nucleoside phosphorylase active center and implications for the catalytic mechanism.
J Mol Biol 2002 315 351-371
PubMed: 11786017
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