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Catalytic Site Atlas

CSA LITERATURE entry for 1ula

E.C. namepurine-nucleoside phosphorylase
SpeciesHomo sapiens (Human)
E.C. Number (IntEnz) 2.4.2.1
CSA Homologues of 1ulaThere are 68 Homologs
CSA Entries With UniProtID P00491
CSA Entries With EC Number 2.4.2.1
PDBe Entry 1ula
PDBSum Entry 1ula
MACiE Entry M0017

Literature Report

IntroductionPurine-nucleoside phosphorylase (PNP) catalyses the reversible phosphorolysis of purine nucleosides to generate the corresponding purine base and ribose 1-phosphate. There are two types of this enzyme, showing reasonably high sequence similarity within families and little identity between them. Type I tend to be trimeric, are found mainly in mammals, are specific for inosine/guanine nucleosides and have a molecular mass of around 90kDa. Type II tend to be hexameric (although some are thought to be tetramers), have broad substrate specificity, are found mainly in prokaryotes and have a molecular mass between 110 and 150 kDa. There are also some PNP enzymes which fall into neither class.
MechansimHis86, which is hydrogen bonded to Glu89, abstracts a proton from the phosphate ion, which causes strain and weakening of the glycosidic bond. The glycosidic bond is cleaved, forming an oxycarnenium ion which is stabilised by the phosphate dianion. Therefore the phosphate is used for both the initiation of bond cleavage and stabilisation of an intermediate.
Reaction

Catalytic Sites for 1ula

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
AsnA243243macie:sideChain
HisA8686macie:sideChain
GluA8989macie:sideChain

Literature References

Notes:
Craig SP 3rd
Purine phosphoribosyltransferases
J Biol Chem 2000 38 20231-20234
PubMed: 10816600
Koellner G.
Crystal structure of calf spleen purine nucleoside phosphorylase in a complex with hypoxanthine at 2.15 A resolution
J Mol Biol 1997 265 202-216
PubMed: 9020983
Erion MD.
Purine nucleoside phosphorylase. 1. Structure-function studies
Biochemistry 1997 36 11725-11734
PubMed: 9305962
Erion MD
Purine nucleoside phosphorylase. 2. Catalytic mechanism.
Biochemistry 1997 36 11735-11748
PubMed: 9305963
Mao C.
Calf spleen purine nucleoside phosphorylase complexed with substrates and substrate analogues
Biochemistry 1998 37 7135-7146
PubMed: 9585525
Koellner G.
Crystal structure of the ternary complex of E. coli purine nucleoside phosphorylase with formycin B, a structural analogue of the substrate inosine, and phosphate (Sulphate) at 2.1 A resolution
J Mol Biol 1998 280 153-166
PubMed: 9653038
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