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Catalytic Site Atlas Search Results
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Catalytic Site Atlas

CSA LITERATURE entry for 1l1r

E.C. nameadenine phosphoribosyltransferase
SpeciesGiardia lamblia (GLV)
E.C. Number (IntEnz) 2.4.2.7
CSA Homologues of 1l1rThere are 31 Homologs
CSA Entries With UniProtID
CSA Entries With EC Number 2.4.2.7
PDBe Entry 1l1r
PDBSum Entry 1l1r
MACiE Entry 1l1r

Literature Report

IntroductionAdenine phosphoribosyltransferase (APRTase) catalyses the reversible Mg2+ dependent reaction of adenine with 5-phospho-alpha-D-ribosyl-1-pyrophosphate (PRPP) to produce AMP and pyrophosphate. This reaction is important in adenine salvage and recycling, and the enzyme is present in species ranging from bacteria to mammals. In humans, APRTase has the sole metabolic function of recycling adenine formed in the polyamine pathway, and the effects of APRTase deficiency are relatively mild. Some protozoan parasite, including Giardia lamblia, are deficient in de-novo purine synthesis and so purine uptake from the host and the APRTase reaction are especially important in these organisms.
MechansimThe catalytic reaction involves electrophile migration of the ribosyl anomeric carbon between pyrophosphate and the N9 of adenine. The pyrophosphate, adenine base and 5'-monophosphate remain relatively fixed during this process, which passes through a oxacarbenium-like transition state. Glu 100 functions as a general base to deprotonate N7 of guanine, while an Mg2+ ion and Arg 63 stabilise accumulation of negative charge on the pyrophosphate leaving group.
Reaction

Catalytic Sites for 1l1r

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
GluA100100macie:sideChainDeprotonates N7 of adenine.
ArgA6363macie:sideChainStabilises accumulation of negative charge on the pyrophosphate leaving group.

Literature References

Notes:
Shi W
Closed site complexes of adenine phosphoribosyltransferase from Giardia lamblia reveal a mechanism of ribosyl migration.
J Biol Chem 2002 277 39981-39988
PubMed: 12171925
Shi W
Structural analysis of adenine phosphoribosyltransferase from Saccharomyces cerevisiae.
Biochemistry 2001 40 10800-10809
PubMed: 11535055
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