Crystal structure of Human purine nucleoside phosphorylase complexed with INOSINE
[PNPH_HUMAN] Defects in PNP are the cause of purine nucleoside phosphorylase deficiency (PNPD) [MIM:613179]. It leads to a severe T-cell immunodeficiency with neurologic disorder in children.  
[PNPH_HUMAN] The purine nucleoside phosphorylases catalyze the phosphorolytic breakdown of the N-glycosidic bond in the beta-(deoxy)ribonucleoside molecules, with the formation of the corresponding free purine bases and pentose-1-phosphate.
Publication Abstract from PubMed
Human purine nucleoside phosphorylase (PNP) is a ubiquitous enzyme which plays a key role in the purine salvage pathway, and PNP deficiency in humans leads to an impairment of T-cell function, usually with no apparent effect on B-cell function. PNP is highly specific for 6-oxopurine nucleosides and exhibits negligible activity for 6-aminopurine nucleosides. The catalytic efficiency for inosine is 350,000-fold greater than for adenosine. Adenine nucleosides and nucleotides are deaminated by adenosine deaminase and AMP deaminase to their corresponding inosine derivatives which, in turn, may be further degraded. Here we report the crystal structures of human PNP in complex with inosine and 2('),3(')-dideoxyinosine, refined to 2.8A resolution using synchrotron radiation. The present structures provide explanation for ligand binding, refine the purine-binding site, and can be used for future inhibitor design.
Structures of human purine nucleoside phosphorylase complexed with inosine and ddI.,Canduri F, dos Santos DM, Silva RG, Mendes MA, Basso LA, Palma MS, de Azevedo WF, Santos DS Biochem Biophys Res Commun. 2004 Jan 23;313(4):907-14. PMID:14706628
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.