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Document<br />

5<br />

<strong>Design</strong> of Purine Nucleoside Phosphorylase Inhibitors<br />

Y. Sudhakara Babu, John A. Montgomery, and Charles E. Bugg<br />

BioCryst Pharmaceuticals, Inc., Birmingham, Alabama<br />

W. Michael Carson, Sthanam V. L. Narayana, and William J. Cook<br />

The University of Alabama at Birmingham, Birmingham, Alabama<br />

Steven E. Ealick<br />

Cornell University, Ithaca, New York<br />

Wayne C. Guida and Mark D. Erion *<br />

Ciba-Geigy Corporation, Summit, New Jersey<br />

John A. Secrist, III<br />

Southern Research Institute, Birmingham, Alabama<br />

I. Introduction<br />

A. Enzymology<br />

Page 151<br />

Purine nucleoside phosphorylase (PNP, E.C. 2.4.2.1) catalyzes the reversible phosphorylysis of<br />

ribonucleosides and 2'-deoxyribonucleosides of guanine, hypoxanthine, and related nucleoside analogs<br />

[1]. It normally acts in the phosphorolytic direction in intact cells, although the isolated enzyme<br />

catalyzes the nucleoside synthesis under equilibrium conditions. Figure 1 shows the chemical reaction.<br />

The enzyme has been isolated from both eukaryotic and prokaryotic organisms [2] and functions in the<br />

purine salvage pathway [1,3]. Purine nucleoside phosphorylase isolated from human erythrocytes is<br />

specific for the 6-oxypurines and many of their analogs [4] while PNPs from other organisms vary in<br />

their specificity [5]. The human enzyme is a trimer with identical subunits and a total molecular mass of<br />

about 97,000 daltons [6,7]. Each subunit contains 289 amino acid residues.<br />

* Current affiliation: Gensia, Inc., San Diego, California.<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_151.html [4/5/2004 5:01:07 PM]

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