Rational design of quinazoline-based irreversible inhibitors of human erythrocyte purine nucleoside phosphorylase

Biochemistry. 1991 Aug 27;30(34):8480-7. doi: 10.1021/bi00098a028.


Described herein is the rational design of irreversible inhibitors of human erythrocyte purine nucleoside phosphorylase (PNPase). Inhibitor design started with the observation that the amino group of 8-aminoquinazolin-4(3H)-one interacts with enzyme-bound phosphate. This observation correctly predicted that the 5,8-dione (quinone) and 5,8-dihydroxy (hydroquinone) derivatives of quinazolin-4(3H)-ones would enter the active site. The amine-phosphate interaction also served to confirm that a quinazolin-4(3H)-one binds in the PNPase active sites like a purine substrate. From models of the PNPase active site it was possible to design quinazoline-based quinones that undergo a reductive-addition reaction with an active-site glutamate residue. The best inhibitor studied, 2-(chloromethyl)quinazoline-4,5,8(3H)-trione, rapidly inactivates PNPase by a first-order process with an inhibitor to enzyme stoichiometry of 150. The active-site hydroquinone adduct of this inhibitor eliminates a leaving group to afford a quinone methide species positioned to alkylate another active-site glutamate residue. Thus, this inhibitor is designed to cross-link the PNPase active site by reductive addition followed by the generation of an alkylating quinone methide species.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Binding Sites / drug effects
  • Cross-Linking Reagents
  • Drug Design
  • Enzyme Activation / drug effects
  • Erythrocytes / enzymology*
  • Humans
  • Kinetics
  • Purine-Nucleoside Phosphorylase / antagonists & inhibitors*
  • Purine-Nucleoside Phosphorylase / blood
  • Purine-Nucleoside Phosphorylase / isolation & purification
  • Quinazolines / chemical synthesis*
  • Quinazolines / chemistry
  • Quinazolines / pharmacology
  • Substrate Specificity / drug effects


  • Cross-Linking Reagents
  • Quinazolines
  • Purine-Nucleoside Phosphorylase