title: Rational design of quinazoline-based irreversible inhibitors of human erythrocyte purine nucleoside phosphorylase.
abstract: 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.
authors.affiliation: Department of Chemistry, Arizona State University, Tempe 85287-1604.
authors.forename: R O
authors.initials: RO
authors.lastname: Dempcy
authors.forename: E B
authors.initials: EB
authors.lastname: Skibo
mesh_terms: D001665:Binding Sites / Q000187:drug effects; D003432:Cross-Linking Reagents; D015195:Drug Design; D004789:Enzyme Activation / Q000187:drug effects; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D011683:Purine-Nucleoside Phosphorylase / Q000037:antagonists & inhibitors* / Q000097:blood / Q000302:isolation & purification; D011799:Quinazolines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013379:Substrate Specificity / Q000187:drug effects
chemical_list: D003432:Cross-Linking Reagents; D011799:Quinazolines; D011683:Purine-Nucleoside Phosphorylase