title: Efficient elimination of nonstoichiometric enzyme inhibitors from HTS hit lists.
abstract: High-throughput screening often identifies not only specific, stoichiometrically binding inhibitors but also undesired compounds that unspecifically interfere with the targeted activity by nonstoichiometrically binding, unfolding, and/or inactivating proteins. In this study, the effect of such unwanted inhibitors on several different enzyme targets was assessed based on screening results for over a million compounds. In particular, the shift in potency on variation of enzyme concentration was used as a means to identify nonstoichiometric inhibitors among the screening hits. These potency shifts depended on both compound structure and target enzyme. The approach was confirmed by statistical analysis of thousands of dose-response curves, which showed that the potency of competitive and therefore clearly stoichiometric inhibitors was not affected by increasing enzyme concentration. Light-scattering measurements of thermal protein unfolding further verified that compounds that stabilize protein structure by stoichiometric binding show the same potency irrespective of enzyme concentration. In summary, measuring inhibitor IC(50) values at different enzyme concentrations is a simple, cost-effective, and reliable method to identify and eliminate compounds that inhibit a specific target enzyme via nonstoichiometric mechanisms.
authors.affiliation: Lead Finding Platform, Protein Structure Unit, Novartis Institutes for Biomedical Research, Center for Proteomic Chemistry, Basel, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Habig
authors.forename: Anke
authors.initials: A
authors.lastname: Blechschmidt
authors.forename: Sigmar
authors.initials: S
authors.lastname: Dressler
authors.forename: Barbara
authors.initials: B
authors.lastname: Hess
authors.forename: Viral
authors.initials: V
authors.lastname: Patel
authors.forename: Andreas
authors.initials: A
authors.lastname: Billich
authors.forename: Christian
authors.initials: C
authors.lastname: Ostermeier
authors.forename: David
authors.initials: D
authors.lastname: Beer
authors.forename: Martin
authors.initials: M
authors.lastname: Klumpp
mesh_terms: D003902:Detergents / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical / Q000379:methods*; D004791:Enzyme Inhibitors / Q000032:analysis* / Q000737:chemistry; D017830:Octoxynol / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors; D055550:Protein Stability / Q000187:drug effects; D012015:Reference Standards; D013696:Temperature; D000099157:Sphingosine Kinase
chemical_list: D003902:Detergents; D004791:Enzyme Inhibitors; D017830:Octoxynol; D017853:Phosphotransferases (Alcohol Group Acceptor); D000099157:Sphingosine Kinase; C023088:pantothenate kinase; C022642:shikimate kinase