title: The importance of the active site histidine for the activity of epoxide- or aziridine-based inhibitors of cysteine proteases.
abstract: In the present study the importance of the active site histidine residue (His) for the activity of epoxide- or aziridine-based cysteine protease inhibitors is examined theoretically. To account for all important effects, QM/MM hybrid approaches are employed which combine quantum mechanical (QM) methods that are necessary to describe bond-breaking and formation processes, with molecular mechanics (MM) methods that incorporate the influence of the protein environment. Using various model systems, the computations exclude a direct proton shift from the active site His residue to the inhibitor, but show that one water molecule is sufficient to establish a very efficient relay system. This relay system allows an easy proton transfer from the active site His residue to the inhibitor and is thus essential for the activity of both types of inhibitors. Differences between the epoxides and the aziridines are discussed, along with some implications for the rational design of optimized inhibitors. The work presented herein represents the first QM/MM study into the mode of action of these important inhibitor classes.
authors.affiliation: Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Milena
authors.initials: M
authors.lastname: Mladenovic
authors.forename: Tanja
authors.initials: T
authors.lastname: Schirmeister
authors.forename: Stefan
authors.initials: S
authors.lastname: Thiel
authors.forename: Walter
authors.initials: W
authors.lastname: Thiel
authors.forename: Bernd
authors.initials: B
authors.lastname: Engels
mesh_terms: D001388:Aziridines / Q000737:chemistry*; D001665:Binding Sites; D002384:Catalysis; D003198:Computer Simulation; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D004852:Epoxy Compounds / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry*; D007700:Kinetics; D011789:Quantum Theory; D013329:Structure-Activity Relationship
chemical_list: D001388:Aziridines; D015853:Cysteine Proteinase Inhibitors; D004852:Epoxy Compounds; D006639:Histidine; C033132:aziridine; D003546:Cysteine Endopeptidases