title: Kinetics of novel competitive inhibitors of urease enzymes by a focused library of oxadiazoles/thiadiazoles and triazoles.
abstract: Based on structure of the substrate of urease and for the purpose of designing pharmacophore models for urease inhibitors, which could be effective in physiological and pharmacological studies, a series of twenty-five 1,3,4-diazole-2(3H)-thiones-2(3H)-thiones, 1,3,4-diazoles-2(3H)-thiones, and 1,2,4-tri-3-thiones (OSNs) were designed, synthesized, and evaluated for various kinetic parameters of urease inhibition. OSNs inhibited the activity of urease(s) in a concentration dependent fashion. Dixon as well as Lineweaver-Burk plots and their secondary replots indicated that the nature of inhibition was of pure competitive type for all the 25 compounds. 5-[4-(hydroxy)phenyl]-1,3,4-thiadiazole-2(3H)-thione was found to be the most active one with a Ki value of 2 microM. The Ki values were increased with an increase in substrate concentrations. Apparently, OSNs employ a homologous mechanism of action by exploiting a common transition catalysis state and acting as ligand chelators to form octahedral complexes with the urease enzymes in an orientation-specific mode. The inhibition was slightly potentiated by lower pH and not abolished in the presence of NH2OH (a scavenger of histidine residue). Because of their safe profile in the genotoxic assay, they may be pursued in the near future for human testing
authors.affiliation: International Center for Chemical Sciences, HEJ Research Institute of Chemistry, University of Karachi, Karachi 75270, Pakistan. zareen_amtul@fulbrightweb.org
authors.forename: Zareen
authors.initials: Z
authors.lastname: Amtul
authors.forename: Maimoona
authors.initials: M
authors.lastname: Rasheed
authors.forename: Mohammad Iqbal
authors.initials: MI
authors.lastname: Choudhary
authors.forename: Rosanna
authors.initials: R
authors.lastname: Supino
authors.forename: Khalid M
authors.initials: KM
authors.lastname: Khan
authors.lastname: Atta-Ur-Rahman
authors.forename: Supino
authors.initials: S
authors.lastname: Rosanna
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D010069:Oxadiazoles / Q000737:chemistry / Q000494:pharmacology*; D013830:Thiadiazoles / Q000737:chemistry; D014230:Triazoles / Q000737:chemistry / Q000494:pharmacology*; D014510:Urease / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D004791:Enzyme Inhibitors; D010069:Oxadiazoles; D013830:Thiadiazoles; D014230:Triazoles; D014510:Urease