title: Kinetic and structural studies on the interaction of cholinesterases with the anti-Alzheimer drug rivastigmine.
abstract: Rivastigmine, a carbamate inhibitor of acetylcholinesterase, is already in use for treatment of Alzheimer's disease under the trade name of Exelon. Rivastigmine carbamylates Torpedo californica acetylcholinesterase very slowly (k(i) = 2.0 M(-1) min(-1)), whereas the bimolecular rate constant for inhibition of human acetylcholinesterase is >1600-fold higher (k(i) = 3300 M(-1) min(-1)). For human butyrylcholinesterase and for Drosophila melanogaster acetylcholinesterase, carbamylation is even more rapid (k(i) = 9 x 10(4) and 5 x 10(5) M(-1) min(-1), respectively). Spontaneous reactivation of all four conjugates is very slow, with <10% reactivation being observed for the Torpedo enzyme after 48 h. The crystal structure of the conjugate of rivastigmine with Torpedo acetylcholinesterase was determined to 2.2 A resolution. It revealed that the carbamyl moiety is covalently linked to the active-site serine, with the leaving group, (-)-S-3-[1-(dimethylamino)ethyl]phenol, being retained in the "anionic" site. A significant movement of the active-site histidine (H440) away from its normal hydrogen-bonded partner, E327, was observed, resulting in disruption of the catalytic triad. This movement may provide an explanation for the unusually slow kinetics of reactivation.
authors.affiliation: Departmentof Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: P
authors.initials: P
authors.lastname: Bar-On
authors.forename: C B
authors.initials: CB
authors.lastname: Millard
authors.forename: M
authors.initials: M
authors.lastname: Harel
authors.forename: H
authors.initials: H
authors.lastname: Dvir
authors.forename: A
authors.initials: A
authors.lastname: Enz
authors.forename: J L
authors.initials: JL
authors.lastname: Sussman
authors.forename: I
authors.initials: I
authors.lastname: Silman
mesh_terms: D000110:Acetylcholinesterase / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002219:Carbamates / Q000378:metabolism*; D002800:Cholinesterase Inhibitors / Q000378:metabolism*; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004331:Drosophila melanogaster; D004789:Enzyme Activation; D007700:Kinetics; D018696:Neuroprotective Agents / Q000378:metabolism*; D048448:Phenylcarbamates; D011487:Protein Conformation; D000068836:Rivastigmine; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014101:Torpedo
chemical_list: D002219:Carbamates; D002800:Cholinesterase Inhibitors; D018696:Neuroprotective Agents; D048448:Phenylcarbamates; D000110:Acetylcholinesterase; D000068836:Rivastigmine