Kinetic and structural studies on the interaction of cholinesterases with the anti-Alzheimer drug rivastigmine.

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 (ki = 2.0 M-1 min-1), whereas the bimolecular rate constant for inhibition of human acetylcholinesterase is >1600-fold higher (ki = 3300 M-1 min-1). For human butyrylcholinesterase and for Drosophila melanogaster acetylcholinesterase, carbamylation is even more rapid (ki = 9 × 104 and 5 × 105 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 ...