Carbamates with differential mechanism of inhibition toward acetylcholinesterase and butyrylcholinesterase.
Most carbamates are pseudoirreversible inhibitors of cholinesterases. Phenothiazine carbamates exhibit this inhibition of acetylcholinesterase but produce reversible inhibition of butyrylcholinesterase, suggesting that they do not form a covalent bond with the catalytic serine. This atypical inhibition is attributable to pi-pi interaction of the phenothiazine moiety with F329 and Y332 in butyrylcholinesterase. These residues are in a helical segment, referred to here as the E-helix because it contains E325 of the catalytic triad. The involvement of the E-helix in phenothiazine carbamate reversible inhibition of butyrylcholinesterase is confirmed using mutants of this enzyme at A328, F329, or Y332 that show typical pseudoirreversible inhibition. Thus, in addition to various domains of the butyrylcholinesterase active site gorge, such as the peripheral anionic site and the pi-cationic site of the Omega-loop, the E-helix represents a domain that could be exploited for development of specific inhibitors to treat dementias.
Darvesh
Sultan
S
Department of Medicine (Neurology), Dalhousie University, Halifax, Nova Scotia, Canada. sultan.darvesh@dal.ca
Darvesh
Katherine V
KV
McDonald
Robert S
RS
Mataija
Diane
D
Walsh
Ryan
R
Mothana
Sam
S
Lockridge
Oksana
O
Martin
Earl
E
D000110:Acetylcholinesterase / Q000187:drug effects* / Q000378:metabolism; D002091:Butyrylcholinesterase / Q000187:drug effects* / Q000378:metabolism; D002219:Carbamates / Q000494:pharmacology*; D002384:Catalysis; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D021241:Spectrometry, Mass, Electrospray Ionization; D013329:Structure-Activity Relationship
D002219:Carbamates; D002800:Cholinesterase Inhibitors; D000110:Acetylcholinesterase; D002091:Butyrylcholinesterase