engleski

Oxime reactivation of cholinesterases inhibited by enantiomeric organophosphonates

Mouse acetylcholinesterase (AChE) and its mutants, and mouse butyrylcholinesterase (BChE), were inhibited with enantiomeric SP- and RP- cycloheptyl- (CHMP), isopropyl- (iPrMP), and dimethylbutyl- (DMBMP) methylphosphonyl thiocholines and resulting conjugates subjected to reactivation with oximes 2-PAM or HI-6. Mutations of AChE were in the two active site domains important for specificity of substrates and inhibitors: the acyl pocket (F295L, F297I) and the choline binding site (Y337A). The F295L mutation enhanced the HI-6 induced reactivation rates of the SP- conjugates up to 10-20 fold, whereas the F297I mutation preferentially enhanced 2-PAM reactivation by same or greater magnitude. Y337A showed a 5 and 25 fold faster HI-6 reactivation rate for SP- DMBMP and SP- CHMP respectively, and a 12-fold slower rate for SP- iPrMP compared to wildtype AChE. The RP- conjugates were far more resistant to reactivation, and little enhancement of reactivation rates was seen with mutants. Complete removal of the aromatic residues as in BChE, which has L, I and A at positions corresponding to 295, 297 and 337, did not enhance reactivation of most of the SP and RP conjugated phosphonates. Hence, both access of the oxime nucleophile to the phosphorus and the configuration of the conjugated phosphonate in the active center appeared critical to reactivation. (Supported by GM18360, DAMD1718014 and a fellowship of the Ministry of Science and Technology of the Republic of Croatia)

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