Key active site residues in the inhibition of acetylcholinesterases by soman

Abstract
Molecular modeling (GEMM 7.3) and molecular mechanics calculations (YETI V 5.3) using the X‐ray coordinates for acetylcholinesterase (AChE) from Torpedo californica indicate electrostatic stabilization by the active site. Glu‐199, of the developing positive charge on the incipient carbonium ion in the dealkylation in the adducts of AChE with PSCR and PsCs diastereomers of 2‐(3,3‐dimethylbutyl) methylphosphonofluoridate (soman). His‐440 is indispensable as a general acid catalyst of C‐O bond breaking in the dealkylation reaction and that of bond breaking to the Ser γ‐O in reactivation. This demand for catalysis seems to be satisfied for the reactivation of enzyme from the PsCs, diastereomer of soman, but not from the P(S)C(R) diastereomer.

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