Kinetic constants for the inhibition of eel and rabbit brain acetylcholinesterase by some organophosphates and carbamates of military significance.

The kinetics of the inhibition of eel and rabbit brain acetylcholinesterase by a number of organophosphates and carbamates has been studied. Five organophosphates (tabun, sarin, soman, GF, and VX) and two carbamates (neostigmine and physostigmine) were used. Small but significant differences have been found between the two enzyme preparations in both the dissociation constant and the rate constants for the irreversible step. The values of k2 ranged from 0.56 to 1.08 sec-1 for the eel enzyme and 0.19 to 0.73 sec-1 for the rabbit enzyme. Kd varied from 0.3 to 24.5 microM for the eel and 0.3 to 9.3 microM for the rabbit enzyme. The similarity between the enzymes is remarkable considering the differences in the species of origin.