Studies on the inhibition of honey bee cholinesterase by carbamates

Abstract

The kinetic constants for the inhibition (I₅₀, Ka, K₂c, -Ki, K_3, and Ka' values) of honey bee cholinesterase by furadan and its two analogues were determined and evaluated. Furadan proved to be a potent inhibitor of honey bee enzyme. All the three carbamates showed a high affinity for honey-bee ChE. The affinity constants ranged from 0.22 to 2 .6 8 x 1 0 ^-- M. There was little variation among the carbamylation constants, indicating a minor role for the carbamylation step in the inhibition process. The significant variation in the bimolecular reaction constants of the three carbamates could be attributed to the variations in the affinity constants rather than to the carbamylation constants. In most cases, the average apparent affinity constants were comparable with the Ka values and increased progressively with the concentration of inhibitor.