Kinetic study on inhibition of earthworm acetylcholinesterase by carbamate insecticides.

The specific activity parameters of Acetylcholinesterase (AChE) in adult and immature stages of earthworm (Lumbricus terrestris) were determined. The results show that the tissues of immature and adult stages differ in their affinity rate (Ka) to substrate and maximum enzymic hydrolysis (Vmax). The AChE form of adult stage had higher Vmax value, while the most higher Ka value was shown in the AChE of the immature stage. The studies of inhibition power on the two sources of ACChE indicated that the highest bimolecular inhibition constant value (Ki) was obtained by carbofuran on the AChE of the adult tissues, while aldicarb was the most potent on the immature tissues. The inhibition progress of the AChE by aldicarb was relatively rapid more than the other two tested inhibitors: carbofuran and methomyl.