ABSTRACT
Pentavalent phosphorus esters have phosphorylating and alkylating properties. The insecticidal activity and mammalian toxicity are generally accepted as due to the phosphorylation of acetylcholinesterase. The target of organophosphorus esters, including insecticides and nerve gases, is acetylcholinesterase, which is one of the hydrolytic enzymes for acetylcholine. The inhibition of the enzyme disturbs the normal nervous function, finally resulting in the death of animals. In the nervous system of vertebrates, noradrenaline serves as the transmitter at most of the postganglionic sympathetic nerve terminals. Catecholamines are also found in insects, and the possibility of the existence of an adrenergic synaptic mechanism in the insect central nervous system, particularly in the sixth abdominal ganglion of the cockroach, was suggested. Cholinesterases are distinguished from other B esterases by their specific properties to hydrolyze choline esters in preference to other carboxylic esters and to be inhibited by physostigmine at low concentrations.
