The inactivation of acetylcholinesterase by alpha-terthienyl and ultraviolet light Studies in vitro and in larvae of the mosquito Aedes aegypti

Abstract

Acetylcholinesterase (EC 3.1.1.7) was inactivated photochemically in solution, in the presence of dissolved terthiophene sensitizers. Alpha-terthienyl (2,2′:5,2″-terthiophene) and its isomers 3,2′:5′,2″- and 3,2′:5′,3″-terthiophenes showed very similar sensitizing properties. With all three terthiophenes, the photosensitization was completely suppressed under anaerobic conditions, and therefore the inactivation process required the presence of oxygen. The enzyme was inactivated in vivo when fourth instar larvae of the mosquito Aedes aegypti were treated with alpha-terthienyl in the presence of long-wavelength ultraviolet light. No inactivation was observed when the organisms were treated with the ultraviolet light alone, with the chemical alone, or with a previously irradiated sample of the chemical. This paper represents the first example of acetylcholinesterase inactivation in vivo by a photoactive insecticide.