Acetylcholinesterase characteristics of termite queen exposed to anticholinesterase compounds.

A regional profile of AChE activity was noted in the Indian termite queen Odontotermes redemanni with the head recording the higher and body the lower range of activity. The enzyme characteristics such as substrate and temperature optima were more or less similar while pH requirement for optimum AChE activity varied from 7.0 to 7.6 In vitro inhibition of head and body AChE was studied using pure and commercial anticholinesterase compounds. Interestingly, the commercial formulations like Metacid-50 and Carbaryl are potent enough at 1 x 10(-8) M to produce 50% in vitro inhibition of AChE of head and body regions within 15 min of preincubation. A 20 min of preincubation (t0.5) was necessary to record 50% in vitro inhibition of AChE with known and pure anticholinesterase compounds such as DFP (3.5 x 10(-10) M) and physostigmine (3.6 x 10(-10) M). It is surmised that (a) the response of the head and body AChE to the commercial formulations of the insecticides may be used as a reliable and sensitive bioindicator of pesticidal contamination of the terrestrial environment and (b) termite control may be successfully done with the application of organophosphate or carbamate compounds.