Characterisation of insecticide-insensitive acetylcholinesterase: Microcomputer-based analysis of enzyme inhibition in homogenates of individual house fly (Musca domestica) heads

A spectrophotometer interfaced with a microcomputer to collect and analyse data automatically was used to study the inhibition kinetics of house fly acetylcholinesterase by malaoxon and dichlorvos in the presence of substrate. This system simply and unequivocally identified insecticide-insensitive enzymes from single fly heads, even when these enzymes were hitherto uncharacterised. As well as identifying individual insects homozygous for a particular form of acetylcholinesterase, the method also recognised heterozygotes because the mixture of enzymes then present gave a heterogeneous response to inhibitors. In the latter case, each component enzyme present could be identified. The technique is valuable for characterising heterogeneous insect populations collected from the field, for establishing homozygous strains, and for more detailed biochemical study.