Acetylcholinesterase from the cockroach Periplaneta americana L.: purification, properties and correlation with behavioural changes in the animal

Beesley, P. W (1977) Acetylcholinesterase from the cockroach Periplaneta americana L.: purification, properties and correlation with behavioural changes in the animal. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The enzyme acetylcholinesterase has a high specific activity and plays an important role in nervous transmission in the INS of insects. Previous work has correlated a 50% decrease in the specific activity of the enzyme in the metathoracic ganglion of Periplaneta americana with shock avoidance learning in the insect. Therefore the properties of the enzyme fromPeriplaneta americana were investigated.The enzyme rapidly loses up to 50% of its activity in crude nervetissue homogenates. This loss is stabilised by the detergents triton-X-100, lubrol-PX and deoxycholate. Only deoxycholate will release the decayed activity into an assayable form. Two procedures for accurately determining the total acetylcholinesterase activity of such homogenates are described.All three detergents solubilised a large fraction of the membrane bound enzyme. Gel electrophoresis and gel filtration studies showed the existence of multiple forms of the soluble enzyme. Certain properties of crude and partially purified preparations of the enzyme were investigated.The results of experiments attempting to correlate a decrease in the specific activity of acetylcholinesterase with shock avoidance learning are equivocal. Possible reasons for this discrepancy in the results are discussed, including the effects of environmental conditions on acetylcholinesterase activity. ' An increase in ambient temperature resulted in a decrease in the specific activity of acetylcholinesterase in the metathoracic ganglion.

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