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Title: Studies concerning esterase enzymes and organophosphate insecticide resistance in Musca Domestica L
Author: Ahmad, Sami
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1969
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Aliesterases are an important class of B-esterases, which have been shown to be correlated with organophosphate resistance in houseflies. Little is known of the role of these enzymes in the living insect, and their distinction from other carboxylesterases is vague at present, owing to their highly non-specific nature. In the present work the distribution of aliesterases in various parts of a susceptible and an organophosphorus resistant strain of housefly has been examined, using histological, titrometric and manometric methods. Aliphatic ester hydrolysis due to other B-esterases, namely cholinesterase, lipase and peptidase, has been distinguished from aliphatic ester hydrolysis due to aliesterase. The rate of recovery of aliesterase activity has been studied and the nature of recovery after inhibition with organophosphates is discussed. A method of vertical gel electrophoresis, modified to resolve housefly esterases more efficiently than hitherto is described. The pattern of aliesterases in a susceptible and an OP-resistant strain have been shown to differ from those obtained in other strains by previous workers. The nature of phosphokinetic esterase in the housefly has been studied. This appears to be a dual-enzyme which can act both as aliesterase and phosphatase. Aliesterases from various parts of the body of the adult and larval houseflies have been separated and their distribution studied. Electrophoresis of housefly homogenate that had been treated with radioactively labelled organophosphate showed a separation of phosphorylenzyme, corresponding to the major aliesterase, present in the gut; the significance of this finding is discussed. Some in vitro experiments in which radioactive insecticides were used to study the extent of phosphorylation in susceptible and resistant strains are described. On the basis of the data collected, the possible physiological roles of aliesterases as enzymes are discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available