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Evolutionary genetics of Drosophila esterases
J G Oakeshott1, E A van Papenrecht, T M Boyce
1CSIRO Division of Entomology, Canberra ACT, Australia.
Genetica
|January 1, 1993
Summary
Carboxylester hydrolases in fruit flies form a multigene family with conserved structures, though sequence variations impact function and insecticide resistance. Polymorphisms in D. melanogaster esterase 6 (EST6) affect substrate interactions and in vivo fitness.
Area of Science:
- Biochemistry
- Genetics
- Evolutionary Biology
Background:
- Over 30 carboxylester hydrolases exist in Drosophila melanogaster, primarily acetyl, carboxyl, and cholinesterases.
- Sequence and structural data support classifying these as a carboxyl/cholinesterase multigene family within the broader beta-hydrolase superfamily.
Purpose of the Study:
- To investigate the evolutionary conservation and functional divergence of carboxylester hydrolases in D. melanogaster.
- To understand the structural basis of functional differences, particularly concerning insecticide resistance and substrate specificity.
Main Methods:
- Comparative sequence analysis of esterase genes across Drosophila species.
- Interpretation of sequence differences against conserved super-secondary structures.
- In vitro biochemical assays and in vivo demographic analysis of enzyme polymorphisms.
Main Results:
- Two carboxyl esterases are conserved and linked to insecticide resistance in Diptera.
- Sequence differences between EST6 and acetylcholinesterase are widespread, affecting substrate binding and active sites.
- Conserved EST6 structure shows species-specific functional adaptations, including substrate binding site polymorphisms linked to differential in vitro activity and in vivo selective equivalence.
Conclusions:
- The carboxyl/cholinesterase multigene family exhibits both conserved structural features and significant functional divergence.
- EST6 polymorphisms in D. melanogaster represent adaptive evolution impacting enzyme function and fitness.
- Understanding these esterases is crucial for insights into insecticide resistance mechanisms and evolutionary processes.