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Dimeric forms of cholinesterase in Sipunculus nudus
V Talesa1, G B Principato, E Giovannini
1Department of Experimental Medicine, University of Perugia, Italy.
European Journal of Biochemistry
|July 15, 1993
Summary
Researchers studied cholinesterase (ChE) in the marine worm Sipunculus nudus, purifying two forms (LSS and DS ChE) and characterizing their structure and substrate specificity. This provides insights into invertebrate enzyme evolution.
Area of Science:
- Biochemistry
- Marine Biology
- Enzymology
- Evolutionary Biology
Background:
- Cholinesterase (ChE) evolution in invertebrates is not well understood.
- Sipunculus nudus, an unsegmented marine worm, was selected for studying ChE.
- Understanding ChE in diverse organisms aids in tracing enzyme evolution.
Purpose of the Study:
- To investigate the cholinesterase (ChE) enzyme in the marine worm Sipunculus nudus.
- To characterize the different forms of ChE present and their properties.
- To compare S. nudus ChE with enzymes from other species to understand evolutionary relationships.
Main Methods:
- Solubilization of ChE activity through sequential extraction (low-salt, detergent, high-salt soluble).
- Purification of LSS and DS ChE using affinity chromatography on edrophonium-Sepharose.
- Characterization using SDS/PAGE, density-gradient centrifugation, and immunological cross-reactivity.
Main Results:
- Two major ChE forms, LSS (27%) and DS (68%), were purified to homogeneity.
- Both LSS and DS ChE are globular dimers (Mr ~130,000) with a 67,000 subunit.
- LSS ChE is amphiphilic, DS ChE is membrane-bound via a phosphatidylinositol anchor; both show broad substrate specificity, with reduced affinity to a molluscan enzyme.
Conclusions:
- S. nudus possesses distinct amphiphilic and membrane-bound ChE forms with broad substrate specificity.
- These enzymes exhibit some structural differences compared to molluscan ChE.
- The study contributes to understanding ChE diversity and evolution in invertebrates.