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Ca(2+)-ATPase activity and lens lipid composition in reconstituted systems
J Zeng1, Z Zhang, C A Paterson
1Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, 40202, USA.
Experimental Eye Research
|September 2, 1999
Summary
Human lens lipids, particularly sphingolipids, significantly reduce Ca(2+)-ATPase pump activity. This suggests age-related changes in lens lipid composition may impact calcium homeostasis and clarity.
Area of Science:
- Biochemistry
- Ophthalmology
- Membrane Biophysics
Background:
- Lens lipid composition and structure change with age, affecting lens clarity.
- Calcium homeostasis, maintained by the lens Ca(2+)-ATPase pump, is crucial for lens transparency.
Purpose of the Study:
- To investigate the impact of human lens lipids on Ca(2+)-ATPase activity.
- To explore the relationship between lipid structure, saturation, and enzyme function.
Main Methods:
- Reconstitution of muscle sarcoplasmic reticulum Ca(2+)-ATPase with bovine lens lipids and dihydrosphingomyelin.
- Assay of Ca(2+)-ATPase activity in reconstituted systems with varying cholesterol content.
Main Results:
- Ca(2+)-ATPase activity was approximately 5-fold lower with lens lipids or dihydrosphingomyelin compared to native lipids.
- Enzyme activity correlated inversely with hydrocarbon chain saturation, linked to high sphingolipid content.
- Cholesterol addition did not affect reconstituted Ca(2+)-ATPase activity.
Conclusions:
- Lens lipid composition and structure, particularly high saturation due to sphingolipids, can significantly reduce Ca(2+)-ATPase activity.
- Changes in lens lipid profiles may contribute to impaired calcium homeostasis and cataract formation.
- This study provides initial insights into the structure-function relationship of lens lipids and Ca(2+)-ATPase.