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CDP-diglyceride:inositol transferase from rat liver. Purification and properties
The Journal of Biological Chemistry
|August 10, 1977
Summary
Researchers purified CDP-diglyceride:inositol transferase, crucial for phosphatidylinositol synthesis, from rat liver microsomes. The enzyme requires phospholipids and divalent cations for activity, with specific kinetic properties identified.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Phosphatidylinositol is a vital membrane phospholipid.
- Its de novo synthesis involves CDP-diglyceride:inositol transferase.
- Understanding this enzyme is key to lipid metabolism research.
Purpose of the Study:
- To solubilize and purify CDP-diglyceride:inositol transferase from rat liver microsomes.
- To characterize the kinetic and cofactor requirements of the purified enzyme.
Main Methods:
- Enzyme solubilization using sodium cholate.
- Purification via ammonium sulfate fractionation, sucrose density gradient centrifugation, and DEAE-cellulose chromatography.
- Enzyme activity assays, molecular weight determination (SDS-PAGE), and kinetic analysis (Michaelis-Menten kinetics).
Main Results:
- A nearly homogeneous preparation of CDP-diglyceride:inositol transferase was obtained with 3-3.3% recovery.
- The enzyme's molecular weight was estimated to be 60,000 Da.
- The enzyme requires exogenous phospholipids, Mn2+ or Mg2+, and exhibits optimal activity at pH 8.6. Kinetic parameters (Km) for myo-inositol and CDP-diglyceride were determined.
Conclusions:
- The study successfully purified and characterized CDP-diglyceride:inositol transferase.
- The enzyme's dependence on phospholipids and divalent cations highlights its complex regulatory mechanism.
- Kinetic data provides insights into the regulation of phosphatidylinositol synthesis.