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Cholesterol ester hydrolase in human red blood cells
Biochimica Et Biophysica Acta
|March 28, 1975
Summary
Human red blood cells contain a cholesterol ester hydrolytic enzyme, sterol-ester hydrolase. This enzyme, found in the cell membrane, may prevent esterified cholesterol buildup in erythrocytes.
Area of Science:
- Biochemistry
- Cell Biology
- Enzymology
Background:
- Human red blood cells possess a complex membrane lipid composition.
- Cholesterol is a key component of the erythrocyte membrane, primarily in its unesterified form.
Purpose of the Study:
- To detect and characterize cholesterol ester hydrolytic activity in human red blood cells.
- To investigate the localization and regulatory factors of this enzyme activity.
Main Methods:
- Assay of sterol-ester hydrolase (EC 3.1.1.13) activity in red blood cell preparations.
- Analysis of enzyme activity in response to antioxidants, inhibitors, and varying pH levels.
- Fractionation of red blood cells to identify enzyme localization, including the use of red cell ghosts.
Main Results:
- Cholesterol ester hydrolytic activity was identified in human red blood cells, primarily localized to the cell membrane and red cell ghosts.
- Enzyme activity was stimulated by antioxidants like D-alpha-tocopherol and butylated hydroxytoluene.
- Activity was inhibited by erythrocyte hemolysate, sodium taurocholate, and Triton X-100, with optimal activity at pH 5.4–5.7.
Conclusions:
- A sterol-ester hydrolase is present in the human red blood cell membrane.
- The enzyme's activity is modulated by specific antioxidants and inhibitors.
- It is hypothesized that this hydrolase plays a role in maintaining the erythrocyte membrane by preventing the accumulation of esterified cholesterol.