Related Experiment Videos
Cholesterol esterases from normal and FEC hamster liver
A Nègre1, S Karm, R Sablé-Amplis
1Laboratoire de Biochimie, Faculté de Médecine, Toulouse, France.
Summary
Hamster liver contains four enzymes that hydrolyze cholesteryl esters. Two cholesterol esterases handle medium- to long-chain esters, while two carboxylesterases process short-chain esters, showing distinct properties and sensitivities.
Area of Science:
- Biochemistry
- Enzymology
- Lipid Metabolism
Background:
- Cholesteryl esters are crucial lipids in cellular metabolism.
- Understanding the enzymes involved in their hydrolysis is key to metabolic research.
- Hamster liver is a model system for studying lipid-modifying enzymes.
Purpose of the Study:
- To identify and characterize enzymes that hydrolyze synthetic cholesteryl esters in hamster liver.
- To differentiate between various hydrolyzing enzymes based on their substrate specificity and response to effectors.
- To investigate potential differences in enzyme activity between normal and fatty liver (FEC) hamster livers.
Main Methods:
- Hydrolysis of synthetic cholesteryl esters with varying acyl chain lengths (C2-C18) by hamster liver enzymes.
- Enzyme characterization using inhibitors (E600), divalent cations (Mn2+, Mg2+), detergents (Triton X-100), pH variations, and substrate specificity analysis.
- Comparison of enzyme activities between normal and FEC hamster liver homogenates.
Main Results:
- Four distinct enzymes were identified: two cholesterol esterases (E600 resistant) for medium/long-chain esters and two carboxylesterases (E600 sensitive) for short-chain esters.
- Acid cholesterol esterase (lysosomal lipase) optimal at pH 5.0, activated by taurocholate.
- Alkaline cholesterol esterase optimal at pH 7.5, insensitive to tested effectors.
- Both acid and alkaline carboxylesterases required divalent cations (Mn2+ or Mg2+).
- Acid carboxylesterase inhibited by Triton X-100; alkaline carboxylesterase activated by Triton X-100.
- No significant activity differences were found between normal and FEC hamster livers.
Conclusions:
- Hamster liver possesses distinct cholesterol esterases and carboxylesterases with specific substrate preferences and sensitivities to environmental factors.
- These enzymes play specialized roles in cholesteryl ester hydrolysis.
- Enzyme activities related to cholesteryl ester hydrolysis do not appear to be altered in FEC hamster livers compared to normal livers.