Continuous monitoring of cholesterol oleate hydrolysis by hormone-sensitive lipase and other cholesterol esterases.
Hormone-sensitive lipase (HSL) contributes importantly to the hydrolysis of cholesteryl ester in steroidogenic tissues, releasing the cholesterol required for adrenal steroidogenesis. HSL has broad substrate specificity, because it hydrolyzes triacylglycerols (TAGs), diacylglycerols, monoacylglycerols, and cholesteryl esters. In this study, we developed a specific cholesterol esterase assay using cholesterol oleate (CO) dispersed in phosphatidylcholine and gum arabic by sonication. To continuously monitor the hydrolysis of CO by HSL, we used the pH-stat technique. For the sake of comparison, the hydrolysis of CO dispersion was also tested using other cholesteryl ester-hydrolyzing enzymes. The specific activities measured on CO were found to be 18, 100, 27, and 3 micromol/min/mg for HSL, cholesterol esterase from Pseudomonas species, Candida rugosa lipase-3, and cholesterol esterase from bovine pancreas, respectively. The activity of HSL on CO is approximately 4- to 5-fold higher than on long-chain TAGs. In contrast, with all other enzymes tested, the rates of TAG hydrolysis were higher than those of CO hydrolysis. The relatively higher turnover of HSL on CO observed in vitro adds further molecular insight on the physiological importance of HSL in cholesteryl ester catabolism in vivo. Thus, HSL could be considered more as a cholesteryl ester hydrolase than as a TAG lipase.
Ali
Yassine Ben
YB
Enzymology at Interfaces and Physiology of Lipolysis, Unité Propre de Recherche 9025, Centre National de la Recherche Scientifique, 13402 Marseille Cedex 20, France.
Carrière
Frédéric
F
Verger
Robert
R
Petry
Stefan
S
Muller
Günter
G
Abousalham
Abdelkarim
A
D002788:Cholesterol Esters / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D008066:Lipolysis; D011994:Recombinant Proteins / Q000378:metabolism; D002787:Sterol Esterase / Q000378:metabolism*
D002788:Cholesterol Esters; D011994:Recombinant Proteins; C014409:cholesteryl oleate; D002787:Sterol Esterase