Arterial neutral cholesteryl esterase. A hormone-sensitive enzyme distinct from lysosomal cholesteryl esterase.

TitleArterial neutral cholesteryl esterase. A hormone-sensitive enzyme distinct from lysosomal cholesteryl esterase.
Publication TypeJournal Article
Year of Publication1983
AuthorsHajjar DP, Minick CR, Fowler S
JournalJ Biol Chem
Date Published1983 Jan 10
KeywordsAnimals, Aorta, Thoracic, Bile Acids and Salts, Carboxylic Ester Hydrolases, Hot Temperature, Hydrogen-Ion Concentration, Kinetics, Lysosomes, Micelles, Phospholipids, Rabbits, Sterol Esterase

We describe here an activable neutral cholesteryl esterase (EC in arteries similar to the hormone-sensitive lipase of adipose tissue and adrenal cortex. Maximum enzyme activity in rabbit aorta was given by cholesteryl ester substrates dispersed as a mixed micelle with phosphatidylcholine and Na taurocholate (molar ratio 1:4:2). A quantitative assay of enzymic activity was obtained with the following component concentrations: 6.0 microM cholesteryl [1-14C]oleate, 23.7 microM phosphatidylcholine, 12.5 microM Na taurocholate, 0.04% serum albumin, and 85 mM K phosphate buffer, pH 7.0. The enzymic activity in aortic homogenates was stimulated 2-fold by addition of 5 microM glucagon or 100 microM dibutyryl cAMP. This activation was Mg-ATP dependent. Addition of 50 micrograms/ml of exogenous protein kinase could reverse the action of protein kinase inhibitor on dibutyryl cAMP activation of the neutral cholesteryl esterase. In addition to activation by cAMP-dependent protein kinase, the enzyme could be distinguished from the more active arterial lysosomal cholesteryl esterase by its pH 7.0 optimum, relative stability to preincubation at elevated temperatures, and exclusive localization in the cell cytosol. Subcellular fractionation of lipid-laden arterial foam cells revealed a significant portion of the neutral cholesteryl esterase bound to cytoplasmic cholesteryl ester-rich lipid droplets. Our results suggest that the breakdown of cytoplasmic cholesteryl ester droplets in arterial cells may be under hormonal regulation.

Alternate JournalJ Biol Chem
PubMed ID6848493
Grant ListHL-18157 / HL / NHLBI NIH HHS / United States
HL-18828 / HL / NHLBI NIH HHS / United States
HL-28179 / HL / NHLBI NIH HHS / United States
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David P. Hajjar, Ph.D.

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