Biosynthesis and hydrolysis of cholesteryl esters by rat skin subcellular fractions. Regulation by prostaglandins

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Abstract
The properties and subcellular distribution of the enzymes involved with the synthesis and hydrolysis of cholesteryl esters were investigated in skin of normal and essential fatty acid-deficient rats. Most of the activity of the cholesterol-esterifying enzyme(s) is associated with the 12000g and 105000g particulate fractions. The dependence of the enzyme reaction on ATP and CoA suggests that the esterification of cholesterol by rat skin is mediated by a fatty acyl-CoA–cholesterol acyltransferase (EC 2.3.1.–). On the other hand, most of the activity of the cholesteryl ester hydrolase (EC 3.1.1.13) is localized in the 105000g supernatant fraction. Although the activity of the cholesterol-esterifying enzyme(s) was elevated in skin preparations from essential fatty acid-deficient rats, the activity of the hydrolase was significantly decreased. These observations may explain in part the elevated concentrations of sterol esters in the skin of these animals. Prostaglandin E2 at low concentrations exerted marked inhibitory effect on the activity of the cholesterol-esterifying enzyme(s), whereas no effect was observed on the activity of the hydrolase at similar concentrations. However, at high concentrations prostaglandin E2 exerted moderate stimulatory effect on the activity of the hydrolase. These results suggest a possible physiological role of this substance in regulating the production of sterol esters in this tissue.