Effects of Phosphatidylcholine/Phosphatidylethanolamine Composition in Cholesteryl Ester–Micellar Substrates on Neutral Cholesterol Esterase Activity

• Published in: Analytical biochemistry Vol. 268; no. 2; pp. 238 - 244
• Main Authors: Chiba, Tsuyoshi, Uematsu, Shogo, Sawamura, Fusae, Sugawara, Mika, Tomita, Isao, Kajiyama, Fumiyasu, Tomita, Takako
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15-03-1999
• Subjects: Adipose Tissue - enzymology; Animals; Cholesterol Esters - chemistry; Cholesterol Esters - metabolism; Chromatography, Gel; Drug Stability; Kinetics; Male; Micelles; neutral cholesterol esterase (N-CEase); phosphatidylcholine (PC); Phosphatidylcholines - analysis; Phosphatidylcholines - metabolism; phosphatidylethanolamine (PE); Phosphatidylethanolamines - analysis; Phosphatidylethanolamines - metabolism; Rats; Rats, Wistar; Sterol Esterase - metabolism; substrate; Substrate Specificity; phosphatidylethanolamine (PE); micelles; neutral cholesterol esterase (N-CEase); phosphatidylcholine (PC); substrate
• ISSN: 0003-2697; 1096-0309
• DOI: 10.1006/abio.1998.3071

The effect of phospholipid composition in cholesteryl ester (CE)–micellar substrates on neutral cholesterol esterase (N-CEase) activity was examined. N-CEase preparation was incubated with micelles composed of cholesteryl-[1-14C]-oleate, sodium taurocholate, and phosphatidylcholine (PC)/phosphatidylethanolamine (PE) at varying ratios (%PE:0 = PC only, 17, 33, 50, 66, 83). The activity increased dependently with the increase in PE content; the activity with the micelles containing the highest ratio of PE was 2.5-fold compared with the micelles consisting of PC only.Vmaxwith the micelles of 83, 66, and 50% PE was 3.1-, 2.7-, and 1.9-fold, respectively, compared with the micelles of PC only. Each micellar preparation was chromatographed through a Superose 6 column by the FPLC system. In 66 and 83% PE-containing micelles, PC, PE, CE, and part of sodium taurocholate eluted completely together in a single peak, whereas in micelles with 33 and 50% PE they eluted loosely together. The micelles with PC only or 17% PE formed PC–micelles without including CE and PE. It is concluded that PE plays a critical role in the formation of CE micelles with PC, and in the interaction with N-CEase. The CE–micelles with 66–83% PE serve as substrates for sensitive and reproducible N-CEase assay.