抄録
The purpose of the present study was to characterize the properties of cholesterol esterase (CEase) in human skin fibroblasts and monocyte-derived macrophages. Acid and neutral CEases exist in lysosome and microsome, respectively in both cells. Acid CEase activity was higher than neutral CEase activity. Other properties of acid and neutral CEase of fibroblasts and macrophages were similar with respect to Km, effect of phospholipids and divalent cations for phosphatidyl choline (PC) emulsified cholesterol ester (CE).
But optimal pH of CE hydrolysing activity in low density lipoprotein (LDL) was located at pH 4.5 and was not detected at neutral or alkaline range, whereas there was two pH optima for CEase activity when PC emulsified CE was used as substrate. This result suggests that LDL-CE hydrolysis can be performed only in lysosome. The uptake and hydrolysis by fibroblasts of 125I-LDL were determined. The uptake of LDL in fibroblasts of familial hypercholesterolemic patients (FHC) was lesser than that of normals, but the hydrolysis of LDL was increased. The amount of uptake of a-LDL in macrophages of FHC was not different from that of normals, but the hydrolysis of LDL was decreased.
