Side-chain oxysterols produced from cholesterol either enzymatically or non-enzymatically show various bioactivities. Lecithin-cholesterol acyltransferase (LCAT) esterifies the C3-hydroxyl group of these sterols as well as cholesterol. Lysosomal phospholipase A2 (LPLA2) is related to LCAT but does not catalyze esterification of cholesterol. First, esterification of side-chain oxysterols by LPLA2 was investigated using recombinant mouse LPLA2 and dioleoyl-PC/sulfatide/oxysterol liposomes under acidic conditions. TLC and LC-MS/MS showed that the C3 and C27-hydroxyl groups of 27-hydroxycholesterol could be individually esterified by LPLA2 to form a monoester with the C27-hydroxyl preference. Cholesterol did not inhibit this reaction. Also, LPLA2 esterified other side-chain oxysterols. Their esterifications by mouse serum containing LCAT supported the idea that their esterifications by LPLA2 occur at the C3-hydroxyl group. N-acetylsphingosine (NAS) acting as an acyl acceptor in LPLA2 transacylation inhibited the side-chain oxysterol esterification by LPLA2. This suggests a competition between hydroxycholesterol and NAS on the acyl-LPLA2 intermediate formed during the reaction. Raising cationic amphiphilic drug concentration or ionic strength in the reaction mixture evoked a reduction of the side-chain oxysterol esterification by LPLA2. This indicates that the esterification could progress via an interfacial interaction of LPLA2 with the lipid membrane surface through an electrostatic interaction. The docking model of acyl-LPLA2 intermediate and side-chain oxysterol provided new insight to elucidate the transacylation mechanism of sterols by LPLA2. Finally, exogenous 25-hydroxycholesterol esterification within alveolar macrophages prepared from wild-type mice was significantly higher than that from LPLA2 deficient mice. This suggests that there is an esterification pathway of side-chain oxysterols via LPLA2.

由胆固醇酶促或非酶促产生的侧链氧固醇显示出各种生物活性。卵磷脂胆固醇酰基转移酶（LCAT）酯化这些固醇的C3-羟基以及胆固醇。溶酶体磷脂酶A2（LPLA2）与LCAT有关，但不催化胆固醇的酯化。首先，在酸性条件下，使用重组小鼠LPLA2和油酰-PC /硫脂/氧固醇脂质体研究了LPLA2对侧链氧固醇的酯化作用。TLC和LC-MS / MS表明，LPLA2可以将27-羟基胆固醇的C3和C27-羟基分别酯化，形成具有C27-羟基优先级的单酯。胆固醇不抑制该反应。同样，LPLA2酯化了其他侧链氧固醇。ñ-乙酰基鞘氨醇（NAS）在LPLA2转酰作用中充当酰基受体，抑制了LPLA2引起的侧链氧固醇酯化。这表明羟基胆固醇和NAS之间在反应过程中形成的酰基-LPLA2中间体之间存在竞争。通过提高反应混合物中的阳离子两亲药物浓度或离子强度，可以减少LPLA2引起的侧链氧固醇酯化反应。这表明酯化可以通过LPLA2与脂质膜表面通过静电相互作用的界面相互作用而进行。酰基-LPLA2中间体和侧链氧固醇的对接模型为阐明LPLA2固醇的酰基转移机理提供了新的见识。最后，由野生型小鼠制备的肺泡巨噬细胞内的外源性25-羟基胆固醇酯化显着高于来自LPLA2缺陷小鼠的肺泡巨噬细胞。这表明存在通过LPLA2的侧链氧固醇的酯化途径。