Department of Nutrition and Health Sciences, University of Nebraska, Lincoln, NE 68583-0806, USA.
J Nutr Biochem. 2010 Aug;21(8):736-40. doi: 10.1016/j.jnutbio.2009.04.008. Epub 2009 Jul 16.
Consumption of plant sterols or stanols (collectively referred to as phytosterols) and their esters results in decreased low-density lipoprotein cholesterol, which is associated with decreased atherosclerotic risk. The mechanisms by which phytosterols impart their effects, however, are incompletely characterized. The objective of the present study is to determine if pancreatic cholesterol esterase (PCE; EC 3.1.1.13), the enzyme primarily responsible for cholesterol ester hydrolysis in the digestive tract, is capable of hydrolyzing various phytosterol esters and to compare the rates of sterol ester hydrolysis in vitro. We found that PCE hydrolyzes palmitate, oleate and stearate esters of cholesterol, stigmasterol, stigmastanol and sitosterol. Furthermore, we found that the rate of hydrolysis was dependent on both the sterol and the fatty acid moieties in the following order of rates of hydrolysis: cholesterol>(sitosterol=stigmastanol)>stigmasterol; oleate>(palmitate=stearate). The addition of free phytosterols to the system did not change hydrolytic activity of PCE, while addition of palmitate, oleate or stearate increased activity. Thus, PCE may play an important but discriminatory role in vivo in the liberation of free phytosterols to compete with cholesterol for micellar solubilization and absorption.
植物固醇或甾烷醇（统称为植物固醇）的消耗会导致低密度脂蛋白胆固醇降低，从而降低动脉粥样硬化的风险。然而，植物固醇发挥作用的机制尚未完全阐明。本研究的目的是确定胰腺胆固醇酯酶（PCE；EC 3.1.1.13）是否能够水解各种植物固醇酯，以及比较体外甾醇酯水解的速率，胰腺胆固醇酯酶是消化道中胆固醇酯水解的主要酶。我们发现 PCE 可水解胆固醇、豆甾醇、谷甾醇和菜油固醇的棕榈酸酯、油酸酯和硬脂酸酯。此外，我们发现水解速率取决于甾醇和脂肪酸部分，水解速率的顺序如下：胆固醇>(菜油固醇=谷甾醇)>豆甾醇；油酸酯>(棕榈酸酯=硬脂酸酯)。向系统中添加游离植物固醇不会改变 PCE 的水解活性，而添加棕榈酸酯、油酸酯或硬脂酸酯会增加活性。因此，PCE 可能在体内发挥重要但有区别的作用，将游离植物固醇释放出来，与胆固醇竞争胶束溶解和吸收。
