Bengtsson G, Olivecrona T
Biochim Biophys Acta. 1983 Apr 13;751(2):254-9. doi: 10.1016/0005-2760(83)90180-7.
This paper demonstrates a striking difference between the effects of salt and pH on the activity of lipoprotein lipase against two different substrates: Intralipid and bovine milk fat droplets. With the former substrate 1 M NaCl caused only a slight reduction in enzyme activity and the stimulation by apolipoprotein C-II was the same from 0.1 to 1.1 M NaCl. In contrast, 0.5 M or more NaCl virtually abolished the enzyme activity in the milk system. In this system the salt also abolished binding of the enzyme to the lipid droplets, whereas in the Intralipid system most of the enzyme remained bound even at 1 M NaCl. A similar picture was obtained with respect to effects of pH. In the milk system the activity decreased sharply at pH values above 8.5, whereas in the Intralipid system it continues to rise to pH 10, and the stimulation by activator protein is the same at all pH values. Correlating with this, the binding of the enzyme to the lipid droplets was highly dependent on pH values in the milk systems, with optimum binding around pH 8, whereas in the Intralipid system most of the enzyme remained bound to the lipid droplets at all pH values. These studies demonstrate that apolipoprotein C-II can activate lipoprotein lipase at a wide range of salt concentrations and of pH. They suggest that the well-known effects of high salt concentrations and of high pH to decrease lipoprotein lipase activity are exerted primarily on the enzyme itself.
本文证明了盐和pH值对脂蛋白脂肪酶作用于两种不同底物（英脱利匹特和牛乳脂肪球）的活性具有显著差异。对于前一种底物，1M氯化钠仅使酶活性略有降低，并且在0.1至1.1M氯化钠范围内，载脂蛋白C-II的刺激作用相同。相比之下，0.5M或更高浓度的氯化钠几乎使牛奶体系中的酶活性丧失。在该体系中，盐还消除了酶与脂质球的结合，而在英脱利匹特体系中，即使在1M氯化钠存在下，大部分酶仍保持结合状态。关于pH值的影响也得到了类似的结果。在牛奶体系中，pH值高于8.5时活性急剧下降，而在英脱利匹特体系中，其活性持续上升至pH 10，并且在所有pH值下激活蛋白的刺激作用相同。与此相关的是，在牛奶体系中，酶与脂质球的结合高度依赖于pH值，在pH 8左右结合最佳，而在英脱利匹特体系中，在所有pH值下大部分酶仍与脂质球结合。这些研究表明，载脂蛋白C-II可以在广泛的盐浓度和pH值范围内激活脂蛋白脂肪酶。它们表明，高盐浓度和高pH值降低脂蛋白脂肪酶活性的众所周知的作用主要作用于酶本身。
