Bengtsson G, Marklung S E, Olivecrona T
Eur J Biochem. 1977 Sep 15;79(1):211-23. doi: 10.1111/j.1432-1033.1977.tb11799.x.
Egg yolk lipoproteins of very low density were found to contain proteins with cofactor activity for lipoprotein lipase. When delipidated very low density lipoproteins were dissolved in 10 mM HCl and fractionated by gel filtration about two thirds of the protein were in several components with estimated molecular weights of 60000 to more than 170000. The major low-molecular-weight proteins were the dimeric and monomeric forms of a previously characterized 9000-dalton peptide. The cofactor activity was not associated with any of these major proteins. A large-scale fractionation method was developed by which two proteins fractions with cofactor activity for lipoprotein lipase were purified more than thousand-fold. One fraction had a molecular size of about 9000 daltons and the other had a size of about 5000 daltons. Both these fractions could be further separated on the basis of charge into several fractions with cofactor activity. The cofactor proteins were relatively soluble both at high and at low pH. The retained their cofactor activity after denaturation in guanidinium hydrochloride and after reduction. During the initial steps in the purification of the cofactor proteins another low-molecular-weight protein followed the cofactors. It had a single 17500-dalton peptide chain and was present in four variants, three of which contained carbohydrate.
研究发现，极低密度脂蛋白的蛋黄脂蛋白含有对脂蛋白脂肪酶具有辅助因子活性的蛋白质。当脱脂的极低密度脂蛋白溶解于10 mM盐酸中并通过凝胶过滤进行分级分离时，约三分之二的蛋白质存在于几种组分中，其估计分子量为60000至超过170000。主要的低分子量蛋白质是先前鉴定的9000道尔顿肽的二聚体和单体形式。辅助因子活性与这些主要蛋白质均无关。开发了一种大规模分级分离方法，通过该方法，两种对脂蛋白脂肪酶具有辅助因子活性的蛋白质组分被纯化了一千多倍。一个组分的分子大小约为9000道尔顿，另一个组分的大小约为5000道尔顿。这两种组分都可以根据电荷进一步分离成几个具有辅助因子活性的组分。辅助因子蛋白在高pH和低pH下都相对可溶。它们在盐酸胍中变性并还原后仍保留其辅助因子活性。在辅助因子蛋白纯化的初始步骤中，另一种低分子量蛋白质与辅助因子一起出现。它有一条单一的17500道尔顿肽链，存在四种变体，其中三种含有碳水化合物。
