Tu A Y, Nishida H I, Nishida T
Burnsides Research Laboratory, Department of Food Science, University of Illinois, Urbana 61801.
J Biol Chem. 1993 Nov 5;268(31):23098-105.
Phospholipid transfer protein (PLTP) was purified from lipoprotein-free human plasma, obtained upon treatment of plasma with dextran sulfate and Ca2+, by employing a series of column chromatography. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified PLTP showed a single main band, corresponding to the molecular mass of 78 kDa. However, isoelectric focusing of the purified preparation gave multiple bands with pI ranging from 4.3 to 5.1, indicative of microheterogeneity. Purified PLTP was shown to possess not only phospholipid transfer activity, but also high density lipoprotein (HDL) conversion activity (Tu, A.-Y., Nishida, H. I., and Nishida, T. (1990), FASEB J. 4, A2148; Jauhiainen, M., Metso, J., Pahlman, R., Blomqvist, S., van Tol, A., and Ehnholm, C. (1993) J. Biol. Chem. 268, 4032-4036). Isolated HDL3 was enlarged to the size of HDL2b upon incubation with purified PLTP for 6 h at 37 degrees C at the PLTP/HDL3 molar ratio of approximately 1:45. Both the HDL conversion and the phosphatidylcholine transfer activities of purified PLTP were effectively inhibited by rabbit anti-PLTP immunoglobulin G. The primary importance of PLTP in the HDL enlargement that occurs in human plasma upon incubation at 37 degrees C was shown by the strong inhibitory effect of the anti-PLTP immunoglobulin G. The process of PLTP-mediated HDL enlargement was accompanied by the release of apoproteins, primarily apoA-I. HDL3 enlargement mediated by PLTP was effectively inhibited by the addition of free fatty acids.
磷脂转运蛋白（PLTP）是从无脂蛋白的人血浆中纯化得到的。通过一系列柱色谱法，先用硫酸葡聚糖和Ca2+处理血浆，再从中获取该蛋白。经十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析，纯化后的PLTP呈现出一条单一的主带，其分子量对应为78 kDa。然而，对该纯化制剂进行等电聚焦时出现了多条带，其pI范围为4.3至5.1，表明存在微不均一性。已证明纯化后的PLTP不仅具有磷脂转运活性，还具有高密度脂蛋白（HDL）转化活性（涂爱玉、西田浩一、西田哲（1990年），《美国实验生物学会联合会杂志》4，A2148；约海亚宁、梅索、帕尔曼、布洛姆奎斯特、范托尔、埃恩霍尔姆（1993年）《生物化学杂志》268，4032 - 4036）。在37℃下，以大约1:45的PLTP/HDL3摩尔比将分离的HDL3与纯化后的PLTP孵育6小时后，HDL3增大至HDL2b的大小。纯化后的PLTP的HDL转化活性和磷脂酰胆碱转运活性均被兔抗PLTP免疫球蛋白G有效抑制。抗PLTP免疫球蛋白G的强烈抑制作用表明了PLTP在人血浆于37℃孵育时发生的HDL增大过程中的首要重要性。PLTP介导的HDL增大过程伴随着载脂蛋白的释放，主要是载脂蛋白A-I。添加游离脂肪酸可有效抑制PLTP介导的HDL3增大。
