Physiological roles of non-polar lipid transfer reaction between plasma lipoproteins and the reaction mechanism of its catalyst protein.

点击翻译按钮获取中文摘要

1. [ <^(14)C> ]cholesteryl ester-labeled LDL was prepared by using its selective sorbent, dextran sulfatecellulose. HUman plasma d 1.006 fraction was incubated with lecithin liposome containing radiolabeled labeled cholesteryl ester(CE) and LDL was adsorbed by the sorbent. Then d 1.063 fraction was isolated from the eluted fraction from the sorbent. Chemical composition and apoB were intact in the labeled LDL.2. The rate of CE transfer was measured between LDL and HDL in human plasma. Labeled LDL was added to the plasma(d 1.006). The radioactivity transferred to HDL was monitored at 37゜C and the results were analyzed according to a bilateral equilibrium transfer model. The calculated rates were much faster than those of CE generation by LCAT in plasma and were proportional to the product of LDL and HDL concentrations. Consequently, CE generated in plasma is promptly distributed among lipoproteins and the rate is related to the frequency of the collision between the lipid particles.3. Lipid transfer protein(LTP) was partially purified from human plasma by 2000 times. Lipoprotein free plasma after its precipitation with dextran sulfate was fractionated further with phenyl-Sepharose, CM-cellulose and DEAE-Sepharose and the final preparation with the yield of 10% did not contain any apolipoproteins.4. CE transfer reaction was observed between LDL and LDL-size lecithin/triolein microemulsion. In the absence of apolipoproteins, both particles fused each other and CE was spontaneously transferred from LDL to the emulsion. LTP did not affect on this process. In the presence of apolipoproteins, the emulsion was stabilized against LDL and spontaneous transfer of membrane cholesterol was only observed. LTP calyzed the exchange of triglyceride and CE in this condition and there was no specificity of any apolipoproteins with respect to this effect.