Hussain M M, Kancha R K, Zhou Z, Luchoomun J, Zu H, Bakillah A
Department of Pathology, Medical College of Pennsylvania, Philadelphia 19129, USA. hussain@medcolpa. edu
Biochim Biophys Acta. 1996 May 20;1300(3):151-70. doi: 10.1016/0005-2760(96)00041-0.
Chylomicrons are lipoproteins synthesized exclusively by the intestine to transport dietary fat and fat-soluble vitamins. Synthesis of apoB48, a translational product of the apob gene, is required for the assembly of chylomicrons. The apob gene transcription in the intestine results in 14 and 7 kb mRNAs. These mRNAs are post-transcriptionally edited creating a stop codon. The edited mRNAs chylomicrons from the shorter apoB48 peptide remains to be elucidated. In addition, the roles of proteins involved in the assembly pathway, e.g. apobec-1, MTP and apoA-IV, needs to be studied. Cloning of enzymes involved in the intestinal biosynthesis of triglycerides will be crucial to fully appreciate the assembly of chylomicrons. There is a need for cell culture and transgenic animal models that can be used for intestinal lipoprotein assembly. The catabolism of chylomicrons is far more complex and efficient than the catabolism of VLDL. Even though the major steps involved in the catabolism of chylomicrons are now known, the determinants for apolipoprotein exchange, processing of remnants in the space of Disse, as well as the mechanism of uptake of these particles by extra-hepatic tissue needs further exploration.
乳糜微粒是仅由肠道合成的脂蛋白，用于运输膳食脂肪和脂溶性维生素。乳糜微粒的组装需要载脂蛋白B48（apob基因的翻译产物）的合成。肠道中apob基因转录产生14 kb和7 kb的mRNA。这些mRNA在转录后被编辑产生一个终止密码子。编辑后的mRNA如何产生较短的载脂蛋白B48肽从而形成乳糜微粒仍有待阐明。此外，参与组装途径的蛋白质，如载脂蛋白编辑催化蛋白-1（apobec-1）、微粒体甘油三酯转运蛋白（MTP）和载脂蛋白A-IV（apoA-IV）的作用也需要研究。克隆参与肠道甘油三酯生物合成的酶对于全面了解乳糜微粒的组装至关重要。需要能够用于肠道脂蛋白组装的细胞培养和转基因动物模型。乳糜微粒的分解代谢比极低密度脂蛋白（VLDL）的分解代谢要复杂得多且效率更高。尽管现在已知乳糜微粒分解代谢的主要步骤，但载脂蛋白交换的决定因素、狄氏间隙中残余物的处理以及这些颗粒被肝外组织摄取的机制仍需进一步探索。
