Vance Jean E
Group on the Molecular and Cell Biology of Lipids and Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
J Lipid Res. 2008 Jul;49(7):1377-87. doi: 10.1194/jlr.R700020-JLR200. Epub 2008 Jan 19.
Phosphatidylserine (PS) and phosphatidylethanolamine (PE) are two aminophospholipids whose metabolism is interrelated. Both phospholipids are components of mammalian cell membranes and play important roles in biological processes such as apoptosis and cell signaling. PS is synthesized in mammalian cells by base-exchange reactions in which polar head groups of preexisting phospholipids are replaced by serine. PS synthase activity resides primarily on mitochondria-associated membranes and is encoded by two distinct genes. Studies in mice in which each gene has been individually disrupted are beginning to elucidate the importance of these two synthases for biological functions in intact animals. PE is made in mammalian cells by two completely independent major pathways. In one pathway, PS is converted into PE by the mitochondrial enzyme PS decarboxylase. In addition, PE is made via the CDP-ethanolamine pathway, in which the final reaction occurs on the endoplasmic reticulum and nuclear envelope. The relative importance of these two pathways of PE synthesis has been investigated in knockout mice. Elimination of either pathway is embryonically lethal, despite the normal activity of the other pathway. PE can also be generated from a base-exchange reaction and by the acylation of lyso-PE. Cellular levels of PS and PE are tightly regulated by the implementation of multiple compensatory mechanisms.
磷脂酰丝氨酸（PS）和磷脂酰乙醇胺（PE）是两种代谢相互关联的氨基磷脂。这两种磷脂都是哺乳动物细胞膜的组成成分，在细胞凋亡和细胞信号传导等生物学过程中发挥着重要作用。PS在哺乳动物细胞中通过碱基交换反应合成，即预先存在的磷脂的极性头部基团被丝氨酸取代。PS合成酶活性主要存在于与线粒体相关的膜上，由两个不同的基因编码。对每个基因分别被破坏的小鼠的研究开始阐明这两种合成酶对完整动物生物学功能的重要性。PE在哺乳动物细胞中通过两条完全独立的主要途径合成。在一条途径中，PS通过线粒体酶PS脱羧酶转化为PE。此外，PE通过CDP-乙醇胺途径合成，其中最终反应发生在内质网和核膜上。在基因敲除小鼠中研究了这两条PE合成途径的相对重要性。尽管另一条途径活性正常，但消除任何一条途径都会导致胚胎致死。PE也可以通过碱基交换反应和溶血PE的酰化作用产生。PS和PE的细胞水平通过多种补偿机制的实施受到严格调控。
