Hooper N M
School of Biochemistry and Molecular Biology, University of Leeds, UK.
Clin Chim Acta. 1997 Oct 9;266(1):3-12. doi: 10.1016/s0009-8981(97)00161-7.
Several mammalian enzymes are anchored to the outer surface of the plasma membrane by a covalently attached glycosyl-phosphatidylinositol (GPI) structure. These include acetylcholinesterase, alkaline phosphatase, membrane dipeptidase and 5'-nucleotidase. All GPI anchors determined to date have the conserved core structure ethanolamine-PO4-6Man alpha 1-2Man alpha 1-6Man alpha 1-4GlcNH2 alpha 1-6myo-inositol-1-PO4- lipid. In most mammalian GPI anchors the lipid is 1-alkyl-2-acyl-glycerol, although in porcine membrane dipeptidase it is diacylglycerol. Attached to the conserved core are various side chain residues that appear to be either protein- or tissue-specific. In addition to membrane attachment, a GPI anchor may confer additional properties on the protein, such as the susceptibility to cleavage by phospholipases and the potential to cluster in detergent-insoluble domains. GPI anchors can also act as intracellular targeting signals, in transmembrane signalling, in the clathrin-independent endocytic process of potocytosis and as hormone mediators. Thus, a GPI anchor can confer additional properties on enzymes that may be important in their physiological and pathophysiological functioning.
几种哺乳动物酶通过共价连接的糖基磷脂酰肌醇（GPI）结构锚定在质膜的外表面。这些酶包括乙酰胆碱酯酶、碱性磷酸酶、膜二肽酶和5'-核苷酸酶。迄今为止确定的所有GPI锚都具有保守的核心结构：乙醇胺 - 磷酸 - 6甘露糖α1-2甘露糖α1-6甘露糖α1-4葡糖胺α1-6肌醇-1-磷酸 - 脂质。在大多数哺乳动物GPI锚中，脂质是1-烷基-2-酰基甘油，尽管在猪膜二肽酶中它是二酰基甘油。连接在保守核心上的是各种侧链残基，这些残基似乎是蛋白质特异性或组织特异性的。除了膜附着外，GPI锚可能赋予蛋白质其他特性，如对磷脂酶切割的敏感性以及在去污剂不溶性结构域中聚集的可能性。GPI锚还可以作为细胞内靶向信号、参与跨膜信号传导、在网格蛋白非依赖性的胞饮作用内吞过程中以及作为激素介质。因此，GPI锚可以赋予酶在其生理和病理生理功能中可能重要的其他特性。
