French W C, Henner J A, Bahl O P
Arch Biochem Biophys. 1984 May 1;230(2):560-79. doi: 10.1016/0003-9861(84)90437-5.
The biosynthesis of lipid-linked oligosaccharides has been studied in first trimester human placentas. Tissue was pulsed with [2-3H]mannose, [1-3H]glucosamine, and [1-3H]galactose (for [3H]glucose incorporation). The lipid-linked oligosaccharides (OSL) were purified on DEAE-cellulose. After cleaving the lipid from OSL the oligosaccharides were purified by paper chromatography and borate high-voltage electrophoresis. Four major oligosaccharides with the composition Glc(0-3)Man9GlcNAc2 thus obtained were characterized enzymatically by digestion with endo-beta-N-acetylglucosaminidase H and alpha-mannosidase, and chemically by methylation, acetolysis, and Smith degradation. While identical Glc(1-3)Man9GlcNAc2 oligosaccharides have been isolated from other in vivo systems, the presence of Man9Glc2 is novel for human placenta. Furthermore, Man9GlcNAc2 is present in appreciable amounts in placenta. Second, one mannose in Man9GlcNAc2 had a significantly higher specific radioactivity than the other mannosyl residues of the Glc(0-3)Man9GlcNAc2 oligosaccharides. Third, the differential labeling in Man9GlcNAc2 and our pulse-chase studies indicate that Man9GlcNAc2 is not a major precursor of Glc3Man9GlcNAc2. The data also suggest that the ninth mannose, which has the highest radioactivity, may be incorporated in a different subcellular compartment and may serve as a regulatory step in the biosynthesis of lipid-linked oligosaccharides. A model is proposed which outlines possible multiple pathways of lipid-linked oligosaccharide biosynthesis in human placenta.
已对孕早期人胎盘脂质连接寡糖的生物合成进行了研究。用[2-³H]甘露糖、[1-³H]葡糖胺和[1-³H]半乳糖（用于掺入[³H]葡萄糖）对组织进行脉冲标记。脂质连接寡糖（OSL）在DEAE-纤维素上进行纯化。从OSL上裂解脂质后，寡糖通过纸层析和硼酸盐高压电泳进行纯化。由此获得的四种主要寡糖，其组成为Glc(0-3)Man9GlcNAc2，通过用内切β-N-乙酰葡糖胺酶H和α-甘露糖苷酶消化进行酶学表征，并通过甲基化、乙酰解和史密斯降解进行化学表征。虽然已从其他体内系统中分离出相同的Glc(1-3)Man9GlcNAc2寡糖，但Man9Glc2的存在在人胎盘中是新发现的。此外，Man9GlcNAc2在胎盘中大量存在。其次，Man9GlcNAc2中的一个甘露糖的比放射性明显高于Glc(0-3)Man9GlcNAc2寡糖的其他甘露糖残基。第三，Man9GlcNAc2中的差异标记以及我们的脉冲追踪研究表明，Man9GlcNAc2不是Glc3Man9GlcNAc2的主要前体。数据还表明，具有最高放射性的第九个甘露糖可能在不同的亚细胞区室中掺入，并且可能在脂质连接寡糖的生物合成中作为一个调节步骤。提出了一个模型，概述了人胎盘脂质连接寡糖生物合成可能的多条途径。
