Moraes C T, Bosch M, Parodi A J
Instituto de Investigaciones Bioquímicas Fundación Campomar, Buenos Aires, Argentina.
Biochemistry. 1988 Mar 8;27(5):1543-9. doi: 10.1021/bi00405a022.
It was reported before that cells of the trypanosomatid Leptomonas samueli incubated with [14C]glucose synthesized dolichol-P-P-linked Man9GlcNAc2 as the main and largest derivative. It is now reported that this protozoan is deficient in dolichol-P-Glc synthesis as judged from results obtained in a cell-free assay. We have structurally characterized several endo-beta-N-acetylglucosaminidase H sensitive oligosaccharides present in mature glycoproteins of this parasite. The compounds appeared to have the compositions Gal3Man9GlcNAc2, Gal2Man9GlcNAc2, Gal1Man9GlcNAc2, Man9GlcNAc2, Gal1Man8GlcNAc2, Man8GlcNAc2, Gal1Man7GlcNAc2, and Man7GlcNAc2. The galactose residues were in all cases in the furanose form and linked to mannoses in nonreducing ends. In the cases of Gal1Man8GlcNAc2 and Gal1Man7GlcNAc2, the galactose-substituted mannose units were the nonreducing residues originally present in the oligosaccharide transferred from dolichol-P-P (Man9GlcNAc2) and not the nonreducing termini generated by demannosylation of the latter oligosaccharide. Except for Gal3Man9GlcNAc2, the other galactosylated compounds appeared to be mixtures of several isomers.
之前有报道称，用[14C]葡萄糖培养的锥虫利什曼原虫细胞合成了以多萜醇-P-P连接的Man9GlcNAc2作为主要且最大的衍生物。现在有报道称，根据无细胞试验的结果判断，这种原生动物缺乏多萜醇-P-葡萄糖的合成。我们对该寄生虫成熟糖蛋白中存在的几种内切-β-N-乙酰葡糖胺酶H敏感的寡糖进行了结构表征。这些化合物的组成似乎为Gal3Man9GlcNAc2、Gal2Man9GlcNAc2、Gal1Man9GlcNAc2、Man9GlcNAc2、Gal1Man8GlcNAc2、Man8GlcNAc2、Gal1Man7GlcNAc2和Man7GlcNAc2。在所有情况下，半乳糖残基均为呋喃糖形式，并连接到非还原端的甘露糖上。在Gal1Man8GlcNAc2和Gal1Man7GlcNAc2的情况下，半乳糖取代的甘露糖单元是最初存在于从多萜醇-P-P转移的寡糖（Man9GlcNAc2）中的非还原残基，而不是由后者寡糖的去甘露糖基化产生的非还原末端。除了Gal3Man9GlcNAc2外，其他半乳糖基化化合物似乎是几种异构体的混合物。
