Parodi A J, Cazzulo J J
J Biol Chem. 1982 Jul 10;257(13):7641-5.
The protein-bound oligosaccharides were isolated from Trypanosoma cruzi cells incubated with [U-14C]glucose by means of as proteolytic digestion of delipidated proteinaceous pellets, followed by separation of oligosaccharides from glycopeptides through incubation with endo-N-acetylglucosaminidase H. The saccharides obtained after very short incubation periods were tentatively identified as Glc1Man9GlcNAc, Glc1Man8GlcNAc and Glc1Man7GlcNAc and the label was almost exclusively present in the glucose residues. On longer incubations, however, two more labeled oligosaccharides could be isolated, Man9GlcNAc (which appeared first) and Man9GlcNAc. The relative proportion of the three glucose-containing saccharides did not change with the length of the incubation of cells with [U-14C]glucose nor after chasing the label with the unlabeled monosaccharide. Moreover, the more internal mannose residues were labeled before in Man9GlcNAc than in Glc1Man9GlcNAc.l All this evidence indicated that Glc1Man9GlcNAc was not an intermediate in the formation of the other saccharides. On the basis of these results and of those reported in the preceding paper, the following pathway is proposed for the first stages of protein glycosylation: (formula, see text).
通过对脱脂蛋白质颗粒进行蛋白水解消化，从用[U-14C]葡萄糖孵育的克氏锥虫细胞中分离出蛋白质结合的寡糖，然后通过与内切N-乙酰葡糖胺酶H孵育从糖肽中分离出寡糖。在极短的孵育时间后获得的糖类初步鉴定为Glc1Man9GlcNAc、Glc1Man8GlcNAc和Glc1Man7GlcNAc，并且标记几乎只存在于葡萄糖残基中。然而，在更长时间的孵育后，可以分离出另外两种标记的寡糖，Man9GlcNAc（首先出现）和Man9GlcNAc。三种含葡萄糖的糖类的相对比例在细胞与[U-14C]葡萄糖孵育的时间长度内以及在用未标记的单糖追踪标记后均未改变。此外，在Man9GlcNAc中比在Glc1Man9GlcNAc中，更多内部的甘露糖残基先被标记。所有这些证据表明Glc1Man9GlcNAc不是其他糖类形成的中间体。基于这些结果以及前一篇论文中报道的结果，提出了蛋白质糖基化第一阶段的以下途径：（公式，见正文）。
