Parodi A J, Mendelzon D H, Lederkremer G Z
J Biol Chem. 1983 Jul 10;258(13):8260-5.
Calf thyroid slices incubated with [U-14C]glucose synthesized protein-bound Glc3Man9GlcNAc2, Glc2-Man9GlcNAc2, Glc1Man9GlcNAc2, Glc1Man8GlcNAc2, and Glc1Man7GlcNAc2. Although label in the glucose residues of the last three compounds could be detected within 5 min of incubation, appearance of radioactivity in the mannose residues of the alpha-mannosidase-resistant cores of Glc1Man8GlcNAc2 and Glc1Man7GlcNAc2 took more than 30 and 60 min, respectively, to appear after label was detected in the same mannose residues of Glc1Man9GlcNAc2. The glucose residues were removed upon chasing the slices with unlabeled glucose. The last compound to disappear was Glc1Man9GlcNAc2. Calf thyroid microsomes incubated with UDP-[U-14C]Glc synthesized the five protein-bound oligosaccharides mentioned above. Although addition to GDP-Man to the incubation mixtures greatly diminished the formation of Glc3Man9GlcNAc2 bound either to dolichol-P-P or to protein, labeling of Glc1Man9GlcNAc2, Glc1Man8GlcNAc2, and Glc1Man7GlcNAc2 was not affected. Addition of kojibiose prevented deglucosylation of protein-bound Glc3Man9GlcNAc2 without affecting the formation of Glc1Man8GlcNAc2 and Glc1Man7GlcNAc2 and only partially diminishing that of Glc1Man9GlcNAc2. These results indicate that Glc1Man8GlcNAc2 and Glc1Man7GlcNAc2 were formed by glucosylation of the unglucosylated species and not be demannosylation of Glc1Man9GlcNAc2 and that probably part of the latter compound was formed in the same way.
用[U-14C]葡萄糖孵育的小牛甲状腺切片合成了与蛋白质结合的Glc3Man9GlcNAc2、Glc2-Man9GlcNAc2、Glc1Man9GlcNAc2、Glc1Man8GlcNAc2和Glc1Man7GlcNAc2。尽管在孵育5分钟内就能检测到后三种化合物葡萄糖残基上的标记，但在Glc1Man8GlcNAc2和Glc1Man7GlcNAc2的α-甘露糖苷酶抗性核心的甘露糖残基中放射性的出现，在Glc1Man9GlcNAc2的相同甘露糖残基中检测到标记后，分别需要30多分钟和60多分钟才会出现。用未标记的葡萄糖追踪切片后，葡萄糖残基被去除。最后消失的化合物是Glc1Man9GlcNAc2。用UDP-[U-14C]Glc孵育的小牛甲状腺微粒体合成了上述五种与蛋白质结合的寡糖。尽管向孵育混合物中添加GDP-Man大大减少了与多萜醇-P-P或蛋白质结合的Glc3Man9GlcNAc2的形成，但Glc1Man9GlcNAc2、Glc1Man8GlcNAc2和Glc1Man7GlcNAc2的标记不受影响。添加曲二糖可防止与蛋白质结合的Glc3Man9GlcNAc2的去糖基化，而不影响Glc1Man8GlcNAc2和Glc1Man7GlcNAc2的形成，并且仅部分减少Glc1Man9GlcNAc2的形成。这些结果表明，Glc1Man8GlcNAc2和Glc1Man7GlcNAc2是由未糖基化的物种糖基化形成的，而不是由Glc1Man9GlcNAc2的去甘露糖基化形成的，并且后者化合物可能部分也是以同样的方式形成的。
