A new beta-1,2-N-acetylglucosaminyltransferase that may play a role in the biosynthesis of mammalian O-mannosyl glycans.
A new beta-1,2-N-acetylglucosaminyltransferase that may play a role in the biosynthesis of mammalian O-mannosyl glycans.
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DOI：
10.1093/glycob/11.1.37
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发表时间：
2001
期刊：
影响因子：
4.3
通讯作者：
Seiichiro Takahashi;T. Sasaki;H. Manya;Yasunori Chiba;A. Yoshida;Mamoru Mizuno;Hideki Ishida;Fumihiko Ito;T. Inazu;Norihiro Kotani;Seiichi Takasaki;Makoto Takeuchi;Tamao Endo
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文献类型：
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作者：
Seiichiro Takahashi;T. Sasaki;H. Manya;Yasunori Chiba;A. Yoshida;Mamoru Mizuno;Hideki Ishida;Fumihiko Ito;T. Inazu;Norihiro Kotani;Seiichi Takasaki;Makoto Takeuchi;Tamao Endo
最近的研究表明，O-甘露糖基聚糖存在于几种哺乳动物糖蛋白中。尽管关于这些聚糖功能作用的知识不断积累，但它们的生物合成途径却知之甚少。在这里，我们报告了新生大鼠大脑微粒体部分中能够形成 GlcNAc beta 1-2Man 连接的新型酶的鉴定和初步表征，即 UDP-N-乙酰氨基葡萄糖：O-连接甘露糖 beta-1,2-N-乙酰氨基葡萄糖转移酶。该酶将 GlcNAc 转移到 β 连接的甘露糖残基上，根据双球菌 β-N-乙酰己糖胺酶敏感性和高 pH 阴离子交换色谱法，所形成的连接被确认为 β 1-2。其活性与时间、蛋白质浓度和底物浓度呈线性关系，并且在锰离子存在时增强。其活性并非归因于 UDP-N-乙酰葡糖胺：α-3-D-甘露糖苷 β-1,2-N-乙酰葡糖胺基转移酶 I (GnT-I) 或 UDP-N-乙酰葡糖胺：α-6-D-甘露糖苷 β-1,2-D-乙酰葡糖胺基转移酶 II (GnT-II)，后者作用于 N-聚糖生物合成的早期步骤，因为酵母细胞中表达的 GnT-I 或 GnT-II 没有表现出任何针对合成甘露糖基肽的 GlcNAc 转移活性。综上所述，结果表明此处描述的 GlcNAc 转移酶活性与哺乳动物中的 O-甘露糖基聚糖途径相关。
Recent studies have shown that O-mannosyl glycans are present in several mammalian glycoproteins. Although knowledge on the functional roles of these glycans is accumulating, their biosynthetic pathways are poorly understood. Here we report the identification and initial characterization of a novel enzyme capable of forming GlcNAc beta 1-2Man linkage, namely UDP-N-acetylglucosamine: O-linked mannose beta-1,2-N-acetylglucosaminyltransferase in the microsome fraction of newborn rat brains. The enzyme transfers GlcNAc to beta-linked mannose residues, and the formed linkage was confirmed to be beta 1-2 on the basis of diplococcal beta-N-acetylhexosaminidase susceptibility and by high-pH anion-exchange chromatography. Its activity is linearly dependent on time, protein concentration, and substrate concentration and is enhanced in the presence of manganese ion. Its activity is not due to UDP-N-acetylglucosamine: alpha-3-D-mannoside beta-1,2-N-acetylglucosaminyltransferase I (GnT-I) or UDP-N-acetylglucosamine: alpha-6-D-mannoside beta-1,2-D-acetylglucosaminyltransferase II (GnT-II), which acts on the early steps of N-glycan biosynthesis, because GnT-I or GnT-II expressed in yeast cells did not show any GlcNAc transfer activity against a synthetic mannosyl peptide. Taken together, the results suggest that the GlcNAc transferase activity described here is relevant to the O-mannosyl glycan pathway in mammals.