Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, Japan.
Carbohydr Res. 2010 Apr 19;345(6):787-91. doi: 10.1016/j.carres.2010.01.008. Epub 2010 Jan 18.
Plants use UDP-arabinofuranose (UDP-Araf) to donate Araf residues in the biosynthesis of Araf-containing complex carbohydrates. UDP-Araf itself is formed from UDP-arabinopyranose (UDP-Arap) by UDP-arabinopyranose mutase (UAM). However, the mechanism by which this enzyme catalyzes the interconversion of UDP-Arap and UDP-Araf has not been determined. To gain insight into this reaction, functionally recombinant rUAMs were reacted with UDP-Glc or UDP-Araf. The glycosylated recombinant UAMs were fragmented with trypsin, and the glycopeptides formed were then identified and sequenced by LC-MS/MS. The results of these experiments, together with site-directed mutagenesis studies, suggest that in functional UAMs an arginyl residue is reversibly glycosylated with a single glycosyl residue, and that this residue is required for mutase activity. We also provide evidence that a DXD motif is required for catalytic activity.
植物利用 UDP-阿拉伯呋喃糖（UDP-Araf）在含 Araf 的复杂碳水化合物的生物合成中提供 Araf 残基。UDP-Araf 本身是由 UDP-阿拉伯吡喃糖（UDP-Arap）通过 UDP-阿拉伯吡喃糖变位酶（UAM）形成的。然而，该酶催化 UDP-Arap 和 UDP-Araf 相互转化的机制尚未确定。为了深入了解这一反应，用 UDP-Glc 或 UDP-Araf 反应功能重组 rUAMs。用胰蛋白酶对糖基化重组 UAMs 进行片段化，然后通过 LC-MS/MS 鉴定和测序形成的糖肽。这些实验的结果，以及定点突变研究表明，在功能性 UAMs 中，单个糖基残基可逆地糖基化精氨酸残基，并且该残基是变位酶活性所必需的。我们还提供了证据表明，DXD 基序是催化活性所必需的。
