Rhomberg Simone, Fuchsluger Christina, Rendić Dubravko, Paschinger Katharina, Jantsch Verena, Kosma Paul, Wilson Iain B H
Department für Chemie, Universität für Bodenkultur, Vienna, Austria.
FEBS J. 2006 May;273(10):2244-56. doi: 10.1111/j.1742-4658.2006.05239.x.
The deoxyhexose sugar fucose has an important fine-tuning role in regulating the functions of glycoconjugates in disease and development in mammals. The two genetic model organisms Caenorhabditis elegans and Drosophila melanogaster also express a range of fucosylated glycans, and the nematode particularly has a number of novel forms. For the synthesis of such glycans, the formation of GDP-fucose, which is generated from GDP-mannose in three steps catalysed by two enzymes, is required. By homology we have identified and cloned cDNAs encoding these two proteins, GDP-mannose dehydratase (GMD; EC 4.2.1.47) and GDP-keto-6-deoxymannose 3,5-epimerase/4-reductase (GER or FX protein; EC 1.1.1.271), from both Caenorhabditis and Drosophila. Whereas the nematode has two genes encoding forms of GMD (gmd-1 and gmd-2) and one GER-encoding gene (ger-1), the insect has, like mammalian species, only one homologue of each (gmd and gmer). This compares to the presence of two forms of both enzymes in Arabidopsis thaliana. All corresponding cDNAs from Caenorhabditis and Drosophila, as well as the previously uncharacterized Arabidopsis GER2, were separately expressed, and the encoded proteins found to have the predicted activity. The biochemical characterization of these enzymes is complementary to strategies aimed at manipulating the expression of fucosylated glycans in these organisms.
脱氧己糖岩藻糖在调节哺乳动物疾病和发育过程中糖缀合物的功能方面具有重要的微调作用。两种遗传模式生物秀丽隐杆线虫和黑腹果蝇也表达一系列岩藻糖基化聚糖，特别是线虫有许多新的形式。为了合成这些聚糖，需要由两种酶催化分三步从GDP-甘露糖生成GDP-岩藻糖。通过同源性分析，我们从秀丽隐杆线虫和果蝇中鉴定并克隆了编码这两种蛋白质的cDNA，即GDP-甘露糖脱水酶（GMD；EC 4.2.1.47）和GDP-酮-6-脱氧甘露糖3,5-表异构酶/4-还原酶（GER或FX蛋白；EC 1.1.1.271）。线虫有两个编码GMD形式的基因（gmd-1和gmd-2）和一个编码GER的基因（ger-1），而昆虫与哺乳动物一样，每种酶只有一个同源物（gmd和gmer）。相比之下，拟南芥中有两种形式的这两种酶。分别表达了来自秀丽隐杆线虫和果蝇的所有相应cDNA，以及之前未鉴定的拟南芥GER2，并发现编码的蛋白质具有预测的活性。这些酶的生化特性补充了旨在操纵这些生物体中岩藻糖基化聚糖表达的策略。
