Kotake Toshihisa, Hojo Sachiko, Yamaguchi Daisuke, Aohara Tsutomu, Konishi Tomoyuki, Tsumuraya Yoichi
Division of Life Science, Graduate School of Science and Engineering, Saitama University, Shimo-Okubo, Saitama, Japan.
Biosci Biotechnol Biochem. 2007 Mar;71(3):761-71. doi: 10.1271/bbb.60605. Epub 2007 Mar 7.
UDP-sugar pyrophosphorylase catalyzes the conversion of various monosaccharide 1-phosphates to the respective UDP-sugars in the salvage pathway. Using the genomic database, we cloned a putative gene for UDP-sugar pyrophosphorylase from Arabidopsis. Although relatively stronger expression was detected in the vascular tissue of leaves and the pollen, AtUSP is expressed in most cell types of Arabidopsis, indicating a housekeeping function in nucleotide sugar metabolism. Recombinant AtUSP expressed in Escherichia coli exhibited broad specificity toward monosaccharide 1-phosphates, resulting in the formation of various UDP-sugars such as UDP-glucose, -galactose, -glucuronic acid, -xylose and -L-arabinose. A loss-of-function mutation in the AtUSP gene caused by T-DNA insertion completely abolished male fertility. These results indicate that AtUSP functions as a UDP-sugar pyrophosphorylase in the salvage pathway, and that the generation of UDP-sugars from monosaccharide 1-phosphates catalyzed by AtUSP is essential for pollen development in Arabidopsis.
UDP-糖焦磷酸化酶在补救途径中催化各种单糖1-磷酸转化为相应的UDP-糖。利用基因组数据库，我们从拟南芥中克隆了一个推定的UDP-糖焦磷酸化酶基因。虽然在叶片的维管组织和花粉中检测到相对较强的表达，但AtUSP在拟南芥的大多数细胞类型中都有表达，表明其在核苷酸糖代谢中具有管家功能。在大肠杆菌中表达的重组AtUSP对单糖1-磷酸表现出广泛的特异性，从而形成各种UDP-糖，如UDP-葡萄糖、-半乳糖、-葡萄糖醛酸、-木糖和-L-阿拉伯糖。由T-DNA插入导致的AtUSP基因突变功能丧失完全消除了雄性育性。这些结果表明，AtUSP在补救途径中作为UDP-糖焦磷酸化酶发挥作用，并且由AtUSP催化的从单糖1-磷酸生成UDP-糖对于拟南芥花粉发育至关重要。
