Environmental Microbiology, Institute of Biosciences, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany.
EMBL Hamburg, Notkestr. 85, 22607 Hamburg, Germany.
Int J Mol Sci. 2019 Nov 19;20(22):5809. doi: 10.3390/ijms20225809.
Uridine-5'-diphosphate (UDP)-glucose is reported as one of the most versatile building blocks within the metabolism of pro- and eukaryotes. The activated sugar moiety is formed by the enzyme UDP-glucose pyrophosphorylase (GalU). Two homologous enzymes (designated as GalU1 and GalU2) are encoded by most strains, known for their capability to degrade numerous compounds, but also to synthesize natural products such as trehalose comprising biosurfactants. To evaluate their functionality respective genes of a trehalose biosurfactant producing model organism- 1CP-were cloned and expressed, proteins produced (yield up to 47 mg per L broth) and initially biochemically characterized. In the case of GalU2, the was determined to be 177 U mg (uridine-5'-triphosphate (UTP)) and to be 0.51 mM (UTP), respectively. Like other GalUs this enzyme seems to be rather specific for the substrates UTP and glucose 1-phosphate, as it accepts only dTTP and galactose 1-phoshate in addition, but both with solely 2% residual activity. In comparison to other bacterial GalU enzymes the GalU2 was found to be somewhat higher in activity (factor 1.8) even at elevated temperatures. However, GalU1 was not obtained in an active form thus it remains enigmatic if this enzyme participates in metabolism.
尿苷二磷酸葡萄糖（UDP-葡萄糖）被报道为原核生物和真核生物代谢中最通用的构建块之一。活化的糖部分由酶 UDP-葡萄糖焦磷酸化酶（GalU）形成。大多数菌株都编码两种同源酶（分别命名为 GalU1 和 GalU2），它们具有降解多种化合物的能力，但也能合成包括生物表面活性剂在内的天然产物，如海藻糖。为了评估它们的功能，海藻糖生物表面活性剂生产模型生物 1CP 的相应基因被克隆和表达，产生的蛋白质（产量高达每升培养液 47 毫克）并进行了初步的生化特性分析。在 GalU2 的情况下，分别确定其 UTP 米氏常数（ ）为 177 U mg（尿苷-5'-三磷酸（UTP））和 0.51 mM（UTP）。像其他 GalUs 一样，该酶似乎对 UTP 和葡萄糖 1-磷酸等底物具有相当的特异性，因为它仅接受 dTTP 和半乳糖 1-磷酸作为底物，但仅具有 2%的残余活性。与其他细菌 GalU 酶相比，GalU2 的活性更高（因子 1.8），即使在高温下也是如此。然而，GalU1 没有以活性形式获得，因此它是否参与代谢仍然是个谜。
