Satomura Takenori, Kusumi Kaori, Ohshima Toshihisa, Sakuraba Haruhiko
Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, Fukui, Japan.
Biosci Biotechnol Biochem. 2011;75(10):2049-51. doi: 10.1271/bbb.110375. Epub 2011 Oct 7.
A gene encoding a UDP-glucose dehydrogenase homologue was identified in the hyperthermophilic archaeon, Pyrobaculum islandicum. This gene was expressed in Escherichia coli, and the product was purified and characterized. The expressed enzyme is the most thermostable UDP-glucose dehydrogenase so far described, with a half-life of 10 min at 90 °C. The enzyme retained its full activity after incubating in a pH range of 5.0-10.0 for 10 min at 80 °C. The temperature dependence of the kinetic parameters for this enzyme was examined at 37-70 °C. A decrease in K(m)s for UDP-glucose and NAD was observed with decreasing temperature. This resulted in the enzyme still retaining high catalytic efficiency (V(max)/K(m)) for the substrate and cofactor, even at 37 °C. These characteristics make the enzyme potentially useful for its application at a much lower temperature such as 37 °C than the optimum growth temperature of 100 °C for P. islandicum.
在嗜热古菌冰岛嗜火菌（Pyrobaculum islandicum）中鉴定出一个编码UDP-葡萄糖脱氢酶同源物的基因。该基因在大肠杆菌中表达，其产物经过纯化和特性鉴定。所表达的酶是迄今为止所描述的最耐热的UDP-葡萄糖脱氢酶，在90℃下的半衰期为10分钟。该酶在80℃下于pH 5.0 - 10.0的范围内孵育10分钟后仍保留其全部活性。在37 - 70℃下研究了该酶动力学参数的温度依赖性。随着温度降低，观察到UDP-葡萄糖和NAD的K(m)值下降。这使得该酶即使在37℃时，对于底物和辅因子仍保持高催化效率（V(max)/K(m)）。这些特性使得该酶在比冰岛嗜火菌的最佳生长温度100℃低得多的温度（如37℃）下具有潜在的应用价值。
