Thermus thermophilus Glycosynthases for the Efficient Synthesis of Galactosyl and Glucosyl β-(1→3)-Glycosides
作者:Jullien Drone、Hui-yong Feng、Charles Tellier、Lionel Hoffmann、Vinh Tran、Claude Rabiller、Michel Dion
DOI:10.1002/ejoc.200500014
日期:2005.5
were much more efficient than E338A. Moreover, our results showed that these enzymes were inactive in the hydrolysis of the α-D-glycopyranosyl fluorides used as donors, and so suitable experimental conditions, under which the rate of spontaneous hydrolysis of the donor was considerably lower than that of enzymatic transglycosidation, provided galactosyl and glucosyl β-(13)-glycosides in yields of up
根据Withers 策略设计反转突变体糖合酶,从保留Tt-β-Gly 糖苷酶的野生型嗜热栖热菌开始。丙氨酸、丝氨酸和甘氨酸对催化亲核试剂谷氨酸 338 的定向诱变分别提供了 E338A、E338S 和 E338G 突变酶。正如所料,突变体不能催化转糖苷产物的水解。与之前的结果一致,E338S 和 E338G 催化剂比 E338A 高效得多。此外,我们的结果表明,这些酶在用作供体的 α-D-吡喃糖基氟的水解中是无活性的,因此在合适的实验条件下,供体的自发水解速率远低于酶促转糖苷的速率,以高达 90% 的产率提供半乳糖基和葡萄糖基 β-(13)-糖苷。蛋白质数据库中可用的天然 Tt-β-Gly 的结构为通过分子建模解释我们的结果提供了良好的基础。因此,在 E338S 突变体的情况下,当供体和受体处于形成 β-(13)-糖苷键的正确位置时,系统的能量较低。(© Wiley-VCH Verlag GmbH