Luzio G A, Parnaik V K, Mayer R M
Carbohydr Res. 1983 Sep 16;121:269-78. doi: 10.1016/0008-6215(83)84023-3.
A D-glucosylated form of dextransucrase, whose preparation and characteristics have just been reported in Carbohydr. Res., was employed in a series of studies designed to explore the question of whether the bound sugars participate in the reactions catalyzed by the enzyme. When exposed to maltose, a good acceptor-substrate, monomeric D-glucosyl groups were rapidly transferred to the disaccharide, affording a trisaccharide. In the absence of an acceptor, monomeric D-glucose was released from the enzyme by hydrolysis. In a reaction with D-fructose, the charged enzyme catalyzed the formation of sucrose. Finally, in the presence of unlabeled sucrose, monomeric D-glucosyl groups were chased into enzyme-associated oligomers. Evidence is also presented which indicates that the various pathways for the bound D-glucosyl groups are competitive. The significance of these observations is discussed.
一种葡聚糖蔗糖酶的D-葡萄糖基化形式，其制备方法和特性刚刚在《碳水化合物研究》上报道，被用于一系列研究中，旨在探讨结合糖是否参与该酶催化的反应这一问题。当暴露于麦芽糖（一种良好的受体底物）时，单体D-葡萄糖基迅速转移到二糖上，生成一种三糖。在没有受体的情况下，单体D-葡萄糖通过水解从酶中释放出来。在与D-果糖的反应中，带电荷的酶催化蔗糖的形成。最后，在未标记蔗糖存在的情况下，单体D-葡萄糖基被追踪到与酶相关的寡聚物中。还提供了证据表明结合的D-葡萄糖基的各种途径是相互竞争的。讨论了这些观察结果的意义。
