A newly cloned 4-α-glucanotransferase (αGT) from Deinococcus geothermalis and two typical bacterial αGTs from Thermus scotoductus and Escherichia coli (MalQ) were investigated. Among 4 types of catalysis, cyclization activity of αGTs that produces cycloamylose (CA), a valuable carbohydrate making inclusion complexes, was intensively studied. The new αGT, DgαGT showed close protein sequence to the αGT from T. scotoductus (TsαGT). MalQ was clearly separated from the other two αGTs in the phylogenetic and the conserved regions analyses. Reaction velocities of disproportionation, cyclization, coupling, hydrolysis of three αGTs were determined. Intriguingly, MalQ exhibited more than 100-fold lower cyclization activity than the others. To lesser extent, disproportionation activity of MalQ was relatively low. DgαGT and TsαGT showed similar kinetics results, but TsαGT had nearly 10-fold lower hydrolysis activity than DgαGT. Because of very low cyclizing activity of MalQ, DgαGT and TsαGT were selected for further analyses. When amylose was treated with DgαGT or TsαGT, CA having a broad DP range was generated immediately. DP distribution of CA had a bimodal shape (DP 7 and 27 as peaks) for the both enzymes, but larger DPs of CA quickly decreased in the DgαGT. Cyclomaltopentaose, a rare cyclic sugar, was produced at early reaction stage and accumulated as the reactions went by in the both enzymes, but the increase was more profound in the TsαGT. Taken together, we clearly demonstrated the catalytic differences between αGT groups from thermophilic and pathogenic bacteria that implies different roles of the αGTs in different lifestyles.

中文翻译：

---

比较细菌 4-α-葡聚糖转移酶的催化特性，重点是它们的环化活性。

研究了一种新克隆的来自地热异常球菌的 4-α-葡聚糖转移酶 (αGT)和来自Thermus scotoductus和大肠杆菌(MalQ) 的两种典型细菌 αGT 。在 4 种催化类型中，对产生环直链淀粉 (CA) 的 αGT 的环化活性进行了深入研究，环直链淀粉是一种有价值的碳水化合物制造包合物。新的 αGT，DgαGT 显示出与T. scotoductus的 αGT 接近的蛋白质序列(TsαGT)。在系统发育和保守区域分析中，MalQ 与其他两个 αGT 明显分开。测定了三种αGT的歧化、环化、偶联、水解反应速度。有趣的是，MalQ 的环化活性比其他的低 100 多倍。在较小程度上，MalQ 的歧化活性相对较低。DgαGT 和 TsαGT 表现出相似的动力学结果，但 TsαGT 的水解活性比 DgαGT 低近 10 倍。由于 MalQ 的环化活性非常低，因此选择 DgαGT 和 TsαGT 进行进一步分析。当用 DgαGT 或 TsαGT 处理直链淀粉时，立即生成具有宽 DP 范围的 CA。对于这两种酶，CA 的 DP 分布具有双峰形状（DP 7 和 27 作为峰），但较大的 CA DP 在 DgαGT 中迅速降低。Cyclomaltopentaose 是一种罕见的环状糖，在早期反应阶段产生并随着反应的进行在两种酶中积累，但 TsαGT 中的增加更为深刻。综上所述，我们清楚地证明了来自嗜热菌和致病菌的 αGT 组之间的催化差异，这意味着 αGT 在不同生活方式中的不同作用。