State Key Laboratory of Dairy Biotechnology, Shanghai Engineering Research Center of Dairy Biotechnology, Dairy Research Institute, Bright Dairy and Food Co., Ltd., Shanghai, China.
Synergetic Innovation Center for Food Safety and Nutrition, Jiangnan University, Wuxi, China.
Appl Environ Microbiol. 2018 Apr 16;84(9). doi: 10.1128/AEM.02810-17. Print 2018 May 1.
Glucansucrases (GSs) in glycoside hydrolase family 70 (GH70) catalyze the synthesis of α-glucans from sucrose, a reaction that is widely seen in lactic acid bacteria (LAB). These enzymes have been implicated in many aspects of microbial life. Products of GSs have great commercial value as food supplements and medical materials; therefore, these enzymes have attracted much attention from both science and industry. Certain issues concerning the origin and evolution of GSs are still to be addressed, although an increasing number of GH70 enzymes have been characterized. This study describes a GS enzyme with the appearance of a branching sucrase (BrS). Structural analysis indicated that this GS enzyme produced a type of glucan composed of an α-(1→6) glucosidic backbone and α-(1→4) branches, as well as a considerable amount of α-(1→3) branches, distinguishing it from the GSs identified so far. Moreover, sequence-based analysis of the catalytic core of this enzyme suggested that it might be an evolutionary intermediate between the BrS and GS subgroups. These results provide an evolutionary link between these subgroups of GH70 enzymes and shed new light on the origination of GSs. GH70 GSs catalyze the synthesis of α-glucans from sucrose, a reaction that is widely seen in LAB. Products of these enzymes have great commercial value as food supplements and medical materials. Moreover, these enzymes have attracted much attention from scientists because they have potential in tailored synthesis of α-glucans with desired structures and properties. Although more and more GSs have been characterized, the origin and evolution of these enzymes have not been well addressed. This study describes a GS with the appearance of a BrS (i.e., high levels of similarity to BrSs in sequence analysis). Further analysis indicated that this enzyme synthesized a type of insoluble glucan composed of an α-(1→6) glucosidic backbone and many α-(1→4)- and α-(1→3)-linked branches, the linkage composition of which has rarely been reported in the literature. This BrS-like GS enzyme might be an evolutionary intermediate between BrS and GS enzymes.
葡聚糖蔗糖酶（GSs）属于糖苷水解酶家族 70（GH70），能够催化蔗糖合成α-葡聚糖，这一反应广泛存在于乳酸菌（LAB）中。这些酶在微生物生命的许多方面都发挥着重要作用。GSs 的产物作为食品补充剂和医疗材料具有巨大的商业价值；因此，这些酶引起了科学界和工业界的广泛关注。尽管已经有越来越多的 GH70 酶被鉴定出来，但关于 GSs 的起源和进化仍有一些问题尚未解决。本研究描述了一种具有分支蔗糖酶（BrS）外观的 GS 酶。结构分析表明，这种 GS 酶产生的葡聚糖由α-（1→6）糖苷键主链和α-（1→4）支链以及相当数量的α-（1→3）支链组成，与迄今为止鉴定的 GSs 不同。此外，对该酶催化核心的序列分析表明，它可能是 BrS 和 GS 亚组之间的进化中间体。这些结果为 GH70 酶的这些亚组之间提供了进化联系，并为 GSs 的起源提供了新的认识。GH70 GSs 能够催化蔗糖合成α-葡聚糖，这一反应广泛存在于 LAB 中。这些酶的产物作为食品补充剂和医疗材料具有巨大的商业价值。此外，由于它们在具有所需结构和性质的α-葡聚糖的定制合成方面具有潜力，因此这些酶引起了科学家们的广泛关注。尽管已经有越来越多的 GSs 被鉴定出来，但这些酶的起源和进化仍未得到很好的解决。本研究描述了一种具有 BrS 外观的 GS（即序列分析中与 BrS 高度相似）。进一步的分析表明，这种酶合成了一种不溶性葡聚糖，由α-（1→6）糖苷键主链和许多α-（1→4）-和α-（1→3）-连接的支链组成，其连接组成在文献中很少报道。这种 BrS 样 GS 酶可能是 BrS 和 GS 酶之间的进化中间体。
