Glycoside hydrolase family 57 glycogen branching enzymes (GH57GBE) catalyze the formation of an α-1,6 glycosidic bond between α-1,4 linked glucooliogosaccharides. As an atypical family, a limited number of GH57GBEs have been biochemically characterized so far. This study aimed at acquiring a better understanding of the GH57GBE family by a systematic sequence-based bioinformatics analysis of almost 2500 gene sequences and determining the branching activity of several native and mutant GH57GBEs. A correlation was found in a very low or even no branching activity with the absence of a flexible loop, a tyrosine at the loop tip, and two β-strands.

中文翻译：

---

决定糖苷水解酶家族 57 糖原分支酶转糖基化活性的结构元素

糖苷水解酶家族 57 糖原分支酶 (GH57GBE) 催化 α-1,4 连接的葡糖寡糖之间形成 α-1,6 糖苷键。作为一个非典型家族，迄今为止已经对有限数量的 GH57GBE 进行了生化表征。本研究旨在通过对近 2500 个基因序列进行系统的基于序列的生物信息学分析，并确定几种天然和突变 GH57GBE 的分支活性，从而更好地了解 GH57GBE 家族。在非常低或什至没有分支活性中发现了与没有柔性环、环尖端处的酪氨酸和两个β-链的相关性。