Transglucosidases belonging to the glycoside hydrolase (GH) family 70 are promising enzymatic tools for the synthesis of α-glucans with defined structures from renewable sucrose and starch substrates. Depending on the GH70 enzyme specificity, α-glucans with different structures and physicochemical properties are produced, which have found diverse (potential) commercial applications, e.g. in food, health and as biomaterials. Originally, the GH70 family was established only for glucansucrase enzymes of lactic acid bacteria that catalyze the synthesis of α-glucan polymers from sucrose. In recent years, we have identified 3 novel subfamilies of GH70 enzymes (designated GtfB, GtfC and GtfD), inactive on sucrose but converting starch/maltodextrin substrates into novel α-glucans. These novel starch-acting enzymes considerably enlarge the panel of α-glucans that can be produced. They also represent very interesting evolutionary intermediates between sucrose-acting GH70 glucansucrases and starch-acting GH13 α-amylases. Here we provide an overview of the repertoire of GH70 enzymes currently available with focus on these novel starch-acting GH70 enzymes and their biotechnological potential. Moreover, we discuss key developments in the understanding of structure-function relationships of GH70 enzymes in the light of available three-dimensional structures, and the protein engineering strategies that were recently applied to expand their natural product specificities.

属于糖苷水解酶（GH）家族70的转葡糖苷酶是从可再生蔗糖和淀粉底物中合成具有确定结构的α-葡聚糖的有前途的酶促工具。取决于GH70酶的特异性，产生具有不同结构和理化性质的α-葡聚糖，其已发现多种（潜在的）商业应用，例如在食品，健康和作为生物材料中。最初，GH70家族仅建立用于乳酸菌的葡聚糖蔗糖酶，该酶催化从蔗糖合成α-葡聚糖聚合物。近年来，我们已经确定了3个新的GH70酶亚家族（命名为GtfB，GtfC和GtfD），它们对蔗糖没有活性，但是将淀粉/麦芽糊精底物转化为新型α-葡聚糖。这些新颖的淀粉作用酶大大扩大了可生产的α-葡聚糖的种类。它们还代表了作用于蔗糖的GH70葡聚糖酶和作用于淀粉的GH13α-淀粉酶之间非常有趣的进化中间体。在这里，我们提供了目前可用的GH70酶库的概述，重点是这些新颖的淀粉作用GH70酶及其生物技术潜力。此外，我们讨论了根据可用的三维结构理解GH70酶的结构-功能关系的关键进展，以及最近用于扩展其天然产物特异性的蛋白质工程策略。在这里，我们提供了目前可用的GH70酶库的概述，重点是这些新颖的淀粉作用GH70酶及其生物技术潜力。此外，我们讨论了根据可用的三维结构理解GH70酶的结构-功能关系的关键进展，以及最近用于扩展其天然产物特异性的蛋白质工程策略。在这里，我们提供了目前可用的GH70酶库的概述，重点是这些新颖的淀粉作用GH70酶及其生物技术潜力。此外，我们讨论了根据可用的三维结构理解GH70酶的结构-功能关系的关键进展，以及最近用于扩展其天然产物特异性的蛋白质工程策略。