Starch debranching enzymes (SDBEs) hydrolyze the α-1,6 glycosidic bonds in polysaccharides such as starch, amylopectin, pullulan and glycogen. SDBEs are also important enzymes for the preparation of sugar syrup, resistant starch and cyclodextrin. As the synergistic catalysis of SDBEs and other starch-acting hydrolases can effectively improve the raw material utilization and production efficiency during starch processing steps such as saccharification and modification, they have attracted substantial research interest in the past decades. The substrate specificities of the two major members of SDBEs, pullulanases and isoamylases, are quite different. Pullulanases generally require at least two α-1,4 linked glucose units existing on both sugar chains linked by the α-1,6 bond, while isoamylases require at least three units of α-1,4 linked glucose. SDBEs mainly belong to glycoside hydrolase (GH) family 13 and 57. Except for GH57 type II pullulanse, GH13 pullulanases and isoamylases share plenty of similarities in sequence and structure of the core catalytic domains. However, the N-terminal domains, which might be one of the determinants contributing to the substrate binding of SDBEs, are distinct in different enzymes. In order to overcome the current defects of SDBEs in catalytic efficiency, thermostability and expression level, great efforts have been made to develop effective enzyme engineering and fermentation strategies. Herein, the diverse biochemical properties and distinct features in the sequence and structure of pullulanase and isoamylase from different sources are summarized. Up-to-date developments in the enzyme engineering, heterologous production and industrial applications of SDBEs is also reviewed. Finally, research perspective which could help understanding and broadening the applications of SDBEs are provided.

淀粉脱支酶 (SDBE) 可水解淀粉、支链淀粉、支链淀粉和糖原等多糖中的 α-1,6 糖苷键。SDBEs也是制备糖浆、抗性淀粉和环糊精的重要酶。由于 SDBE 和其他淀粉作用水解酶的协同催化可以有效提高淀粉加工步骤（如糖化和改性）中的原料利用率和生产效率，因此在过去的几十年中引起了广泛的研究兴趣。SDBE 的两个主要成员支链淀粉酶和异淀粉酶的底物特异性完全不同。普鲁兰酶通常需要至少两个 α-1,4 连接的葡萄糖单元存在于通过 α-1,6 键连接的两条糖链上，而异淀粉酶需要至少三个 α-1,4 连接的葡萄糖单元。SDBE 主要属于糖苷水解酶 (GH) 家族 13 和 57。除 GH57 II 型支链淀粉酶外，GH13 支链淀粉酶和异淀粉酶在核心催化域的序列和结构上有很多相似之处。然而，可能是促成 SDBE 底物结合的决定因素之一的 N 端结构域在不同的酶中是不同的。为了克服目前 SDBEs 在催化效率、热稳定性和表达水平方面的缺陷，人们努力开发有效的酶工程和发酵策略。在此，总结了不同来源的支链淀粉酶和异淀粉酶在序列和结构中的不同生化特性和不同特征。酶工程的最新进展，还回顾了 SDBE 的异源生产和工业应用。最后，提供了有助于理解和拓宽 SDBE 应用的研究视角。