Sequence, Structure, and Engineering of Microbial Starch Debranching Enzymes

Starch dedifferentiating enzymes (SDBEs) belong mainly to the glycoside hydrolase (GH) family 13 and 57, except for type II pullulanases of GH57, GH13 pullulanase, and isoamylases, which share many similarities in the sequence and structure of the core catalytic domain. However, the N-terminal structural domain, which may be one of the determinants contributing to the substrate binding of SDBEs, is different in the different enzymes. To overcome the present deficiencies of SDBEs in terms of chemical action potency, thermal stability, and expression levels, great efforts have been made to develop effective accelerator engineering and fermentation methods. Herein, we summarize the different biochemical properties of pullulanase and isopentosidase from different sources as well as the distinctive features in sequence and structure. Recent developments in the enzymatic engineering, heterologous production, and industrial applications of SDBEs are also reviewed. Finally, research perspectives that contribute to the understanding and broadening of SDBE applications are provided.