Microbial Oligo--1,6-Glucosidase: Current Developments and Future Perspectives

Oligo-alpha-1,6-glucosidase (OGL, EC 3.2.1.10) catalyzes the exo hydrolysis of alpha-1,6-glucoside bonds from the nonreducing ends of panose, palatinose, alpha-limit dextrins, and isomaltooligosaccharides (IMOs, 2-6 glucose units). It has potential applications in the production of high-glucose syrup, novel oligosaccharides and bioethanol. However, OGLs used in these processes must have sufficient acid stability, thermostability, and glucose tolerance. Detailed knowledge of the molecular basis of OGL catalysis and substrate specificities will facilitate the successful discovery and rational design of thermoacidophilic and glucose tolerant OGLs. In this review, the latest progresses on the discovery, molecular, and biochemical characterization as well as heterologous expression of OGLs are systematically summarized. The protein-thermostabilization engineering, catalytic mechanism, and structural determinants for the substrate specificities of these enzymes are also described. Finally, the potential applications and future perspectives of oligo-alpha-1,6-glucosidases are discussed.