Recombinant bacterial amylopullulanases Developments and perspectives

Pullulanases are endo-acting enzymes capable of hydrolyzing alpha-1,6-glycosidic linkages in starch, pullulan, amylopectin, and related oligosaccharides, while amylopullulanases are bifunctional enzymes with an active site capable of cleaving both alpha-1,4 and alpha-1,6 linkages in starch, amylose and other oligosaccharides, and alpha-1,6 linkages in pullulan. The amylopullulanases are classified in GH13 and GH57 family enzymes based on the architecture of catalytic domain and number of conserved sequences. The enzymes with two active sites, one for the hydrolysis of alpha-1,4-glycosidic bond and the other for alpha-1,6-glycosidic bond, are called alpha-amylase-pullulanases, while amylopullulanases have only one active site for cleaving both alpha-1,4- and alpha-1,6-glycosidic bonds. The amylopullulanases produced by bacteria find applications in the starch and baking industries as a catalyst for one step starch liquefaction-saccharification for making various sugar syrups, as antistaling agent in bread and as a detergent additive.