Hui Song
Chinese Academy of Science, China
Title: Study of CBM68: New family of carbohydrate binding modules from a novel type I pullulanase
Biography
Biography: Hui Song
Abstract
Carbohydrate binding modules (CBM) are functional domains most commonly found in carbohydrate active enzymes. The kind of domains can specifically bind to the carbohydrates and play important role in hydrolysis activity and structure stabilization of the parent enzymes. We identified a novel CBM (CBM68 by CAZy database) from a newly discovered Anoxybacillus sp. pullulanase. The truncation of CBM68 resulted in the reduction of enzymatic activity and thermo-stability. In this study we reveal the recognition mechanism of CBM68 with the glycan substrates using site directed mutagenesis in combination with the X-ray crystal structure data. In addition, we also demonstrate further the effects of CBM68 on the catalysis properties and thermo-stability by designed a series of recombinant fusion pullulanases and measured properties through replacing or superposing the N-terminal domain of PulA (CBM68) and an acidic pullulanase (CBM41), respectively. All of the recombinant fusion pullulanases showed varying degrees of changes on the catalytic properties. Among them, two recombinant fusion pullulanases with the optimal pH at 3.5 showed more suitable for starch industry than their wild type. Meanwhile, the results will provide molecular basis for ration design in order to obtain novel pullulanase with enhanced catalytic efficiency.