Improved Hydrolysis of Granular Starches by a Psychrophilic α-Amylase Starch Binding Domain-Fusion

• Published in: Journal of Agricultural and Food Chemistry
• Main Authors: Wang, Yu, Tian, Yu, Zhong, Yuyue, Suleiman, Mohammad Amer, Feller, Georges, Westh, Peter, Blennow, Andreas, Møller, Marie Sofie, Svensson, Birte
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Carbohydrate-binding module; Waxy starch; Normal starch; High-amylose starch; Pseudoalteromonas haloplanktis α-amylase; Heterogenous catalysis; Sabatier principle; Antarc*; Antarctic
• Online Access: https://orbit.dtu.dk/en/publications/7f425908-feb7-495c-9f4d-18ef9b583c4f; https://doi.org/10.1021/acs.jafc.3c01898; https://backend.orbit.dtu.dk/ws/files/345932384/Post_print_Improved_Hydrolysis_of_Granular_Starches_by_a_Psychrophilic_-Amylase_Starch_Binding_Domain-Fusion.pdf

Degradation of starch granules by a psychrophilic α-amylase, AHA, from the Antarctic bacterium Pseudoalteromonas haloplanktis TAB23 was facilitated by C-terminal fusion to a starch-binding domain (SBD) from either Aspergillus niger glucoamylase (SBD GA ) or Arabidopsis thaliana glucan, water dikinase 3 (SBD GWD3 ) via a decapeptide linker. Depending on the waxy, normal or high-amylose starch type and the botanical source, the AHA-SBD fusion enzymes showed up to 3 times higher activity than AHA wild-type. The SBD-fusion thus increased the density of enzyme attack-sites and binding-sites on the starch granules by up to 5- and 7-fold, respectively, as measured using an interfacial catalysis approach that combined conventional Michaelis-Menten kinetics, with the substrate in excess, and inverse kinetics, having enzyme in excess, with enzyme-starch granule adsorption isotherms. Higher substrate affinity of the SBD GA compared to SBD GWD3 was accompanied by the superior activity of AHA-SBD GA in agreement with the Sabatier principle of adsorption limited heterogenous catalysis.