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

• Published in: Journal of agricultural and food chemistry Vol. 71; no. 23; pp. 9040 - 9050
• Main Authors: Wang, Yu, Tian, Yu, Zhong, Yuyue, Suleiman, Mohammad Amer, Feller, Georges, Westh, Peter, Blennow, Andreas, Møller, Marie Sofie, Svensson, Birte
• Format: Journal Article Web Resource
• Language: English
• Published: United States American Chemical Society 14-06-2023
• Subjects: Biochemistry, biophysics & molecular biology; Biochimie, biophysique & biologie moléculaire; Biotechnology and Biological Transformations; Life sciences; Sciences du vivant; heterogenous catalysis; Sabatier principle; high-amylose starch; normal starch; waxy starch; carbohydrate-binding module; Pseudoalteromonas haloplanktis α-amylase
• ISSN: 0021-8561; 1520-5118; 1520-5118
• DOI: 10.1021/acs.jafc.3c01898

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 (SBDGA) or Arabidopsis thaliana glucan, water dikinase 3 (SBDGWD3) 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 SBDGA compared to SBDGWD3 was accompanied by the superior activity of AHA-SBDGA in agreement with the Sabatier principle of adsorption limited heterogenous catalysis.