The starch binding domain of glucoamylase from Aspergillus niger: Overview of its structure, function, and role in raw-starch hydrolysis

A carbohydrate-binding module is defined as a contiguous amino-acid sequence within a carbohydrate-active enzyme, with a discrete fold having carbohydrate-binding activity. Glucoamylase 1 from Aspergillus niger contains a C-terminal starch-binding domain (SBD), which is connected to the catalytic domain via a semi-rigid linker. Over the last 20 years, a combination of techniques (mutagenesis, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, isothermal titration calorimetry, ultraviolet difference spectroscopy, atomic force microscopy, protein engineering) have been used to investigate the structure-function relationships of this particular domain. This review focuses on recent findings on the structure, role in ligand binding, cooperation in the hydrolysis of granular starch, and engineering of the A. niger glucoamylase SBD.