Three-dimensional structure of a variant 'Termamyl-like' Geobacillus stearothermophilus alpha-amylase at 1.9 angstrom resolution

摘要

The enzyme-catalysed degradation of starch is central to many industrial processes, including sugar manufacture and first-generation biofuels. Classical biotechnological platforms involve steam explosion of starch followed by the action of endo-acting glycoside hydrolases termed -amylases and then exo-acting -glucosidases (glucoamylases) to yield glucose, which is subsequently processed. A key enzymatic player in this pipeline is the `Termamyl' class of bacterial -amylases and designed/evolved variants thereof. Here, the three-dimensional structure of one such Termamyl -amylase variant based upon the parent Geobacillus stearothermophilus-amylase is presented. The structure has been solved at 1.9 angstrom resolution, revealing the classical three-domain fold stabilized by Ca2+ and a Ca2+-Na+-Ca2+ triad. As expected, the structure is similar to the G. stearothermophilus-amylase but with main-chain deviations of up to 3 angstrom in some regions, reflecting both the mutations and differing crystal-packing environments.