Three-dimensional structure of a variant `Termamyl-like' Geobacillus stearothermophilusα-amylase at 1.9 Å resolution

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 α‐amylases and then exo‐acting α‐glucosidases (glucoamylases) to yield glucose, which is subsequently processed. A key enzymatic player in this pipeline is the `Termamyl' class of bacterial α‐amylases and designed/evolved variants thereof. Here, the three‐dimensional structure of one such Termamyl α‐amylase variant based upon the parent Geobacillus stearothermophilusα‐amylase is presented. The structure has been solved at 1.9 Å 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. stearothermophilusα‐amylase but with main‐chain deviations of up to 3 Å in some regions, reflecting both the mutations and differing crystal‐packing environments.