Structure of the AliC GH13 α−amylase from Alicyclobacillus sp, reveals accommodation of starch branching points in the α−amylase family

Jon Agirre, Olga V. Moroz, Sebastian Meier, Jesper Braak, Astrid Munch, Tine Hoff, Carsten Anderson, Keith S. Wilson*, Gideon J. Davies

*Corresponding author for this work

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Abstract

α−amylases are glycoside hydrolases that break the α−1,4 bonds in starch and related glycans. The degradation of starch is rendered difficult by varying degrees of α−1,6 branch points and their possible accommodation within the active centre of α−amylase enzymes. Given the myriad industrial uses for starch and thus also for α−amylase-catalysed starch degradation and modification, there is considerable interest in how different α−amylases might accommodate these branches thus impacting on the potential limit dextrins and societal applications. Here, we sought to probe the branch-point accommodation of the Alicyclobacillus sp. CAZy family GH13 α−amylase, prompted by our observation of a molecule of glucose in the position that may represent a branch point in an acarbose complex solved at 2.1 Å resolution. Limit digest analysis, by 2D NMR, using both pullulan (a regular linear polysaccharide of α−1,4, α−1,4, α−1,6 repeating trisaccharides) and amylopectin starch showed how the Alicyclobacillus sp enzyme could accept α−1,6 branches in, at least, -2, +1 and +2 subsites consistent with 3-D structures with glucosyl moieties in +1 and +2 subsites and the solvent exposure of the -2 6-hydroxyl group. Together the work provides a rare insight into branch point acceptance in these industrial catalysts.
Original languageEnglish
JournalActa crystallographica Section D: Structural biology
Volume75
Issue number1
Pages (from-to)1-7
Number of pages7
ISSN2059-7983
DOIs
Publication statusPublished - 2019

Keywords

  • AliC GH13 α-analyse
  • Starch brancing points
  • Glycoside hydrolases
  • Pullulan
  • Carbohydrate-active enzymes
  • Alicyclobacillus

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