The structure of the AliC GH13 α-amylase from Alicyclobacillus sp. reveals the accommodation of starch branching points in the α-amylase family

TY - JOUR

T1 - The structure of the AliC GH13 α-amylase from Alicyclobacillus sp. reveals the accommodation of starch branching points in the α-amylase family

AU - Agirre, Jon

AU - Moroz, Olga

AU - Meier, Sebastian

AU - Brask, Jesper

AU - Munch, Astrid

AU - Hoff, Tine

AU - Andersen, Carsten

AU - Wilson, Keith S

AU - Davies, Gideon J

N1 - open access.

PY - 2019/1/1

Y1 - 2019/1/1

N2 - 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 the presence of 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 processing of highly branched post-hydrolysis remnants (known as limit dextrins) and societal applications. Here, it was sought to probe the branch-point accommodation of the Alicyclobacillus sp. CAZy family GH13 α-amylase AliC, prompted by the observation of a molecule of glucose in a position that may represent a branch point in an acarbose complex solved at 2.1 Å resolution. Limit digest analysis by two-dimensional 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 the -2, +1 and +2 subsites, consistent with the three-dimensional structures with glucosyl moieties in the +1 and +2 subsites and the solvent-exposure of the -2 subsite 6-hydroxyl group. Together, the work provides a rare insight into branch-point acceptance in these industrial catalysts.

AB - 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 the presence of 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 processing of highly branched post-hydrolysis remnants (known as limit dextrins) and societal applications. Here, it was sought to probe the branch-point accommodation of the Alicyclobacillus sp. CAZy family GH13 α-amylase AliC, prompted by the observation of a molecule of glucose in a position that may represent a branch point in an acarbose complex solved at 2.1 Å resolution. Limit digest analysis by two-dimensional 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 the -2, +1 and +2 subsites, consistent with the three-dimensional structures with glucosyl moieties in the +1 and +2 subsites and the solvent-exposure of the -2 subsite 6-hydroxyl group. Together, the work provides a rare insight into branch-point acceptance in these industrial catalysts.

KW - AliC GH13 α-amylase

KW - Alicyclobacillus

KW - carbohydrate-active enzymes

KW - glycoside hydrolases

KW - pullulan

KW - starch branching points

U2 - 10.1107/S2059798318014900

DO - 10.1107/S2059798318014900

M3 - Article

C2 - 30644839

SN - 2059-7983

VL - 75

SP - 1

EP - 7

JO - Acta crystallographica. Section D, Structural biology

JF - Acta crystallographica. Section D, Structural biology

IS - 1

ER -