Journal:Acta Cryst D:S2059798318014900
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The enzymatic degradation of starch has a myriad industrial applications. However, the branched nature of the polysaccharides that compose it poses problems, as branches have to be accommodated within an active centre best suited to linear polysaccharides. Alpha-amylases are glycoside hydrolases that break the α-1,4 bonds in starch and related glycans. The present work provides a rare insight into branch-point acceptance in these industrial catalysts. | The enzymatic degradation of starch has a myriad industrial applications. However, the branched nature of the polysaccharides that compose it poses problems, as branches have to be accommodated within an active centre best suited to linear polysaccharides. Alpha-amylases are glycoside hydrolases that break the α-1,4 bonds in starch and related glycans. The present work provides a rare insight into branch-point acceptance in these industrial catalysts. | ||
| - | The complex of α-amylase from ''Alicyclobacillus sp.'' 18711 (AliC) with acarbose was solved by molecular replacement, with two molecules of AliC in the asymmetric unit, at a resolution of 2.1 Å. The fold, as expected, is a canonical <scene name='79/799580/Cv/5'>three-domain arrangement</scene> with the A, B and C domains defined approximately as <span style="color:deepskyblue;background-color:black;font-weight:bold;">A, residues 4–104 and 210–397 (in deepskyblue)</span>, <span style="color:yellow;background-color:black;font-weight:bold;">B, residues 105–209 (in yellow)</span>, and <span style="color:white;background-color:black;font-weight:bold;">C, residues 398–484 (in white)</span>. A classical Ca<sup>2+</sup>–Na<sup>+</sup>–Ca<sup>2+</sup> <scene name='79/799580/Cv/6'>triad</scene> <ref name="Machius">PMID:9551551</ref>,<ref name="Brzozowski">PMID:10924103</ref> is found at the A/B-domain interface. The structure of AliC was determined in the presence of the inhibitor acarbose. As with many (retaining) α-amylase complexes, the acarbose is observed as a transglycosylated species, here a hexasaccharide which contains two of the acarviosin disaccharide motifs. The complex defines six subsites, -4 to +2, with the expected catalytic GH13 signature triad of Asp234 (nucleophile), Glu265 (acid/base) and Asp332. | + | The complex of α-amylase from ''Alicyclobacillus sp.'' 18711 (AliC) with acarbose was solved by molecular replacement, with two molecules of AliC in the asymmetric unit, at a resolution of 2.1 Å. The fold, as expected, is a canonical <scene name='79/799580/Cv/5'>three-domain arrangement</scene> with the A, B and C domains defined approximately as <span style="color:deepskyblue;background-color:black;font-weight:bold;">A, residues 4–104 and 210–397 (in deepskyblue)</span>, <span style="color:yellow;background-color:black;font-weight:bold;">B, residues 105–209 (in yellow)</span>, and <span style="color:white;background-color:black;font-weight:bold;">C, residues 398–484 (in white)</span>. A classical Ca<sup>2+</sup>–Na<sup>+</sup>–Ca<sup>2+</sup> <scene name='79/799580/Cv/6'>triad</scene> <ref name="Machius">PMID:9551551</ref>,<ref name="Brzozowski">PMID:10924103</ref> is found at the A/B-domain interface. The structure of AliC was determined in the presence of the <scene name='79/799580/Cv/8'>inhibitor acarbose</scene>. As with many (retaining) α-amylase complexes, the acarbose is observed as a transglycosylated species, here a hexasaccharide which contains two of the acarviosin disaccharide motifs. The complex defines six subsites, -4 to +2, with the expected catalytic GH13 signature triad of Asp234 (nucleophile), Glu265 (acid/base) and Asp332. |
<b>References</b><br> | <b>References</b><br> | ||
Revision as of 13:09, 21 November 2018
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