کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1391013 | 983177 | 2006 | 6 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Structure of a complex of Thermoactinomyces vulgaris R-47 α-amylase 2 with maltohexaose demonstrates the important role of aromatic residues at the reducing end of the substrate binding cleft Structure of a complex of Thermoactinomyces vulgaris R-47 α-amylase 2 with maltohexaose demonstrates the important role of aromatic residues at the reducing end of the substrate binding cleft](/preview/png/1391013.png)
Thermoactinomyces vulgaris R-47 α-amylase 2 (TVAII) can efficiently hydrolyze both starch and cyclomaltooligosaccharides (cyclodextrins). The crystal structure of an inactive mutant TVAII in a complex with maltohexaose was determined at a resolution of 2.1 Å. TVAII adopts a dimeric structure to form two catalytic sites, where substrates are found to bind. At the catalytic site, there are many hydrogen bonds between the enzyme and substrate at the non-reducing end from the hydrolyzing site, but few hydrogen bonds at the reducing end, where two aromatic residues, Trp356 and Tyr45, make effective interactions with a substrate. Trp356 drastically changes its side-chain conformation to achieve a strong stacking interaction with the substrate, and Tyr45 from another molecule forms a water-mediated hydrogen bond with the substrate. Kinetic analysis of the wild-type and mutant enzymes in which Trp356 and/or Tyr45 were replaced with Ala suggested that Trp356 and Tyr45 are essential to the catalytic reaction of the enzyme, and that the formation of a dimeric structure is indispensable for TVAII to hydrolyze both starch and cyclodextrins.
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Journal: Carbohydrate Research - Volume 341, Issue 8, 12 June 2006, Pages 1041–1046