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Multi‐site substrate binding and interplay in barley α‐amylase 1
Author(s) -
Nielsen Morten Munch,
Seo Eun-Seong,
Bozonnet Sophie,
Aghajari Nushin,
Robert Xavier,
Haser Richard,
Svensson Birte
Publication year - 2008
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2008.06.027
Subject(s) - active site , binding site , chemistry , amylase , biochemistry , substrate (aquarium) , oligosaccharide , carbohydrate binding module , starch , mutant , hydrolysis , glycoside hydrolase , carbohydrate , enzyme , biology , ecology , gene
Certain starch hydrolases possess secondary carbohydrate binding sites outside of the active site, suggesting that multi‐site substrate interactions are functionally significant. In barley α‐amylase both Tyr 380 , situated on a remote non‐catalytic domain, and Tyr 105 in subsite −6 of the active site cleft are principal carbohydrate binding residues. The dual active site/secondary site mutants Y105A/Y380A and Y105A/Y380M show that each of Tyr 380 and Tyr 105 is important, albeit not essential for binding, degradation, and multiple attack on polysaccharides, while Tyr 105 predominates in oligosaccharide hydrolysis. Additional delicate structure/function relationships of the secondary site are uncovered using Y380A/H395A, Y380A, and H395A AMY1 mutants.