PMID: 18588886

Authors:

Nielsen MM, Seo ES, Bozonnet S, Aghajari N, Robert X, Haser R, Svensson B

Title:

Multi-site substrate binding and interplay in barley alpha-amylase 1.

Journal:

FEBS Lett. 2008 Jul 23;582(17):2567-71. Epub 2008 Jun 25.

Abstract:

Certain starch hydrolases possess secondary carbohydrate binding sites outside of the active site, suggesting that multi-site substrate interactions are functionally significant. In barley alpha-amylase both Tyr380, situated on a remote non-catalytic domain, and Tyr105 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 Tyr380 and Tyr105 is important, albeit not essential for binding, degradation, and multiple attack on polysaccharides, while Tyr105 predominates in oligosaccharide hydrolysis. Additional delicate structure/function relationships of the secondary site are uncovered using Y380A/H395A, Y380A, and H395A AMY1 mutants.