alpha-Amylase adsorption on starch crystallites.
The goal of this work was to characterize the adsorption of Bacillus subtills alpha-amylase onto crystalline starchy materials of the B-type polymorph. Monodisperse spherulitic particles (R approximately equal to 5.0 microm), essentially resistant to alpha-amylolysis at 25 degrees C were prepared from short amylose chains (DP(n) approximately equal to 15). The alpha-amylase adsorbed specifically onto the spherulites, and adsorption was found to be a prerequisite step for hydrolysis. Adsorption was inhibited by the presence of maltose and maltotriose in the reaction mixture. Adsorption isotherm of the enzyme on the particles showed a well developed plateau of 1.62 microg/cm(2) at 25 degrees C corresponding to a monolayer adsorption process. The binding free energy calculated from the initial slope of the isotherm was DeltaG approximately equal to -20.7 kJ/mol. This is smaller than published values for the binding of alpha-amylase to soluble amylosic chains (DeltaG < -30 kJ/mol).
Leloup
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Institut National de la Recherche Agronomique, BP 527-44026 Nantes Cedex 03, France.
Colonna
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Ring
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