Multimolecular Complexes of α-Amylase with Glycogen Limit Dextrin

Hog pancreatic α-amylase interacted with macromolecular limit dextrins of glycogen to form stable complexes. These were characterized by ultracentrifugation, light scattering, and electron microscopy. The sedimentation coefficient of the complex varied in the range of 7 S to 23 S depending on the dextrin to enzyme ratio in the reaction mixture. The S values of the enzyme and the dextrin were about 4.5 and 3, respectively. Light scattering measurements showed that the complex reached a molecular weight of about 3 x 105. Since the molecular weight of the enzyme and the dextrin were 5 x 104 and 7 x 104, respectively, it could be concluded that the enzyme and the dextrin interact to form a multimolecular complex. Electron microscopy indeed indicated formation of chains consisting of several units. The existence on the enzyme of two apparently independent binding sites, required for the formation of a multimolecular complex, was also demonstrated. Measurements by equilibrium dialysis showed that 1 mole of enzyme specifically bound 2 moles of maltotriose.