title: Studies on the substrate specificity of Taka-amylase A1. XIV. Preparation of 6-deoxy-6-halogenomaltotrioses and their hydrolysis by Taka-amylase A.
abstract: 1. O-6-Deoxy-alpha-D-glucopyranosyl-(1 leads to 4)-O-alpha-D-glucopyranosyl-(1 leads to 4)-D-glucopyranose, O-6-chloro-6-deoxy-alpha-D-glucopyranosyl-(1 leads to 4)-O-alpha-D-glucopyranosyl-(1 leads to 4)-D-glucopyranose, O-6-bromo-6-deoxy-alpha-D-glucopyranosyl-(1 leads to 4)-O-alpha-D-glucopyranosyl-(1 leads to 4)-D-glucopyranose, and O-6-deoxy-6-iodo-alpha-D-glucopyranosyl-(1 leads to 4)-O-alpha-D-glucopyranosyl-(1 leads to 4)-D-glucopyranose were prepared, taking advantage of the substrate specificities of Taka-amylase A and glucoamylase, and the action of Taka-amylase A on these substrates was investigated. 2. The Michaelis constant Km and the molecular activity ko were determined at 37 degrees C and pH 5.2 using the modified maltotrioses. The values of Km and ko decreased upon modification of maltotriose and those of ko/Km were in agreement with the comparative initial rates for the corresponding derivatives of phenyl alpha-maltoside at low substrate concentrations. This result suggested that a subsite of the enzyme may have a specific interaction with halogen atoms in the substrate. 3. All halogenomaltotrioses examined showed substrate inhibition at high substrate concentrations.
mesh_terms: D000681:Amylases / Q000378:metabolism*; D003837:Deoxy Sugars; D007700:Kinetics; D008968:Molecular Conformation; D009844:Oligosaccharides; D013379:Substrate Specificity; D014312:Trisaccharides; D000516:alpha-Amylases / Q000378:metabolism*
chemical_list: D003837:Deoxy Sugars; D009844:Oligosaccharides; D014312:Trisaccharides; D000681:Amylases; D000516:alpha-Amylases