title: Selective inhibition of histidine-modified pancreatic alpha-amylase by proteinaceous inhibitor from Phaseolus vulgaris.
abstract: Chemical modification of two histidine residues of porcine pancreatic alpha-amylase (EC 3.2.1.1) by diethyl pyrocarbonate in the presence of a high concentration of maltotriose caused a decrease of amylase activity and an increase of maltosidase activity (hydrolysis of p-nitrophenyl-alpha-maltoside). By binding a proteinaceous inhibitor from Phaseolus vulgaris (white kidney bean) with the modified enzyme, the amylase activity was further decreased but the maltosidase activity was retained to about 100% that of the native enzyme. Both amylase and maltosidase activities of the native enzyme were almost completely inhibited by the proteinaceous inhibitor. The increase of maltosidase activity by histidine modification was due to an increase of kcat, whereas the Km value was not changed; but binding of the proteinous inhibitor affected mainly the Km value of the modified enzyme.
authors.affiliation: Department of Food Science and Technology, Faculty of Agriculture, Kyoto University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nakatani
mesh_terms: D000818:Animals; D001665:Binding Sites; D004047:Diethyl Pyrocarbonate; D004791:Enzyme Inhibitors / Q000302:isolation & purification / Q000494:pharmacology*; D007887:Fabaceae / Q000032:analysis*; D006639:Histidine / Q000502:physiology; D007700:Kinetics; D010940:Plant Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D010946:Plants, Medicinal; D013552:Swine; D014312:Trisaccharides / Q000494:pharmacology; D000516:alpha-Amylases / Q000037:antagonists & inhibitors*
chemical_list: D004791:Enzyme Inhibitors; D010940:Plant Proteins; D014312:Trisaccharides; D006639:Histidine; C008317:maltotriose; D000516:alpha-Amylases; D004047:Diethyl Pyrocarbonate