α-Amylase inhibitors were purified from Tora bean and Uzura bean by water extraction, ammonium sulfate fractionation, DEAE-Sepharose FF ion-exchange chromatography and Sephacryl S-200HR gel filtration and referred to as TAI and UAI, respectively. Isoelectric points of TAI and UAI were 4.6 and 4.54. The carbohydrate content was determined to be about 15% for both inhibitors by the phenol sulfuric acid method. TAI and UAI had the same molecular weight of about 45,000 and showed extremely similar amino acid compositions to each other. Subunit components of TAI and UAI were detected by SDS-PAGE and each inhibitor was found to be composed of at least four kinds of subunit with molecular weights between 14,000 and 20,000. TAI and UAI also showed almost the same heat stability and inhibitory activity against porcine pancreatic α-amylase. These results suggest that α-amylase inhibitors, TAI and UAI were the same protein
