title: Isolation and characterization of the subunits of a heat-labile alpha-amylase inhibitor from Phaseolus vulgaris white kidney bean.
abstract: The heat-labile one of the two alpha-amylase inhibitors of the white kidney bean (Phaseolus vulgaris) was found to be composed of three kinds of subunits, and they were isolated and characterized. The alpha-subunit was free from tryptophan and cysteine and the beta-subunit contained no methionine or cysteine. There was no marked resemblance in tryptic peptide maps between the alpha- and beta-subunit polypeptides. The alpha-subunit contained 30% by weight of carbohydrate, mainly made up of high mannose-oligosaccharides, and the sugar moiety of the beta-subunit amounted 7% and appeared to be predominantly composed of xylomannose-type oligosaccharides. The largest subunit, gamma, was very similar in molecular features to a postulated alpha beta-dimer and its N-terminal sequence coincided with that of the alpha-subunit. The molecular weights of the polypeptides of alpha, beta-, and gamma-subunits were shown to be 7,800, 14,000, and 22,000, respectively, by SDS-PAGE. It seemed likely that the alpha- and beta-subunits are common to both of the inhibitors and that the heat-lability of this inhibitor arises from the gamma-subunit.
authors.affiliation: Department of Agricultural Chemistry, College of Agriculture, University of Osaka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yamaguchi
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000606:Amino Sugars / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D004591:Electrophoresis, Polyacrylamide Gel; D006358:Hot Temperature; D037102:Lectins / Q000032:analysis / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010449:Peptide Mapping; D037121:Plant Lectins; D010940:Plant Proteins; D014674:Plant Proteins, Dietary / Q000032:analysis / Q000302:isolation & purification*; D000516:alpha-Amylases / Q000037:antagonists & inhibitors*
chemical_list: D000596:Amino Acids; D000606:Amino Sugars; D037102:Lectins; D037121:Plant Lectins; D010940:Plant Proteins; D014674:Plant Proteins, Dietary; C061510:alpha-amylase inhibitor, Phaseolus vulgaris; D000516:alpha-Amylases