Characterization and functional properties of the alpha-amylase inhibitor (alpha-AI) from kidney bean (Phaseolus vulgaris) seeds.
Alpha-amylase inhibitor (alpha-AI) from kidney bean (Phaseolus vulgaris L. cv Tendergreen) seeds has been purified to homogeneity by heat treatment in acidic medium, ammonium sulphate fractionation, chromatofocusing and gel filtration. Two isoforms, alpha-AI1 and alpha-AI1', of 43 kDa have been isolated which differ from each other by their isoelectric points and neutral sugar contents. The major isoform alpha-AI1 inhibited human and porcine pancreatic alpha-amylases (PPA) but was devoid of activity on alpha-amylases of bacterial or fungal origins. As shown on the Lineweaver-Burk plots, the nature of the inhibition is explained by a mixed non-competitive inhibition mechanism. Alpha-AI1 formed a 1:2 stoichiometric complex with PPA which showed an optimum pH of 4.5 at 30 degrees C. Owing to the low optimum pH found for alpha-AI activity, inhibitor-containing diets such as beans or transgenic plants expressing alpha-AI should be devoid of any harmful effect on human health.
Le Berre-Anton
V
V
Institut de Pharmacologie et Biologie Structurale, UPS-CNRS No. 9062, Toulouse, France.
Bompard-Gilles
C
C
Payan
F
F
Rougé
P
P
D000818:Animals; D007887:Fabaceae / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010946:Plants, Medicinal; D013552:Swine; D013696:Temperature; D014361:Trypsin Inhibitors; D000516:alpha-Amylases / Q000037:antagonists & inhibitors
D010940:Plant Proteins; D014361:Trypsin Inhibitors; D000516:alpha-Amylases