Le Berre-Anton, V.; Bompard-Gilles, C.; Payan, F.; Rouge, P.
JOURNAL NAME- Biochim Biophys Acta
VOL. 1343
1997 Nov 14
PP. 31-40
DOCUMENT TYPE- Journal Article
JOURNAL CODE- 0217513
JOURNAL SUBSET- MEDJSIM
ISSN- 0006-3002
CORPORATE AUTHOR- Institut de Pharmacologie et Biologie Structurale, UPS-CNRS No. 9062, Toulouse, France.
PUBLICATION COUNTRY- NETHERLANDS
LANGUAGE- English NDN- 236-0056-0578-3

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.