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Characterization of a Hydrophobic Amylase Inhibitor from Corn (Zea mays) Seeds with Activity Against Amylase from Fusarium verticillioides

August 2003 , Volume 93 , Number  8
Pages  917 - 922

Edson L. Z. Figueira , Elisa Y. Hirooka , Elizabeth Mendiola-Olaya , and Alejandro Blanco-Labra

First and second authors: Universidade Estadual de Londrina, Campus Universitário, Caixa Postal 6001, CEP 86051-990, Londrina-PR, Brazil; and third and fourth authors: Centro de Investigación y de Estudios Avanzados del IPN, Unidad Irapuato, Apdo. Postal 629, 36500 Irapuato-Gto, Mexico

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Accepted for publication 31 December 2002.

A hydrophobic 19.7-kDa amylase inhibitor (AI) was purified from corn kernels by 95% ethanol extraction and anionic exchange chromatography. The AI has an isoelectric point of 3.6 and was very stable at different pH values and high temperatures, maintaining 47.6% activity after heating to 94°C for 60 min. Amino acid analysis indicated high valine, leucine, glycine, alanine, and glutamic acid/glutamine content, and especially high valine content (41.2 mol%). This inhibitor is not a glycoprotein. It required 30-min preincubation to maximize complex enzyme-inhibitor formation when the amylase from Fusarium verticillioides was tested. The optimal pH of interaction was 6.5. It showed broad-spectrum activity including the following amylases: human saliva, porcine pancreas, F. verticillioides, as well as those from some insects of agricultural importance (Acanthoscelides obtectus, Zabrotes subfasciatus, Sitophilus zeamais, and Prostephanus truncatus). This novel hydrophobic protein not only inhibited the amylase from F. verticillioides but also decreased the conidia germination. Thus, this protein represents an approach to decrease the production of fumonisin in corn, either by using it as a molecular marker to detect fungal resistance or through genetic engineering.

© 2003 The American Phytopathological Society