Divergence in properties of two closely related α-amylase inhibitors of barley |
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Authors: | Gloria García-Casado Rosa Sánchez-Monge Xose S Puente Gabriel Salcedo |
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Institution: | Unidad de Bioquímica, Dpto. Biotecnología, E.T.S. Ingenieros Agrónomos, Ciudad Univ., E-28040 Madrid, Spain;Dpto de Biología Funcional, Facultad de Medicina, Univ. de Oviedo, E-33006 Oviedo, Spain. |
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Abstract: | The only inhibitor of human salivary α-amylase identified so far in Hordeum has been isolated from barley cv. Bomi endosperm. This protein has the same N-terminal sequence (23 residues), molecular mass, and isoelectric point as one of the subunits of the barley tetrameric inhibitor previously characterized. However, enzymatic cleavage of both proteins with endoproteinase Glu-C revealed that they are products of different genes. The two isoforms have diverged in their aggregative and inhibitory properties. Thus, the subunit previously characterized forms, along with two other subunits, a tetramer active towards insect but not human salivary α-amylase, while the isoform reported here behaves as a homodimer effective against the human enzyme. These results are discussed in the context of the evolution of the cereal α-amylase inhibitor family. |
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Keywords: | α-Amylase inhibitor barley differential inhibitory specificity endosperm Hordeum vulgare isoforms |
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