A heterotetrameric alpha-amylase inhibitor from emmer (Triticum dicoccon Schrank) seeds

Plants have developed a constitutive defense system against pest attacks, which involves the expressionof a set of inhibitors acting on heterologous amylases of different origins.Investigating the soluble protein complement of the hulled wheat emmer we have isolated and characterizeda heterotetrameric a-amylase inhibitor (ETI). Based on mass spectrometry data, it is an assemblyof proteins highly similar to the CM2/CM3/CM16 found in durum wheat. Our data indicate that theseproteins can also inhibit exogenous a-amylases in binary assemblies. The calculated dissociation constants(Ki) for the pancreatic porcine amylase- and human salivary amylase-ETI complexes are similarto those found in durum and soft wheat. Homology modeling of the CM subunits indicate structural similaritieswith other proteins belonging to the cereal family of trypsin/a-amylase inhibitors; a possiblehomology modeled structure for a tetrameric assembly of the subunits is proposed