A plant-seed inhibitor of two classes of α-amylases: X-ray analysis of Tenebrio molitor larvae α-amylase in complex with the bean Phaseolus vulgaris inhibitor

The alpha-amylase from Tenebrio molitor larvae (TMA) has been crystallized in complex with the alpha-amylase inhibitor (alpha-AI) from the bean Phaseolus vulgaris. A molecular-replacement solution of the structure was obtained using the refined pig pancreatic alpha-amylase (PPA) and alpha-AI atomic coordinates as starting models. The structural analysis showed that although TMA has the typical structure common to alpha-amylases, large deviations from the mammalian alpha-amylase models occur in the loops. Despite these differences in the interacting loops, the bean inhibitor is still able to inhibit both the insect and mammalian alpha-amylase.