Identification of a novel bean α-amylase inhibitor with chitinolytic activity

Zabrotes subfasciatus is a devastating starch-dependent storage bean pest. In this study, we attempted to identify novel α-amylase inhibitors from wild bean seeds, with efficiency toward pest α-amylases. An inhibitor named Phaseolus vulgaris chitinolytic α-amylase inhibitor (PvCAI) was purified and mass spectrometry analyses showed a protein with 33 330 Da with the ability to form dimers. Purified PvCAI showed significant inhibitory activity against larval Z. subfasciatus α-amylases with no activity against mammalian enzymes. N-terminal sequence analyses showed an unexpected high identity to plant chitinases from the glycoside hydrolase family 18. Furthermore, their chitinolytic activity was also detected. Our data provides compelling evidence that PvCAI also possessed chitinolytic activity, indicating the emergence of a novel α-amylase inhibitor class.