Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This paper describes the characterization of a trypsin inhibitor from Poincianella pyramidalis seeds (PpyTI). The partial sequencing of PpyTI revealed homology to Kunitz inhibitors, clustered as a member of Family 103 in MEROPS database. PpyTI has a single polypeptide chain of 19,042 Da and presents stability at high temperatures (up to 70 degrees C) and a wide range of pH. In vitro assays showed that disulfide bridges have an important stabilization role of reactive site in PpyTI, a characteristic shared among several Kunitz inhibitors. Bioassays carried out with the Mediterranean flour moth (Anagasta kuehniella) revealed a significant decrease in both larval weight and survival of PpyTI-fed larvae, besides a larval stage extension. Through biochemical analysis, we demonstrated that the PpyTI insecticide effects were triggered by digestion process commitment, through the inhibition of trypsin and chymotrypsin activities, the major digestive enzymes in this species. The insecticide effects and biochemical characterization of PpyTI encourage further studies using this inhibitor for insect pest control. (C) 2014 Elsevier Inc. All rights reserved.118 19Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FINEP (Financier of Studies and Projects)FUNDECT (Foundation to Support Development of Education, Science and Technology of the State of Mato Grosso do Sul)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)