Seed Proteinase Inhibitors from Annual Medics Active against Insect Pests

11-19 ABSTRACT Several different species of annual medics have been tested for the occurrence and concentration of trypsin inhibitors in the seed. Trypsin Inhibitory Activity (TIA) has been in fact related to the level of resistance to biotic and abiotic stresses. Wide variation was found for TIA among species, with the highest values shown by the snail medic (Medicago scutellata). After a simple and rapid procedure of chromatographic purification, the Trypsin Inhibitor (TI) from snail medic has been tested towards the trypsin-like proteinases extracted from larvae of different phytophagous insects, showing high levels of Inhibitory Activity. The complete amino acid sequence of the snail medic TI consists of 62 residues, corresponding to a relative molecular weight of 6925. Sequence comparison shows significant similarity to other proteins belonging to the Bowman-Birk trypsin inhibitory family, and the closest identity (81%) with the woundinduced trypsin inhibitor from M. sativa leaves.