Polygalacturonase-inhibiting proteins (PGIPs) are extracellular plant proteins bound to the plant cell wall containing leucine-rich repeats (LRR). They play an important role in plant defence being able to inhibit fungal endopolygalacturonases (EPGs), the first enzymes secreted by phytopathogenic fungi during plant infection. In the present work, a novel PGIP (LsPGIP) has been isolated from Lathyrus sativus seeds. LsPGIP exhibited an inhibitory activity towards EPGs from Aspergillus niger and Rhizopus spp. A pI value of 8.3 and a molecular mass of 40 kDa were determined for the purified inhibitor. Furthermore, N-terminal sequence up to residue 20 revealed that LsPGIP exhibit a high percentage of identity with PGIP from Actinidia deliciosa. A secondary structure similar to those of other polygalacturonase inhibitors was also inferred form circular dichroism data.
Keywords: Polygalacturonase-inhibiting protein, Edman degradation, Lathyrus sativus, protein purification, pathogens, β-1, 3-glucanases , protease inhibitors, glycoproteins, extracellular space, oligogalacturonides