Purification and characterization of polygalacturonase-inhibitory proteins from Psidium guajava']java Linn. (guava) fruit

The presence of polygalacturonase inhibitory proteins [PGIPs] in plant cell walls, has acquired importance since the finding that they play a role in resistance of plants to fungal attack. PGIP activity has been demonstrated in many plant species in diverse families. PGIPs have now been shown to be similar to signal transaction molecules and have been found to be homologous to some signal transduction molecules from other species. We are investigating the PGIPs present in Psidium guajava Linn. (guava). A purification protocol involving acetone precipitation, ion-exchange chromatography and gel filtration was adopted and three isoforms of PGIP were identified. These inhibitors were found to be stable upto 60 degreesC and showed widely different effectivily for PGs from different fungal strains. Kinetic studies suggest that the inhibition caused by these proteins is of a mixed type. (C) 2002 Published by Elsevier Science Ireland Ltd.