Insecticidal and antifungal activity of a protein from Pouteria torta seeds with lectin-like properties

This paper describes the purification and characterization of a novel protein from the seeds of Pouteria torta (family Sapotaceae). The protein was purified by a combination of gel filtration, ion-exchange, and reverse phase chromatographies. SDS-PAGE of the purified protein resulted in a single protein band of 14 kDa in the presence and absence of DTT. The lectin-like activity of pouterin was best inhibited by glycoproteins such as fetuin, asialofetuin, heparin, orosomucoid, and ovoalbumin. Pouterin inhibited the growth of the fungi Fusarium oxysporum and Colletotrichum musae and of the yeast Saccharomyces cerevisiae. The incorporation of pouterin into an artificial diet (final concentration = 0.12%, w/w) caused 50% mortality in larvae of the insect Callosobruchus maculatus, whereas 0.08% pouterin produced an ED50.