Protease Inhibitor in Passion Fruit

Abstract

A protease inhibitor (PEPI) was isolated and purified from the juice of the passion fruit (Passiflora edulis Sim) by DEAE-Sephacel and trypsin-Sepharose 4B column chromatography. The molecular weight of PEPI was found to be 25 kDa by gel filtration. PEPI exhibited a single band in native and SDSPAGE gels under non-reducing conditions. Under reducing conditions in SDS-PAGE gel, PEPI exhibited three protein bands with estimated molecular weights of 25, 22, 18 kDa, respectively. The three protein bands were stained with PAS reagent. PEPI inhibited trypsin and chymotrypsin activities, but did not inhibit papain activity. The trypsin-inhibitory activity of PEPI was heat-stable, retaining 50% of the original activity even after exposure to 100°C for 10 min. The trypsin-inhibitory activity of PEPI was stable over a pH range of 2-12.