Characterization of Partially Purified Trypsin and Chymotrypsin Inhibitor of Vigna pilosa

Trypsin inhibitors are often associated with their negative effect as an antinutritional factor, but it is now known that they are beneficial for human health due to their anticarcinogenic, anti-inflammatory, and antiulcer activities. Vigna pilosa is a crop plant belonging to the family Leguuminosae. A proteinacious inhibitor of trypsin (VPTI) and chymotrypsin (VPCI) was isolated from Vigna pilosa seeds. Protein was extracted in 0.1 M Tris–Cl buffer (pH-8.0) and subjected to precipitation using 60% ammonium sulphate, dialyzed against 0.1 M phosphate buffer and eluted on DEAE cellulose column chromatography. Fold purification obtained was 16.79for VPTI and 12.99 for VPCI. Purified sample was analyzed on gelatin embedded native PAGE for isoform detection. Two isoforms of VPTI were observed. SDS-PAGE analysis of Vigna pilosa protease inhibitor (VPPI) showed closely related two polypeptide bands of ~20 and ~19.5 kDa. Solution assay with BApNa and BTpNa at 38 μg and 55 μg of inhibitor concentration showed 50% inhibition of VPTI and VPCI respectively. Both the inhibitors showed activity between pH ranges 6.5 to 7.5. It lost its complete activity when heated at 100°C for 50 minutes. Thermal stability of V. pilosa inhibitor was assessed to check whether it can withstand high temperatures. Preliminary results suggest that the trypsin inhibitor was not stable to heat.