Proteinase Inhibitors from Pea Seeds:  Purification and Characterization

Six protease inhibitors (denoted PSTI I, PSTI II, PSTI III, PSTI IVa, PSTI IVb, and PSTI V) have been purified from winter pea seeds (cv. Frilene) by ammonium sulfate precipitation, gel filtration, and anion and cation exchange chromatography. Their molecular masses were determined by electrospray mass spectrometry to be 6916, 6807, 7676, 7944, 7848, and 7844 Da, respectively. The sequences of the first 20 N-terminal amino acid residues of these six inhibitors were found to be identical and similar to those of Vicia faba and Vicia angustifolia inhibitors, which belong to the Bowman-Birk class of trypsin inhibitors.