PURIFICATION AND PARTIAL CHARACTERIZATION OF A PROTEINASE-INHIBITOR FROM TEPARY BEAN (PHASEOLUS-ACUTIFOLIUS) SEEDS

In a qualitative screening of 36 accessions of tepary beans seeds, all the accessions inhibit the activity of bovine trypsin and trypsin-lik e proteinases from the insect P. truncatus, and the majority of them i nhibit alpha-amylase activity of several important insect pests. A pro tein proteinase inhibitor was purified from accession L-242-45, using fractional precipitation, gelfiltration, ion exchange chromatography a nd reverse-phase HPLC. The protein showed an apparent molecular weight of 7,100 by PAGE. However, contrary to other inhibitors previously re ported, the inhibitory activity was only present in the trimeric form. The protein was characterized as a serine-proteinase inhibitor that r ecognized trypsin, chymotrypsin and trypsin-like proteinases, but it a lso recognized aspartic acid proteinases from different insects. It co ntained no carbohydrate residues and showed a high stability at 96C at low pH.