Purification and some properties of trypsin and chymotrypsin inhibitor from tepary bean seeds prolamine fraction

Abstract EN

A protein inhibitor of trypsin and chymotrypsin was purified to homogeneity from topiary bean protamine fraction by ethanol extraction, acetone precipitation, followed by ion exchange chromatography with DEAE, hydrophobic chromatography with Phenyl Rephrase and gel filtration chromatography with Sephardic G-75.

The inhibitor has a molecular weight of 17800 Daltons as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by molecular-sieve chromatography on Sephardic G-75.

The amino acid composition of protamine fraction inhibitor closely resemble those of low molecular weight inhibitors of other legume seeds (Bowmen-Birk type), they contain large amounts of aspartic acid, half cysteine, serine and glutamic acid.

The protamine fraction inhibitor exhibited high stability under conditions of extreme pH.

Inhibition data showed that 1.0 mole of the inhibitor inhibited 2.0 mole of trypsin and 1.0 mole of chymotrypsin, indicating that the inhibitor is double-headed.