The contribution of trypsin inhibitors to the nutritional value of chick pea seed protein

Abstract

AbstractThe trypsin inhibitors (TI) from seeds of chick pea (Cicer arietinum L.) were isolated using trypsin–Sepharose 6B affinity chromatography and found to constitute 5.03% of extractable seed protein. The TI consisted predominantly of low molecular weight species, estimated at 9000 and 8000 daltons by disc gel electrophoresis. Polypeptides in these regions of the gel were preferentially labelled by 35SO2‐4 fed via the cut stem to fruiting stalks of chick pea plants. A molar ratio of 1.8 was determined for the inhibition of trypsin by these inhibitors, whereas chymotrypsin was uninhibited. They are therefore ‘double‐headed’ inhibitors with both sites specific for trypsin, rather than with one site specific for each of trypsin and chymotrypsin, as reported for other lines of chick pea. Thus TI may contribute to the high quality of the albumin fraction of chick pea seeds in two ways: by virtue of their contents of essential amino acids, and by their failure to affect chymotrypsin.