Antinutritional and biochemical properties of winged bean trypsin inhibitors.

Abstract

The trypsin inhibitors (TI) of winged bean (Psophocarpus tetragonolobus) isolated by affinity chromatography consisted of 8 protein bands by disc polyacrylamide electrophoresis. All the bands exhibited trypsin inhibitor activity (TIA) with two of the major bands also exhibiting chymotrypsin inhibitor activity (CIA). Electrofocusing separated the TI into 5 protein bands. Two bands with dual TIA/CIA activities had acidic pI while 3 bands with TIA only had alkaline pI. The TI belonged to two molecular weight groups of 20,900 and 16,600, as determined by NaDodSo4 polyacrylamide electrophoresis. Sufficient quantities of TI were isolated by affinity chromatography for rat feeding. Raw winged bean was toxic to rats, causing death after 12 days of feeding. Autoclaved winged bean was not toxic but caused growth inhibition. When fed with casein, the isolated inhibitor caused slight growth inhibition, pancreatic and spleen hypertrophy. It was concluded that TI in winged bean was not primarily responsible for the toxicity of raw winged bean.