A microassay for the analysis of trypsin inhibitor activity in peas

A microassay has been developed, for determining trypsin inhibitor activities in peas, that requires only small amounts of sample (5 mg pea flour) and reagents. Acid extracts of peas were tested for their ability to inhibit the activity of bovine trypsin using the synthetic substrate, Nα-benzoyl-dl-arginine p-nitroanilide, in a microtitre plate. The extent of colour reactions were then rapidly determined using a plate reader. This new procedure allows a large number of assays to be performed in 1 day (up to 80), without significant loss of accuracy compared to the most commonly used larger scale Kakade assay. The method can be applied by plant breeders to screen the trypsin inhibitor activity of large numbers of pea samples and to the analysis of samples in genetics programmes where the quantity of material can be limited to a single seed.