SCREENING FOR CYSTEINE PROTEINASE-INHIBITOR ACTIVITY IN LEGUME SEEDS

Extracts of 44 legume seeds were assayed for cysteine proteinase inhibitory (CPI) activity, using a papain/azocasein assay. Extracts with high papain inhibitory activity were further assayed with a crude gut extract (CGE) of larval Acanthoscelides obtectus (Say) (common bean weevil) against H-3-methemoglobin. Soybeans (Glycine max L Merrill), lima beans (Phaseolus lunatus L), tepary beans (Phaseolus acutifolius A Gray), and lupine seeds (Lupinus albus L) were found to be highest in CPI activity. Soybean hypocotyl extracts were found to have much greater CPI activity, relative to protein concentration, than cotyledon extracts. Papain was much more inhibited by soybean hypocotyl and cotyledon extracts than was A obtectus CGE. Water extracts of soybean hypocotyl flour were, slightly higher in CPI activity than extracts with 0.2 M sodium phosphate buffer, pH 6.2.