Angiotensin I-converting enzyme inhibitory activity in tropical legume seed proteins modified by microbial proteolytic enzymes

The microbial enzymes Alcalase® and Flavourzyme® were used individually and sequentially to hydrolyze protein concentrates from the seeds of the tropical legumes Lima bean (Phaseolus lunatus), black bean (Phaseolus vulgaris, fresh and hard-to-cook) and cowpea (Vigna unguiculata). Each hydrolysate was fractionated by ultrafiltration, and its degree of hydrolysis (%) and ACE-I inhibitory activity quantified. The endopeptidase Alcalase® and the fungal protease complex Flavourzyme® generated protein hydrolysates with high DH and significant amounts of peptides of molecular weight <1 kDa with potential biological activity. The best treatment was hydrolysis of hard-to-cook P. vulgaris with the Alcalase®-Flavourzyme® sequential system because the resulting <1kDa fraction exhibited the highest ACE-I inhibitory activity. Hydrolysis of peptide bonds catalyzed by microbial enzymes produced peptide fractions with biological activity and commercial potential as 'health-enhancing ingredients' in functional foods production.