Isolation and biochemical characterisation of angiotensin-converting enzyme inhibitory peptides derived from the enzymatic hydrolysis of cupuassu seed protein isolate

The consumption of cupuassu (Theobroma grandiflorum) currently involves the pulp alone; the protein-rich seeds are viewed as leftovers by the food industry. Since some proteins may be sources of cryptic bioactive peptides (cryptides) with functions unrelated to the precursor, this study aimed to isolate and biochemically characterise angiotensin I-converting enzyme (ACE) inhibitor peptides derived from subtilisin hydrolysed cupuassu seed proteins. Eight ACE inhibitory peptides were sequenced de novo using mass spectrometry, yielding five novel sequences. The synthetic analogues were obtained and assayed for ACE IC50 and K-i determination. The peptides MVVDKLF and LDNK were competitive inhibitors, whereas FLEK and MEKHS were non-competitive. Interestingly, GSGKHVSP, which yielded the lowest IC50 and Ki values, behaved as a mixed-type inhibitor. The cupuassu cryptides presented here are not only novel alternative biotechnological tools in the field of antihypertension, but may also contribute to the reuse of the raw material as a functional food ingredient. (C) 2016 Elsevier Ltd. All rights reserved.