Abstract: The body wall of sea cucumber (Stichopus japonicus) was hydrolyzed by protamex proteinase to produce angiotensin I-converting enzyme (ACE) inhibitory peptides. Using one-factor-at-a-time method, the optimum hydrolysis conditions to obtain the highest ACE inhibitory activity were determined as follows: solid to liquid ratio, 1:6 (g/mL); proteinase dosage, 0.8% (m/m); hydrolysis time, 6 h; and hydrolysis pH, 7.0. Ultrafiltration of the resulting hydrolysate yielded a less than 3 kDa fraction with ACE inhibitory activity, whose IC50 was 0.8 mg/mL. Kinetic analysis showed that the inhibitory action of the fraction on ACE was non-competitive. The ACE inhibitory peptides were stable under high temperature, acidic or alkaline conditions and were resistant to gastrointestinal digestion in vitro. Furthermore, these peptides could significantly decrease systolic blood pressure in spontaneously hypertensive rats (SHRs). The present work could provide a theoretical basis for the development of sea cucumber peptides with ACE inhibitory activity as potential antihypertensive food ingredients.

Key words: sea cucumber, ACE inhibitory peptide, stability, mode of inhibition, spontaneously hypertensive rats (SHRs)