A novel angiotensin I-converting enzyme inhibitory peptide from Phascolosoma esculenta water-soluble protein hydrolysate

The water-soluble protein from Phascolosoma esculenta was hydrolyzed by pepsin to obtain the hydrolysate with angiotensin I-converting enzyme (ACE) inhibitory activity. The hydrolysate (PEPH) was then further separated by membrane bioreactor system, ion-exchange chromatography, gel filtration, and reversed phase high-performance liquid chromatography (RP-HPLC) and a novel ACE inhibitory peptide named as PeP with the IC50 value of 135 M was isolated. The amino acid sequence, Ala-Trp-Leu-His-Pro-Gly-Ala-Pro-Lys-Val-Phe, was identified by matrix-assisted laser desorption ionization-time of flight/time of flight (MALDI-TOF/TOF). Inhibitory kinetics study suggested that PeP acted as competitive inhibitor against ACE. Single oral administration of synthesized PeP at 10 mg/kg dose in spontaneously hypertensive rats could reduce the systolic blood pressure around 30 mmHg and the effect could last for more than 8 h. The results suggest that peptide from P. esculenta could be a potent natural ingredient for functional foods or pharmaceuticals against hypertension.