Angiotensin I-converting enzyme inhibitory peptides from an enzymatic hydrolysate of flounder fish (Paralichthys olivaceus) muscle as a potent anti-hypertensive agent

Abstract The aim of this study was to purify peptides with anti-hypertensive properties from a hydrolysate of flounder fish muscle. Among four proteolytic hydrolysates, pepsin showed the strongest angiotensin-I converting enzyme (ACE) inhibitory activity. The pepsin hydrolysate was fractionated by ultrafiltration, gel filtration chromatography and reverse-phase high performance liquid chromatography, and two novel peptides were purified. The IC 50 values of the two peptides were 79 μM and 105 μM, respectively, and the Lineweaver–Burk plots suggested that they act as a competitive and a non-competitive inhibitor of ACE, respectively. Moreover, we predicted the 3D structure of ACE and used a molecular docking program to simulate binding between ACE and the peptides. These molecular modeling results indicated strong binding and interaction energies, and systolic blood pressures were reduced by administration of both peptides in spontaneously hypertensive rats. These results suggested that the enzymatic hydrolysate of flounder fish muscle includes novel ACE inhibitory peptides that may be beneficial as a functional food for treating hypertension.