Angiotensin I-converting enzyme inhibitory peptide from yellowfin sole (Limanda aspera) frame protein and its antihypertensive effect in spontaneously hypertensive rats

In order to utilize yellowfin sole (Limanda aspera) frame protein, which is normally discarded as industrial waste in the process of fish manufacture, yellowfin sole frame protein was hydrolysed by α-chymotrypsin. Yellowfin sole frame protein hydrolysates (YFPHs) were fractionated into three ranges of molecular weight (YFPH-I, 30–10 kDa; YFPH-II, 10–5 kDa; YFPH-III, below 5 kDa) using an ultrafiltration (UF) membrane bioreactor system. Angiotensin I-converting enzyme (ACE) inhibitory activity was detected on YFPH-III, and the ACE inhibitory peptide (YFP) was purified from YFPH-III using consecutive chromatographic techniques. The YFP with a molecular mass of 1.3 kDa consisted of 11 amino acids, Met-Ile-Phe-Pro-Gly-Ala-Gly-Gly-Pro-Glu-Leu, and its IC50 value was 28.7 μg/ml. Lineweaver–Burk plots suggest that YFP acts as a non-competitive inhibitor to inhibit ACE. Antihypertensive effects of YFP on spontaneously hypertensive rats (SHR) following oral administration was determined as the blood pressure significantly decreased after peptide ingestion.