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 IC 50 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.