Kinetics of the inhibition of renin and angiotensin I-converting enzyme by cod (Gadus morhua)
protein hydrolysates and their antihypertensive effects in spontaneously hypertensive rats
Sammanfattning
Background: Cod muscle has a balanced protein profile that contains potentially bioactive amino
acid sequences. However, there is limited information on release of these peptides from the parent
proteins and their ability to modulate mammalian blood pressure.
Objective: The aim of this study was to generate cod antihypertensive peptides with potent in vitro
inhibitory effects against angiotensin-converting enzyme (ACE) and renin. The most active peptides
were then tested for systolic blood pressure (SBP)-reducing ability in spontaneously hypertensive
rats (SHRs).
Design: Cod protein hydrolysate (CPH) was produced by subjecting the muscle proteins to
proteolysis first by pepsin and followed by trypsin+chymotrypsin combination. In order to enhance
peptide activity, the CPH was subjected to reverse-phase (RP)-HPLC separation to yield four fractions
(CF1, CF2, CF3, and CF4). The CPH and RP-HPLC fractions were each tested at 1 mg/mL for ability to
inhibit in vitro ACE and renin activities. CPH and the most active RP-HPLC fraction (CF3) were then
used for enzyme inhibition kinetics assays followed by oral administration (200 and 30 mg/kg body
weight for CPH and CF3, respectively) to SHRs and SBP measurements within 24 h.
Results: The CPH, CF3, and CF4 had similar ACE-inhibitory activities of 84, 85, and 87%, which were
significantly (p<0.05) higher than the values for CF1 (69%) and CF2 (79%). Conversely, the CF3 had
the highest (63%) renin-inhibitory activity (p<0.05) when compared to CPH (43%), CF1 (15%), and CF4
(44%). CPH and CF3 exhibited uncompetitive mode of ACE inhibition, whereas renin inhibition was
non-competitive. Even at a 6.7-fold lower dosage, the CF3 significantly (p<0.05) reduced SBP
(maximum -40.0 mmHg) better than CPH (maximum -19.1 mmHg).
Conclusions: RP-HPLC fractionation led to enhanced antihypertensive effects of cod peptides, which
may be due to a stronger renin-inhibitory activity.