Abstract
Three novel peptide sequences identified from palm kernel cake (PKC) generated protein hydrolysate including YLLLK, WAFS and GVQEGAGHYALL were used for stability study against angiotensin-converting enzyme (ACE), ACE-inhibition kinetics and molecular docking studies. Results showed that the peptides were degraded at different cleavage degrees of 94%, 67% and 97% for YLLLK, WAFS and GVQEGAGHYALL, respectively, after 3 h of incubation with ACE. YLLLK was found to be the least stable (decreased ACE-inhibitory activity) compared to WAFS and GVQEGAGHYALL (increased ACE-inhibitory activity). YLLLK showed the lowest Ki (1.51 mM) in inhibition kinetics study when compared to WAFS and GVQEGAGHYALL with Ki of 2 mM and 3.18 mM, respectively. In addition, ACE revealed the lowest and and higher catalytic efficiency (CE) in the presence of YLLLK at different concentrations, implying that the enzyme catalysis decreased and hence the inhibition mode increased. Furthermore, YLLLK showed the lowest docking score of −8.224 and seven interactions with tACE, while peptide GVQEGAGHYALL showed the higher docking score of −7.006 and five interactions with tACE.
Highlights
Bioactive peptides are protein-based compounds having amino acid residues in the range of 2 to 20 and possess numerous biological effects on human health
From HPLC chromatograms, YLLLK showed that the number of peaks was 1 at the first 30 min with 91.7% of peptide cleavage and it decreased to 4 peaks in 3 h of pre-incubation with 94.3%
Lineweaver-Burk plots revealed that the inhibition mode of the peptides at different concentrations was mixed-type inhibition, implying that the peptides can compete with the substrate to bind to the active site of the enzyme and at other non-active sites
Summary
Bioactive peptides are protein-based compounds having amino acid residues in the range of 2 to 20 and possess numerous biological effects on human health. They are produced from different protein sources via a variety of production approaches such as the use of proteolytic enzymes, fermentation using different bacteria or fungi and digestion of food proteins after their consumption [1,2]. Antihypertensive peptides are natural alternatives to synthetic angiotensin-converting enzyme (ACE) inhibitors, of which the latter would produce mild to severe adverse side effects such as dry cough, dizziness, headaches and fatigue. The ACE inhibitory activity of bio-peptides are lower than synthetic ACE inhibitors, they are safer with a reduced health risk, less costly and provide additional nutritional benefits as a source of essential amino acids [9,10].
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