ACE inhibitory effect of the protein hydrolysates prepared from commercially available nori product by pepsin-trypsin digestion

We studied angiotensin I converting enzyme (ACE) inhibitory effect of the protein hydrolysates prepared from commercially available nori products that contain Pyropia pseudolinearis as the main ingredient. The water extract of the nori product consisted mainly of phycobiliproteins and RubisCO. The proteins in the aqueous extracts were sequentially hydrolyzed with pepsin and trypsin, and the peptides in the pepsin-trypsin digests were fractionated by reversed-phase HPLC. As a result, 12 ACE inhibitory peptides containing ten novel peptides were identified. These peptides are suggested to have originated from the alpha- and beta-subunits of phycobiliproteins and the large subunits of RubisCO of P. pseudolinearis. The interactions of eight peptides (ALR, FAR, FSR, FDR, EVYR, AYR, GRP, and MVT) with ACE were then simulated using the flexible docking tool Auto Dock Vina. The results showed that all peptides interacted with the active center of ACE, and their docking scores ranged from - 6.8 to - 10.2 kcal/mol. In addition, we synthesized four peptides (AYR, FAR, EVYR, and GRP) and measured the IC50 values of these peptides for ACE. Consequently, FAR and GRP showed considerably low IC50 values (0.29 mu mol and 0.45 mu mol, respectively) in addition to other ACE inhibitory peptides. Moreover, FAR, which is specific to the nori product, was predicted to bind to the S1, S1 ', and S2 ' subsites of the catalytic center of ACE. Therefore, it can be expected that daily intake of nori products may have a positive effect on the prevention of hypertension.

Automated summary

This study examined the ACE inhibitory effect of protein hydrolysates from nori products containing Pyropia pseudolinearis. Twelve ACE inhibitory peptides, including ten novel ones, were identified, with FAR and GRP showing particularly low IC50 values. The peptide FAR, specific to nori, was predicted to bind to the catalytic center of ACE, suggesting a potential role in hypertension prevention.