Abstract
More than 7000 red algae species have been classified. Although most of them are underused, they are a protein-rich marine resource. The hydrolysates of red algal proteins are good candidates for the inhibition of the angiotensin-I-converting enzyme (ACE). The ACE is one of the key factors for cardiovascular disease, and the inhibition of ACE activity is related to the prevention of high blood pressure. To better understand the relationship between the hydrolysates of red algal proteins and the inhibition of ACE activity, we attempted to identify novel ACE inhibitory peptides from Pyropia pseudolinearis. We prepared water soluble proteins (WSP) containing phycoerythrin, phycocyanin, allophycocyanin, and ribulose 1,5-bisphosphate carboxylase/oxygenase. In vitro analysis showed that the thermolysin hydrolysate of the WSP had high ACE inhibitory activity compared to that of WSP. We then identified 42 peptides in the hydrolysate by high-performance liquid chromatography and mass spectrometry. Among 42 peptides, 23 peptides were found in chloroplast proteins. We then synthesized the uncharacterized peptides ARY, YLR, and LRM and measured the ACE inhibitory activity. LRM showed a low IC50 value (0.15 μmol) compared to ARY and YLR (1.3 and 5.8 μmol). In silico analysis revealed that the LRM sequence was conserved in cpcA from Bangiales and Florideophyceae, indicating that the novel ACE inhibitory peptide LRM was highly conserved in red algae.
Highlights
Japan’s Ministry of Agriculture, Forestry and Fisheries promotes “Shokuiku” (Food and Nutrition Education)
A previous study revealed that 55,000 MW of the protein in the water-extract of red algae was the Rubisco large subunit [47], suggesting that the water soluble proteins (WSP)
To find novel angiotensin-I-converting enzyme (ACE) inhibitory peptides, we focused on the rest of the peptides from phycobiliproteins
Summary
Japan’s Ministry of Agriculture, Forestry and Fisheries promotes “Shokuiku” (Food and Nutrition Education). There have been various reports for the functions of bioactive peptides, such as decreases in blood pressure, glucose, cholesterol, and neutral lipids and increases in immune response [1]. Among these peptides, several antihypertensive peptides from natural sources, such as sesame, milk, sardine, and seaweed have been used as food for specified health uses (FOSHU) in Japan [2,3]. This study is useful for the evaluation of proteins from red algae as a source of ACE inhibitory peptides
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