Isolation and Characterization of Bioactive Pro-Peptides with in Vitro Renin Inhibitory Activities from the Macroalga Palmaria palmata

Renin is the initial rate limiting step in the renin angiotensinogen system (RAS). To combat hypertension, various stages of the RAS can be positively affected. The aim of this study was to isolate and characterize renin inhibitory peptides from the red seaweed P. palmata for use in functional foods. Palmaria palmata protein was extracted and hydrolyzed with the food grade enzyme Papain to generate renin inhibitory peptides. Following proteolytic hydrolysis of P. palmata protein, reverse phase-high performance liquid chromatography (RP-HPLC) was employed to enrich for peptides with renin inhibitory activities. Fraction 25 (Fr-25) inhibited renin activities by 58.97% (+/- 1.26) at a concentration of 1 mg/mL. This fraction was further characterized using nano-electrospray ionization quadropole/time-of-flight mass spectrometry (ESI-Q/TOF MS). A number of novel peptide sequences were elucidated, and the parent protein from which they were derived was determined using MS in tandem with protein database searches. All sequences were confirmed using de novo sequencing. The renin inhibitory peptide IleArg-Leu-Ile-Ile-Val-Leu-Met-Pro-Ile-Leu-Met-Ala (IRLIIVLMPILMA) was chemically synthesized and its bioactivity confirmed using the renin inhibitory assay. Other stages of the RAS have recently been inhibited by bioactive peptides sourced from macroalgae, but this is the first study to isolate and characterize renin inhibitory peptides from the macroalgae.