Discovery and molecular mechanism of a novel antihypertensive peptide from Chlamydomonas reinhardtii based on molecular docking, molecular dynamics simulation, in vitro, and in vivo analysis.

Chlamydomonas reinhardtii, a nutrient-rich microalga and emerging food resource, remains largely unexplored as a source of bioactive peptides. In this study, eight protease hydrolysates were prepared from C. reinhardtii. Among these, the alkaline protease hydrolysate (CRPA) demonstrated the most potent activity, exhibiting strong angiotensin-I converting enzyme (ACE) inhibitory activity in vitro and significant in vivo antihypertensive activity in spontaneously hypertensive rats (SHRs), with the effective dose corresponding to an estimated human-equivalent dose of 16 mg/kg/day. Using bioassay-guided isolation strategy, the first ACE-inhibitory peptide IDYRY (ID-5) was identified from C. reinhardtii, exhibiting an IC50 value of 18.54 ± 5.57 μM. ID-5 was characterized as a noncompetitive ACE inhibitor with confirmed antihypertensive activity both in vitro and in vivo. Molecular dynamics simulations revealed that ID-5 forms unique hydrogen bonds with Asp415 and Arg522, distinguishing its binding mechanism from that of captopril or lisinopril. Collectively, these findings highlight the enhanced bioactivity of CRPA and position C. reinhardtii as a sustainable microalgal source for developing functional foods and nutraceuticals aimed at blood pressure management.