Characterisation of Bioactive Peptides from Red Alga Gracilariopsis chorda.

In this study, we studied the bioactive peptides produced by thermolysin hydrolysis of a water-soluble protein (WSP) from the red alga Gracilariopsis chorda, whose major components are phycobiliproteins and Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCo). The results showed that WSP hydrolysate exhibited significantly higher ACE inhibitory activity (92% inhibition) compared to DPP-IV inhibitory activity and DPPH scavenging activity. The phycobiliproteins and RuBisCo of G. chorda contain a high proportion of hydrophobic (31.0-46.5%) and aromatic (5.1-46.5%) amino acid residues, which was considered suitable for the formation of peptides with strong ACE inhibitory activity. Therefore, we searched for peptides with strong ACE inhibitory activity and identified two novel peptides (IDHY and LVVER). Then, their interaction with human ACE was evaluated by molecular docking, and IDHY was found to be a promising inhibitor. In silico analysis was then performed on the structural factors affecting ACE inhibitory peptide release, using the predicted 3D structures of phycobiliproteins and RuBisCo. The results showed that most of the ACE inhibitory peptides are located in the highly solvent accessible α-helix. Therefore, it was suggested that G. chorda is a good source of bioactive peptides, especially ACE-inhibitory peptides.

Investigation on antioxidant, angiotensin converting enzyme and dipeptidyl peptidase IV inhibitory activity of Bambara bean protein hydrolysates.

Protein isolate was hydrolysed by Alcalase, thermolysin and trypsin. BBPH produced by Alcalase showed highest angiotensin-converting enzyme (ACE) inhibitory properties (IC50: 52 µg/mL). Hydrolysates produced by Alcalase and thermolysin exhibited similar dipeptidyl peptidase-IV (DPP-IV) inhibitory activity (IC50: 1.73 mg/mL), while low inhibitory activity was observed for hydrolysate produced by trypsin. BBPH also showed protective effect against oxidative stress with significant 2,2-diphenyl-1-picrylhydrazyl radical scavenging and ferrous chelating activity. Bioactive peptides of BBPH produced by thermolysin showed better resistance to simulated gastrointestinal digestion (SGID), while the DPP-IV and ACE inhibitory properties were significantly reduced. Molecular weight distribution showed significant reduction in peptides of the molecular weight range 200-400 Da in BBPH produced by Alcalase, after SGID. LC-ESI-TOF-MS and in silico analysis showed the presence of potential peptides with both ACE and DPP-IV inhibitory properties in BBPH produced by thermolysin.